Internet Draft James Pinkerton
draft-ietf-rddp-security-05.txtdraft-ietf-rddp-security-06.txt Microsoft Corporation Category: Standards Track Ellen Deleganes Expires: February,June, 2005 Intel Corporation Sara Bitan Microsoft Corporation AugustDecember 2004 DDP/RDMAP Security 1 Status of this Memo This document is an Internet-DraftBy submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, or will be disclosed, and isany of which I become aware will be disclosed, in full conformanceaccordance with all provisions of Section 10 of RFC2026.RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 2 Abstract This document analyzes security issues around implementation and use of the Direct Data Placement Protocol(DDP) and Remote Direct Memory Access Protocol (RDMAP). It first defines an architectural model for an RDMA Network Interface Card (RNIC), which can implement DDP or RDMAP and DDP. The document reviews various attacks against the resources defined in the architectural model and the countermeasures that can be used to protect the system. Attacks are grouped into spoofing, tampering, information disclosure, denial of service, and elevation of privilege. Finally, the document concludes with a summary of security services for DDP and RDMAP, such as IPsec. J. Pinkerton, et al. Expires FebruaryJune, 2005 1 Table of Contents 1 Status of this Memo.........................................1Memo..........................................1 2 Abstract....................................................1Abstract.....................................................1 2.1 Revision History............................................3History.............................................3 2.1.1 Changes from -04 to-05 to -06 version............................3 2.1.2 Changes from -03 to-04 to -05 version............................4 2.1.3 Changes from -03 to -04 version............................5 2.1.4 Changes from -02 to -03 version............................4 2.1.4version............................5 2.1.5 Changes from the -01 to the -02 version....................5 2.1.5version....................6 2.1.6 Changes from the -00 to -01 version........................5version........................6 3 Introduction................................................7Introduction.................................................8 4 Architectural Model.........................................9Model.........................................10 4.1 Components.................................................10Components..................................................11 4.2 Resources..................................................11Resources...................................................12 4.2.1 Stream Context Memory.....................................11Memory.....................................12 4.2.2 Data Buffers..............................................11Buffers..............................................12 4.2.3 Page Translation Tables...................................12Tables...................................13 4.2.4 STag Namespace............................................12Namespace............................................13 4.2.5 Completion Queues.........................................12Queues.........................................13 4.2.6 Asynchronous Event Queue..................................13Queue..................................14 4.2.7 RDMA Read Request Queue...................................13Queue...................................14 4.2.8 RNIC Interactions.........................................13Interactions.........................................14 126.96.36.199 Privileged Control Interface Semantics................13Semantics.................14 188.8.131.52 Non-Privileged Data Interface Semantics...............14Semantics................15 184.108.40.206 Privileged Data Interface Semantics...................14Semantics....................15 4.2.9 Initialization of RNIC Data Structures for Data Transfer..14Transfer..15 4.2.10 RNIC Data Transfer Interactions.........................16Interactions..........................17 5 Trust and Resource Sharing.................................17Sharing..................................18 6 Attacker Capabilities......................................18Capabilities.......................................19 7 Attacks and Countermeasures................................19Countermeasures.................................20 7.1 Tools for Countermeasures..................................19Countermeasures...................................20 7.1.1 Protection Domain (PD)....................................19(PD)....................................20 7.1.2 Limiting STag Scope.......................................20Scope.......................................21 7.1.3 Access Rights.............................................21Rights.............................................22 7.1.4 Limiting the Scope of the Completion Queue................21Queue................22 7.1.5 Limiting the Scope of an Error............................21Error............................22 7.2 Spoofing...................................................21Spoofing....................................................23 7.2.1 Impersonation.............................................22Impersonation.............................................23 7.2.2 Stream Hijacking..........................................22Hijacking..........................................23 7.2.3 Man in the Middle Attack..................................22Attack..................................24 7.2.4 Using an STag on a Different Stream.......................23Stream.......................24 7.3 Tampering..................................................24Tampering...................................................25 7.3.1 Buffer Overrun - RDMA Write or Read Response..............24Response..............26 7.3.2 Modifying a Buffer After Indication.......................25Indication.......................26 7.3.3 Multiple STags to access the same buffer..................25buffer..................27 7.3.4 Network based modification of buffer content..............25content..............27 7.4 Information Disclosure.....................................26Disclosure......................................27 7.4.1 Probing memory outside of the buffer bounds...............26bounds...............27 7.4.2 Using RDMA Read to Access Stale Data......................26Data......................27 7.4.3 Accessing a Buffer After the Transfer.....................26Transfer.....................28 7.4.4 Accessing Unintended Data With a Valid STag...............26STag...............28 7.4.5 RDMA Read into an RDMA Write Buffer.......................27Buffer.......................28 7.4.6 Using Multiple STags Which Alias to the Same Buffer.......27Buffer.......29 7.4.7 Remote Node Loading Firmware onto the RNIC................28RNIC................29 7.4.8 Controlling Access to PTT & STag Mapping..................28Mapping..................29 7.4.9 Network based eavesdropping...............................28eavesdropping...............................30 7.5 Denial of Service (DOS)....................................29(DOS).....................................30 7.5.1 RNIC Resource Consumption.................................29Consumption.................................30 7.5.2 Resource Consumption By Active ULPs.......................30ULPs.......................31 220.127.116.11 Multiple Streams Sharing Receive Buffers..............30Buffers...............31 18.104.22.168 Local ULP Attacking a Shared CQ.......................31CQ........................33 22.214.171.124 Local or Remote Peer Attacking a Shared CQ.....................32CQ.............33 126.96.36.199 Attacking the RDMA Read Request Queue.................35Queue..................36 7.5.3 Resource Consumption by Idle ULPs.........................36ULPs.........................37 7.5.4 Exercise of non-optimal code paths........................36paths........................38 7.5.5 Remote Invalidate an STag Shared on Multiple Streams......37Streams......38 7.5.6 Remote Peer attacking an Unshared CQ......................38 7.6 Elevation of Privilege.....................................37Privilege......................................39 8 Security Services for RDMARDMAP and DDP.........................38DDP.........................40 8.1 Introduction to Security Options...........................38Options............................40 8.1.1 Introduction to IPsec.....................................38IPsec.....................................40 8.1.2 Introduction to SSL Limitations on RDMAP..................40RDMAP..................42 8.1.3 ULPs Which Provide Security...............................40Security...............................42 8.2 Requirements for IPsec Encapsulation of DDP................41DDP.................43 9 Security considerations....................................42considerations.....................................44 10 References.................................................43References..................................................45 10.1 Normative References......................................43References......................................45 10.2 Informative References....................................43References....................................45 11 Appendix A: ULP Issues for RDDP Client/Server Protocols....44Protocols.....46 12 Appendix B: Summary of RNIC and ULP Implementation Requirements.....................................................48Requirements.....................................................50 13 Appendix C: Partial Trust Taxonomy.........................50Taxonomy..........................52 14 Author’s Addresses.........................................52AuthorÆs Addresses..........................................54 15 Acknowledgments............................................53Acknowledgments.............................................55 16 Full Copyright Statement...................................54Statement....................................56 Table of Figures Figure 1 - RDMA Security Model...................................10Model...................................11 2.1 Revision History 2.1.1 Changes from -05 to -06 version * Appendix A: ULP Issues for RDDP Client/Server Protocols, Section 188.8.131.52. 