draft-ietf-rddp-security-06.txt   draft-ietf-rddp-security-07.txt 
Internet Draft James Pinkerton Internet Draft James Pinkerton
draft-ietf-rddp-security-06.txt Microsoft Corporation draft-ietf-rddp-security-07.txt Microsoft Corporation
Category: Standards Track Ellen Deleganes Category: Standards Track Ellen Deleganes
Expires: June, 2005 Intel Corporation Expires: October, 2005 Intel Corporation
Sara Bitan Sara Bitan
Microsoft Corporation Microsoft Corporation
December 2004 April 2005
DDP/RDMAP Security DDP/RDMAP Security
1 Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that
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patent or other IPR claims of which I am aware have been aware have been or will be disclosed, and any of which he or she
disclosed, or will be disclosed, and any of which I become aware becomes aware will be disclosed, in accordance with Section 6 of
will be disclosed, in accordance with RFC 3668. BCP 79.
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2 Abstract Abstract
This document analyzes security issues around implementation and This document analyzes security issues around implementation and
use of the Direct Data Placement Protocol(DDP) and Remote Direct use of the Direct Data Placement Protocol(DDP) and Remote Direct
Memory Access Protocol (RDMAP). It first defines an architectural Memory Access Protocol (RDMAP). It first defines an architectural
model for an RDMA Network Interface Card (RNIC), which can model for an RDMA Network Interface Card (RNIC), which can
implement DDP or RDMAP and DDP. The document reviews various implement DDP or RDMAP and DDP. The document reviews various
attacks against the resources defined in the architectural model attacks against the resources defined in the architectural model
and the countermeasures that can be used to protect the system. and the countermeasures that can be used to protect the system.
Attacks are grouped into spoofing, tampering, information Attacks are grouped into spoofing, tampering, information
disclosure, denial of service, and elevation of privilege. disclosure, denial of service, and elevation of privilege.
Finally, the document concludes with a summary of security Finally, the document concludes with a summary of security
services for DDP and RDMAP, such as IPsec. services for DDP and RDMAP, such as IPsec.
J. Pinkerton, et al. Expires June, 2005 1 J. Pinkerton, et al. Expires October, 2005 1
Table of Contents Table of Contents
1 Status of this Memo..........................................1 1 Introduction.................................................4
2 Abstract.....................................................1 2 Architectural Model..........................................6
2.1 Revision History.............................................3 2.1 Components...................................................7
2.1.1 Changes from -05 to -06 version............................3 2.2 Resources....................................................8
2.1.2 Changes from -04 to -05 version............................4 2.2.1 Stream Context Memory......................................8
2.1.3 Changes from -03 to -04 version............................5 2.2.2 Data Buffers...............................................8
2.1.4 Changes from -02 to -03 version............................5 2.2.3 Page Translation Tables....................................9
2.1.5 Changes from the -01 to the -02 version....................6 2.2.4 STag Namespace.............................................9
2.1.6 Changes from the -00 to -01 version........................6 2.2.5 Completion Queues..........................................9
3 Introduction.................................................8 2.2.6 Asynchronous Event Queue..................................10
4 Architectural Model.........................................10 2.2.7 RDMA Read Request Queue...................................10
4.1 Components..................................................11 2.2.8 RNIC Interactions.........................................10
4.2 Resources...................................................12 2.2.8.1 Privileged Control Interface Semantics.................10
4.2.1 Stream Context Memory.....................................12 2.2.8.2 Non-Privileged Data Interface Semantics................11
4.2.2 Data Buffers..............................................12 2.2.8.3 Privileged Data Interface Semantics....................11
4.2.3 Page Translation Tables...................................13 2.2.9 Initialization of RNIC Data Structures for Data Transfer..11
4.2.4 STag Namespace............................................13 2.2.10 RNIC Data Transfer Interactions..........................13
4.2.5 Completion Queues.........................................13 3 Trust and Resource Sharing..................................14
4.2.6 Asynchronous Event Queue..................................14 4 Attacker Capabilities.......................................15
4.2.7 RDMA Read Request Queue...................................14 5 Attacks and Countermeasures.................................16
4.2.8 RNIC Interactions.........................................14 5.1 Tools for Countermeasures...................................16
4.2.8.1 Privileged Control Interface Semantics.................14 5.1.1 Protection Domain (PD)....................................16
4.2.8.2 Non-Privileged Data Interface Semantics................15 5.1.2 Limiting STag Scope.......................................17
4.2.8.3 Privileged Data Interface Semantics....................15 5.1.3 Access Rights.............................................18
4.2.9 Initialization of RNIC Data Structures for Data Transfer..15 5.1.4 Limiting the Scope of the Completion Queue................18
4.2.10 RNIC Data Transfer Interactions..........................17 5.1.5 Limiting the Scope of an Error............................18
5 Trust and Resource Sharing..................................18 5.2 Spoofing....................................................19
6 Attacker Capabilities.......................................19 5.2.1 Impersonation.............................................19
7 Attacks and Countermeasures.................................20 5.2.2 Stream Hijacking..........................................19
7.1 Tools for Countermeasures...................................20 5.2.3 Man in the Middle Attack..................................20
7.1.1 Protection Domain (PD)....................................20 5.2.4 Using an STag on a Different Stream.......................20
7.1.2 Limiting STag Scope.......................................21 5.3 Tampering...................................................21
7.1.3 Access Rights.............................................22 5.3.1 Buffer Overrun - RDMA Write or Read Response..............22
7.1.4 Limiting the Scope of the Completion Queue................22 5.3.2 Modifying a Buffer After Indication.......................22
7.1.5 Limiting the Scope of an Error............................22 5.3.3 Multiple STags to access the same buffer..................23
7.2 Spoofing....................................................23 5.3.4 Network based modification of buffer content..............23
7.2.1 Impersonation.............................................23 5.4 Information Disclosure......................................23
7.2.2 Stream Hijacking..........................................23 5.4.1 Probing memory outside of the buffer bounds...............23
7.2.3 Man in the Middle Attack..................................24 5.4.2 Using RDMA Read to Access Stale Data......................23
7.2.4 Using an STag on a Different Stream.......................24 5.4.3 Accessing a Buffer After the Transfer.....................24
7.3 Tampering...................................................25 5.4.4 Accessing Unintended Data With a Valid STag...............24
7.3.1 Buffer Overrun - RDMA Write or Read Response..............26 5.4.5 RDMA Read into an RDMA Write Buffer.......................24
7.3.2 Modifying a Buffer After Indication.......................26 5.4.6 Using Multiple STags Which Alias to the Same Buffer.......25
7.3.3 Multiple STags to access the same buffer..................27 5.4.7 Remote Node Loading Firmware onto the RNIC................25
7.3.4 Network based modification of buffer content..............27 5.4.8 Controlling Access to PTT & STag Mapping..................25
7.4 Information Disclosure......................................27 5.4.9 Network based eavesdropping...............................26
7.4.1 Probing memory outside of the buffer bounds...............27 5.5 Denial of Service (DOS).....................................26
7.4.2 Using RDMA Read to Access Stale Data......................27 5.5.1 RNIC Resource Consumption.................................26
7.4.3 Accessing a Buffer After the Transfer.....................28 5.5.2 Resource Consumption By Active ULPs.......................27
7.4.4 Accessing Unintended Data With a Valid STag...............28 5.5.2.1 Multiple Streams Sharing Receive Buffers...............27
7.4.5 RDMA Read into an RDMA Write Buffer.......................28 5.5.2.2 Local ULP Attacking a Shared CQ........................29
7.4.6 Using Multiple STags Which Alias to the Same Buffer.......29 5.5.2.3 Local or Remote Peer Attacking a Shared CQ.............29
7.4.7 Remote Node Loading Firmware onto the RNIC................29 5.5.2.4 Attacking the RDMA Read Request Queue..................32
7.4.8 Controlling Access to PTT & STag Mapping..................29 5.5.3 Resource Consumption by Idle ULPs.........................33
7.4.9 Network based eavesdropping...............................30 5.5.4 Exercise of non-optimal code paths........................34
7.5 Denial of Service (DOS).....................................30 5.5.5 Remote Invalidate an STag Shared on Multiple Streams......34
7.5.1 RNIC Resource Consumption.................................30 5.5.6 Remote Peer attacking an Unshared CQ......................34
7.5.2 Resource Consumption By Active ULPs.......................31 5.6 Elevation of Privilege......................................35
7.5.2.1 Multiple Streams Sharing Receive Buffers...............31 6 Security Services for RDMAP and DDP.........................36
7.5.2.2 Local ULP Attacking a Shared CQ........................33 6.1 Introduction to Security Options............................36
7.5.2.3 Local or Remote Peer Attacking a Shared CQ.............33 6.1.1 Introduction to IPsec.....................................36
7.5.2.4 Attacking the RDMA Read Request Queue..................36 6.1.2 Introduction to SSL Limitations on RDMAP..................38
7.5.3 Resource Consumption by Idle ULPs.........................37 6.1.3 ULPs Which Provide Security...............................38
7.5.4 Exercise of non-optimal code paths........................38 6.2 Requirements for IPsec Encapsulation of DDP.................39
7.5.5 Remote Invalidate an STag Shared on Multiple Streams......38 7 Security considerations.....................................40
7.5.6 Remote Peer attacking an Unshared CQ......................38 8 IANA Considerations.........................................41
7.6 Elevation of Privilege......................................39 9 References..................................................42
8 Security Services for RDMAP and DDP.........................40 9.1 Normative References........................................42
8.1 Introduction to Security Options............................40 9.2 Informative References......................................42
8.1.1 Introduction to IPsec.....................................40 10 Appendix A: ULP Issues for RDDP Client/Server Protocols.....43
8.1.2 Introduction to SSL Limitations on RDMAP..................42 11 Appendix B: Summary of RNIC and ULP Implementation
8.1.3 ULPs Which Provide Security...............................42 Requirements.....................................................47
8.2 Requirements for IPsec Encapsulation of DDP.................43 12 Appendix C: Partial Trust Taxonomy..........................49
9 Security considerations.....................................44 13 Author's Addresses..........................................51
10 References..................................................45 14 Acknowledgments.............................................52
10.1 Normative References......................................45 15 Full Copyright Statement....................................53
10.2 Informative References....................................45
11 Appendix A: ULP Issues for RDDP Client/Server Protocols.....46
12 Appendix B: Summary of RNIC and ULP Implementation
Requirements.....................................................50
13 Appendix C: Partial Trust Taxonomy..........................52
14 Author∆s Addresses..........................................54
15 Acknowledgments.............................................55
16 Full Copyright Statement....................................56
Table of Figures Table of Figures
Figure 1 - RDMA Security Model...................................11 Figure 1 - RDMA Security Model....................................7
2.1 Revision History
2.1.1 Changes from -05 to -06 version
* Appendix A: ULP Issues for RDDP Client/Server Protocols,
Section 7.5.2.2. Changed usage of MUST, MAY, etc to be
lower case if just repeating prior requirements, upper
case if a new requirement. Completed writeup on section
7.5.2.2 for client/server protocols.
* Added new attack - section 7.5.6 Remote Peer attacking an
Unshared CQ on page 38.
* Minor clarification in section 7.6 - clarified that the
threat is for local and remote peer (unauthorized loading
of firmware). Also removed redundant sentence at end of
section.
* Added new normative statements per the last IETF meeting
(7.2.4, 7.3.2)
* Provided better insight on what is at the ULP level
verses what is at the protocol level. Provided
definitions for "Local Peer", "Remote Peer", and added
new concept of "local ULP". Then swept the document for
Local Peer and either left it unchanged, changed it local
ULP, or add both. Remote Peer left unchanged because it's
difficult to separate the ULP from the protocol on the
remote end.
* Included detailed review changes from Tom Talpey and
Mallikarjun Chadalapaka. Includes:
* More formal definition of Remote Peer and Local Peer,
and subdividing Local Peer better between local ULP
and Local Peer. Recommend careful review of where
"local ULP" is used to make sure I got it right.
* Changed some instances where "ULP" was used talk
about shared resources to "Stream".
* Clarified the Attacker Capabilities a bit.
* Fixed misc minor issues, including capitalization
issues.
* Clarification on zero-length RDMA Read messages.
2.1.2 Changes from -04 to -05 version
* Small modifications to normative statements per phone
call review.
* 4.1 - Moved MUST statement from Privileged Resource
Manager to section 5. Also added additional normative
statements around resource sharing and assumptions of
who trusts whom.
* 7.2.4 - changed last paragraph SHOULD to should.
* 7.4.4 - changed last paragraph MUST to SHOULD.
* 7.5.2.2 - clarified it is the ULP at issue, and
removed reference to Protection Domain - key issue is
whether they share partial mutual trust.
* 7.5.2.4 - remove MUST statement at the end of the 3rd
paragraph - it was replaced with a more general MUST.
Also changed the cap on the number of outstanding
RDMA Read Requests at the sender to a SHOULD (from
MUST).
* 8.1 - first paragraph after enumerated list. Change
MAY to may. It is a ULP issue.
* Removed "application" from the document and replaced it
with "ULP". In some cases also changed "Local Peer" to
ULP to clarify what the text meant.
2.1.3 Changes from -03 to -04 version
* Removed "issues" section because all issues have been
resolved.
* Completed section "ULPs Which Provide Security" by
providing a cross reference to channel bindings.
* Substantial rewrite of Section 11 Appendix A: ULP Issues
for RDDP Client/Server Protocols. Retargeted it to focus
on server application requirements, rather than RNIC
requirements.
* Changed "IPSec" to "IPsec" everywhere to match the RFC.
* Added new ULP requirement in section 7.5.2.4 Attacking
the RDMA Read Request Queue.
* Reviesed Sectio 12 Appendix B: Summary of RNIC and ULP
Implementation Requirements slightly to add one ULP
requirement and one RNIC requirement which is stated in
the document but was missed in this summary.
2.1.4 Changes from -02 to -03 version
* ID changed from Informational to Standards Track. This
caused previous RECOMMENDATIONS to be categorized into
the categories of MUST, SHOULD, MAY, RECOMMENDED, and in
one case, "recommended".
* Completed Appendix B: Summary of Attacks to provide a
summary of implementation requirements for applications
using RDDP and for RNICs in Appendix B: Summary of
Attacks.
* Modified intro to better explain when concept of Partial
Mutual Trust is useful.
* Misc minor changes from Tom Talpey's extensive review,
including:
* Send Queue/Receive Queue formally defined/used.
* RI is gone, now use RNIC interface, RNIC, and Remote
Invalidate.
* Clarified attackers capabilities.
* In many cases replaced "session" with "Stream".
* Added definitions for equation variables in section
7.5.2.3.
* Changed section 8.2 to normative xref to IPS Security,
plus comment on the value of end-to-end IPsec.
* Added clarifying example on STag invalidation (e.g. One-
Shot STag discussion).
* Added clarifying text on why SSL is a bad idea.
* Normative statement on mitigation for Shared RQ.
2.1.5 Changes from the -01 to the -02 version
Minimal - some typos, deleted some text previously marked for
deletion.
2.1.6 Changes from the -00 to -01 version
* Added two pages to the architectural model to describe
the Asynchronous Event Queue, and the types of
interactions that can occur between the RNIC and the
modules above it.
* Addressed Mike Krauses comments submitted on 12/8/2003
* Moved "Trust Models" from the body of the document to an
appendix. Removed references to it throughout the
document (including use of "partial trust". Document now
assumes Remote Peer is untrusted. Thus the key issue is
whether local resources are shared, and what the resource
is.
* Misc cleanup throughout the document.
* The Summary of Attacks at the end of the document is now
an Appendix. It also now provides a summary. Cleared
change bars because became unreadable. Also shortened
section names for attacks to fit in table.
* Added a new concept of "Partial Mutual Trust" between a
collection of Streams to better characterize a set of
attacks in a client/server environment.
* Filled in Security Services for RDMA and DDP section
(almost all is new, except IPsec overview).
* Globally tried to change "connection" to "Stream". In
some cases it can be either a connection or Stream.
3 Introduction 1 Introduction
RDMA enables new levels of flexibility when communicating between RDMA enables new levels of flexibility when communicating between
two parties compared to current conventional networking practice two parties compared to current conventional networking practice
(e.g. a stream-based model or datagram model). This flexibility (e.g. a stream-based model or datagram model). This flexibility
brings new security issues that must be carefully understood when brings new security issues that must be carefully understood when
designing Upper Layer Protocols (ULPs) utilizing RDMA and when designing Upper Layer Protocols (ULPs) utilizing RDMA and when
implementing RDMA-aware NICs (RNICs). Note that for the purposes implementing RDMA-aware NICs (RNICs). Note that for the purposes
of this security analysis, an RNIC may implement RDMAP and DDP, of this security analysis, an RNIC may implement RDMAP and DDP,
or just DDP. Also, a ULP may be an application or it may be a or just DDP. Also, a ULP may be an application or it may be a
middleware library. middleware library.
The document first develops an architectural model that is The document first develops an architectural model that is
relevant for the security analysis - it details components, relevant for the security analysis - it details components,
resources, and system properties that may be attacked in Section resources, and system properties that may be attacked in Section
4. The document uses Local Peer to represent the RDMA/DDP 2. The document uses Local Peer to represent the RDMA/DDP
protocol implementation on the local end of a Stream. The local protocol implementation on the local end of a Stream. The local
Upper-Layer-Protocol (ULP) is used to represent the application Upper-Layer-Protocol (ULP) is used to represent the application
or middle-ware layer above the Local Peer. The document does not or middle-ware layer above the Local Peer. The document does not
attempt to differentiate between a Remote Peer and a Remote ULP attempt to differentiate between a Remote Peer and a Remote ULP
(an RDMA/DDP protocol implementation on the remote end of a (an RDMA/DDP protocol implementation on the remote end of a
Stream versus the application on the remote end) for several Stream versus the application on the remote end) for several
reasons: often the source of the attack is difficult to know for reasons: often the source of the attack is difficult to know for
sure; and regardless of the source, the mitigations required of sure; and regardless of the source, the mitigations required of
the Local Peer or local ULP are the same. Thus the document the Local Peer or local ULP are the same. Thus the document
generically refers to a Remote Peer rather than trying to further generically refers to a Remote Peer rather than trying to further
delineate the attacker. delineate the attacker.
The document then defines what resources a local ULP may share The document then defines what resources a local ULP may share
across Streams and what resources the local ULP may share with across Streams and what resources the local ULP may share with
the Remote Peer across Streams in Section 5. the Remote Peer across Streams in Section 3.
Intentional sharing of resources between multiple Streams may Intentional sharing of resources between multiple Streams may
imply some level of trust between the Streams. However, some imply some level of trust between the Streams. However, some
types of resource sharing have unmitigated security attacks which types of resource sharing have unmitigated security attacks which
would mandate not sharing a specific type of resource unless would mandate not sharing a specific type of resource unless
there is some level of trust between the Streams sharing there is some level of trust between the Streams sharing
resources. resources.
This document defines a new term, "Partial Mutual Trust" to This document defines a new term, "Partial Mutual Trust" to
address this concept: address this concept:
Partial Mutual Trust - a collection of RDMAP/DDP Streams, Partial Mutual Trust - a collection of RDMAP/DDP Streams,
which represent the local and remote end points of the which represent the local and remote end points of the
Stream, which are willing to assume that the Streams from Stream, which are willing to assume that the Streams from
the collection will not perform malicious attacks against the collection will not perform malicious attacks against
any of the other Streams in the collection. any of the other Streams in the collection.
ULPs have explicit control of which collection of endpoints is in ULPs have explicit control of which collection of endpoints is in
a Partial Mutual Trust collection through tools discussed in a Partial Mutual Trust collection through tools discussed in
Section 7.1 Tools for Countermeasures on page 20. Section 5.1 Tools for Countermeasures on page 16.
An untrusted peer relationship is appropriate when a ULP wishes An untrusted peer relationship is appropriate when a ULP wishes
to ensure that it will be robust and uncompromised even in the to ensure that it will be robust and uncompromised even in the
face of a deliberate attack by its peer. For example, a single face of a deliberate attack by its peer. For example, a single
ULP that concurrently supports multiple unrelated Streams (e.g. a ULP that concurrently supports multiple unrelated Streams (e.g. a
server) would presumably treat each of its peers as an untrusted server) would presumably treat each of its peers as an untrusted
peer. For a collection of Streams which share Partial Mutual peer. For a collection of Streams which share Partial Mutual
Trust, the assumption is that any Stream not in the collection is Trust, the assumption is that any Stream not in the collection is
untrusted. For the untrusted peer, a brief list of capabilities untrusted. For the untrusted peer, a brief list of capabilities
is enumerated in Section 6. is enumerated in Section 4.
The rest of the document is focused on analyzing attacks and The rest of the document is focused on analyzing attacks and
recommending specific mitigations to the attacks. First, the recommending specific mitigations to the attacks. First, the
tools for mitigating attacks are listed (Section 7.1), and then a tools for mitigating attacks are listed (Section 5.1), and then a
series of attacks on components, resources, or system properties series of attacks on components, resources, or system properties
is listed in the rest of Section 7. For each attack, possible is listed in the rest of Section 5. For each attack, possible
countermeasures are reviewed. countermeasures are reviewed.
ULPs within a host are divided into two categories - Privileged ULPs within a host are divided into two categories - Privileged
and Non-Privileged. Both ULP types can send and receive data and and Non-Privileged. Both ULP types can send and receive data and
request resources. The key differences between the two are: request resources. The key differences between the two are:
The Privileged ULP is trusted by the local system to not The Privileged ULP is trusted by the local system to not
maliciously attack the operating environment, but it is not maliciously attack the operating environment, but it is not
trusted to optimize resource allocation globally. For trusted to optimize resource allocation globally. For
example, the Privileged ULP could be a kernel ULP, thus the example, the Privileged ULP could be a kernel ULP, thus the
skipping to change at page 10, line 5 skipping to change at page 6, line 5
the Privileged ULP's. It is assumed by the local system that the Privileged ULP's. It is assumed by the local system that
a Non-Privileged ULP is untrusted. All Non-Privileged ULP a Non-Privileged ULP is untrusted. All Non-Privileged ULP
interactions with the RNIC Engine that could affect other interactions with the RNIC Engine that could affect other
ULPs need to be done through a trusted intermediary that can ULPs need to be done through a trusted intermediary that can
verify the Non-Privileged ULP requests. verify the Non-Privileged ULP requests.
If all recommended mitigations are in place the implemented usage If all recommended mitigations are in place the implemented usage
models, the RDMAP/DDP protocol can be shown to not expose any new models, the RDMAP/DDP protocol can be shown to not expose any new
security vulnerabilities. security vulnerabilities.
4 Architectural Model 2 Architectural Model
This section describes an RDMA architectural reference model that This section describes an RDMA architectural reference model that
is used as security issues are examined. It introduces the is used as security issues are examined. It introduces the
components of the model, the resources that can be attacked, the components of the model, the resources that can be attacked, the
types of interactions possible between components and resources, types of interactions possible between components and resources,
and the system properties which must be preserved. and the system properties which must be preserved.
Figure 1 shows the components comprising the architecture and the Figure 1 shows the components comprising the architecture and the
interfaces where potential security attacks could be launched. interfaces where potential security attacks could be launched.
External attacks can be injected into the system from a ULP that External attacks can be injected into the system from a ULP that
skipping to change at page 11, line 6 skipping to change at page 7, line 6
| | | |
| RNIC Engine | <-- Firmware | RNIC Engine | <-- Firmware
| | | |
+--------------------------------------+ +--------------------------------------+
^ ^
| |
v v
Internet Internet
Figure 1 - RDMA Security Model Figure 1 - RDMA Security Model
4.1 Components 2.1 Components
The components shown in Figure 1 - RDMA Security Model are: The components shown in Figure 1 - RDMA Security Model are:
* RDMA Network Interface Controller Engine (RNIC) - the * RDMA Network Interface Controller Engine (RNIC) - the
component that implements the RDMA protocol and/or DDP component that implements the RDMA protocol and/or DDP
protocol. protocol.
* Privileged Resource Manager - the component responsible * Privileged Resource Manager - the component responsible
for managing and allocating resources associated with the for managing and allocating resources associated with the
RNIC Engine. The Resource Manager does not send or RNIC Engine. The Resource Manager does not send or
receive data. Note that whether the Resource Manager is receive data. Note that whether the Resource Manager is
an independent component, part of the RNIC, or part of an independent component, part of the RNIC, or part of
the ULP is implementation dependent. If a specific the ULP is implementation dependent.
implementation does not wish to address security issues
resolved by the Resource Manager, there may in fact be no
resource manager at all.
* Privileged ULP - See Section 3 Introduction for a * Privileged ULP - See Section 1 Introduction for a
definition of Privileged ULP. The local host definition of Privileged ULP. The local host
infrastructure can enable the Privileged ULP to map a infrastructure can enable the Privileged ULP to map a
data buffer directly from the RNIC Engine to the host data buffer directly from the RNIC Engine to the host
through the RNIC Interface, but it does not allow the through the RNIC Interface, but it does not allow the
Privileged ULP to directly consume RNIC Engine resources. Privileged ULP to directly consume RNIC Engine resources.
* Non-Privileged ULP - See Section 3 Introduction for a * Non-Privileged ULP - See Section 1 Introduction for a
definition of Non-Privileged ULP. definition of Non-Privileged ULP.
A design goal of the DDP and RDMAP protocols is to allow, under A design goal of the DDP and RDMAP protocols is to allow, under
constrained conditions, Non-Privileged ULP to send and receive constrained conditions, Non-Privileged ULP to send and receive
data directly to/from the RDMA Engine without Privileged Resource data directly to/from the RDMA Engine without Privileged Resource
Manager intervention - while ensuring that the host remains Manager intervention - while ensuring that the host remains
secure. Thus, one of the primary goals of this document is to secure. Thus, one of the primary goals of this document is to
analyze this usage model for the enforcement that is required in analyze this usage model for the enforcement that is required in
the RNIC Engine to ensure the system remains secure. the RNIC Engine to ensure the system remains secure.
skipping to change at page 12, line 27 skipping to change at page 8, line 25
* Figure 1 also shows the ability to load new firmware in * Figure 1 also shows the ability to load new firmware in
the RNIC Engine. Not all RNICs will support this, but it the RNIC Engine. Not all RNICs will support this, but it
is shown for completeness and is also reviewed under is shown for completeness and is also reviewed under
potential attacks. potential attacks.
If Internet control messages, such as ICMP, ARP, RIPv4, etc. are If Internet control messages, such as ICMP, ARP, RIPv4, etc. are
processed by the RNIC Engine, the threat analyses for those processed by the RNIC Engine, the threat analyses for those
protocols is also applicable, but outside the scope of this protocols is also applicable, but outside the scope of this
document. document.
4.2 Resources 2.2 Resources
This section describes the primary resources in the RNIC Engine This section describes the primary resources in the RNIC Engine
that could be affected if under attack. For RDMAP, all of the that could be affected if under attack. For RDMAP, all of the
defined resources apply. For DDP, all of the resources except the defined resources apply. For DDP, all of the resources except the
RDMA Read Queue apply. RDMA Read Queue apply.
4.2.1 Stream Context Memory 2.2.1 Stream Context Memory
The state information for each Stream is maintained in memory, The state information for each Stream is maintained in memory,
which could be located in a number of places - on the NIC, inside which could be located in a number of places - on the NIC, inside
RAM attached to the NIC, in host memory, or in any combination of RAM attached to the NIC, in host memory, or in any combination of
the three, depending on the implementation. the three, depending on the implementation.
Stream Context Memory includes state associated with Data Stream Context Memory includes state associated with Data
Buffers. For Tagged Buffers, this includes how STag names, Data Buffers. For Tagged Buffers, this includes how STag names, Data
Buffers, and Page Translation Tables (see section 4.2.3 on page Buffers, and Page Translation Tables (see section 2.2.3 on page
13) interrelate. It also includes the list of Untagged Data 9) interrelate. It also includes the list of Untagged Data
Buffers posted for reception of Untagged Messages (commonly Buffers posted for reception of Untagged Messages (commonly
called the Receive Queue), and a list of operations to perform to called the Receive Queue), and a list of operations to perform to
send data (commonly called the Send Queue). send data (commonly called the Send Queue).
4.2.2 Data Buffers 2.2.2 Data Buffers
There are two different ways to expose a local ULP's data buffer; There are two different ways to expose a local ULP's data buffer;
a buffer can be exposed for receiving RDMAP Send Type Messages a buffer can be exposed for receiving RDMAP Send Type Messages
(a.k.a. DDP Untagged Messages) on DDP Queue zero or the buffer (a.k.a. DDP Untagged Messages) on DDP Queue zero or the buffer
can be exposed for remote access through STags (a.k.a. DDP Tagged can be exposed for remote access through STags (a.k.a. DDP Tagged
Messages). This distinction is important because the attacks and Messages). This distinction is important because the attacks and
the countermeasures used to protect against the attack are the countermeasures used to protect against the attack are
different depending on the method for exposing the buffer to the different depending on the method for exposing the buffer to the
network. network.
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Actual implementations may support scatter/gather capabilities to Actual implementations may support scatter/gather capabilities to
enable multiple physical data buffers to be accessed with a enable multiple physical data buffers to be accessed with a
single STag, but from a threat analysis perspective it is assumed single STag, but from a threat analysis perspective it is assumed
that a single STag enables access to a single logical Data that a single STag enables access to a single logical Data
Buffer. Buffer.
In any event, it is the responsibility of the Privileged Resource In any event, it is the responsibility of the Privileged Resource
Manager to ensure that no STag can be created that exposes memory Manager to ensure that no STag can be created that exposes memory
that the consumer had no authority to expose. that the consumer had no authority to expose.
4.2.3 Page Translation Tables 2.2.3 Page Translation Tables
Page Translation Tables are the structures used by the RNIC to be Page Translation Tables are the structures used by the RNIC to be
able to access ULP memory for data transfer operations. Even able to access ULP memory for data transfer operations. Even
though these structures are called "Page" Translation Tables, though these structures are called "Page" Translation Tables,
they may not reference a page at all - conceptually they are used they may not reference a page at all - conceptually they are used
to map a ULP address space representation (e.g. a virtual to map a ULP address space representation (e.g. a virtual
address) of a buffer to the physical addresses that are used by address) of a buffer to the physical addresses that are used by
the RNIC Engine to move data. If on a specific system a mapping the RNIC Engine to move data. If on a specific system a mapping
is not used, then a subset of the attacks examined may be is not used, then a subset of the attacks examined may be
appropriate. Note that the Page Translation Table may or may not appropriate. Note that the Page Translation Table may or may not
be a shared resource. be a shared resource.
4.2.4 STag Namespace 2.2.4 STag Namespace
The DDP specification defines a 32-bit namespace for the STag. The DDP specification defines a 32-bit namespace for the STag.
Implementations may vary in terms of the actual number of STags Implementations may vary in terms of the actual number of STags
that are supported. In any case, this is a bounded resource that that are supported. In any case, this is a bounded resource that
can come under attack. Depending upon STag namespace allocation can come under attack. Depending upon STag namespace allocation
algorithms, the actual name space to attack may be significantly algorithms, the actual name space to attack may be significantly
less than 2^32. less than 2^32.
4.2.5 Completion Queues 2.2.5 Completion Queues
Completion Queues are used in this document to conceptually Completion Queues are used in this document to conceptually
represent how the RNIC Engine notifies the ULP about the represent how the RNIC Engine notifies the ULP about the
completion of the transmission of data, or the completion of the completion of the transmission of data, or the completion of the
reception of data through the Data Transfer Interface. Because reception of data through the Data Transfer Interface. Because
there could be many transmissions or receptions in flight at any there could be many transmissions or receptions in flight at any
one time, completions are modeled as a queue rather than a single one time, completions are modeled as a queue rather than a single
event. An implementation may also use the Completion Queue to event. An implementation may also use the Completion Queue to
notify the ULP of other activities, for example, the completion notify the ULP of other activities, for example, the completion
of a mapping of an STag to a specific ULP buffer. Completion of a mapping of an STag to a specific ULP buffer. Completion
Queues may be shared by a group of Streams, or may be designated Queues may be shared by a group of Streams, or may be designated
to handle a specific Stream's traffic. to handle a specific Stream's traffic.
Some implementations may allow this queue to be manipulated Some implementations may allow this queue to be manipulated
directly by both Non-Privileged and Privileged ULPs. directly by both Non-Privileged and Privileged ULPs.
4.2.6 Asynchronous Event Queue 2.2.6 Asynchronous Event Queue
The Asynchronous Event Queue is a queue from the RNIC to the The Asynchronous Event Queue is a queue from the RNIC to the
Privileged Resource Manager of bounded size. It is used by the Privileged Resource Manager of bounded size. It is used by the
RNIC to notify the host of various events which might require RNIC to notify the host of various events which might require
management action, including protocol violations, Stream state management action, including protocol violations, Stream state
changes, local operation errors, low water marks on receive changes, local operation errors, low water marks on receive
queues, and possibly other events. queues, and possibly other events.
The Asynchronous Event Queue is a resource that can be attacked The Asynchronous Event Queue is a resource that can be attacked
because Remote or Local Peers and/or ULPs can cause events to because Remote or Local Peers and/or ULPs can cause events to
occur which have the potential of overflowing the queue. occur which have the potential of overflowing the queue.
Note that an implementation is at liberty to implement the Note that an implementation is at liberty to implement the
functions of the Asynchronous Event Queue in a variety of ways, functions of the Asynchronous Event Queue in a variety of ways,
including multiple queues or even simple callbacks. All including multiple queues or even simple callbacks. All
vulnerabilities identified are intended to apply regardless of vulnerabilities identified are intended to apply regardless of
the implementation of the Asynchronous Event Queue. For example, the implementation of the Asynchronous Event Queue. For example,
a callback function may be viewed as simply a very short queue. a callback function may be viewed as simply a very short queue.
4.2.7 RDMA Read Request Queue 2.2.7 RDMA Read Request Queue
The RDMA Read Request Queue is the memory that holds state The RDMA Read Request Queue is the memory that holds state
information for one or more RDMA Read Request Messages that have information for one or more RDMA Read Request Messages that have
arrived, but for which the RDMA Read Response Messages have not arrived, but for which the RDMA Read Response Messages have not
yet been completely sent. Because potentially more than one RDMA yet been completely sent. Because potentially more than one RDMA
Read Request can be outstanding at one time, the memory is Read Request can be outstanding at one time, the memory is
modeled as a queue of bounded size. Some implementations may modeled as a queue of bounded size. Some implementations may
enable sharing of a single RDMA Read Request Queue across enable sharing of a single RDMA Read Request Queue across
multiple Streams. multiple Streams.
4.2.8 RNIC Interactions 2.2.8 RNIC Interactions
With RNIC resources and interfaces defined, it is now possible to With RNIC resources and interfaces defined, it is now possible to
examine the interactions supported by the generic RNIC functional examine the interactions supported by the generic RNIC functional
interfaces through each of the 3 interfaces - Privileged Control interfaces through each of the 3 interfaces - Privileged Control
Interface, Privileged Data Interface, and Non-Privileged Data Interface, Privileged Data Interface, and Non-Privileged Data
Interface. Interface.
4.2.8.1 Privileged Control Interface Semantics 2.2.8.1 Privileged Control Interface Semantics
Generically, the Privileged Control Interface controls the RNICs Generically, the Privileged Control Interface controls the RNIC's
allocation, deallocation, and initialization of RNIC global allocation, deallocation, and initialization of RNIC global
resources. This includes allocation and deallocation of Stream resources. This includes allocation and deallocation of Stream
Context Memory, Page Translation Tables, STag names, Completion Context Memory, Page Translation Tables, STag names, Completion
Queues, RDMA Read Request Queues, and Asynchronous Event Queues. Queues, RDMA Read Request Queues, and Asynchronous Event Queues.