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 184.108.40.206 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. * 220.127.116.11 - clarified it is the ULP at issue, and removed reference to Protection Domain - key issue is whether they share partial mutual trust. * 18.104.22.168 - remove MUST statement at the end of the 3rd paragraph - it was replaced with a more general MUST in section <TBD>.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. 22.214.171.124.3 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 126.96.36.199 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. 188.8.131.52.4 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 184.108.40.206. * 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. 220.127.116.11.5 Changes from the -01 to the -02 version Minimal - some typos, deleted some text previously marked for deletion. 18.104.22.168.6 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.Stream. 3 Introduction RDMA enables new levels of flexibility when communicating between two parties compared to current conventional networking practice (e.g. a stream-based model or datagram model). This flexibility brings new security issues that must be carefully understood when designing Upper Layer Protocols (ULPs) utilizing RDMA and when implementing RDMA-aware NICs (RNICs). Note that for the purposes 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 middleware library. The specificationdocument first develops an architectural model that is relevant for the security analysis - it details components, resources, and system properties that may be attacked in Section 4. ItThe document uses Local Peer to represent the RDMA/DDP protocol implementation on the local end of a Stream. The local Upper-Layer-Protocol (ULP) is used to represent the application or middle-ware layer above the Local Peer. The document does not attempt to differentiate between a Remote Peer and a Remote ULP (an RDMA/DDP protocol implementation on the remote end of a Stream versus the application on the remote end) for several reasons: often the source of the attack is difficult to know for sure; and regardless of the source, the mitigations required of the Local Peer or local ULP are the same. Thus the document generically refers to a Remote Peer rather than trying to further delineate the attacker. The document then defines what resources a local ULP may share locallyacross Streams and what resources the local ULP may share with the Remote Peer across Streams in Section 5. Intentional sharing of resources between multiple Streams may imply some level of trust between the Streams. However, some types of resource sharing have unmitigated security attacks which would mandate not sharing a specific type of resource unless there is some level of trust between the Streams sharing resources. PartialThis document defines a new term, "Partial Mutual Trust is definedTrust" to address this concept: Partial Mutual Trust - a collection of RDMAP/DDP Streams, which represent the local and remote end points of the Stream, which are willing to assume that the Streams from the collection will not perform malicious attacks against any of the other Streams in the collection. ULPs have explicit control of which collection of endpoints is in thea Partial Mutual Trust collection through tools discussed in Section 7.1 Tools for Countermeasures on page 19.20. An untrusted peer relationship is appropriate when a ULP wishes to ensure that it will be robust and uncompromised even in the face of a deliberate attack by its peer. For example, a single ULP that concurrently supports multiple unrelated Streams (e.g. a server) would presumably treat each of its peers as an untrusted peer. For a collection of Streams which share Partial Mutual Trust, the assumption is that any Stream not in the collection is untrusted. For the untrusted peer, a brief list of capabilities is enumerated in Section 6. The rest of the specificationdocument is focused on analyzing attacks and recommending specific mitigations to the attacks. First, the tools for mitigating attacks are listed (Section 7.1), and then a series of attacks on components, resources, or system properties is enumeratedlisted in the rest of Section 7. For each attack, possible countermeasures are reviewed. If all recommended mitigations are in place the implemented usage models, the RDMAP/DDP protocol can be shown to not expose any new security vulnerabilities.ULPs within a host are divided into two categories - Privileged and Non-Privileged. Both ULP types can send and receive data and request resources. The key differences between the two are: The Privileged ULP is trusted by the local system to not maliciously attack the operating environment, but it is not trusted to optimize resource allocation globally. For example, the Privileged ULP could be a kernel ULP, thus the kernel presumably has in some way vetted the ULP before allowing it to execute. A Non-Privileged ULP's capabilities are a logical sub-set of the Privileged ULP's. It is assumed by the local system that a Non-Privileged ULP is untrusted. All Non-Privileged ULP interactions with the RNIC Engine that could affect other ULPs need to be done through a trusted intermediary that can verify the Non-Privileged ULP requests. If all recommended mitigations are in place the implemented usage models, the RDMAP/DDP protocol can be shown to not expose any new security vulnerabilities. 4 Architectural Model This section describes an RDMA architectural reference model that is used as security issues are examined. It introduces the components of the model, the resources that can be attacked, the types of interactions possible between components and resources, and the system properties which must be preserved. Figure 1 shows the components comprising the architecture and the interfaces where potential security attacks could be launched. External attacks can be injected into the system from a ULP that sits above the RNIC Interface or from the network. The intent here is to describe high level components and capabilities which affect threat analysis, and not focus on specific implementation options. Also note that the architectural model is an abstraction, and an actual implementation may choose to subdivide its components along different boundary lines than defined here. For example, the Privileged Resource Manager may be partially or completely encapsulated in the Privileged ULP. Regardless, it is expected that the security analysis of the potential threats and countermeasures still apply. +-------------+ | Privileged | | Resource | Admin<-+>| Manager | ULP Control Interface | | |<------+-------------------+ | +-------------+ | | | ^ v v | | +-------------+ +-----------------+ |---------------->| Privileged | | Non-Privileged | | | ULP | | ULP | | +-------------+ +-----------------+ | ^ ^ |Privileged |Privileged |Non-Privileged |Control |Data |Data |Interface |Interface |Interface RNIC | | | Interface v v v ================================================================= +--------------------------------------+ | | | RNIC Engine | <-- Firmware | | +--------------------------------------+ ^ | v Internet Figure 1 - RDMA Security Model 4.1 Components The components shown in Figure 1 - RDMA Security Model are: * RNICRDMA Network Interface Controller Engine (RNIC) - the component that implements the RDMA protocol and/or DDP protocol. * Privileged Resource Manager - the component responsible for managing and allocating resources associated with the RNIC Engine. The Resource Manager does not send or receive data. Note that whether the Resource Manager is an independent component, part of the RNIC, or part of the ULP is implementation dependent. If a specific 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 definition of Privileged ULP. The local host infrastructure can enable the Privileged ULP to map a data buffer directly from the RNIC Engine to the host through the RNIC Interface, but it does not allow the Privileged ULP to directly consume RNIC Engine resources. * Non-Privileged ULP - See Section 3 Introduction for a definition of Non-Privileged ULP. A design goal of the DDP and RDMAP protocols is to allow, under constrained conditions, Non-Privileged ULP to send and receive data directly to/from the RDMA Engine without Privileged Resource Manager intervention - while ensuring that the host remains secure. Thus, one of the primary goals of this paperdocument is to analyze this usage model for the enforcement that is required in the RNIC Engine to ensure the system remains secure. The host interfaces that could be exercised include: * Privileged Control Interface - A Privileged Resource Manager uses the RNIC Interface to allocate and manage RNIC Engine resources, control the state within the RNIC Engine, and monitor various events from the RNIC Engine. It also uses this interface to act as a proxy for some operations that a Non-Privileged ULP may require (after performing appropriate countermeasures). * ULP Control Interface - An ULP uses this interface to the Privileged Resource Manager to allocate RNIC Engine resources. The Privileged Resource Manager implements countermeasures to ensure that if the Non-Privileged ULP launches an attack it can prevent the attack from affecting other ULPs. * Non-Privileged Data Transfer Interface - A Non-Privileged ULP uses this interface to initiate and to check the status of data transfer operations. * Privileged Data Transfer Interface - A superset of the functionality provided by the Non-Privileged Data Transfer Interface. The ULP is allowed to directly manipulate RNIC Engine mapping resources to map an STag to a ULP data buffer. * Figure 1 also shows the ability to load new firmware in the RNIC Engine. Not all RNICs will support this, but it is shown for completeness and is also reviewed under potential attacks. If Internet control messages, such as ICMP, ARP, RIPv4, etc. are processed by the RNIC Engine, the threat analyses for those protocols is also applicable, but outside the scope of this paper.document. 