The Privileged Control Interface is also typically used for The Privileged Control Interface is also typically used for
managing Non-Privileged ULP resources for the Non-Privileged ULP managing Non-Privileged ULP resources for the Non-Privileged ULP
(and possibly for the Privileged ULP as well). This includes (and possibly for the Privileged ULP as well). This includes
initialization and removal of Page Translation Table resources, initialization and removal of Page Translation Table resources,
and managing RNIC events (possibly managing all events for the and managing RNIC events (possibly managing all events for the
Asynchronous Event Queue). Asynchronous Event Queue).
4.2.8.2 Non-Privileged Data Interface Semantics 2.2.8.2 Non-Privileged Data Interface Semantics
The Non-Privileged Data Interface enables data transfer (transmit The Non-Privileged Data Interface enables data transfer (transmit
and receive) but does not allow initialization of the Page and receive) but does not allow initialization of the Page
Translation Table resources. However, once the Page Translation Translation Table resources. However, once the Page Translation
Table resources have been initialized, the interface may enable a Table resources have been initialized, the interface may enable a
specific STag mapping to be enabled and disabled by directly specific STag mapping to be enabled and disabled by directly
communicating with the RNIC, or create an STag mapping for a communicating with the RNIC, or create an STag mapping for a
buffer that has been previously initialized in the RNIC. buffer that has been previously initialized in the RNIC.
For RDMAP, ULP data can be sent by using RDMAP Send Type For RDMAP, ULP data can be sent by using RDMAP Send Type
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Messages. For data reception, for DDP it can receive Untagged Messages. For data reception, for DDP it can receive Untagged
Messages into buffers that have been posted on the Receive Queue Messages into buffers that have been posted on the Receive Queue
or Shared Receive Queue. It can also receive Tagged DDP Messages or Shared Receive Queue. It can also receive Tagged DDP Messages
into buffers that have previously been exposed for external write into buffers that have previously been exposed for external write
access through advertisement of an STag. access through advertisement of an STag.
Completion of data transmission or reception generally entails Completion of data transmission or reception generally entails
informing the ULP of the completed work by placing completion informing the ULP of the completed work by placing completion
information on the Completion Queue. information on the Completion Queue.
4.2.8.3 Privileged Data Interface Semantics 2.2.8.3 Privileged Data Interface Semantics
The Privileged Data Interface semantics are a superset of the The Privileged Data Interface semantics are a superset of the
Non-Privileged Data Transfer semantics. The interface can do Non-Privileged Data Transfer semantics. The interface can do
everything defined in the prior section, as well as everything defined in the prior section, as well as
create/destroy buffer to STag mappings directly. This generally create/destroy buffer to STag mappings directly. This generally
entails initialization or clearing of Page Translation Table entails initialization or clearing of Page Translation Table
state in the RNIC. state in the RNIC.
4.2.9 Initialization of RNIC Data Structures for Data Transfer 2.2.9 Initialization of RNIC Data Structures for Data Transfer
Initialization of the mapping between an STag and a Data Buffer Initialization of the mapping between an STag and a Data Buffer
can be viewed in the abstract as two separate operations: can be viewed in the abstract as two separate operations:
a. Initialization of the allocated Page Translation Table a. Initialization of the allocated Page Translation Table
entries with the location of the Data Buffer, and entries with the location of the Data Buffer, and
b. Initialization of a mapping from an allocated STag name b. Initialization of a mapping from an allocated STag name
to a set of Page Translation Table entry(s) or partial- to a set of Page Translation Table entry(s) or partial-
entries. entries.
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outside the scope of this document. outside the scope of this document.
For a Tagged Data Buffer, either the Privileged ULP, the Non- For a Tagged Data Buffer, either the Privileged ULP, the Non-
Privileged ULP, or the Privileged Resource Manager acting on Privileged ULP, or the Privileged Resource Manager acting on
behalf of the Non-Privileged ULP may initialize a mapping from an behalf of the Non-Privileged ULP may initialize a mapping from an
STag to a Page Translation Table, or may have the ability to STag to a Page Translation Table, or may have the ability to
simply enable/disable an existing STag to Page Translation Table simply enable/disable an existing STag to Page Translation Table
mapping. There may also be multiple STag names which map to a mapping. There may also be multiple STag names which map to a
specific group of Page Translation Table entries (or sub- specific group of Page Translation Table entries (or sub-
entries). Specific security issues with this level of flexibility entries). Specific security issues with this level of flexibility
are examined in Section 7.3.3 Multiple STags to access the same are examined in Section 5.3.3 Multiple STags to access the same
buffer on page 27. buffer on page 23.
There are a variety of implementation options for initialization There are a variety of implementation options for initialization
of Page Translation Table entries and mapping an STag to a group of Page Translation Table entries and mapping an STag to a group
of Page Translation Table entries which have security of Page Translation Table entries which have security
repercussions. This includes support for separation of Mapping an repercussions. This includes support for separation of Mapping an
STag versus mapping a set of Page Translation Table entries, and STag versus mapping a set of Page Translation Table entries, and
support for ULPs directly manipulating STag to Page Translation support for ULPs directly manipulating STag to Page Translation
Table entry mappings (versus requiring access through the Table entry mappings (versus requiring access through the
Privileged Resource Manager). Privileged Resource Manager).
4.2.10 RNIC Data Transfer Interactions 2.2.10 RNIC Data Transfer Interactions
RNIC Data Transfer operations can be subdivided into send RNIC Data Transfer operations can be subdivided into send
operations and receive operations. operations and receive operations.
For send operations, there is typically a queue that enables the For send operations, there is typically a queue that enables the
ULP to post multiple operation requests to send data (referred to ULP to post multiple operation requests to send data (referred to
as the Send Queue). Depending upon the implementation, Data as the Send Queue). Depending upon the implementation, Data
Buffers used in the operations may or may not have Page Buffers used in the operations may or may not have Page
Translation Table entries associated with them, and may or may Translation Table entries associated with them, and may or may
not have STags associated with them. Because this is a local host not have STags associated with them. Because this is a local host
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also support sharing of the sequential queue between multiple also support sharing of the sequential queue between multiple
Streams. In this case defining "sequential" becomes non-trivial - Streams. In this case defining "sequential" becomes non-trivial -
in general the buffers for a single Stream are consumed from the in general the buffers for a single Stream are consumed from the
queue in the order that they were placed on the queue, but there queue in the order that they were placed on the queue, but there
is no consumption order guarantee between Streams. is no consumption order guarantee between Streams.
For receive Tagged Data Buffers, at some time prior to data For receive Tagged Data Buffers, at some time prior to data
transfer, the mapping of the STag to specific Page Translation transfer, the mapping of the STag to specific Page Translation
Table entries (if present) and the mapping from the Page Table entries (if present) and the mapping from the Page
Translation Table entries to the Data Buffer must have been Translation Table entries to the Data Buffer must have been
initialized (see section 4.2.9 for interaction details). initialized (see section 2.2.9 for interaction details).
5 Trust and Resource Sharing 3 Trust and Resource Sharing
It is assumed that in general the Local and Remote Peer are It is assumed that in general the Local and Remote Peer are
untrusted, and thus attacks by either should have mitigations in untrusted, and thus attacks by either should have mitigations in
place. place.
A separate, but related issue is resource sharing between A separate, but related issue is resource sharing between
multiple Streams. If local resources are not shared, the multiple Streams. If local resources are not shared, the
resources are dedicated on a per Stream basis. Resources are resources are dedicated on a per Stream basis. Resources are
defined in Section 4.2 Resources on page 12. The advantage of not defined in Section 2.2 Resources on page 8. The advantage of not
sharing resources between Streams is that it reduces the types of sharing resources between Streams is that it reduces the types of
attacks that are possible. The disadvantage of not sharing attacks that are possible. The disadvantage of not sharing
resources is that ULPs might run out of resources. Thus there can resources is that ULPs might run out of resources. Thus there can
be a strong incentive for sharing resources, if the security be a strong incentive for sharing resources, if the security
issues associated with the sharing of resources can be mitigated. issues associated with the sharing of resources can be mitigated.
It is assumed in this document that the component that implements It is assumed in this document that the component that implements
the mechanism to control sharing of the RNIC Engine resources is the mechanism to control sharing of the RNIC Engine resources is
the Privileged Resource Manager. The RNIC Engine exposes its the Privileged Resource Manager. The RNIC Engine exposes its
resources through the RNIC Interface to the Privileged Resource resources through the RNIC Interface to the Privileged Resource
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could affect other ULPs MUST be done using the Privileged could affect other ULPs MUST be done using the Privileged
Resource Manager as a proxy. All ULP resource allocation requests Resource Manager as a proxy. All ULP resource allocation requests
for scarce resources MUST also be done using a Privileged for scarce resources MUST also be done using a Privileged
Resource Manager. Resource Manager.
The sharing of resources across Streams should be under the The sharing of resources across Streams should be under the
control of the ULP, both in terms of the trust model the ULP control of the ULP, both in terms of the trust model the ULP
wishes to operate under, as well as the level of resource sharing wishes to operate under, as well as the level of resource sharing
the ULP wishes to give local processes. For more discussion on the ULP wishes to give local processes. For more discussion on
types of trust models which combine partial trust and sharing of types of trust models which combine partial trust and sharing of
resources, see Appendix C: Partial Trust Taxonomy on page 52. resources, see Appendix C: Partial Trust Taxonomy on page 49.
The Privileged Resource Manager MUST NOT assume different Streams The Privileged Resource Manager MUST NOT assume different Streams
share Partial Mutual Trust unless there is a mechanism to ensure share Partial Mutual Trust unless there is a mechanism to ensure
that the Streams do indeed share Partial Mutual Trust. This can that the Streams do indeed share Partial Mutual Trust. This can
be done in several ways, including explicit notification from the be done in several ways, including explicit notification from the
ULP that owns the Streams. ULP that owns the Streams.
6 Attacker Capabilities 4 Attacker Capabilities
An attackers capabilities delimit the types of attacks that An attacker's capabilities delimit the types of attacks that
attacker is able to launch. RDMAP and DDP require that the attacker is able to launch. RDMAP and DDP require that the
initial LLP Stream (and connection) be set up prior to initial LLP Stream (and connection) be set up prior to
transferring RDMAP/DDP Messages. This requires at least one transferring RDMAP/DDP Messages. This requires at least one
round-trip handshake to occur. round-trip handshake to occur.
If the attacker is not the Remote Peer that created the initial If the attacker is not the Remote Peer that created the initial
connection, then the attacker's capabilities can be segmented connection, then the attacker's capabilities can be segmented
into send only capabilities or send and receive capabilities. into send only capabilities or send and receive capabilities.
Attacking with send only capabilities requires the attacker to Attacking with send only capabilities requires the attacker to
first guess the current LLP Stream parameters before they can first guess the current LLP Stream parameters before they can
attack RNIC resources (e.g. TCP sequence number). If this class attack RNIC resources (e.g. TCP sequence number). If this class
of attacker also has receive capabilities, they are typically of attacker also has receive capabilities, they are typically
referred to as a "man-in-the-middle" attacker, and they have a referred to as a "man-in-the-middle" attacker, and they have a
much wider ability to attack RNIC resources. The breadth of much wider ability to attack RNIC resources. The breadth of
attack is essentially the same as that of an attacking Remote attack is essentially the same as that of an attacking Remote
Peer (i.e. the Remote Peer that setup the initial LLP Stream). Peer (i.e. the Remote Peer that setup the initial LLP Stream).
7 Attacks and Countermeasures 5 Attacks and Countermeasures
This section describes the attacks that are possible against the This section describes the attacks that are possible against the
RDMA system defined in Figure 1 - RDMA Security Model and the RDMA system defined in Figure 1 - RDMA Security Model and the
RNIC Engine resources defined in Section 4.2. The analysis RNIC Engine resources defined in Section 2.2. The analysis
includes a detailed description of each attack, what is being includes a detailed description of each attack, what is being
attacked, and a description of the countermeasures that can be attacked, and a description of the countermeasures that can be
taken to thwart the attack. taken to thwart the attack.
Note that connection setup and teardown is presumed to be done in Note that connection setup and teardown is presumed to be done in
stream mode (i.e. no RDMA encapsulation of the payload), so there stream mode (i.e. no RDMA encapsulation of the payload), so there
are no new attacks related to connection setup/teardown beyond are no new attacks related to connection setup/teardown beyond
what is already present in the LLP (e.g. TCP or SCTP). Note, what is already present in the LLP (e.g. TCP or SCTP). Note,
however, that RDMAP/DDP parameters may be exchanged in stream however, that RDMAP/DDP parameters may be exchanged in stream
mode, and if they are corrupted by an attacker unintended mode, and if they are corrupted by an attacker unintended
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the LLP Stream type. the LLP Stream type.
The attacks are classified into five categories: Spoofing, The attacks are classified into five categories: Spoofing,
Tampering, Information Disclosure, Denial of Service (DoS) Tampering, Information Disclosure, Denial of Service (DoS)
attacks, and Elevation of Privileges. Tampering is any attacks, and Elevation of Privileges. Tampering is any
modification of the legitimate traffic (machine internal or modification of the legitimate traffic (machine internal or
network). Spoofing attack is a special case of tampering where network). Spoofing attack is a special case of tampering where
the attacker falsifies an identity of the Remote Peer (identity the attacker falsifies an identity of the Remote Peer (identity
can be an IP address, machine name, ULP level identity etc.). can be an IP address, machine name, ULP level identity etc.).
7.1 Tools for Countermeasures 5.1 Tools for Countermeasures
The tools described in this section are the primary mechanisms The tools described in this section are the primary mechanisms
that can be used to provide countermeasures to potential attacks. that can be used to provide countermeasures to potential attacks.
7.1.1 Protection Domain (PD) 5.1.1 Protection Domain (PD)
A Protection Domain (PD) is a local construct to the RDMA A Protection Domain (PD) is a local construct to the RDMA
implementation, and never visible over the wire. Protection implementation, and never visible over the wire. Protection
Domains are assigned to two of the resources of concern, Stream Domains are assigned to two of the resources of concern, Stream
Context Memory and STags associated with Page Translation Table Context Memory and STags associated with Page Translation Table
entries and data buffers. A correct implementation of a entries and data buffers. A correct implementation of a
Protection Domain requires that resources which belong to a given Protection Domain requires that resources which belong to a given
Protection Domain can not be used on a resource belonging to Protection Domain can not be used on a resource belonging to
another Protection Domain, because Protection Domain membership another Protection Domain, because Protection Domain membership
is checked by the RNIC prior to taking any action involving such is checked by the RNIC prior to taking any action involving such
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Mutual Trust with each other. Mutual Trust with each other.
Note that a ULP (either Privileged or Non-Privileged) can Note that a ULP (either Privileged or Non-Privileged) can
potentially have multiple Protection Domains. This could be used, potentially have multiple Protection Domains. This could be used,
for example, to ensure that multiple clients of a server do not for example, to ensure that multiple clients of a server do not
have the ability to corrupt each other. The server would allocate have the ability to corrupt each other. The server would allocate
a Protection Domain per client to ensure that resources covered a Protection Domain per client to ensure that resources covered
by the Protection Domain could not be used by another (untrusted) by the Protection Domain could not be used by another (untrusted)
client. client.
7.1.2 Limiting STag Scope 5.1.2 Limiting STag Scope
The key to protecting a local data buffer is to limit the scope The key to protecting a local data buffer is to limit the scope
of its STag to the level appropriate for the Streams which share of its STag to the level appropriate for the Streams which share
Partial Mutual Trust. The scope of the STag can be measured in Partial Mutual Trust. The scope of the STag can be measured in
multiple ways. multiple ways.
* Number of Connections and/or Streams on which the STag is * Number of Connections and/or Streams on which the STag is
valid. One way to limit the scope of the STag is to limit valid. One way to limit the scope of the STag is to limit
the connections and/or Streams that are allowed to use the connections and/or Streams that are allowed to use
the STag. As noted in the previous section, use of the STag. As noted in the previous section, use of
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to guess which STag(s) are currently in use, it makes it to guess which STag(s) are currently in use, it makes it
more difficult for an attacker to guess the correct more difficult for an attacker to guess the correct
value. As stated in the RDMAP specification [RDMAP], an value. As stated in the RDMAP specification [RDMAP], an
invalid STag will cause the RDMAP Stream to be invalid STag will cause the RDMAP Stream to be
terminated. For the case of [DDP], at a minimum it must terminated. For the case of [DDP], at a minimum it must
signal an error to the ULP. This permits the ULP to signal an error to the ULP. This permits the ULP to
detect such attempts, and take countermeasures. Commonly, detect such attempts, and take countermeasures. Commonly,
the ULP will cause the DDP Stream to be immediately the ULP will cause the DDP Stream to be immediately
terminated. terminated.
7.1.3 Access Rights 5.1.3 Access Rights
Access Rights associated with a specific advertised STag or Access Rights associated with a specific advertised STag or
RDMAP/DDP Stream provide another mechanism for ULPs to limit the RDMAP/DDP Stream provide another mechanism for ULPs to limit the
attack capabilities of the Remote Peer. The local ULP can control attack capabilities of the Remote Peer. The local ULP can control
whether a data buffer is exposed for local only, or local and whether a data buffer is exposed for local only, or local and
remote access, and assign specific access privileges (read, remote access, and assign specific access privileges (read,
write, read and write) on a per Stream basis. write, read and write) on a per Stream basis.
For DDP, when an STag is advertised, the Remote Peer is For DDP, when an STag is advertised, the Remote Peer is
presumably given write access rights to the data (otherwise there presumably given write access rights to the data (otherwise there
was not much point to the advertisement). For RDMAP, when a ULP was not much point to the advertisement). For RDMAP, when a ULP
advertises an STag, it can enable write-only, read-only, or both advertises an STag, it can enable write-only, read-only, or both
write and read access rights. write and read access rights.
Similarly, some ULPs may wish to provide a single buffer with Similarly, some ULPs may wish to provide a single buffer with
different access rights on a per-Stream basis. For example, some different access rights on a per-Stream basis. For example, some
Streams may have read-only access, some may have remote read and Streams may have read-only access, some may have remote read and
write access, while on other Streams only the local ULP/Local write access, while on other Streams only the local ULP/Local
Peer is allowed access. Peer is allowed access.
7.1.4 Limiting the Scope of the Completion Queue 5.1.4 Limiting the Scope of the Completion Queue
Completions associated with sending and receiving data, or Completions associated with sending and receiving data, or
setting up buffers for sending and receiving data, could be setting up buffers for sending and receiving data, could be
accumulated in a shared Completion Queue for a group of RDMAP/DDP accumulated in a shared Completion Queue for a group of RDMAP/DDP
Streams, or a specific RDMAP/DDP Stream could have a dedicated Streams, or a specific RDMAP/DDP Stream could have a dedicated
Completion Queue. Limiting Completion Queue association to one, Completion Queue. Limiting Completion Queue association to one,
or a small number of RDMAP/DDP Streams can prevent several forms or a small number of RDMAP/DDP Streams can prevent several forms
of Denial of Service attacks, by sharply limiting the scope of of Denial of Service attacks, by sharply limiting the scope of
the attacks effect. the attack's effect.
7.1.5 Limiting the Scope of an Error 5.1.5 Limiting the Scope of an Error
To prevent a variety of attacks, it is important that an To prevent a variety of attacks, it is important that an
RDMAP/DDP implementation be robust in the face of errors. If an RDMAP/DDP implementation be robust in the face of errors. If an
error on a specific Stream can cause other unrelated Streams to error on a specific Stream can cause other unrelated Streams to
fail, then a broad class of attacks are enabled against the fail, then a broad class of attacks are enabled against the
implementation. implementation.
For example, an error on a specific RDMAP Stream should not cause For example, an error on a specific RDMAP Stream should not cause
the RNIC to stop processing incoming packets, or corrupt a the RNIC to stop processing incoming packets, or corrupt a
receive queue for an unrelated Stream. receive queue for an unrelated Stream.
7.2 Spoofing 5.2 Spoofing
Spoofing attacks can be launched by the Remote Peer, or by a Spoofing attacks can be launched by the Remote Peer, or by a
network based attacker. A network based spoofing attack applies network based attacker. A network based spoofing attack applies
to all Remote Peers. to all Remote Peers.
Because the RDMAP Stream requires an LLP Stream to be fully Because the RDMAP Stream requires an LLP Stream to be fully
initialized (e.g. for [TCP] it is in the ESTABLISHED state), initialized (e.g. for [TCP] it is in the ESTABLISHED state),
certain types of traditional forms of wire attacks do not apply - certain types of traditional forms of wire attacks do not apply -
- an end-to-end handshake must have occurred to establish the - an end-to-end handshake must have occurred to establish the
RDMAP Stream. So, the only form of spoofing that applies is one RDMAP Stream. So, the only form of spoofing that applies is one
when an attacker can both send and receive packets. Yet even with when an attacker can both send and receive packets. Yet even with
this limitation the Stream is still exposed to the following this limitation the Stream is still exposed to the following
spoofing attacks. spoofing attacks.
7.2.1 Impersonation 5.2.1 Impersonation
A network based attacker can impersonate a legal RDMAP/DDP Peer A network based attacker can impersonate a legal RDMAP/DDP Peer
(by spoofing a legal IP address), and establish an RDMAP/DDP (by spoofing a legal IP address), and establish an RDMAP/DDP
Stream with the victim. End-to-end authentication (i.e. IPsec, Stream with the victim. End-to-end authentication (i.e. IPsec,
SSL or ULP authentication) provides protection against this SSL or ULP authentication) provides protection against this
attack. For additional information see Section 8, Security attack. For additional information see Section 6, Security
Services for RDMAP and DDP, on page 40. Services for RDMAP and DDP, on page 36.
7.2.2 Stream Hijacking 5.2.2 Stream Hijacking
Stream hijacking happens when a network based attacker eavesdrops Stream hijacking happens when a network based attacker eavesdrops
the LLP connection through the Stream establishment phase, and the LLP connection through the Stream establishment phase, and
waits until the authentication phase (if such a phase exists) is waits until the authentication phase (if such a phase exists) is
completed successfully. The attacker then spoofs the IP address completed successfully. The attacker then spoofs the IP address
and re-direct the Stream from the victim to its own machine. For and re-direct the Stream from the victim to its own machine. For
example, an attacker can wait until an iSCSI authentication is example, an attacker can wait until an iSCSI authentication is
completed successfully, and then hijack the iSCSI Stream. completed successfully, and then hijack the iSCSI Stream.
The best protection against this form of attack is end-to-end The best protection against this form of attack is end-to-end
integrity protection and authentication, such as IPsec (see integrity protection and authentication, such as IPsec (see
Section 8, Security Services for RDMAP and DDP, on page 40), to Section 6, Security Services for RDMAP and DDP, on page 36), to
prevent spoofing. Another option is to provide physical security. prevent spoofing. Another option is to provide physical security.
Discussion of physical security is out of scope for this Discussion of physical security is out of scope for this
document. document.
Because the connection and/or Stream itself is established by the Because the connection and/or Stream itself is established by the
LLP, some LLPs are more difficult to hijack than others. Please LLP, some LLPs are more difficult to hijack than others. Please
see the relevant LLP documentation on security issues around see the relevant LLP documentation on security issues around
connection and/or Stream hijacking. connection and/or Stream hijacking.
7.2.3 Man in the Middle Attack 5.2.3 Man in the Middle Attack
If a network based attacker has the ability to delete, inject If a network based attacker has the ability to delete, inject
replay, or modify packets which will still be accepted by the LLP replay, or modify packets which will still be accepted by the LLP
(e.g., TCP sequence number is correct) then the Stream can be (e.g., TCP sequence number is correct) then the Stream can be
exposed to a man in the middle attack. One style of attack is for exposed to a man in the middle attack. One style of attack is for
the man-in-the-middle to send Tagged Messages (either RDMAP or the man-in-the-middle to send Tagged Messages (either RDMAP or
DDP). If it can discover a buffer that has been exposed for STag DDP). If it can discover a buffer that has been exposed for STag
enabled access, then the man-in-the-middle can use an RDMA Read enabled access, then the man-in-the-middle can use an RDMA Read
operation to read the contents of the associated data buffer, operation to read the contents of the associated data buffer,
perform an RDMA Write Operation to modify the contents of the perform an RDMA Write Operation to modify the contents of the
associated data buffer, or invalidate the STag to disable further associated data buffer, or invalidate the STag to disable further
access to the buffer. access to the buffer.
The best protection against this form of attack is end-to-end The best protection against this form of attack is end-to-end
integrity protection and authentication, such as IPsec (see integrity protection and authentication, such as IPsec (see
Section 8 Security Services for RDMAP and DDP on page 40), to Section 6 Security Services for RDMAP and DDP on page 36), to
prevent spoofing or tampering. If Stream or session level prevent spoofing or tampering. If Stream or session level
authentication and integrity protection are not used, then authentication and integrity protection are not used, then
physical protection must be employed, lest a man-in-the-middle physical protection must be employed, lest a man-in-the-middle
attack occur, enabling spoofing and tampering. attack occur, enabling spoofing and tampering.
Because the connection/Stream itself is established by the LLP, Because the connection/Stream itself is established by the LLP,
some LLPs are more exposed to man-in-the-middle attack than some LLPs are more exposed to man-in-the-middle attack than
others. Please see the relevant LLP documentation on security others. Please see the relevant LLP documentation on security
issues around connection and/or Stream hijacking. issues around connection and/or Stream hijacking.
Another approach is to restrict access to only the local Another approach is to restrict access to only the local
subnet/link, and provide some mechanism to limit access, such as subnet/link, and provide some mechanism to limit access, such as
physical security or 802.1.x. This model is an extremely limited physical security or 802.1.x. This model is an extremely limited
deployment scenario, and will not be further examined here. deployment scenario, and will not be further examined here.
7.2.4 Using an STag on a Different Stream 5.2.4 Using an STag on a Different Stream
One style of attack from the Remote Peer is for it to attempt to One style of attack from the Remote Peer is for it to attempt to
use STag values that it is not authorized to use. Note that if use STag values that it is not authorized to use. Note that if
the Remote Peer sends an invalid STag to the Local Peer, per the the Remote Peer sends an invalid STag to the Local Peer, per the
DDP and RDMAP specifications, the Stream must be torn down. Thus DDP and RDMAP specifications, the Stream must be torn down. Thus
the threat exists if an STag has been enabled for Remote Access the threat exists if an STag has been enabled for Remote Access
on one Stream and a Remote Peer is able to use it on an unrelated on one Stream and a Remote Peer is able to use it on an unrelated
Stream. If the attack is successful, the attacker could Stream. If the attack is successful, the attacker could
potentially be able to perform either RDMA Read Operations to potentially be able to perform either RDMA Read Operations to
read the contents of the associated data buffer, perform RDMA read the contents of the associated data buffer, perform RDMA
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by-one STag to be used. For additional protection, an by-one STag to be used. For additional protection, an
implementation should allocate STags in such a fashion that it is implementation should allocate STags in such a fashion that it is
difficult to predict the next allocated STag number, and also difficult to predict the next allocated STag number, and also
ensure that STags are reused at as slow a rate as possible. Any ensure that STags are reused at as slow a rate as possible. Any
allocation method which would lead to intentional or allocation method which would lead to intentional or
unintentional reuse of an STag by the peer should be avoided unintentional reuse of an STag by the peer should be avoided
(e.g. a method which always starts with a given STag and (e.g. a method which always starts with a given STag and
monotonically increases it for each new allocation, or a method monotonically increases it for each new allocation, or a method
which always uses the same STag for each operation). which always uses the same STag for each operation).
7.3 Tampering 5.3 Tampering
A Remote Peer or a network based attacker can attempt to tamper A Remote Peer or a network based attacker can attempt to tamper
with the contents of data buffers on a Local Peer that have been with the contents of data buffers on a Local Peer that have been
enabled for remote write access. The types of tampering attacks enabled for remote write access. The types of tampering attacks
that are possible are outlined in the sections that follow. that are possible are outlined in the sections that follow.
7.3.1 Buffer Overrun - RDMA Write or Read Response 5.3.1 Buffer Overrun - RDMA Write or Read Response
This attack is an attempt by the Remote Peer to perform an RDMA This attack is an attempt by the Remote Peer to perform an RDMA
Write or RDMA Read Response to memory outside of the valid length Write or RDMA Read Response to memory outside of the valid length
range of the data buffer enabled for remote write access. This range of the data buffer enabled for remote write access. This
attack can occur even when no resources are shared across attack can occur even when no resources are shared across
Streams. This issue can also arise if the ULP has a bug. Streams. This issue can also arise if the ULP has a bug.
The countermeasure for this type of attack must be in the RNIC The countermeasure for this type of attack must be in the RNIC
implementation, leveraging the STag. When the local ULP specifies implementation, leveraging the STag. When the local ULP specifies
to the RNIC the base address and the number of bytes in the to the RNIC the base address and the number of bytes in the
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buffer referenced by the STag before the STag is enabled for buffer referenced by the STag before the STag is enabled for
access. When an RDMA data transfer operation (which includes an access. When an RDMA data transfer operation (which includes an
STag) arrives on a Stream, a base and bounds byte granularity STag) arrives on a Stream, a base and bounds byte granularity
access check must be performed to ensure the operation accesses access check must be performed to ensure the operation accesses
only memory locations within the buffer described by that STag. only memory locations within the buffer described by that STag.
Thus an RNIC implementation MUST ensure that a Remote Peer is not Thus an RNIC implementation MUST ensure that a Remote Peer is not
able to access memory outside of the buffer specified when the able to access memory outside of the buffer specified when the
STag was enabled for remote access. STag was enabled for remote access.
7.3.2 Modifying a Buffer After Indication 5.3.2 Modifying a Buffer After Indication
This attack can occur if a Remote Peer attempts to modify the This attack can occur if a Remote Peer attempts to modify the
contents of an STag referenced buffer by performing an RDMA Write contents of an STag referenced buffer by performing an RDMA Write
or an RDMA Read Response after the Remote Peer has indicated to or an RDMA Read Response after the Remote Peer has indicated to
the Local Peer or local ULP (by a variety of means) that the STag the Local Peer or local ULP (by a variety of means) that the STag
data buffer contents are ready for use. This attack can occur data buffer contents are ready for use. This attack can occur
even when no resources are shared across Streams. Note that a bug even when no resources are shared across Streams. Note that a bug
in a Remote Peer, or network based tampering, could also result in a Remote Peer, or network based tampering, could also result
in this problem. in this problem.
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Peer could force the ULP down operational paths that were never Peer could force the ULP down operational paths that were never
intended. intended.
The local ULP can protect itself from this type of attack by The local ULP can protect itself from this type of attack by
revoking remote access when the original data transfer has revoking remote access when the original data transfer has
completed and before it validates the contents of the buffer. The completed and before it validates the contents of the buffer. The
local ULP can either do this by explicitly revoking remote access local ULP can either do this by explicitly revoking remote access
rights for the STag when the Remote Peer indicates the operation rights for the STag when the Remote Peer indicates the operation
has completed, or by checking to make sure the Remote Peer has completed, or by checking to make sure the Remote Peer
invalidated the STag through the RDMAP Remote Invalidate invalidated the STag through the RDMAP Remote Invalidate
capability (see section 7.5.5 Remote Invalidate an STag Shared on capability (see section 5.5.5 Remote Invalidate an STag Shared on
Multiple Streams on page 38 for a definition of Remote Multiple Streams on page 34 for a definition of Remote
Invalidate), and if it did not, the local ULP then explicitly Invalidate), and if it did not, the local ULP then explicitly
revokes the STag remote access rights. revokes the STag remote access rights.
The local ULP SHOULD follow the above procedure to protect the The local ULP SHOULD follow the above procedure to protect the
buffer before it validates the contents of the buffer (or uses buffer before it validates the contents of the buffer (or uses
the buffer in any way). the buffer in any way).
An RNIC MUST ensure that network packets using the STag for a An RNIC MUST ensure that network packets using the STag for a
previously advertised buffer can no longer modify the buffer previously advertised buffer can no longer modify the buffer
after the ULP revokes remote access rights for the specific STag. after the ULP revokes remote access rights for the specific STag.
7.3.3 Multiple STags to access the same buffer 5.3.3 Multiple STags to access the same buffer
See section 7.4.6 Using Multiple STags Which Alias to the Same See section 5.4.6 Using Multiple STags Which Alias to the Same
Buffer on page 29 for this analysis. Buffer on page 25 for this analysis.
7.3.4 Network based modification of buffer content 5.3.4 Network based modification of buffer content
This is actually a man in the middle attack - but only on the This is actually a man in the middle attack - but only on the
content of the buffer, as opposed to the man in the middle attack content of the buffer, as opposed to the man in the middle attack
presented above, where both the signaling and content can be presented above, where both the signaling and content can be
modified. See Section 7.2.3 Man in the Middle Attack on page 24. modified. See Section 5.2.3 Man in the Middle Attack on page 20.
7.4 Information Disclosure 5.4 Information Disclosure
The main potential source for information disclosure is through a The main potential source for information disclosure is through a
local buffer that has been enabled for remote access. If the local buffer that has been enabled for remote access. If the
buffer can be probed by a Remote Peer on another Stream, then buffer can be probed by a Remote Peer on another Stream, then
there is potential for information disclosure. there is potential for information disclosure.
The potential attacks that could result in unintended information The potential attacks that could result in unintended information
disclosure and countermeasures are detailed in the following disclosure and countermeasures are detailed in the following
sections. sections.
7.4.1 Probing memory outside of the buffer bounds 5.4.1 Probing memory outside of the buffer bounds
This is essentially the same attack as described in Section This is essentially the same attack as described in Section
7.3.1, except an RDMA Read Request is used to mount the attack. 5.3.1, except an RDMA Read Request is used to mount the attack.
The same countermeasure applies. The same countermeasure applies.
7.4.2 Using RDMA Read to Access Stale Data 5.4.2 Using RDMA Read to Access Stale Data
If a buffer is being used for a combination of reads and writes If a buffer is being used for a combination of reads and writes
(either remote or local), and is exposed to the Remote Peer with (either remote or local), and is exposed to the Remote Peer with
at least remote read access rights, the Remote Peer may be able at least remote read access rights, the Remote Peer may be able
to examine the contents of the buffer before they are initialized to examine the contents of the buffer before they are initialized
with the correct data. In this situation, whatever contents were with the correct data. In this situation, whatever contents were
present in the buffer before the buffer is initialized can be present in the buffer before the buffer is initialized can be
viewed by the Remote Peer, if the Remote Peer performs an RDMA viewed by the Remote Peer, if the Remote Peer performs an RDMA
Read. Read.
Because of this, the local ULP SHOULD ensure that no stale data Because of this, the local ULP SHOULD ensure that no stale data
is contained in the buffer before remote read access rights are is contained in the buffer before remote read access rights are
granted (this can be done by zeroing the contents of the memory, granted (this can be done by zeroing the contents of the memory,
for example). for example).
7.4.3 Accessing a Buffer After the Transfer 5.4.3 Accessing a Buffer After the Transfer
If the Remote Peer has remote read access to a buffer, and by If the Remote Peer has remote read access to a buffer, and by
some mechanism tells the local ULP that the transfer has been some mechanism tells the local ULP that the transfer has been
completed, but the local ULP does not disable remote access to completed, but the local ULP does not disable remote access to
the buffer before modifying the data, it is possible for the the buffer before modifying the data, it is possible for the
Remote Peer to retrieve the new data. Remote Peer to retrieve the new data.