4.2 Resources This section describes the primary resources in the RNIC Engine that could be affected if under attack. For RDMAP, all of the defined resources apply. For DDP, all of the resources except the RDMA Read Queue apply. 4.2.1 Stream Context Memory The state information for each Stream is maintained in memory, 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 the three, depending on the implementation. Stream Context Memory includes state associated with Data Buffers. For Tagged Buffers, this includes how STag names, Data Buffers, and Page Translation Tables inter-relate.(see section 4.2.3 on page 13) interrelate. It also includes the list of Untagged Data Buffers posted for reception of Untagged Messages (commonly called the Receive Queue), and a list of operations to perform to send data (commonly called the Send Queue). 4.2.2 Data Buffers 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.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 Messages). This distinction is important because the attacks and the countermeasures used to protect against the attack are different depending on the method for exposing the buffer to the network. For the purposes of the security discussion, a single logical Data Buffer is exposed with a single STag.Stag on a given Stream. Actual implementations may support scatter/gather capabilities to enable multiple physical data buffers to be accessed with a single STag, but from a threat analysis perspective it is assumed that a single STag enables access to a single logical Data Buffer. In any event, it is the responsibility of the RNICPrivileged Resource Manager to ensure that no STag can be created that exposes memory that the consumer had no authority to expose. 4.2.3 Page Translation Tables Page Translation Tables are the structures used by the RNIC to be able to access ULP memory for data transfer operations. Even though these structures are called "Page" Translation Tables, they may not reference a page at all - conceptually they are used to map a ULP address space representation (e.g. a virtual 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 is not used, then a subset of the attacks examined may be appropriate. Note that the Page Translation Table may or may not be a shared resource. 4.2.4 STag Namespace The DDP specification defines a 32-bit namespace for the STag. Implementations may vary in terms of the actual number of STags that are supported. In any case, this is a bounded resource that can come under attack. Depending upon STag namespace allocation algorithms, the actual name space to attack may be significantly less than 2^32. 4.2.5 Completion Queues Completion Queues are used in this specificationdocument to conceptually represent how the RNIC Engine notifies the ULP about the completion of the transmission of data, or the completion of the reception of data through the Data Transfer Interface. Because there could be many transmissions or receptions in flight at any one time, completions are modeled as a queue rather than a single event. An implementation may also use the Completion Queue to notify the ULP of other activities, for example, the 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 to handle a specific Stream's traffic. Some implementations may allow this queue to be manipulated directly by both Non-Privileged and Privileged ULPs. 4.2.6 Asynchronous Event Queue The Asynchronous Event Queue is a queue from the RNIC to the Privileged Resource Manager of bounded size. It is used by the RNIC to notify the host of various events which might require management action, including protocol violations, Stream state changes, local operation errors, low water marks on receive queues, and possibly other events. The Asynchronous Event Queue is a resource that can be attacked because Remote or Local Peers and/or ULPs can cause events to occur which have the potential of overflowing the queue. Note that an implementation is at liberty to implement the functions of the Asynchronous Event Queue in a variety of ways, including multiple queues or even simple callbacks. All vulnerabilities identified are intended to apply regardless of the implementation of the Asynchronous Event Queue. For example, a callback function ismay be viewed as simply a very short queue. 4.2.7 RDMA Read Request Queue The RDMA Read Request Queue is the memory that holds state information for one or more RDMA Read Request Messages that have arrived, but for which the RDMA Read Response Messages have not yet been completely sent. Because potentially more than one RDMA Read Request can be outstanding at one time, the memory is modeled as a queue of bounded size. Some implementations may enable sharing of a single RDMA Read Request Queue across multiple Streams. 4.2.8 RNIC Interactions With RNIC resources and interfaces defined, it is now possible to examine the interactions supported by the generic RNIC functional interfaces through each of the 3 interfaces - Privileged Control Interface, Privileged Data Interface, and Non-Privileged Data Interface. 22.214.171.124 Privileged Control Interface Semantics Generically, the Privileged Control Interface controls the RNIC’sRNICÆs allocation, deallocation, and initialization of RNIC global resources. This includes allocation and deallocation of Stream Context Memory, Page Translation Tables, STag names, Completion Queues, RDMA Read Request Queues, and Asynchronous Event Queues. The Privileged Control Interface is also typically used for managing Non-Privileged ULP resources for the Non-Privileged ULP (and possibly for the Privileged ULP as well). This includes initialization and removal of Page Translation Table resources, and managing RNIC events (possibly managing all events for the Asynchronous Event Queue). 126.96.36.199 Non-Privileged Data Interface Semantics The Non-Privileged Data Interface enables data transfer (transmit and receive) but does not allow initialization of the Page Translation Table resources. However, once the Page Translation Table resources have been initialized, the interface may enable a specific STag mapping to be enabled and disabled by directly communicating with the RNIC, or create an STag mapping for a buffer that has been previously initialized in the RNIC. For RDMAP, transmittingULP data means sending RDMAP Send Type Messages,can be sent by using RDMAP Send Type Messages, RDMA Read Requests,Responses, and RDMA Writes. ForULP data reception, forreception through RDMAP itcan receivebe done by receiving Send Type Messages into buffers that have been posted on the Receive Queue or Shared Receive Queue. It can also receivebe done by receiving RDMA Write and RDMA Read Response Messages into buffers that have previously been exposed for external write access through advertisement of an STag. Additionally, to cause ULP data to be pulled (read) across the network, RDMAP uses an RDMA Read Request Message (which only contains RDMAP control information necessary to access the ULP buffer to be read), to cause an RDMA Read Response Message to be generated that contains the ULP data. For DDP, transmitting data means sending DDP Tagged or Untagged Messages. For data reception, for DDP it can receive Untagged Messages into buffers that have been posted on the Receive Queue or Shared Receive Queue. It can also receive Tagged DDP Messages into buffers that have previously been exposed for external write access through advertisement of an STag. Completion of data transmission or reception generally entails informing the ULP of the completed work by placing completion information on the Completion Queue. 188.8.131.52 Privileged Data Interface Semantics The Privileged Data Interface semantics are a superset of the Non-Privileged Data Transfer semantics. The interface can do everything defined in the prior section, as well as create/destroy buffer to STag mappings directly. This generally entails initialization or clearing of Page Translation Table state in the RNIC. 4.2.9 Initialization of RNIC Data Structures for Data Transfer Initialization of the mapping between an STag and a Data Buffer can be viewed in the abstract as two separate opertions:operations: a. Initialization of the allocated Page Translation Table entries with the location of the Data Buffer, and b. Initialization of a mapping from an allocated STag name to a set of Page Translation Table entry(s) or partial- entries. Note that an implementation may not have a Page Translation Table (i.e. it may support a direct mapping between an STag and a Data Buffer). In this case threats and mitigations associated with the Page Translation Table are not relevant. Initialization of the contents of the Page Translation Table can be done by either the Privileged ULP or by the Privileged Resource Manager as a proxy for the Non-Privileged ULP. By definition the Non-Privileged ULP is not trusted to directly manipulate the Page Translation Table. In general the concern is that the Non-Privileged ULP may try to maliciously initialize the Page Translation Table to access a buffer for which it does not have permission. The exact resource allocation algorithm for the Page Translation Table is outside the scope of this specification.document. It may be allocated for a specific Data Buffer, or be allocated as a pooled resource to be consumed by potentially multiple Data Buffers, or be managed in some other way. This paperdocument attempts to abstract implementation dependent issues, and focus ongroup them into higher level security issues such as resource starvation and sharing of resources between Streams. The next issue is how an STag name is associated with a Data Buffer. For the case of an Untagged Data Buffer, there is no wire visible mapping between an STag and the Data Buffer. Note that there may, in fact, be an STag which represents the buffer.buffer, if an implementation chooses to internally represent Untagged Data Buffer using STags. However, because the STag by definition is not visible on the wire, this is a local host implementation specific issue which should be analyzed in the context of a local host implementation specific security analysis, and thus is outside the scope of this paper.document. For a Tagged Data Buffer, either the Privileged ULP, the Non- Privileged ULP, or the Privileged Resource Manager acting on behalf of the Non-Privileged Resource ManagerULP may initialize a mapping from an STag to a Page Translation Table, or may have the ability to simply enable/disable an existing STag to Page Translation Table mapping. There may also be multiple STag names which map to a specific group of Page Translation Table entries (or sub-entries).sub- entries). Specific security issues with this level of flexibility are examined in Section 7.3.3 Multiple STags to access the same buffer on page 25.27. 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 which have security repercussions. This includes support for separation of Mapping an STag versesversus mapping a set of Page Translation Table entries, and support for ULPs directly manipulating STag to Page Translation Table entry mappings (verses(versus requiring access through the Privileged Resource Manager). 4.2.10 RNIC Data Transfer Interactions RNIC Data Transfer operations can be subdivided into send operations and receive operations. For send operations, there is typically a queue that enables the ULP to post multiple operationsoperation requests to send data (referred to as the Send Queue). Depending upon the implementation, Data Buffers used in the operations may or may not have Page Translation Table entries associated with them, and may or may not have STags associated with them. Because this is a local host specific implementation issue rather than a protocol issue, the security analysis of threats and mitigations is left to the host implementation. Receive operations are different for Tagged Data Buffers versesversus Untagged Data Buffers. If more than one Untagged Data Buffer can be posted by the ULP, the DDP specification requires that they be consumed in sequential order. Thus the most general implementation is that there is a sequential queue of receive Untagged Data Buffers (Receive Queue). Some implementations may also support sharing of the sequential queue between multiple Streams. In this case defining "sequential" becomes non-trivial - in general the buffers for a single streamStream are consumed from the queue in the order that they were placed on the queue, but there is no consumption order guarantee between streams.Streams. For receive Tagged Data Buffers, at some time prior to data transfer, the mapping of the STag to specific Page Translation Table entries (if present) and the mapping from the Page Translation Table entries to the Data Buffer must have been initialized (see the priorsection 4.2.9 for interaction details). 5 Trust and Resource Sharing It is assumed that in general the Local and Remote Peer are untrusted, and thus attacks by either should have mitigations in place. A separate, but related issue is resource sharing between multiple streams.Streams. If local resources are not shared, the resources are dedicated on a per Stream basis. Resources are defined in Section 4.2 Resources on page 10.12. The advantage of not sharing resources between Streams is that it reduces the types of attacks that are possible. The disadvantage of not sharing resources is that ULPs might run out of resources. Thus there can be a strong incentive for sharing resources, if the security issues associated with the sharing of resources can be mitigated. It is assumed in this paperdocument that the component that implements the mechanism to control sharing of the RNIC Engine resources is the Privileged Resource Manager. The RNIC Engine exposes its resources through the RNIC Interface to the Privileged Resource Manager. All Privileged and Non-Privileged ULPs request resources from the Resource Manager (note that by definition both the Non- Privileged and the Privileged application might try to greedily consume resources, thus creating a potential Denial of Service (DOS) attack.attack). The Resource Manager implements resource management policies to ensure fair access to resources. The Resource Manager should be designed to take into account security attacks detailed in this specification.document. Note that for some systems the Privileged Resource Manager may be implemented within the Privileged ULP. All Non-Privileged ULP interactions with the RNIC Engine that could affect other ULPs MUST be done using the Privileged Resource Manager as a proxy. All ULP resource allocation requests for scarce resources MUST also be done using a Privileged Resource Manager. The sharing of resources across Streams should be under the 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 the ULP wishes to give Local Peerlocal processes. For more discussion on types of trust models which combine partial trust and sharing of resources, see Appendix C: Partial Trust Taxonomy on page 50.52. The Privileged Resource Manager MUST NOT assume different ULPsStreams share Partial Mutual Trust unless there is a mechanism to ensure that the ULPsStreams do indeed share partial mutual trust.Partial Mutual Trust. This can be done in several ways, including explicit notification from the ULP.ULP that owns the Streams. 6 Attacker Capabilities An attacker’sattackerÆs capabilities delimit the types of attacks that attacker is able to launch. RDMAP and DDP require that the initial LLP Stream (and connection) be set up prior to transferring RDMAP/DDP Messages. AttackersThis requires at least one round-trip handshake to occur. If the attacker is not the Remote Peer that created the initial connection, then the attacker's capabilities can be segmented into send only capabilities or send and receive capabilities. Attacking with send only capabilities mustrequires the attacker to first guess the current LLP Stream parameters before they can attack RNIC resources (e.g. TCP sequence number). Attackers with both send andIf this class of attacker also has receive capabilities have presumably setupcapabilities, they are typically referred to as a valid LLP Stream,"man-in-the-middle" attacker, and thusthey have a much wider ability to attack RNIC resources. The breadth of attack is essentially the same as that of an attacking Remote Peer (i.e. the Remote Peer that setup the initial LLP Stream). 7 Attacks and Countermeasures This section describes the attacks that are possible against the RDMA system defined in Figure 1 - RDMA Security Model and the RNIC Engine resources defined in Section 4.2. The analysis includes a detailed description of each attack, what is being attacked, and a description of the countermeasures that can be taken to thwart the attack. Note that connection setup and teardown is presumed to be done in stream mode (i.e. no RDMA encapsulation of the payload), so there are no new attacks related to connection setup/teardown beyond what is already present in the LLP (e.g. TCP or SCTP). Note, however, that RDMAP/DDP parameters may be exchanged in stream mode, and if they are corrupted by an attacker unintended consequences will result. Therefore, any existing mitigations for LLP Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, or Elevation of Privilege continuescontinue to apply (and isare out of scope of this document). Thus the analysis in this section focuses on attacks that are present regardless of the LLP Stream type. The attacks are classified into five categories: Spoofing, Tampering, Information Disclosure, DenailDenial of Service (DoS) attacks, and Elevation of Privileges. Tampering is any modification of the legitimate traffic (machine internal or network). Spoofing attack is a special case of tempering;tampering where the attacker falsifies an identity of the Remote Peer (identity can be an IP address, machine name, ULP level identity etc.). 7.1 Tools for Countermeasures The tools described in this section are the primary mechanisms that can be used to provide countermeasures to potential attacks. 