This is similar to the attack defined in Section 7.3.2 Modifying This is similar to the attack defined in Section 5.3.2 Modifying
a Buffer After Indication on page 26. The same countermeasures a Buffer After Indication on page 22. The same countermeasures
apply. In addition, the local ULP SHOULD grant remote read access apply. In addition, the local ULP SHOULD grant remote read access
rights only for the amount of time needed to retrieve the data. rights only for the amount of time needed to retrieve the data.
7.4.4 Accessing Unintended Data With a Valid STag 5.4.4 Accessing Unintended Data With a Valid STag
If the ULP enables remote access to a buffer using an STag that If the ULP enables remote access to a buffer using an STag that
references the entire buffer, but intends only a portion of the references the entire buffer, but intends only a portion of the
buffer to be accessed, it is possible for the Remote Peer to buffer to be accessed, it is possible for the Remote Peer to
access the other parts of the buffer anyway. access the other parts of the buffer anyway.
To prevent this attack, the ULP SHOULD set the base and bounds of To prevent this attack, the ULP SHOULD set the base and bounds of
the buffer when the STag is initialized to expose only the data the buffer when the STag is initialized to expose only the data
to be retrieved. to be retrieved.
7.4.5 RDMA Read into an RDMA Write Buffer 5.4.5 RDMA Read into an RDMA Write Buffer
One form of disclosure can occur if the access rights on the One form of disclosure can occur if the access rights on the
buffer enabled remote read, when only remote write access was buffer enabled remote read, when only remote write access was
intended. If the buffer contained ULP data, or data from a intended. If the buffer contained ULP data, or data from a
transfer on an unrelated Stream, the Remote Peer could retrieve transfer on an unrelated Stream, the Remote Peer could retrieve
the data through an RDMA Read operation. Note that an RNIC the data through an RDMA Read operation. Note that an RNIC
implementation is not required to support STags that have both implementation is not required to support STags that have both
read and write access. read and write access.
The most obvious countermeasure for this attack is to not grant The most obvious countermeasure for this attack is to not grant
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Thus if a ULP only intends a buffer to be exposed for remote Thus if a ULP only intends a buffer to be exposed for remote
write access, it MUST set the access rights to the buffer to only write access, it MUST set the access rights to the buffer to only
enable remote write access. Note that this requirement is not enable remote write access. Note that this requirement is not
meant to restrict the use of zero-length RDMA Reads. Zero-length meant to restrict the use of zero-length RDMA Reads. Zero-length
RDMA Reads do not expose ULP data. Because they are intended to RDMA Reads do not expose ULP data. Because they are intended to
be used as a mechanism to ensure that all RDMA Writes have been be used as a mechanism to ensure that all RDMA Writes have been
received, and do not even require a valid STag, their use is received, and do not even require a valid STag, their use is
permitted even if a buffer has only been enabled for write permitted even if a buffer has only been enabled for write
access. access.
7.4.6 Using Multiple STags Which Alias to the Same Buffer 5.4.6 Using Multiple STags Which Alias to the Same Buffer
Multiple STags which alias to the same buffer at the same time Multiple STags which alias to the same buffer at the same time
can result in unintentional information disclosure if the STags can result in unintentional information disclosure if the STags
are used by different, mutually untrusted, Remote Peers. This are used by different, mutually untrusted, Remote Peers. This
model applies specifically to client/server communication, where model applies specifically to client/server communication, where
the server is communicating with multiple clients, each of which the server is communicating with multiple clients, each of which
do not mutually trust each other. do not mutually trust each other.
If only read access is enabled, then the local ULP has complete If only read access is enabled, then the local ULP has complete
control over information disclosure. Thus a server which intended control over information disclosure. Thus a server which intended
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Peers do not mutually trust each other, it is possible for one Peers do not mutually trust each other, it is possible for one
Remote Peer to overwrite the contents that have been written by Remote Peer to overwrite the contents that have been written by
the other Remote Peer. the other Remote Peer.
Thus a ULP with multiple Remote Peers which do not share Partial Thus a ULP with multiple Remote Peers which do not share Partial
Mutual Trust MUST NOT grant write access to the same buffer Mutual Trust MUST NOT grant write access to the same buffer
through different STags. A buffer should be exposed to only one through different STags. A buffer should be exposed to only one
untrusted Remote Peer at a time to ensure that no information untrusted Remote Peer at a time to ensure that no information
disclosure or information tampering occurs between peers. disclosure or information tampering occurs between peers.
7.4.7 Remote Node Loading Firmware onto the RNIC 5.4.7 Remote Node Loading Firmware onto the RNIC
If the Remote Peer can cause firmware to be loaded onto the RNIC, If the Remote Peer can cause firmware to be loaded onto the RNIC,
there is an opportunity for information disclosure. See Elevation there is an opportunity for information disclosure. See Elevation
of Privilege in Section 7.5.6 for this analysis. of Privilege in Section 5.5.6 for this analysis.
7.4.8 Controlling Access to PTT & STag Mapping 5.4.8 Controlling Access to PTT & STag Mapping
If a Non-Privileged ULP is able to directly manipulate the RNIC If a Non-Privileged ULP is able to directly manipulate the RNIC
Page Translation Tables (which translate from an STag to a host Page Translation Tables (which translate from an STag to a host
address), it is possible that the Non-Privileged ULP could point address), it is possible that the Non-Privileged ULP could point
the Page Translation Table at an unrelated Stream's or ULPs the Page Translation Table at an unrelated Stream's or ULP's
buffers and thereby be able to gain access to information of the buffers and thereby be able to gain access to information of the
unrelated Stream/ULP. unrelated Stream/ULP.
As discussed in Section 4 Architectural Model on page 10, As discussed in Section 2 Architectural Model on page 6,
introduction of a Privileged Resource Manager to arbitrate the introduction of a Privileged Resource Manager to arbitrate the
mapping requests is an effective countermeasure. This enables the mapping requests is an effective countermeasure. This enables the
Privileged Resource Manager to ensure a local ULP can only Privileged Resource Manager to ensure a local ULP can only
initialize the Page Translation Table (PTT)to point to its own initialize the Page Translation Table (PTT)to point to its own
buffers. buffers.
Thus if Non-Privileged ULPs are supported, the Privileged Thus if Non-Privileged ULPs are supported, the Privileged
Resource Manager MUST verify that the Non-Privileged ULP has the Resource Manager MUST verify that the Non-Privileged ULP has the
right to access a specific Data Buffer before allowing an STag right to access a specific Data Buffer before allowing an STag
for which the ULP has access rights to be associated with a for which the ULP has access rights to be associated with a
specific Data Buffer. This can be done when the Page Translation specific Data Buffer. This can be done when the Page Translation
Table is initialized to access the Data Buffer or when the STag Table is initialized to access the Data Buffer or when the STag
is initialized to point to a group of Page Translation Table is initialized to point to a group of Page Translation Table
entries, or both. entries, or both.
7.4.9 Network based eavesdropping 5.4.9 Network based eavesdropping
An attacker that is able to eavesdrop on the network can read the An attacker that is able to eavesdrop on the network can read the
content of all read and write accesses to a Peers buffers. To content of all read and write accesses to a Peer's buffers. To
prevent information disclosure, the read/written data must be prevent information disclosure, the read/written data must be
encrypted. See also Section 7.2.3 Man in the Middle Attack on encrypted. See also Section 5.2.3 Man in the Middle Attack on
page 24. The encryption can be done either by the ULP, or by a page 20. The encryption can be done either by the ULP, or by a
protocol that provides security services to the LLP (e.g. IPsec protocol that provides security services to the LLP (e.g. IPsec
or SSL). Refer to section 8 for discussion of security services or SSL). Refer to section 6 for discussion of security services
for DDP/RDMA. for DDP/RDMA.
7.5 Denial of Service (DOS) 5.5 Denial of Service (DOS)
A DOS attack is one of the primary security risks of RDMAP. This A DOS attack is one of the primary security risks of RDMAP. This
is because RNIC resources are valuable and scarce, and many ULP is because RNIC resources are valuable and scarce, and many ULP
environments require communication with untrusted Remote Peers. environments require communication with untrusted Remote Peers.
If the remote ULP can be authenticated or encrypted, clearly, the If the remote ULP can be authenticated or encrypted, clearly, the
DOS profile can be reduced. For the purposes of this analysis, it DOS profile can be reduced. For the purposes of this analysis, it
is assumed that the RNIC must be able to operate in untrusted is assumed that the RNIC must be able to operate in untrusted
environments, which are open to DOS style attacks. environments, which are open to DOS style attacks.
Denial of service attacks against RNIC resources are not the Denial of service attacks against RNIC resources are not the
typical unknown party spraying packets at a random host (such as typical unknown party spraying packets at a random host (such as
a TCP SYN attack). Because the connection/Stream must be fully a TCP SYN attack). Because the connection/Stream must be fully
established, the attacker must be able to both send and receive established, the attacker must be able to both send and receive
messages over that connection/Stream, or be able to guess a valid messages over that connection/Stream, or be able to guess a valid
packet on an existing RDMAP Stream. packet on an existing RDMAP Stream.
This section outlines the potential attacks and the This section outlines the potential attacks and the
countermeasures available for dealing with each attack. countermeasures available for dealing with each attack.
7.5.1 RNIC Resource Consumption 5.5.1 RNIC Resource Consumption
This section covers attacks that fall into the general category This section covers attacks that fall into the general category
of a local ULP attempting to unfairly allocate scarce (i.e. of a local ULP attempting to unfairly allocate scarce (i.e.
bounded) RNIC resources. The local ULP may be attempting to bounded) RNIC resources. The local ULP may be attempting to
allocate resources on its own behalf, or on behalf of a Remote allocate resources on its own behalf, or on behalf of a Remote
Peer. Resources that fall into this category include: Protection Peer. Resources that fall into this category include: Protection
Domains, Stream Context Memory, Translation and Protection Domains, Stream Context Memory, Translation and Protection
Tables, and STag namespace. These can be due to attacks by Tables, and STag namespace. These can be due to attacks by
currently active local ULPs or ones that allocated resources currently active local ULPs or ones that allocated resources
earlier, but are now idle. earlier, but are now idle.
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This analysis assumes that the Resource Manager is responsible This analysis assumes that the Resource Manager is responsible
for handing out Protection Domains, and RNIC implementations will for handing out Protection Domains, and RNIC implementations will
provide enough Protection Domains to allow the Resource Manager provide enough Protection Domains to allow the Resource Manager
to be able to assign a unique Protection Domain for each to be able to assign a unique Protection Domain for each
unrelated, untrusted local ULP (for a bounded, reasonable number unrelated, untrusted local ULP (for a bounded, reasonable number
of local ULPs). This analysis further assumes that the Resource of local ULPs). This analysis further assumes that the Resource
Manager implements policies to ensure that untrusted local ULPs Manager implements policies to ensure that untrusted local ULPs
are not able to consume all of the Protection Domains through a are not able to consume all of the Protection Domains through a
DOS attack. Note that Protection Domain consumption cannot result DOS attack. Note that Protection Domain consumption cannot result
from a DOS attack launched by a Remote Peer, unless a local ULP from a DOS attack launched by a Remote Peer, unless a local ULP
is acting on the Remote Peers behalf. is acting on the Remote Peer's behalf.
7.5.2 Resource Consumption By Active ULPs 5.5.2 Resource Consumption By Active ULPs
This section describes DOS attacks from Local and Remote Peers This section describes DOS attacks from Local and Remote Peers
that are actively exchanging messages. Attacks on each RDMA NIC that are actively exchanging messages. Attacks on each RDMA NIC
resource are examined and specific countermeasures are resource are examined and specific countermeasures are
identified. Note that attacks on Stream Context Memory, Page identified. Note that attacks on Stream Context Memory, Page
Translation Tables, and STag namespace are covered in Section Translation Tables, and STag namespace are covered in Section
7.5.1 RNIC Resource Consumption, so are not included here. 5.5.1 RNIC Resource Consumption, so are not included here.
7.5.2.1 Multiple Streams Sharing Receive Buffers 5.5.2.1 Multiple Streams Sharing Receive Buffers
The Remote Peer can attempt to consume more than its fair share The Remote Peer can attempt to consume more than its fair share
of receive data buffers (i.e. Untagged buffers for DDP are or of receive data buffers (i.e. Untagged buffers for DDP are or
Send Type Messages for RDMAP) if receive buffers are shared Send Type Messages for RDMAP) if receive buffers are shared
across multiple Streams. across multiple Streams.
If resources are not shared across multiple Streams, then this If resources are not shared across multiple Streams, then this
attack is not possible because the Remote Peer will not be able attack is not possible because the Remote Peer will not be able
to consume more buffers than were allocated to the Stream. The to consume more buffers than were allocated to the Stream. The
worst case scenario is that the Remote Peer can consume more worst case scenario is that the Remote Peer can consume more
receive buffers than the local ULP allowed, resulting in no receive buffers than the local ULP allowed, resulting in no
buffers being available, which could cause the Remote Peers buffers being available, which could cause the Remote Peer's
Stream to the Local Peer to be torn down, and all allocated Stream to the Local Peer to be torn down, and all allocated
resources to be released. resources to be released.
If local receive data buffers are shared among multiple Streams, If local receive data buffers are shared among multiple Streams,
then the Remote Peer can attempt to consume more than its fair then the Remote Peer can attempt to consume more than its fair
share of the receive buffers, causing a different Stream to be share of the receive buffers, causing a different Stream to be
short of receive buffers, thus possibly causing the other Stream short of receive buffers, thus possibly causing the other Stream
to be torn down. For example, if the Remote Peer sent enough one to be torn down. For example, if the Remote Peer sent enough one
byte Untagged Messages, they might be able to consume all local byte Untagged Messages, they might be able to consume all local
shared receive queue resources with little effort on their part. shared receive queue resources with little effort on their part.
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An effective countermeasure is to create a high-water An effective countermeasure is to create a high-water
notification which alerts the ULP if there is more than a notification which alerts the ULP if there is more than a
specified number of receive buffers "in process" (partially specified number of receive buffers "in process" (partially
consumed, but not completed). The notification is generated when consumed, but not completed). The notification is generated when
more than the specified number of buffers are in process more than the specified number of buffers are in process
simultaneously on a specific Stream (i.e., packets have started simultaneously on a specific Stream (i.e., packets have started
to arrive for the buffer, but the buffer has not yet been to arrive for the buffer, but the buffer has not yet been
delivered to the ULP). delivered to the ULP).
A different countermeasure is for the RNIC Engine to provide the A different countermeasure is for the RNIC Engine to provide the
capability to limit the Remote Peers ability to consume receive capability to limit the Remote Peer's ability to consume receive
buffers on a per Stream basis. Unfortunately this requires a buffers on a per Stream basis. Unfortunately this requires a
large amount of state to be tracked in each RNIC on a per Stream large amount of state to be tracked in each RNIC on a per Stream
basis. basis.
Thus, if an RNIC Engine provides the ability to share receive Thus, if an RNIC Engine provides the ability to share receive
buffers across multiple Streams, the combination of the RNIC buffers across multiple Streams, the combination of the RNIC
Engine and the Privileged Resource Manager MUST be able to detect Engine and the Privileged Resource Manager MUST be able to detect
if the Remote Peer is attempting to consume more than its fair if the Remote Peer is attempting to consume more than its fair
share of resources so that the Local Peer or local ULP can apply share of resources so that the Local Peer or local ULP can apply
countermeasures to detect and prevent the attack. countermeasures to detect and prevent the attack.
7.5.2.2 Local ULP Attacking a Shared CQ 5.5.2.2 Local ULP Attacking a Shared CQ
DOS attacks against a Shared Completion Queue (CQ) can be caused DOS attacks against a Shared Completion Queue (CQ) can be caused
by either the local ULP or the Remote Peer if either attempts to by either the local ULP or the Remote Peer if either attempts to
cause more completions than its fair share of the number of cause more completions than its fair share of the number of
entries, thus potentially starving another unrelated ULP such entries, thus potentially starving another unrelated ULP such
that no Completion Queue entries are available. that no Completion Queue entries are available.
A Completion Queue entry can potentially be maliciously consumed A Completion Queue entry can potentially be maliciously consumed
by a completion from the Send Queue or a completion from the by a completion from the Send Queue or a completion from the
Receive Queue. In the former, the attacker is the local ULP. In Receive Queue. In the former, the attacker is the local ULP. In
the latter, the attacker is the Remote Peer. the latter, the attacker is the Remote Peer.
A form of attack can occur where the local ULPs can consume A form of attack can occur where the local ULPs can consume
resources on the CQ. A local ULP that is slow to free resources resources on the CQ. A local ULP that is slow to free resources
on the CQ by not reaping the completion status quickly enough on the CQ by not reaping the completion status quickly enough
could stall all other local ULPs attempting to use that CQ. could stall all other local ULPs attempting to use that CQ.
For these reasons, an RNIC MUST NOT enable sharing a CQ across For these reasons, an RNIC MUST NOT enable sharing a CQ across
ULPs that do not share Partial Mutual Trust. ULPs that do not share Partial Mutual Trust.
7.5.2.3 Local or Remote Peer Attacking a Shared CQ 5.5.2.3 Local or Remote Peer Attacking a Shared CQ
For an overview of the shared CQ attack model, see Section For an overview of the shared CQ attack model, see Section
7.5.2.2. 5.5.2.2.
The Remote Peer can attack a shared CQ by consuming more than its The Remote Peer can attack a shared CQ by consuming more than its
fair share of CQ entries by using one of the following methods: fair share of CQ entries by using one of the following methods:
* The ULP protocol allows the Remote Peer to reserve a * The ULP protocol allows the Remote Peer to cause the
specified number of CQ entries, possibly leaving local ULP to reserve a specified number of CQ entries,
insufficient entries for other Streams that are sharing possibly leaving insufficient entries for other Streams
the CQ. that are sharing the CQ.
* If the Remote Peer, Local Peer, or local ULP (or any * If the Remote Peer, Local Peer, or local ULP (or any
combination) can attack the CQ by overwhelming the CQ combination) can attack the CQ by overwhelming the CQ
with completions, then completion processing on other with completions, then completion processing on other
Streams sharing that Completion Queue can be affected Streams sharing that Completion Queue can be affected
(e.g. the Completion Queue overflows and stops (e.g. the Completion Queue overflows and stops
functioning). functioning).