7.1.1 Protection Domain (PD) A Protection Domains are associated with two of theDomain (PD) is a local construct to the RDMA implementation, and never visible over the wire. Protection Domains are assigned to two of the resources of concern, Stream Context Memory and STags associated with Page Translation Table entries and data buffers. A correct implementation of a Protection Domain requires that resources which belong to a given Protection Domain can not be used on a resource belonging to another Protection Domain, because Protection Domain membership is checked by the RNIC prior to taking any action involving such a resource. Protection Domains are therefore used mainlyto ensure that an STag can only be used to access thean associated data buffer throughon one or more Streams inthat are associated with the same Protection Domain as thatthe specific STag. If an implementation chooses to not share resources between Streams, it is recommended that each Stream be associated with its own, unique Protection Domain. If an implementation chooses to allow resource sharing, it is recommended that Protection Domain be limited to the numbercollection of Streams that have Partial Mutual Trust.Trust with each other. Note that a ULP (either Privileged or Non-Privileged) can potentially have multiple Protection Domains. This could be used, for example, to ensure that multiple clients of a server do not have the ability to corrupt each other. The server would allocate a Protection Domain per client to ensure that resources covered by the Protection Domain could not be used by another (untrusted) client. 7.1.2 Limiting STag 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 Partial Mutual Trust. The scope of the STag can be measured in multiple ways. * Number of Connections and/or Streams on which the STag is valid. One way to limit the scope of the STag is to limit the connections and/or Streams that are allowed to use the STag. As noted in the previous section, use of Protection Domains appropriately can limit the scope of the STag. The analysis presented in this document assumes two mechanisms for limiting the scope of Streams for which the STag is valid: * Protection Domain scope. The STag is valid if used on any Stream within a specific Protection Domain, and is invalid if used on any Stream that is not a member of the Protection Domain. * Single Stream scope. The STag is valid on a single Stream, regardless of what the Stream association is to a Protection Domain. If used on any other Stream, it is invalid. * Limit the time an STag is valid. By Invalidating an Advertisedadvertised STag (e.g., revoking remote access to the buffers described by an STag when done with the transfer), an entire class of attacks can be eliminated. * Limit the buffer the STag can reference. Limiting the scope of an STag access to *just*just the intended portion of the ULP buffers to be exposed is critical to prevent certain forms of attacks. * Allocating and/or advertising STag numbers in an unpredictable way. If STags are allocated/advertised using an algorithm which makes it hard for the attacker to guess which STag(s) are currently in use, it makes it more difficult for an attacker to guess the correct value. As stated in the RDMAP specification [RDMAP], an invalid STag will cause the RDMAP Stream to be terminated. For the case of [DDP], at a minimum it must signal an error to the ULP,ULP. This permits the ULP to detect such attempts, and commonly thistake countermeasures. Commonly, the ULP will cause the DDP streamStream to be immediately terminated. 7.1.3 Access Rights Access Rights associated with a specific Advertisedadvertised STag or RDMAP/DDP Stream provide another mechanism for ULPs to limit the attack capabilities of the Remote Peer. The Local Peerlocal ULP can control whether a data buffer is exposed for local only, or local and remote access, and assign specific access privileges (read, write, read and write) on a per streamStream basis. For DDP, when an STag is advertised, the Remote Peer is presumably given write access rights to the data (otherwise there was not much point to the advertisement). For RDMAP, when a ULP advertises an STag, it can enable write-only, read-only, or both write and read access rights. Similarly, some ULPs may wish to provide a single buffer with different access rights on a per-Stream or per-Streambasis. For example, some Streams may have read-only access, some may have remote read and write access, while on other Streams only the Locallocal ULP/Local Peer is allowed access. 7.1.4 Limiting the Scope of the Completion Queue Completions associated with sending and receiving data, or setting up buffers for sending and receiving data, could be accumulated in a shared Completion Queue for a group of RDMAP/DDP Streams, or a specific RDMAP/DDP Stream could have a dedicated Completion Queue. Limiting Completion Queue association to one, or a small number of RDMAP/DDP Streams can prevent several forms of Denial of Service attacks.attacks, by sharply limiting the scope of the attackÆs effect. 7.1.5 Limiting the Scope of an Error To prevent a variety of attacks, it is important that an RDMAP/DDP implementation be robust in the face of errors. If an error on a specific Stream can cause other unrelated Streams to fail, then a broad class of attacks are enabled against the implementation. For example, an error on a specific RDMAP streamStream should not cause the RNIC to stop processing incoming packets, or corrupt a receive queue for an unrelated stream.Stream. 7.2 Spoofing Spoofing attacks can be launched by the Remote Peer, or by a network based attacker. A network based spoofing attack applies to all Remote Peers. Because the RDMAP Stream requires an LLP Stream to be fully initialized (e.g. for [TCP] it is in the ESTABLISHED state,state), certain types of traditional forms of wire attacks do not apply --- - an end-to-end handshake must have occurred to establish the RDMAP Stream. So, the only form of spoofing that applies is one when a remote nodean attacker can both send and receive packets. Yet even with this limitation the Stream is still exposed to the following spoofing attacks. 7.2.1 Impersonation A network based attacker can impersonate a legal RDMA/DDP peerRDMAP/DDP Peer (by spoofing a legal IP address), and establish an RDMA/DDPRDMAP/DDP Stream with the victim. End to endEnd-to-end authentication (i.e. IPsec, SSL or ULP authentication) provides protection against this attack. For additional information see Section 8, Security Services for RDMARDMAP and DDP, on page 38.40. 7.2.2 Stream Hijacking Stream hijacking happens when a network based attacker followseavesdrops the LLP connection through the Stream establishment phase, and waits until the authentication phase (if such a phase exists) is completed successfully. He canThe attacker then spoofspoofs the IP address and re-direct the Stream from the victim to its own machine. For example, an attacker can wait until an iSCSI authentication is completed successfully, and then hijack the iSCSI Stream. The best protection against this form of attack is end-to-end integrity protection and authentication, such as IPsec (see Section 8, Security Services for RDMARDMAP and DDP, on page 38),40), to prevent spoofing. Another option is to provide physical security. Discussion of physical security is out of scope for this document. Because the connection and/or Stream itself is established by the LLP, some LLPs are more difficult to hijack than others. Please see the relevant LLP documentation on security issues around connection and/or Stream hijacking. 7.2.3 Man in the Middle Attack If a network based attacker has the ability to delete, inject replay, or modify packets which will still be accepted by the LLP (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 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 enabled access, then the man-in-the-middle can use an RDMA Read operation to read the contents of the associated data buffer, perform an RDMA Write Operation to modify the contents of the associated data buffer, or invalidate the STag to disable further access to the buffer. The only countermeasure for this form of attack is to either secure the RDMAP/DDP Stream (i.e. integrity protect) or attempt to provide physical security to prevent man- in-the-middle type attacks. Thebest protection against this form of attack is end-to-end integrity protection and authentication, such as IPsec (see Section 8 Security Services for RDMARDMAP and DDP on page 38),40), to prevent spoofing or tampering. If Stream or session level authentication and integrity protection are not used, then physical protection must be employed, lest a man- in-the-middleman-in-the-middle attack canoccur, enabling spoofing and tampering. Because the connection/Stream itself is established by the LLP, some LLPs are more exposed to man-in-the-middle attack thenthan others. Please see the relevant LLP documentation on security issues around connection and/or Stream hijacking. Another approach is to restrict access to only the local subnet/link, and provide some mechanism to limit access, such as physical security or 802.1.x. This model is an extremely limited deployment scenario, and will not be further examined here. 7.2.4 Using an STag on a Different Stream 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 the Remote Peer sends an invalid STag to the Local Peer, per the DDP and RDMAP specifications, the Stream must be torn down. Thus the threat exists if aan STag has been enabled for Remote Access on one Stream and a Remote Peer is able to use it on an unrelated Stream. If the attack is successful, the attacker could potentially be able to perform either RDMA Read Operations to read the contents of the associated data buffer, perform RDMA Write Operations to modify the contents of the associated data buffer, or to Invalidateinvalidate the STag to disable further access to the buffer. An attempt by a Remote Peer to access a buffer with an STag on a different Stream in the same Protection Domain may or may not be an attack depending on whether resource sharing is intended (i.e. whether the Streams shared Partial Mutual Trust or not). For some ULPs using an STag on multiple Streams within the same Protection Domain could be desired behavior. For other ULPs attempting to use an STag on a different Stream could be considered to be an attack. Since this varies by ULP, a ULP typically would need to be able to control the scope of the STag. In the case where an implementation does not share resources between Streams (including STags), this attack can be defeated by assigning each Stream to a different Protection Domain. Before allowing remote access to the buffer, the Protection Domain of the Stream where the access attempt was made is matched against the Protection Domain of the STag. If the Protection Domains do not match, access to the buffer is denied, an error is generated, and the RDMAP Stream associated with the attacking Stream should beis terminated. For implementations that share resources between multiple Streams, it may not be practical to separate each Stream into its own Protection Domain. In this case, the ULP can still limit the scope of any of the STags to a single Stream (if it is enabling it for remote access). If the STag scope has been limited to a single Stream, any attempt to use that STag on a different Stream will result in an error, and the RDMARDMAP Stream should beis terminated. Thus for implementations that do not share STags between Streams, each Stream MUST either be in a separate Protection Domain or the scope of an STag MUST be limited to a single Stream. An additional issue may be unintended sharing of STags (i.e.RNIC MUST ensure that a bugspecific Stream in the ULP) ora bug in the Remote Peer which causesspecific Protection Domain can not access an off- by-oneSTag to be used. For additional protection, an implementation should allocate STagsin a different Protection Domain. An RNIC MUST ensure that if an STag is limited in scope to a single Stream, no other Stream can use the STag. An additional issue may be unintended sharing of STags (i.e. a bug in the ULP) or a bug in the Remote Peer which causes an off- by-one STag to be used. For additional protection, an implementation should allocate STags in such a fashion that it is difficult to predict the next allocated STag number. Allocation methodsnumber, and also ensure that STags are reused at as slow a rate as possible. Any allocation method which deterministically allocate the nextwould lead to intentional or unintentional reuse of an STag by the peer should be avoided (e.g. a method which always starts with a given STag equal to oneand monotonically increases it for each new allocation, or a method which always uses the same STag for each operation). 7.3 Tampering 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 enabled for remote write access. The types of tampering attacks that are possible are outlined in the sections that follow. 7.3.1 Buffer Overrun - RDMA Write or Read Response 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 range of the data buffer enabled for remote write access. This attack can occur even when no resources are shared across Streams. This issue can also arise if the ULP has a bug. The countermeasure for this type of attack must be in the RNIC implementation, usingleveraging the STag. When the Local Peerlocal ULP specifies to the RNIC the base address and the number of bytes in the buffer that it wishes to make accessible, the RNIC must ensure that the base and bounds check are applied to any access to the buffer referenced by the STag before the STag is enabled for access. When an RDMA data transfer operation (which includes an STag) arrives on a Stream, a base and bounds byte granularity access check must be performed to ensure the operation accesses only memory locations within the buffer described by that STag. Thus an RNIC implementation MUST ensure that a Remote Peer is not able to access memory outside of the buffer specified when the STag was enabled for remote access. 7.3.2 Modifying a Buffer After Indication This attack can occur if a Remote Peer attempts to modify the contents of an STag referenced buffer by performing an RDMA Write 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 data buffer contents are ready for use. This attack can occur even when no resources are shared across Streams. Note that a bug in a Remote Peer, or network based tampering, could also result in this problem. For example, assume the STag referenced buffer contains ULP control information as well as ULP payload, and the ULP sequence of operation is to first validate the control information and then perform operations on the control information. If the Remote Peer can perform an additional RDMA Write or RDMA Read Response (thus changing the buffer) after the validity checks have been completed but before the control data is operated on, the Remote Peer could force the ULP down operational paths that were never intended. The Local Peerlocal ULP can protect itself from this type of attack by revoking remote access when the original data transfer has completed and before it validates the contents of the buffer. The Local Peerlocal ULP can either do this by explicitly revoking remote access rights for the STag when the Remote Peer indicates the operation has completed, or by checking to make sure the Remote Peer Invalidatedinvalidated the STag through the RDMAP Remote Invalidate capability,capability (see section 7.5.5 Remote Invalidate an STag Shared on Multiple Streams on page 38 for a definition of Remote Invalidate), and if it did not, the Local Peerlocal ULP then explicitly revokes the STag remote access rights. The Local Peerlocal ULP SHOULD follow the above procedure to protect the buffer before it validates the contents of the buffer (or uses the buffer in any way). An RNIC MUST ensure that network packets using the STag for a previously advertised buffer can no longer modify the buffer after the ULP revokes remote access rights for the specific STag. 7.3.3 Multiple STags to access the same buffer See section 7.4.6 Using Multiple STags Which Alias to the Same Buffer on page 2729 for this analysis. 7.3.4 Network based modification of buffer content 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 presented above, where both the signaling and content can be modified. See Section 7.2.3 Man in the Middle Attack on page 22.24. 7.4 Information Disclosure The main potential source for information disclosure is through a local buffer that has been enabled for remote access. If the buffer can be probed by a Remote Peer on another Stream, then there is potential for information disclosure. The potential attacks that could result in unintended information disclosure and countermeasures are detailed in the following sections. 7.4.1 Probing memory outside of the buffer bounds This is essentially the same attack as described in Section 7.3.1, except an RDMA Read Request is used to mount the attack. The same countermeasure applies. 7.4.2 Using RDMA Read to Access Stale Data 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 at least remote read access rights, the Remote Peer may be able to examine the contents of the buffer before they are initialized with the correct data. In this situation, whatever contents were present in the buffer before the buffer is initialized can be viewed by the Remote Peer, if the Remote Peer performs an RDMA Read. Because of this, the Local Peerlocal ULP SHOULD ensure that no stale data is contained in the buffer before remote read access rights are granted (this can be done by zeroing the contents of the memory, for example). 7.4.3 Accessing a Buffer After the Transfer If the Remote Peer has remote read access to a buffer, and by some mechanism tells the Local Peerlocal ULP that the transfer has been completed, but the Local Peerlocal ULP does not disable remote access to the buffer before modifying the data, it is possible for the Remote Peer to retrieve the new data. This is similar to the attack defined in Section 7.3.2 Modifying a Buffer After Indication on page 25.26. The same countermeasures apply. In addition, the Local Peerlocal ULP SHOULD grant remote read access rights only for the amount of time needed to retrieve the data. 7.4.4 Accessing Unintended Data With a Valid STag If the ULP enables remote access to a buffer using an STag that references the entire buffer, but intends only a portion of the buffer to be accessed, it is possible for the Remote Peer to access the other parts of the buffer anyway. 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 to be retrieved. 7.4.5 RDMA Read into an RDMA Write Buffer One form of disclosure can occur if the access rights on the buffer enabled remote read, when only remote write access was intended. If the buffer contained ULP data, or data from a transfer on an unrelated Stream, the Remote Peer could retrieve the data through an RDMA Read operation. Note that an RNIC implementation is not required to support STags that have both read and write access. The most obvious countermeasure for this attack is to not grant remote read access if the buffer is intended to be write-only. Then the Remote Peer would not be able to retrieve data associated with the buffer. An attempt to do so would result in an error and the RDMAP Stream associated with the Stream would be terminated. 