The first method of attack can be avoided if the ULP does not The first method of attack can be avoided if the ULP does not
allow a Remote Peer to reserve CQ entries or there is a trusted allow a Remote Peer to reserve CQ entries or there is a trusted
intermediary such as a Privileged Resource Manager. Unfortunately intermediary such as a Privileged Resource Manager. Unfortunately
it is often unrealistic to not allow a Remote Peer to reserve CQ it is often unrealistic to not allow a Remote Peer to reserve CQ
entries - particularly if the number of completion entries is entries - particularly if the number of completion entries is
dependent on other ULP negotiated parameters, such as the amount dependent on other ULP negotiated parameters, such as the amount
of buffering required by the ULP. Thus an implementation MUST of buffering required by the ULP. Thus an implementation MUST
implement a Privileged Resource Manager to control the allocation implement a Privileged Resource Manager to control the allocation
of CQ entries. See Section 4.1 Components on page 11 for a of CQ entries. See Section 2.1 Components on page 7 for a
definition of Privileged Resource Manager. definition of Privileged Resource Manager.
One way that a Local or Remote Peer can attempt to overwhelm a CQ One way that a Local or Remote Peer can attempt to overwhelm a CQ
with completions is by sending minimum length RDMAP/DDP Messages with completions is by sending minimum length RDMAP/DDP Messages
to cause as many completions (receive completions for the Remote to cause as many completions (receive completions for the Remote
Peer, send completions for the Local Peer) per second as Peer, send completions for the Local Peer) per second as
possible. If it is the Remote Peer attacking, and we assume that possible. If it is the Remote Peer attacking, and we assume that
the Local Peer's receive queue(s) do not run out of receive the Local Peer's receive queue(s) do not run out of receive
buffers (if they do, then this is a different attack, documented buffers (if they do, then this is a different attack, documented
in Section 7.5.2.1 Multiple Streams Sharing Receive Buffers on in Section 5.5.2.1 Multiple Streams Sharing Receive Buffers on
page 31), then it might be possible for the Remote Peer to page 27), then it might be possible for the Remote Peer to
consume more than its fair share of Completion Queue entries. consume more than its fair share of Completion Queue entries.
Depending upon the CQ implementation, this could either cause the Depending upon the CQ implementation, this could either cause the
CQ to overflow (if it is not large enough to handle all of the CQ to overflow (if it is not large enough to handle all of the
completions generated) or for another Stream to not be able to completions generated) or for another Stream to not be able to
generate CQ entries (if the RNIC had flow control on generation generate CQ entries (if the RNIC had flow control on generation
of CQ entries into the CQ). In either case, the CQ will stop of CQ entries into the CQ). In either case, the CQ will stop
functioning correctly and any Streams expecting completions on functioning correctly and any Streams expecting completions on
the CQ will stop functioning. the CQ will stop functioning.
This attack can occur regardless of whether all of the Streams This attack can occur regardless of whether all of the Streams
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all cases, so the CQ resize should be done before sizing all cases, so the CQ resize should be done before sizing
the Send Queue and Receive Queue on the Stream), OR the Send Queue and Receive Queue on the Stream), OR
* Grant fewer resources than the Remote Peer requested (not * Grant fewer resources than the Remote Peer requested (not
supplying the number of Receive Data Buffers requested). supplying the number of Receive Data Buffers requested).
The proper sizing of the CQ is dependent on whether the local The proper sizing of the CQ is dependent on whether the local
ULP(s) will post as many resources to the various queues as the ULP(s) will post as many resources to the various queues as the
size of the queue enables or not. If the local ULP(s) can be size of the queue enables or not. If the local ULP(s) can be
trusted to post a number of resources that is smaller than the trusted to post a number of resources that is smaller than the
size of the specific resources queue, then a correctly sized CQ size of the specific resource's queue, then a correctly sized CQ
means that the CQ is large enough to hold completion status for means that the CQ is large enough to hold completion status for
all of the outstanding Data Buffers (both send and receive all of the outstanding Data Buffers (both send and receive
buffers), or: buffers), or:
CQ_MIN_SIZE = SUM(MaxPostedOnEachRQ) CQ_MIN_SIZE = SUM(MaxPostedOnEachRQ)
+ SUM(MaxPostedOnEachSRQ) + SUM(MaxPostedOnEachSRQ)
+ SUM(MaxPostedOnEachSQ) + SUM(MaxPostedOnEachSQ)
Where: Where:
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share Partial Mutual Trust, then the ULP MUST implement a share Partial Mutual Trust, then the ULP MUST implement a
mechanism to ensure that the Completion Queue can not overflow. mechanism to ensure that the Completion Queue can not overflow.
Note that it is possible to share CQs even if the Remote Peers Note that it is possible to share CQs even if the Remote Peers
accessing the CQs are untrusted if either of the above two accessing the CQs are untrusted if either of the above two
formulas are implemented. If the ULP can be trusted to not post formulas are implemented. If the ULP can be trusted to not post
more than MaxPostedOnEachRQ, MaxPostedOnEachSRQ, and more than MaxPostedOnEachRQ, MaxPostedOnEachSRQ, and
MaxPostedOnEachSQ, then the first formula applies. If the ULP can MaxPostedOnEachSQ, then the first formula applies. If the ULP can
not be trusted to obey the limit, then the second formula not be trusted to obey the limit, then the second formula
applies. applies.
7.5.2.4 Attacking the RDMA Read Request Queue 5.5.2.4 Attacking the RDMA Read Request Queue
If RDMA Read Request Queue resources are pooled across multiple If RDMA Read Request Queue resources are pooled across multiple
Streams, one attack is if the local ULP attempts to unfairly Streams, one attack is if the local ULP attempts to unfairly
allocate RDMA Read Request Queue resources for its Streams. For allocate RDMA Read Request Queue resources for its Streams. For
example, a local ULP attempts to allocate all available resources example, a local ULP attempts to allocate all available resources
on a specific RDMA Read Request Queue for its Streams, thereby on a specific RDMA Read Request Queue for its Streams, thereby
denying the resource to ULPs sharing the RDMA Read Request Queue. denying the resource to ULPs sharing the RDMA Read Request Queue.
The same type of argument applies even if the RDMA Read Request The same type of argument applies even if the RDMA Read Request
is not shared - but a local ULP attempts to allocate all of the is not shared - but a local ULP attempts to allocate all of the
RNIC's resources when the queue is created. RNIC's resources when the queue is created.
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SHOULD prevent a local ULP from allocating more than its fair SHOULD prevent a local ULP from allocating more than its fair
share of resources. share of resources.
Another form of attack is if the Remote Peer sends more RDMA Read Another form of attack is if the Remote Peer sends more RDMA Read
Requests than the depth of the RDMA Read Request Queue at the Requests than the depth of the RDMA Read Request Queue at the
Local Peer. If the RDMA Read Request Queue is a shared resource, Local Peer. If the RDMA Read Request Queue is a shared resource,
this could corrupt the queue. If the queue is not shared, then this could corrupt the queue. If the queue is not shared, then
the worst case is that the current Stream is no longer functional the worst case is that the current Stream is no longer functional
(e.g. torn down). One approach to solving the shared RDMA Read (e.g. torn down). One approach to solving the shared RDMA Read
Request Queue would be to create thresholds, similar to those Request Queue would be to create thresholds, similar to those
described in Section 7.5.2.1 Multiple Streams Sharing Receive described in Section 5.5.2.1 Multiple Streams Sharing Receive
Buffers on page 31. A simpler approach is to not share RDMA Read Buffers on page 27. A simpler approach is to not share RDMA Read
Request Queue resources among Streams or enforce hard limits of Request Queue resources among Streams or enforce hard limits of
consumption per Stream. Thus RDMA Read Request Queue resource consumption per Stream. Thus RDMA Read Request Queue resource
consumption MUST be controlled by the Privileged Resource Manager consumption MUST be controlled by the Privileged Resource Manager
such that RDMAP/DDP Streams which do not share Partial Mutual such that RDMAP/DDP Streams which do not share Partial Mutual
Trust do not share RDMA Read Request Queue resources. Trust do not share RDMA Read Request Queue resources.
If the issue is a bug in the Remote Peers implementation, but If the issue is a bug in the Remote Peer's implementation, but
not a malicious attack, the issue can be solved by requiring the not a malicious attack, the issue can be solved by requiring the
Remote Peers RNIC to throttle RDMA Read Requests. By properly Remote Peer's RNIC to throttle RDMA Read Requests. By properly
configuring the Stream at the Remote Peer through a trusted configuring the Stream at the Remote Peer through a trusted
agent, the RNIC can be made to not transmit RDMA Read Requests agent, the RNIC can be made to not transmit RDMA Read Requests
that exceed the depth of the RDMA Read Request Queue at the Local that exceed the depth of the RDMA Read Request Queue at the Local
Peer. If the Stream is correctly configured, and if the Remote Peer. If the Stream is correctly configured, and if the Remote
Peer submits more requests than the Local Peers RDMA Read Peer submits more requests than the Local Peer's RDMA Read
Request Queue can handle, the requests would be queued at the Request Queue can handle, the requests would be queued at the
Remote Peer∆s RNIC until previous requests complete. If the Remote Peer's RNIC until previous requests complete. If the
Remote Peer∆s Stream is not configured correctly, the RDMAP Remote Peer's Stream is not configured correctly, the RDMAP
Stream is terminated when more RDMA Read Requests arrive at the Stream is terminated when more RDMA Read Requests arrive at the
Local Peer than the Local Peer can handle (assuming the prior Local Peer than the Local Peer can handle (assuming the prior
paragraphs recommendation is implemented). Thus an RNIC paragraph's recommendation is implemented). Thus an RNIC
implementation SHOULD provide a mechanism to cap the number of implementation SHOULD provide a mechanism to cap the number of
outstanding RDMA Read Requests. The configuration of this limit outstanding RDMA Read Requests. The configuration of this limit
is outside the scope of this document. is outside the scope of this document.
7.5.3 Resource Consumption by Idle ULPs 5.5.3 Resource Consumption by Idle ULPs
The simplest form of a DOS attack given a fixed amount of The simplest form of a DOS attack given a fixed amount of
resources is for the Remote Peer to create a RDMAP Stream to a resources is for the Remote Peer to create a RDMAP Stream to a
Local Peer, and request dedicated resources then do no actual Local Peer, and request dedicated resources then do no actual
work. This allows the Remote Peer to be very light weight (i.e. work. This allows the Remote Peer to be very light weight (i.e.
only negotiate resources, but do no data transfer) and consumes a only negotiate resources, but do no data transfer) and consumes a
disproportionate amount of resources at the Local Peer. disproportionate amount of resources at the Local Peer.
A general countermeasure for this style of attack is to monitor A general countermeasure for this style of attack is to monitor
active RDMAP Streams and if resources are getting low, reap the active RDMAP Streams and if resources are getting low, reap the
resources from RDMAP Streams that are not transferring data and resources from RDMAP Streams that are not transferring data and
possibly terminate the Stream. This would presumably be under possibly terminate the Stream. This would presumably be under
administrative control. administrative control.
Refer to Section 7.5.1 for the analysis and countermeasures for Refer to Section 5.5.1 for the analysis and countermeasures for
this style of attack on the following RNIC resources: Stream this style of attack on the following RNIC resources: Stream
Context Memory, Page Translation Tables and STag namespace. Context Memory, Page Translation Tables and STag namespace.
Note that some RNIC resources are not at risk of this type of Note that some RNIC resources are not at risk of this type of
attack from a Remote Peer because an attack requires the Remote attack from a Remote Peer because an attack requires the Remote
Peer to send messages in order to consume the resource. Receive Peer to send messages in order to consume the resource. Receive
Data Buffers, Completion Queue, and RDMA Read Request Queue Data Buffers, Completion Queue, and RDMA Read Request Queue
resources are examples. These resources are, however, at risk resources are examples. These resources are, however, at risk
from a local ULP that attempts to allocate resources, then goes from a local ULP that attempts to allocate resources, then goes
idle. This could also be created if the ULP negotiates the idle. This could also be created if the ULP negotiates the
resource levels with the Remote Peer, which causes the Local Peer resource levels with the Remote Peer, which causes the Local Peer
to consume resources, however the Remote Peer never sends data to to consume resources, however the Remote Peer never sends data to
consume them. The general countermeasure described in this consume them. The general countermeasure described in this
section can be used to free resources allocated by an idle Local section can be used to free resources allocated by an idle Local
Peer. Peer.
7.5.4 Exercise of non-optimal code paths 5.5.4 Exercise of non-optimal code paths
Another form of DOS attack is to attempt to exercise data paths Another form of DOS attack is to attempt to exercise data paths
that can consume a disproportionate amount of resources. An that can consume a disproportionate amount of resources. An
example might be if error cases are handled on a "slow path" example might be if error cases are handled on a "slow path"
(consuming either host or RNIC computational resources), and an (consuming either host or RNIC computational resources), and an
attacker generates excessive numbers of errors in an attempt to attacker generates excessive numbers of errors in an attempt to
consume these resources. Note that for most RDMAP or DDP errors, consume these resources. Note that for most RDMAP or DDP errors,
the attacking Stream will simply be torn down. Thus for this form the attacking Stream will simply be torn down. Thus for this form
of attack to be effective, the Remote Peer needs to exercise data of attack to be effective, the Remote Peer needs to exercise data
paths which do not cause the Stream to be torn down. paths which do not cause the Stream to be torn down.
If an RNIC implementation contains "slow paths" which do not If an RNIC implementation contains "slow paths" which do not
result in the tear down of the Stream, it is recommended that an result in the tear down of the Stream, it is recommended that an
implementation provide the ability to detect the above condition implementation provide the ability to detect the above condition
and allow an administrator to act, including potentially and allow an administrator to act, including potentially
administratively tearing down the RDMAP Stream associated with administratively tearing down the RDMAP Stream associated with
the Stream exercising data paths consuming a disproportionate the Stream exercising data paths consuming a disproportionate
amount of resources. amount of resources.
7.5.5 Remote Invalidate an STag Shared on Multiple Streams 5.5.5 Remote Invalidate an STag Shared on Multiple Streams
If a Local Peer has enabled an STag for remote access, the Remote If a Local Peer has enabled an STag for remote access, the Remote
Peer could attempt to remote invalidate the STag by using the Peer could attempt to remote invalidate the STag by using the
RDMAP Send with Invalidate or Send with SE and Invalidate RDMAP Send with Invalidate or Send with SE and Invalidate
Message. If the STag is only valid on the current Stream, then Message. If the STag is only valid on the current Stream, then
the only side effect is that the Remote Peer can no longer use the only side effect is that the Remote Peer can no longer use
the STag; thus there are no security issues. the STag; thus there are no security issues.
If the STag is valid across multiple Streams, then the Remote If the STag is valid across multiple Streams, then the Remote
Peer can prevent other Streams from using that STag by using the Peer can prevent other Streams from using that STag by using the
remote invalidate functionality. remote invalidate functionality.
Thus if RDDP Streams do not share Partial Mutual Trust (i.e. the Thus if RDDP Streams do not share Partial Mutual Trust (i.e. the
Remote Peer may attempt to remote invalidate the STag Remote Peer may attempt to remote invalidate the STag
prematurely), the ULP MUST NOT enable an STag which would be prematurely), the ULP MUST NOT enable an STag which would be
valid across multiple Streams. valid across multiple Streams.
7.5.6 Remote Peer attacking an Unshared CQ 5.5.6 Remote Peer attacking an Unshared CQ
The Remote Peer can attack an unshared CQ if the Local Peer does The Remote Peer can attack an unshared CQ if the Local Peer does
not size the CQ correctly. For example, if the Local Peer enables not size the CQ correctly. For example, if the Local Peer enables
the CQ to handle completions of received buffers, and the receive the CQ to handle completions of received buffers, and the receive
buffer queue is longer than the Completion Queue, then an buffer queue is longer than the Completion Queue, then an
overflow can potentially occur. The effect on the attackers overflow can potentially occur. The effect on the attacker's
Stream is catastrophic. However if an RNIC does not have the Stream is catastrophic. However if an RNIC does not have the
proper protections in place, then an attack to overflow the CQ proper protections in place, then an attack to overflow the CQ
can also cause corruption and/or termination of an unrelated can also cause corruption and/or termination of an unrelated
Stream. Thus an RNIC MUST ensure that if a CQ overflows, any Stream. Thus an RNIC MUST ensure that if a CQ overflows, any
Streams which do not use the CQ MUST remain unaffected. Streams which do not use the CQ MUST remain unaffected.
7.6 Elevation of Privilege 5.6 Elevation of Privilege
The RDMAP/DDP Security Architecture explicitly differentiates The RDMAP/DDP Security Architecture explicitly differentiates
between three levels of privilege - Non-Privileged, Privileged, between three levels of privilege - Non-Privileged, Privileged,
and the Privileged Resource Manager. If a Non-Privileged ULP is and the Privileged Resource Manager. If a Non-Privileged ULP is
able to elevate its privilege level to a Privileged ULP, then able to elevate its privilege level to a Privileged ULP, then
mapping a physical address list to an STag can provide local and mapping a physical address list to an STag can provide local and
remote access to any physical address location on the node. If a remote access to any physical address location on the node. If a
Privileged Mode ULP is able to promote itself to be a Resource Privileged Mode ULP is able to promote itself to be a Resource
Manager, then it is possible for it to perform denial of service Manager, then it is possible for it to perform denial of service
type attacks where substantial amounts of local resources could type attacks where substantial amounts of local resources could
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There is one issue worth noting, however. If the RNIC There is one issue worth noting, however. If the RNIC
implementation, by some insecure mechanism (or implementation implementation, by some insecure mechanism (or implementation
defect), can enable a Remote Peer or un-trusted local ULP to load defect), can enable a Remote Peer or un-trusted local ULP to load
firmware into the RNIC Engine, it is possible to use the RNIC to firmware into the RNIC Engine, it is possible to use the RNIC to
attack the host. Thus, an RNIC implementation MUST NOT enable attack the host. Thus, an RNIC implementation MUST NOT enable
firmware to be loaded on the RNIC Engine directly from an firmware to be loaded on the RNIC Engine directly from an
untrusted local ULP or Remote Peer, unless they are properly untrusted local ULP or Remote Peer, unless they are properly
authenticated (by a mechanism outside the scope of this document. authenticated (by a mechanism outside the scope of this document.