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 enable remote write access. Note that this requirement is not meant to restrict the use of zero-length RDMA Reads. Zero-length 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 received, and do not even require a valid STag, their use is permitted even if a buffer has only been enabled for write access. 7.4.6 Using Multiple STags Which Alias to the Same Buffer Multiple STags which alias to the same buffer at the same time can result in unintentional information disclosure if the STags are used by different, mutually untrusted, Remote Peers. This model applies specifically to client/server communication, where the server is communicating with multiple clients, each of which do not mutually trust each other. If only read access is enabled, then the Local Peer haslocal ULP has complete control over information disclosure. Thus a server which intended to expose the same data (i.e. buffer) to multiple clients by using multiple STags to the same buffer creates no new security issues beyond what has already been described in this document. Note that if the server did not intend to expose the same data to the clients, it should use separate buffers for each client (and separate STags). When one STag has remote read access enabled and a different STag has remote write access enabled to the same buffer, it is possible for one Remote Peer to view the contents that have been written by another Remote Peer. If both STags have remote write access enabled and the two Remote Peers do not mutually trust each other, it is possible for one Remote Peer to overwrite the contents that have been written by the other Remote Peer. Thus a ULP with multiple Remote Peers which do not share Partial Mutual Trust MUST NOT be grantedgrant write access to the same buffer through different STags. A buffer should be exposed to only one untrusted Remote Peer at a time to ensure that no information disclosure or information tampering occurs between peers. 7.4.7 Remote Node Loading Firmware 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 of Privilege in Section 184.108.40.206 for this analysis. 7.4.8 Controlling Access to PTT & STag Mapping If a Non-Privileged ULP is able to directly manipulate the RNIC Page Translation Tables (which translate from an STag to a host address), it is possible that the Non-Privileged ULP could point the Page Translation Table at an unrelated ULP’sStream's or ULPÆs buffers and thereby be able to gain access to information inof the unrelated ULP.Stream/ULP. As discussed in Section 4 Architectural Model on page 9,10, introduction of a Privileged Resource Manager to arbitrate the mapping requests is an effective countermeasure. This enables the Privileged Resource Manager to ensure a local ULP can only initialize the Page Translation Table (PTT)to point to its own buffers. Thus if Non-Privileged ULPs are supported, the Privileged Resource Manager MUST verify that the Non-Privileged ULP has the right to access a specific Data Buffer before allowing an STag for which the ULP has access rights to be associated with a specific Data Buffer. This can be done when the Page Translation Table is initialized to access the Data Buffer or when the STag is initialized to point to a group of Page Translation Table entries, or both. 7.4.9 Network based eavesdropping An attacker that is able to eavesdrop on the network can read the content of all read and write accessaccesses to the peer’sa PeerÆs buffers. To prevent information disclosure, the read/written data must be encrypted. See also Section 7.2.3 Man in the Middle Attack on page 22.24. The encryption can be done either by the ULP, or by a protocol that provides security services to the LLP (e.g. IPsec or SSL). Refer to section 8 for discussion of security services for DDP/RDMA. 7.5 Denial of Service (DOS) A DOS attack is one of the primary security risks of RDMAP. This is because RNIC resources are valuable and scarce, and many ULP environments require communication with untrusted Remote Peers. If the remote ULP can be authenticated or encrypted, clearly, the DOS profile can be reduced. For the purposes of this analysis, it is assumed that the RNIC must be able to operate in untrusted environments, which are open to DOS style attacks. Denial of service attacks against RNIC resources are not the typical unknown party spraying packets at a random host (such as a TCP SYN attack). Because the connection/Stream must be fully established, the attacker must be able to both send and receive messages over that connection/Stream, or be able to guess a valid packet on an existing RDMAP Stream. This section outlines the potential attacks and the countermeasures available for dealing with each attack. 7.5.1 RNIC Resource Consumption This section covers attacks that fall into the general category of a Local Peerlocal ULP attempting to unfairly allocate scarce (i.e. bounded) RNIC resources. The Local Peerlocal ULP may be attempting to allocate resources on its own behalf, or on behalf of a Remote Peer. Resources that fall into this category include: Protection Domains, Stream Context Memory, Translation and Protection Tables, and STag namespace. These can be due to attacks by currently active Local Peerslocal ULPs or ones that allocated resources earlier, but are now idle. This type of attack can occur regardless of whether or not resources are shared across Streams. The allocation of all scarce resources MUST be placed under the control of a Privileged Resource Manager. This allows the Privileged Resource Manager to: * prevent a Local Peerlocal ULP from allocating more than its fair share of resources. * detect if a Remote Peer is attempting to launch a DOS attack by attempting to create an excessive number of Streams (with associated resources) and take corrective action (such as refusing the request or applying network layer filters against the Remote Peer). This analysis assumes that the Resource Manager is responsible for handing out Protection Domains, and RNIC implementations will provide enough Protection Domains to allow the Resource Manager to be able to assign a unique Protection Domain for each unrelated, untrusted Local Peerlocal ULP (for a bounded, reasonable number of Local Peers).local ULPs). This analysis further assumes that the Resource Manager implements policies to ensure that untrusted Local Peerslocal ULPs are not able to consume all of the Protection Domains through a DOS attack. Note that Protection Domain consumption cannot result from a DOS attack launched by a Remote Peer, unless a Local Peerlocal ULP is acting on the Remote Peer’sPeerÆs behalf. 7.5.2 Resource Consumption By Active ULPs This section describes DOS attacks from Local and Remote Peers that are actively exchanging messages. Attacks on each RDMA NIC resource are examined and specific countermeasures are identified. Note that attacks on Stream Context Memory, Page Translation Tables, and STag namespace are covered in Section 7.5.1 RNIC Resource Consumption, so are not included here. 220.127.116.11 Multiple Streams Sharing Receive Buffers The Remote Peer can attempt to consume more than its fair share of receive data buffers (Untagged DDP(i.e. Untagged buffers orfor RDMAP buffers consumed withDDP are or Send Type Messages)Messages for RDMAP) if receive buffers are shared across multiple Streams. If resources are not shared across multiple Streams, then this attack is not possible because the Remote Peer will not be able to consume more buffers than were allocated to the Stream. The worst case scenario is that the Remote Peer can consume more receive buffers than the Local Peerlocal ULP allowed, resulting in no buffers to bebeing available, which could cause the Remote Peer’sPeerÆs Stream to the Local Peer to be torn down, and all allocated resources to be released. If local receive data buffers are shared among multiple Streams, then the Remote Peer can attempt to consume more than its fair share of the receive buffers, causing a different Stream to be short of receive buffers, thus possibly causing the other Stream to be torn down. For example, if the Remote Peer sent enough one byte Untagged Messages, they might be able to consume all local shared receive queue resources with little effort on their part. One method the Local Peer could use is to recognize that a Remote Peer is attempting to use more than its fair share of resources and terminate the Stream (causing the allocated resources to be released). However, if the Local Peer is sufficiently slow, it may be possible for the Remote Peer to still mount a denial of service attack. One countermeasure that can protect against this attack is implementing a low-water notification. The low-water notification alerts the ULP if the number of buffers in the receive queue is less than a threshold. If all of the following conditions are true, then the Local Peer or local ULP can size the amount of local receive buffers posted on the receive queue to ensure a DOS attack can be stopped. * a low-water notification is enabled, and * the Local Peer is able to bound the amount of time that it takes to replenish receive buffers, and * the Local Peer maintains statistics to determine which Remote Peer is consuming buffers. The above conditions enable the low-water notification to arrive before resources are depleted and thus the Local Peer or local ULP can take corrective action (e.g., terminate the Stream of the attacking Remote Peer). A different, but similar attack is if the Remote Peer sends a significant number of out-of-order packets and the RNIC has the ability to use the ULP buffer (i.e. the Untagged Buffer for DDP or the buffer consumed by a Send Type Message for RDMAP) as a reassembly buffer. In this case the Remote Peer can consume a significant number of ULP buffers, but never send enough data to enable the ULP buffer to be completed to the ULP. An effective countermeasure is to create a high-water notification which alerts the ULP if there is more than a specified number of receive buffers "in process" (partially consumed, but not completed). The notification is generated when more than the specified number of buffers are in process simultaneously on a specific Stream (i.e., packets have started to arrive for the buffer, but the buffer has not yet been delivered to the ULP). A different countermeasure is for the RNIC Engine to provide the capability to limit the Remote Peer’sPeerÆs ability to consume receive buffers on a per Stream basis. Unfortunately this requires a large amount of state to be tracked in each RNIC on a per Stream basis. Thus, if an RNIC Engine provides the ability to share receive buffers across multiple Streams, the combination of the RNIC Engine and the Privileged Resource Manager MUST be able to detect 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 countermeasures to detect and prevent the attack. 