The mechanism presumably entails authenticating that the remote The mechanism presumably entails authenticating that the remote
ULP has the right to perform the update), and the update is done ULP has the right to perform the update), and the update is done
via a secure protocol, such as IPsec (See Section 8 Security via a secure protocol, such as IPsec (See Section 6 Security
Services for RDMAP and DDP on page 40). Services for RDMAP and DDP on page 36).
8 Security Services for RDMAP and DDP 6 Security Services for RDMAP and DDP
RDMAP and DDP are used to control, read and write data buffers RDMAP and DDP are used to control, read and write data buffers
over IP networks. Therefore, the control and the data packets of over IP networks. Therefore, the control and the data packets of
these protocols are vulnerable to the spoofing, tampering and these protocols are vulnerable to the spoofing, tampering and
information disclosure attacks listed in Section 7. information disclosure attacks listed in Section 7.
Generally speaking, Stream confidentiality protects against Generally speaking, Stream confidentiality protects against
eavesdropping. Stream and/or session authentication and integrity eavesdropping. Stream and/or session authentication and integrity
protection is a counter measurement against various spoofing and protection is a counter measurement against various spoofing and
tampering attacks. The effectiveness of authentication and tampering attacks. The effectiveness of authentication and
integrity against a specific attack, depend on whether the integrity against a specific attack, depend on whether the
authentication is machine level authentication (as the one authentication is machine level authentication (as the one
provided by IPsec and SSL), or ULP authentication. provided by IPsec and SSL), or ULP authentication.
8.1 Introduction to Security Options 6.1 Introduction to Security Options
The following security services can be applied to an RDMAP/DDP The following security services can be applied to an RDMAP/DDP
Stream: Stream:
1. Session confidentiality - protects against eavesdropping 1. Session confidentiality - protects against eavesdropping
(section 7.4.9). (section 5.4.9).
2. Per-packet data source authentication - protects against the 2. Per-packet data source authentication - protects against the
following spoofing attacks: network based impersonation following spoofing attacks: network based impersonation
(section 7.2.1), Stream hijacking (section 7.2.2), and man in (section 5.2.1), Stream hijacking (section 5.2.2), and man in
the middle (section 7.2.3). the middle (section 5.2.3).
3. Per-packet integrity - protects against tampering done by 3. Per-packet integrity - protects against tampering done by
network based modification of buffer content (section 7.3.4) network based modification of buffer content (section 5.3.4)
4. Packet sequencing - protects against replay attacks, which is 4. Packet sequencing - protects against replay attacks, which is
a special case of the above tampering attack. a special case of the above tampering attack.
If an RDMAP/DDP Stream may be subject to impersonation attacks, If an RDMAP/DDP Stream may be subject to impersonation attacks,
or Stream hijacking attacks, it is recommended that the Stream be or Stream hijacking attacks, it is recommended that the Stream be
authenticated, integrity protected, and protected from replay authenticated, integrity protected, and protected from replay
attacks; it may use confidentiality protection to protect from attacks; it may use confidentiality protection to protect from
eavesdropping (in case the RDMAP/DDP Stream traverses a public eavesdropping (in case the RDMAP/DDP Stream traverses a public
network). network).
Both IPsec and SSL are capable of providing the above security Both IPsec and SSL are capable of providing the above security
services for IP and TCP traffic respectively. ULP protocols are services for IP and TCP traffic respectively. ULP protocols are
able to provide only part of the above security services. The able to provide only part of the above security services. The
next sections describe the different security options. next sections describe the different security options.
8.1.1 Introduction to IPsec 6.1.1 Introduction to IPsec
IPsec is a protocol suite which is used to secure communication IPsec is a protocol suite which is used to secure communication
at the network layer between two peers. The IPsec protocol suite at the network layer between two peers. The IPsec protocol suite
is specified within the IP Security Architecture [RFC2401], IKE is specified within the IP Security Architecture [RFC2401], IKE
[RFC2409], IPsec Authentication Header (AH) [RFC2402] and IPsec [RFC2409], IPsec Authentication Header (AH) [RFC2402] and IPsec
Encapsulating Security Payload (ESP) [RFC2406] documents. IKE is Encapsulating Security Payload (ESP) [RFC2406] documents. IKE is
the key management protocol while AH and ESP are used to protect the key management protocol while AH and ESP are used to protect
IP traffic. IP traffic.
An IPsec SA is a one-way security association, uniquely An IPsec SA is a one-way security association, uniquely
skipping to change at page 42, line 7 skipping to change at page 38, line 7
The session keys for each IPsec SA are derived from a master key, The session keys for each IPsec SA are derived from a master key,
typically via a MODP Diffie-Hellman computation. Rekeying of an typically via a MODP Diffie-Hellman computation. Rekeying of an
existing IPsec SA pair is accomplished by creating two new IPsec existing IPsec SA pair is accomplished by creating two new IPsec
SAs, making them active, and then optionally deleting the older SAs, making them active, and then optionally deleting the older
IPsec SA pair. Typically the new outbound SA is used immediately, IPsec SA pair. Typically the new outbound SA is used immediately,
and the old inbound SA is left active to receive packets for some and the old inbound SA is left active to receive packets for some
locally defined time, perhaps 30 seconds or 1 minute. Optionally, locally defined time, perhaps 30 seconds or 1 minute. Optionally,
rekeying can use Diffie-Hellman for keying material generation. rekeying can use Diffie-Hellman for keying material generation.
8.1.2 Introduction to SSL Limitations on RDMAP 6.1.2 Introduction to SSL Limitations on RDMAP
SSL and TLS [RFC 2246] provide Stream authentication, integrity SSL and TLS [RFC 2246] provide Stream authentication, integrity
and confidentiality for TCP based ULPs. SSL supports one-way and confidentiality for TCP based ULPs. SSL supports one-way
(server only) or mutual certificates based authentication. (server only) or mutual certificates based authentication.
There are at least two limitations that make SSL underneath RDMAP There are at least two limitations that make SSL underneath RDMAP
less appropriate than IPsec for DDP/RDMA security: less appropriate than IPsec for DDP/RDMA security:
1. The maximum length supported by the TLS record layer protocol 1. The maximum length supported by the TLS record layer protocol
is 2^14 bytes - longer packets must be fragmented (as a is 2^14 bytes - longer packets must be fragmented (as a
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traffic, then SSL must gather all out-of-order packets before traffic, then SSL must gather all out-of-order packets before
RDMAP/DDP can place them into the ULP buffer, which might RDMAP/DDP can place them into the ULP buffer, which might
cause a significant decrease in its efficiency. cause a significant decrease in its efficiency.
If SSL is layered on top of RDMAP or DDP, SSL does not protect If SSL is layered on top of RDMAP or DDP, SSL does not protect
the RDMAP and/or DDP headers. Thus a man-in-the-middle attack can the RDMAP and/or DDP headers. Thus a man-in-the-middle attack can
still occur by modifying the RDMAP/DDP header to incorrectly still occur by modifying the RDMAP/DDP header to incorrectly
place the data into the wrong buffer, thus effectively corrupting place the data into the wrong buffer, thus effectively corrupting
the data stream. the data stream.
8.1.3 ULPs Which Provide Security 6.1.3 ULPs Which Provide Security
ULPs which provide integrated security but wish to leverage ULPs which provide integrated security but wish to leverage
lower-layer protocol security should be aware of security lower-layer protocol security should be aware of security
concerns around correlating a specific channels security concerns around correlating a specific channel's security
mechanisms to the authentication performed by the ULP. See mechanisms to the authentication performed by the ULP. See
[NFSv4CHANNEL] for additional information on a promising approach [NFSv4CHANNEL] for additional information on a promising approach
called "channel binding". From [NFSv4CHANNEL]: called "channel binding". From [NFSv4CHANNEL]:
"The concept of channel bindings allows applications to "The concept of channel bindings allows applications to
prove that the end-points of two secure channels at prove that the end-points of two secure channels at
different network layers are the same by binding different network layers are the same by binding
authentication at one channel to the session protection at authentication at one channel to the session protection at
the other channel. The use of channel bindings allows the other channel. The use of channel bindings allows
applications to delegate session protection to lower layers, applications to delegate session protection to lower layers,
which may significantly improve performance for some which may significantly improve performance for some
applications." applications."
8.2 Requirements for IPsec Encapsulation of DDP 6.2 Requirements for IPsec Encapsulation of DDP
The IP Storage working group has spent significant time and The IP Storage working group has spent significant time and
effort to define the normative IPsec requirements for IP Storage effort to define the normative IPsec requirements for IP Storage
[RFC3723]. Portions of that specification are applicable to a [RFC3723]. Portions of that specification are applicable to a
wide variety of protocols, including the RDDP protocol suite. In wide variety of protocols, including the RDDP protocol suite. In
order to not replicate this effort, an RNIC implementation MUST order to not replicate this effort, an RNIC implementation MUST
follow the requirements defined in RFC3723 Section 2.3 and follow the requirements defined in RFC3723 Section 2.3 and
Section 5, including the associated normative references for Section 5, including the associated normative references for
those sections. those sections.
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leave the Stream up, and if additional traffic is sent on it, to leave the Stream up, and if additional traffic is sent on it, to
bring up another IKE Phase 2 SA to protect it. This avoids the bring up another IKE Phase 2 SA to protect it. This avoids the
potential for continually bringing Streams up and down. potential for continually bringing Streams up and down.
Note that there are serious security issues if IPsec is not Note that there are serious security issues if IPsec is not
implemented end-to-end. For example, if IPsec is implemented as a implemented end-to-end. For example, if IPsec is implemented as a
tunnel in the middle of the network, any hosts between the Peer tunnel in the middle of the network, any hosts between the Peer
and the IPsec tunneling device can freely attack the unprotected and the IPsec tunneling device can freely attack the unprotected
Stream. Stream.
9 Security considerations 7 Security considerations
This entire document is focused on security considerations. This entire document is focused on security considerations.
10 References 8 IANA Considerations
10.1 Normative References IANA considerations are not addressed by this document. Any IANA
considerations resulting from the use of DDP or RDMA must be
addressed in the relevant standards.
9 References
9.1 Normative References
[RFC2828] Shirley, R., "Internet Security Glossary", FYI 36, RFC [RFC2828] Shirley, R., "Internet Security Glossary", FYI 36, RFC
2828, May 2000. 2828, May 2000.
[DDP] Shah, H., J. Pinkerton, R.Recio, and P. Culley, "Direct [DDP] Shah, H., J. Pinkerton, R.Recio, and P. Culley, "Direct
Data Placement over Reliable Transports", Internet-Draft Work Data Placement over Reliable Transports", Internet-Draft Work
in Progress draft-ietf-rddp-ddp-04.txt, December 2004. in Progress draft-ietf-rddp-ddp-04.txt, December 2004.
[RDMAP] Recio, R., P. Culley, D. Garcia, J. Hilland, "An RDMA [RDMAP] Recio, R., P. Culley, D. Garcia, J. Hilland, "An RDMA
Protocol Specification", Internet-Draft Work in Progress Protocol Specification", Internet-Draft Work in Progress
skipping to change at page 45, line 29 skipping to change at page 42, line 29
[RFC3723] Aboba B., et al, "Securing Block Storage Protocols over [RFC3723] Aboba B., et al, "Securing Block Storage Protocols over
IP", Internet draft (work in progress), RFC3723, April 2004. IP", Internet draft (work in progress), RFC3723, April 2004.
[SCTP] R. Stewart et al., "Stream Control Transmission Protocol", [SCTP] R. Stewart et al., "Stream Control Transmission Protocol",
RFC 2960, October 2000. RFC 2960, October 2000.
[TCP] Postel, J., "Transmission Control Protocol - DARPA Internet [TCP] Postel, J., "Transmission Control Protocol - DARPA Internet
Program Protocol Specification", RFC 793, September 1981. Program Protocol Specification", RFC 793, September 1981.
10.2 Informative References 9.2 Informative References
[IPv6-Trust] Nikander, P., J.Kempf, E. Nordmark, "IPv6 Neighbor [IPv6-Trust] Nikander, P., J.Kempf, E. Nordmark, "IPv6 Neighbor
Discovery Trust Models and threats", Informational RFC, Discovery Trust Models and threats", Informational RFC,
RFC3756, May 2004. RFC3756, May 2004.
[NFSv4CHANNEL] Williams, N., "On the Use of Channel Bindings to [NFSv4CHANNEL] Williams, N., "On the Use of Channel Bindings to
Secure Channels", Internet-Draft draft-ietf-nfsv4-channel- Secure Channels", Internet-Draft draft-ietf-nfsv4-channel-
bindings-02.txt, July 2004. bindings-02.txt, July 2004.
11 Appendix A: ULP Issues for RDDP Client/Server Protocols 10 Appendix A: ULP Issues for RDDP Client/Server Protocols
This section is a normative appendix to the document that is This section is a normative appendix to the document that is
focused on client/server ULP implementation requirements to focused on client/server ULP implementation requirements to
ensure a secure server implementation. ensure a secure server implementation.
The prior sections outlined specific attacks and their The prior sections outlined specific attacks and their
countermeasures. This section summarizes the attacks and countermeasures. This section summarizes the attacks and
countermeasures that have been defined in the prior section which countermeasures that have been defined in the prior section which
are applicable to creation of a secure ULP (e.g. application) are applicable to creation of a secure ULP (e.g. application)
server. A ULP server is defined as a ULP which must be able to server. A ULP server is defined as a ULP which must be able to
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can mount on the shared server, by re-stating the previous can mount on the shared server, by re-stating the previous
normative statements to be client/server specific. Note that each normative statements to be client/server specific. Note that each
client/server ULP may employ explicit RDMA operations (RDMA Read, client/server ULP may employ explicit RDMA operations (RDMA Read,
RDMA Write) in differing fashions. Therefore where appropriate, RDMA Write) in differing fashions. Therefore where appropriate,
"Local ULP", "Local Peer" and "Remote Peer" are used in place of "Local ULP", "Local Peer" and "Remote Peer" are used in place of
"server" or "client", in order to retain full generality of each "server" or "client", in order to retain full generality of each
requirement. requirement.
* Spoofing * Spoofing
* Sections 7.2.1 to 7.2.3. For protection against many * Sections 5.2.1 to 5.2.3. For protection against many
forms of spoofing attacks, enable IPsec. forms of spoofing attacks, enable IPsec.
* Section 7.2.4 Using an STag on a Different Stream on * Section 5.2.4 Using an STag on a Different Stream on
page 24. To ensure that one client can not access page 20. To ensure that one client can not access
another client's data via use of the other client's another client's data via use of the other client's
STag, the server ULP must either scope an STag to a STag, the server ULP must either scope an STag to a
single Stream or use a unique Protection Domain per single Stream or use a unique Protection Domain per
client. If a single client has multiple Streams that client. If a single client has multiple Streams that
share Partial Mutual Trust, then the STag can be share Partial Mutual Trust, then the STag can be
shared between the associated Streams by using a shared between the associated Streams by using a
single Protection Domain among the associated Streams single Protection Domain among the associated Streams
(see section 8.1.3 ULPs Which Provide Security on (see section 6.1.3 ULPs Which Provide Security on
page 42 for additional issues). To prevent unintended page 38 for additional issues). To prevent unintended
sharing of STags within the associated Streams, a sharing of STags within the associated Streams, a
server ULP should use STags in such a fashion that it server ULP should use STags in such a fashion that it
is difficult to predict the next allocated STag is difficult to predict the next allocated STag
number. number.
* Tampering * Tampering
* 7.3.2 Modifying a Buffer After Indication on page 26. * 5.3.2 Modifying a Buffer After Indication on page 22.
Before the local ULP operates on a buffer that was Before the local ULP operates on a buffer that was
written by the Remote Peer using an RDMA Write or written by the Remote Peer using an RDMA Write or
RDMA Read, the local ULP MUST ensure the buffer can RDMA Read, the local ULP MUST ensure the buffer can
no longer be modified, by invalidating the STag for no longer be modified, by invalidating the STag for
remote access (note that this is stronger than the remote access (note that this is stronger than the
SHOULD in section 7.3.2). This can either be done SHOULD in section 5.3.2). This can either be done
explicitly by revoking remote access rights for the explicitly by revoking remote access rights for the
STag when the Remote Peer indicates the operation has STag when the Remote Peer indicates the operation has
completed, or by checking to make sure the Remote completed, or by checking to make sure the Remote
Peer Invalidated the STag through the RDMAP Peer Invalidated the STag through the RDMAP
Invalidate capability, and if it did not, the local Invalidate capability, and if it did not, the local
ULP then explicitly revoking the STag remote access ULP then explicitly revoking the STag remote access
rights. rights.
* Information Disclosure * Information Disclosure
* 7.4.2 Using RDMA Read to Access Stale Data on page * 5.4.2 Using RDMA Read to Access Stale Data on page
27. In a general purpose server environment there is 23. In a general purpose server environment there is
no compelling rationale to not require a buffer to be no compelling rationale to not require a buffer to be
initialized before remote read is enabled (and an initialized before remote read is enabled (and an
enormous down side of unintentionally sharing data). enormous down side of unintentionally sharing data).
Thus a local ULP MUST (this is stronger than the Thus a local ULP MUST (this is stronger than the
SHOULD in section 7.4.2) ensure that no stale data is SHOULD in section 5.4.2) ensure that no stale data is
contained in a buffer before remote read access contained in a buffer before remote read access
rights are granted to a Remote Peer (this can be done rights are granted to a Remote Peer (this can be done
by zeroing the contents of the memory, for example). by zeroing the contents of the memory, for example).
* 7.4.3 Accessing a Buffer After the Transfer on page * 5.4.3 Accessing a Buffer After the Transfer on page
28. This mitigation is already covered by section 24. This mitigation is already covered by section
7.3.2 (above). 5.3.2 (above).
* 7.4.4 Accessing Unintended Data With a Valid STag on * 5.4.4 Accessing Unintended Data With a Valid STag on
page 28. The ULP must set the base and bounds of the page 24. The ULP must set the base and bounds of the
buffer when the STag is initialized to expose only buffer when the STag is initialized to expose only
the data to be retrieved. the data to be retrieved.
* 7.4.5 RDMA Read into an RDMA Write Buffer on page 28. * 5.4.5 RDMA Read into an RDMA Write Buffer on page 24.
If a peer only intends a buffer to be exposed for If a peer only intends a buffer to be exposed for
remote write access, it must set the access rights to remote write access, it must set the access rights to
the buffer to only enable remote write access. the buffer to only enable remote write access.
* 7.4.6 Using Multiple STags Which Alias to the Same * 5.4.6 Using Multiple STags Which Alias to the Same
Buffer on page 29. The requirement in section 7.2.4 Buffer on page 25. The requirement in section 5.2.4
(above) mitigates this attack. A server buffer is (above) mitigates this attack. A server buffer is
exposed to only one client at a time to ensure that exposed to only one client at a time to ensure that
no information disclosure or information tampering no information disclosure or information tampering
occurs between peers. occurs between peers.
* 7.4.9 Network based eavesdropping on page 30. * 5.4.9 Network based eavesdropping on page 26.
Confidentiality services should be enabled by the ULP Confidentiality services should be enabled by the ULP
if this threat is a concern. if this threat is a concern.
* Denial of Service * Denial of Service
* 7.5.2.1 Multiple Streams Sharing Receive Buffers on * 5.5.2.1 Multiple Streams Sharing Receive Buffers on
page 31. ULP memory footprint size can be important page 27. ULP memory footprint size can be important
for some server ULPs. If a server ULP is expecting for some server ULPs. If a server ULP is expecting
significant network traffic from multiple clients, significant network traffic from multiple clients,
using a receive buffer queue per Stream where there using a receive buffer queue per Stream where there
is a large number of Streams can consume substantial is a large number of Streams can consume substantial
amounts of memory. Thus a receive queue that can be amounts of memory. Thus a receive queue that can be
shared by multiple Streams is attractive. shared by multiple Streams is attractive.
However, because of the attacks outlined in this However, because of the attacks outlined in this
section, sharing a single receive queue between section, sharing a single receive queue between
multiple clients must only be done if a mechanism is multiple clients must only be done if a mechanism is
in place to ensure one client cannot consume receive in place to ensure one client cannot consume receive
buffers in excess of its limits, as defined by each buffers in excess of its limits, as defined by each
ULP. For multiple Streams within a single client ULP ULP. For multiple Streams within a single client ULP
(which presumably shared Partial Mutual Trust) this (which presumably shared Partial Mutual Trust) this
added overhead may be avoided. added overhead may be avoided.
* 7.5.2.2 Local ULP Attacking a Shared CQ on page 33. * 5.5.2.2 Local ULP Attacking a Shared CQ on page 29.
The normative RNIC mitigations require the RNIC to The normative RNIC mitigations require the RNIC to
not enable sharing of a CQ if the local ULPs do not not enable sharing of a CQ if the local ULPs do not
share Partial Mutual Trust. Thus while the ULP is not share Partial Mutual Trust. Thus while the ULP is not
allowed to enable this feature in an unsafe mode, if allowed to enable this feature in an unsafe mode, if
the two local ULPs share Partial Tutual Trust, they the two local ULPs share Partial Tutual Trust, they
must behave in the following manner: must behave in the following manner:
1) The sizing of the completion queue is based on the 1) The sizing of the completion queue is based on the
size of the receive queue and send queues as size of the receive queue and send queues as
documented in 7.5.2.3 Local or Remote Peer Attacking documented in 5.5.2.3 Local or Remote Peer Attacking
a Shared CQ on page 33. a Shared CQ on page 29.
2) The local ULP ensures that CQ entries are reaped 2) The local ULP ensures that CQ entries are reaped
frequently enough to adhere to section 7.5.2.3's frequently enough to adhere to section 5.5.2.3's
rules. rules.
* 7.5.2.3 Local or Remote Peer Attacking a Shared CQ on * 5.5.2.3 Local or Remote Peer Attacking a Shared CQ on
page 33. There are two mitigations specified in this page 29. There are two mitigations specified in this
section - one requires a worst-case size of the CQ, section - one requires a worst-case size of the CQ,
and can be implemented entirely within the Privileged and can be implemented entirely within the Privileged
Resource Manager. The second approach requires Resource Manager. The second approach requires
cooperation with the local ULP server (to not post cooperation with the local ULP server (to not post
too many buffers), and enables a smaller CQ to be too many buffers), and enables a smaller CQ to be
used. used.
In some server environments, partial trust of the In some server environments, partial trust of the
server ULP (but not the clients) is acceptable, thus server ULP (but not the clients) is acceptable, thus
the smaller CQ fully mitigates the remote attacker. the smaller CQ fully mitigates the remote attacker.
In other environments, the local server ULP could In other environments, the local server ULP could
also contain untrusted elements which can attack the also contain untrusted elements which can attack the
local machine (or have bugs). In those environments, local machine (or have bugs). In those environments,
the worst-case size of the CQ must be used. the worst-case size of the CQ must be used.
* 7.5.2.4 The section requires a server∆s Privileged * 5.5.2.4 The section requires a server's Privileged
Resource Manager to not allow sharing of RDMA Read Resource Manager to not allow sharing of RDMA Read
Request Queues across multiple Streams that do not Request Queues across multiple Streams that do not
share Partial Mutual Trust, for a ULP which performs share Partial Mutual Trust, for a ULP which performs
RDMA Read operations to server buffers. However, RDMA Read operations to server buffers. However,
because the server ULP knows best which of its because the server ULP knows best which of its
Streams share Partial Mutual Trust, this requirement Streams share Partial Mutual Trust, this requirement
can be reflected back to the ULP. The ULP (i.e. can be reflected back to the ULP. The ULP (i.e.
server) requirement in this case is that it MUST NOT server) requirement in this case is that it MUST NOT
allow RDMA Read Request Queues to be shared between allow RDMA Read Request Queues to be shared between
ULPs which do not have Partial Mutual Trust. ULPs which do not have Partial Mutual Trust.
* 7.5.5 Remote Invalidate an STag Shared on Multiple * 5.5.5 Remote Invalidate an STag Shared on Multiple
Streams on page 38. This mitigation is already Streams on page 34. This mitigation is already
covered by section 7.3.2 (above). covered by section 5.3.2 (above).
12 Appendix B: Summary of RNIC and ULP Implementation Requirements 11 Appendix B: Summary of RNIC and ULP Implementation Requirements
This appendix is informative. This appendix is informative.
Below is a summary of implementation requirements for the RNIC: Below is a summary of implementation requirements for the RNIC:
* 5 Trust and Resource Sharing * 3 Trust and Resource Sharing
* 7.2.4 Using an STag on a Different Stream * 5.2.4 Using an STag on a Different Stream
* 7.3.1 Buffer Overrun - RDMA Write or Read Response * 5.3.1 Buffer Overrun - RDMA Write or Read Response
* 7.3.2 Modifying a Buffer After Indication * 5.3.2 Modifying a Buffer After Indication
* 7.4.8 Controlling Access to PTT & STag Mapping * 5.4.8 Controlling Access to PTT & STag Mapping
* 7.5.1 RNIC Resource Consumption * 5.5.1 RNIC Resource Consumption
* 7.5.2.1 Multiple Streams Sharing Receive Buffers * 5.5.2.1 Multiple Streams Sharing Receive Buffers
* 7.5.2.2 Local ULP Attacking a Shared CQ * 5.5.2.2 Local ULP Attacking a Shared CQ
* 7.5.2.3 Local or Remote Peer Attacking a Shared CQ * 5.5.2.3 Local or Remote Peer Attacking a Shared CQ
* 7.5.2.4 Attacking the RDMA Read Request Queue * 5.5.2.4 Attacking the RDMA Read Request Queue
* 7.5.6 Remote Peer attacking an Unshared CQ on page 38. * 5.5.6 Remote Peer attacking an Unshared CQ on page 34.
* 7.6 Elevation of Privilege 39 * 5.6 Elevation of Privilege 35
* 8.2 Requirements for IPsec Encapsulation of DDP * 6.2 Requirements for IPsec Encapsulation of DDP
Below is a summary of implementation requirements for the ULP Below is a summary of implementation requirements for the ULP
above the RNIC: above the RNIC:
* 7.2.4 Using an STag on a Different Stream * 5.2.4 Using an STag on a Different Stream
* 7.3.2 Modifying a Buffer After Indication * 5.3.2 Modifying a Buffer After Indication
* 7.4.2 Using RDMA Read to Access Stale Data * 5.4.2 Using RDMA Read to Access Stale Data
* 7.4.3 Accessing a Buffer After the Transfer * 5.4.3 Accessing a Buffer After the Transfer
* 7.4.4 Accessing Unintended Data With a Valid STag * 5.4.4 Accessing Unintended Data With a Valid STag
* 7.4.5 RDMA Read into an RDMA Write Buffer * 5.4.5 RDMA Read into an RDMA Write Buffer
* 7.4.6 Using Multiple STags Which Alias to the Same Buffer * 5.4.6 Using Multiple STags Which Alias to the Same Buffer
* 7.4.9 Network based eavesdropping * 5.4.9 Network based eavesdropping
* 7.5.2.2 Local ULP Attacking a Shared CQ * 5.5.2.2 Local ULP Attacking a Shared CQ
* 7.5.5 Remote Invalidate an STag Shared on Multiple * 5.5.5 Remote Invalidate an STag Shared on Multiple
Streams Streams
13 Appendix C: Partial Trust Taxonomy 12 Appendix C: Partial Trust Taxonomy
This appendix is informative. This appendix is informative.
Partial Trust is defined as when one party is willing to assume Partial Trust is defined as when one party is willing to assume
that another party will refrain from a specific attack or set of that another party will refrain from a specific attack or set of
attacks, the parties are said to be in a state of Partial Trust. attacks, the parties are said to be in a state of Partial Trust.
Note that the partially trusted peer may attempt a different set Note that the partially trusted peer may attempt a different set
of attacks. This may be appropriate for many ULPs where any of attacks. This may be appropriate for many ULPs where any
adverse effects of the betrayal is easily confined and does not adverse effects of the betrayal is easily confined and does not
place other clients or ULPs at risk. place other clients or ULPs at risk.
The Trust Models described in this section have three primary The Trust Models described in this section have three primary
distinguishing characteristics. The Trust Model refers to a local distinguishing characteristics. The Trust Model refers to a local
ULP and Remote Peer, which are intended to be the local and ULP and Remote Peer, which are intended to be the local and
remote ULP instances communicating via RDMA/DDP. remote ULP instances communicating via RDMA/DDP.
* Local Resource Sharing (yes/no) - When local resources * Local Resource Sharing (yes/no) - When local resources
are shared, they are shared across a grouping of are shared, they are shared across a grouping of
RDMAP/DDP Streams. If local resources are not shared, the RDMAP/DDP Streams. If local resources are not shared, the
resources are dedicated on a per Stream basis. Resources resources are dedicated on a per Stream basis. Resources
are defined in Section 4.2 - Resources on page 12. The are defined in Section 2.2 - Resources on page 8. The
advantage of not sharing resources between Streams is advantage of not sharing resources between Streams is
that it reduces the types of attacks that are possible. that it reduces the types of attacks that are possible.
The disadvantage is that ULPs might run out of resources. The disadvantage is that ULPs might run out of resources.
* Local Partial Trust (yes/no) - Local Partial Trust is * Local Partial Trust (yes/no) - Local Partial Trust is
determined based on whether the local grouping of determined based on whether the local grouping of
RDMAP/DDP Streams (which typically equates to one ULP or RDMAP/DDP Streams (which typically equates to one ULP or
group of ULPs) mutually trust each other to not perform a group of ULPs) mutually trust each other to not perform a
specific set of attacks. specific set of attacks.
* Remote Partial Trust (yes/no) - The Remote Partial Trust * Remote Partial Trust (yes/no) - The Remote Partial Trust
level is determined based on whether the local ULP of a level is determined based on whether the local ULP of a
specific RDMAP/DDP Stream partially trusts the Remote specific RDMAP/DDP Stream partially trusts the Remote
Peer of the Stream (see the definition of Partial Trust Peer of the Stream (see the definition of Partial Trust
in Section 3 Introduction). in Section 1 Introduction).
Not all of the combinations of the trust characteristics are Not all of the combinations of the trust characteristics are
expected to be used by ULPs. This document specifically analyzes expected to be used by ULPs. This document specifically analyzes
five ULP Trust Models that are expected to be in common use. The five ULP Trust Models that are expected to be in common use. The
Trust Models are as follows: Trust Models are as follows:
* NS-NT - Non-Shared Local Resources, no Local Trust, no * NS-NT - Non-Shared Local Resources, no Local Trust, no
Remote Trust - typically a server ULP that wants to run Remote Trust - typically a server ULP that wants to run
in the safest mode possible. All attack mitigations are in the safest mode possible. All attack mitigations are
in place to ensure robust operation. in place to ensure robust operation.
* NS-RT - Non-Shared Local Resources, no Local Trust, * NS-RT - Non-Shared Local Resources, no Local Trust,
Remote Partial Trust - typically a peer-to-peer ULP, Remote Partial Trust - typically a peer-to-peer ULP,
which has, by some method outside of the scope of this which has, by some method outside of the scope of this
document, authenticated the Remote Peer. Note that unless document, authenticated the Remote Peer. Note that unless
some form of key based authentication is used on a per some form of key based authentication is used on a per
RDMA/DDP Stream basis, it may not be possible be possible RDMA/DDP Stream basis, it may not be possible be possible
for man-in-the-middle attacks to occur. See section 8, for man-in-the-middle attacks to occur. See section 6,
Security Services for RDMAP and DDP on page 40. Security Services for RDMAP and DDP on page 36.
* S-NT - Shared Local Resources, no Local Trust, no Remote * S-NT - Shared Local Resources, no Local Trust, no Remote
Trust - typically a server ULP that runs in an untrusted Trust - typically a server ULP that runs in an untrusted
environment where the amount of resources required is environment where the amount of resources required is
either too large or too dynamic to dedicate for each either too large or too dynamic to dedicate for each
RDMAP/DDP Stream. RDMAP/DDP Stream.
* S-LT - Shared Local Resources, Local Partial Trust, no * S-LT - Shared Local Resources, Local Partial Trust, no
Remote Trust - typically a ULP, which provides a session Remote Trust - typically a ULP, which provides a session
layer and uses multiple Streams, to provide additional layer and uses multiple Streams, to provide additional
skipping to change at page 54, line 5 skipping to change at page 51, line 5
neither local ULPs nor the Remote Peer is trusted. Sometimes neither local ULPs nor the Remote Peer is trusted. Sometimes
optimizations can be done that enable sharing of Page Translation optimizations can be done that enable sharing of Page Translation
Tables across multiple local ULPs, thus Model S-LT can be Tables across multiple local ULPs, thus Model S-LT can be
advantageous. Model S-T is typically used when resource scaling advantageous. Model S-T is typically used when resource scaling
across a large parallel ULP makes it infeasible to use any other across a large parallel ULP makes it infeasible to use any other
model. Resource scaling issues can either be due to performance model. Resource scaling issues can either be due to performance
around scaling or because there simply are not enough resources. around scaling or because there simply are not enough resources.
Model NS-RT is probably the least likely model to be used, but is Model NS-RT is probably the least likely model to be used, but is
presented for completeness. presented for completeness.
14 Author∆s Addresses 13 Author's Addresses
James Pinkerton James Pinkerton
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA. 98052 USA Redmond, WA. 98052 USA
Phone: +1 (425) 705-5442 Phone: +1 (425) 705-5442
Email: jpink@windows.microsoft.com Email: jpink@windows.microsoft.com
Ellen Deleganes Ellen Deleganes
Intel Corporation Intel Corporation
MS JF5-355 MS JF5-355
2111 NE 25th Ave. 2111 NE 25th Ave.
Hillsboro, OR 97124 USA Hillsboro, OR 97124 USA
Phone: +1 (503) 712-4173 Phone: +1 (503) 712-4173
Email: ellen.m.deleganes@intel.com Email: ellen.m.deleganes@intel.com
Sara Bitan Sara Bitan
Microsoft Corporation Microsoft Corporation
Email: sarab@microsoft.com Email: sarab@microsoft.com
15 Acknowledgments 14 Acknowledgments
Allyn Romanow Allyn Romanow
Cisco Systems Cisco Systems
170 W Tasman Drive 170 W Tasman Drive
San Jose, CA 95134 USA San Jose, CA 95134 USA
Phone: +1 408 525 8836 Phone: +1 408 525 8836
Email: allyn@cisco.com Email: allyn@cisco.com
Catherine Meadows Catherine Meadows
Naval Research Laboratory Naval Research Laboratory
skipping to change at page 56, line 5 skipping to change at page 53, line 5
Caitlin Bestler Caitlin Bestler
Email: cait@asomi.com Email: cait@asomi.com
Bernard Aboba Bernard Aboba
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA. 98052 USA Redmond, WA. 98052 USA
Phone: +1 (425) 706-6606 Phone: +1 (425) 706-6606
Email: bernarda@windows.microsoft.com Email: bernarda@windows.microsoft.com
16 Full Copyright Statement 15 Full Copyright Statement
Copyright (C) The Internet Society (2004). Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78 and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided This document and the information contained herein are provided
on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY
THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY
RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE. FOR A PARTICULAR PURPOSE.
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