18.104.22.168 Local ULP Attacking a Shared CQ DOS attacks against a Shared Completion Queue (CQ) can be caused by either the Local Peer'slocal ULP or the Remote Peer if either attempts to cause more completions than its fair share of the number of entries, thus potentially starving another unrelated ULP such that no Completion Queue entries are available. A Completion Queue entry can potentially be maliciously consumed by a completion from the Send Queue or a completion from the Receive Queue. In the former, the attacker is the Local Peer'slocal ULP. In the later,latter, the attacker is the Remote Peer. A form of attack can occur where the Local Peerlocal ULPs can consume resources on the CQ. A Local Peerlocal ULP that is slow to free resources on the CQ by not reaping the completion status quickly enough could stall all other Local Peerlocal ULPs attempting to use that CQ. One of two countermeasures can be used to avoid this kind of attack. The first is to only share a CQ between ULPs that share Partial Mutual Trust. The other is to use a trusted Local Peer to act as a third party to free resources on the CQ and place the status in intermediate storage until the untrusted ULP reaps the status information.For these reasons, an RNIC MUST NOT enable sharing a CQ across ULPs that do not share partial mutual trust.Partial Mutual Trust. 22.214.171.124 Local or Remote Peer Attacking a Shared CQ For an overview of the Sharedshared CQ attack model, see Section 126.96.36.199. <TBD: add text that says if not shared there is no security threat). If you get a CQ overflow it MUST NOT affect any resource outside the scope of the current Stream.>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: * The ULP protocol allows the Remote Peer to reserve a specified number of CQ entries, possibly leaving insufficient entries for other Streams that are sharing the CQ. * If the Remote Peer orPeer, Local PeerPeer, or local ULP (or both)any combination) can attack the CQ by overwhelming the CQ with completions, then completion processing on other Streams sharing that Completion Queue can be affected (e.g. the Completion Queue overflows and stops functioning). 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 intermediary such as a Privileged Resource Manager. Unfortunately it is often unrealistic to not allow a Remote Peer to reserve CQ entries - particularly if the number of completion entries is dependent on other ULP negotiated parameters, such as the amount of buffering required by the ULP. Thus an implementation MUST implement a Privileged Resource Manager to control the allocation of CQ entries. See Section 4.1 Components on page 1011 for a definition of Privileged Resource Manager. One way that a Local or Remote Peer can attempt to overwhelm a CQ with completions is by sending minimum length RDMAP/DDP Messages to cause as many completions (receive completions for the Remote Peer, send completions for the Local Peer) per second as possible. If it is the Remote Peer attacking, and we assume that the Local Peer doesPeer's receive queue(s) do not run out of receive buffers (if they do, then this is a different attack, documented in Section 188.8.131.52 Multiple Streams Sharing Receive Buffers on page 30),31), then it might be possible for the Remote Peer to consume more than its fair share of Completion Queue entries. Depending upon the CQ implementation, this could either cause 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 generate CQ entries (if the RNIC had flow control on generation of CQ entries into the CQ). In either case, the CQ will stop functioning correctly and any Streams expecting completions on the CQ will stop functioning. This attack can occur regardless of whether all of the Streams associated with the CQ are in the same Protection Domain or are in different Protection Domains - the key issue is that the number of Completion Queue entries is less than the number of all outstanding operations that can cause a completion. The Local Peer can protect itself from this type of attack using either of the following methods: * Size the CQ to the appropriate level, as specified below (note that if the CQ currently exists, and it needs to be resized, resizing the CQ can fail,is not required to succeed in all cases, so the CQ resize should be done before sizing the Send Queue and Receive Queue on the Stream), OR * Grant fewer resources than the Remote Peer requested (not supplying the number of Receive Data Buffers requested). The proper sizing of the CQ is dependent on whether the Local Peerlocal ULP(s) will post as many resources to the various queues as the size of the queue enables or not. If the Local Peerlocal ULP(s) can be trusted to post a number of resources that is smaller than the size of the specific resource’sresourceÆs queue, then a correctly sized CQ means that the CQ is large enough to hold completion status for all of the outstanding Data Buffers (both send and receive buffers), or: CQ_MIN_SIZE = SUM(MaxPostedOnEachRQ) + SUM(MaxPostedOnEachSRQ) + SUM(MaxPostedOnEachSQ) Where: MaxPostedOnEachRQ = the maximum number of requests which can cause a completion that will be posted on a specific Receive Queue. MaxPostedOnEachSRQ = the maximum number of requests which can cause a completion that will be posted on a specific Shared Receive Queue. MaxPostedOnEachSQ = the maximum number of requests which can cause a completion that will be posted on a specific Send Queue. If the local peerULP must be able to completely fill the queues, or can not be trusted to observe a limit smaller than the queues, then the CQ must be sized to accommodate the maximum number of operations that it is possible to post at any one time. Thus the equation becomes: CQ_MIN_SIZE = SUM(SizeOfEachRQ) + SUM(SizeOfEachSRQ) + SUM(SizeOfEachSQ) Where: SizeOfEachRQ = the maximum number of requests which can cause a completion that can ever be posted on a specific Receive Queue. SizeOfEachSRQ = the maximum number of requests which can cause a completion that can ever be posted on a specific Shared Receive Queue. SizeOfEachSQ = the maximum number of requests which can cause a completion that can ever be posted on a specific Send Queue. Where MaxPosted*OnEach*Q and SizeOfEach*Q varies on a per Stream or per Shared Receive Queue basis. If the ULP is sharing a CQ across multiple streamsStreams which do not share partial mutual trust,Partial Mutual Trust, then the ULP MUST implement a mechanism to ensure that the Completion Queue can not overflow. Note that it is possible to share CQs even if the Remote Peers accessing the CQs are untrusted if either of the above two formulas are implemented. If the ULP can be trusted to not post more than MaxPostedOnEachRQ, MaxPostedOnEachSRQ, and MaxPostedOnEachSQ, then the first formula applies. If the ULP can not be trusted to obey the limit, then the second formula applies. 184.108.40.206 Attacking the RDMA Read Request Queue If RDMA Read Request Queue resources are pooled across multiple Streams, one attack is if the Local Peerlocal ULP attempts to unfairly allocate RDMA Read Request Queue resources for its Streams. For example, the Local Peer attemptsa local ULP attempts to allocate all available resources on a specific RDMA Read Request Queue for its Streams, thereby denying the resource to ULPs sharing the RDMA Read Request Queue. The same type of argument applies even if the RDMA Read Request is not shared - but a Local Peerlocal ULP attempts to allocate all of the RNICs resourceRNIC's resources when the queue is created. Thus access to interfaces that allocate RDMA Read Request Queue entries MUST be restricted to a trusted Local Peer, such as a Privileged Resource Manager. The Privileged Resource Manager SHOULD prevent a Local Peerlocal ULP from allocating more than its fair share of resources. 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 Local Peer. If the RDMA Read Request Queue is a shared resource, this could corrupt the queue. If the queue is not shared, then the worst case is that the current Stream is disabled.no longer functional (e.g. torn down). One approach to solving the shared RDMA Read Request Queue would be to create thresholds, similar to those described in Section 220.127.116.11 Multiple Streams Sharing Receive Buffers on page 30.31. A simpler approach is to not share RDMA Read Request Queue resources amoungamong Streams or enforce hard limits of consumption per Stream. Thus RDMA Read Request Queue resource consumption MUST be controlled by the Privileged Resource Manager such that RDMAP/DDP Streams which do not share Partial Mutual Trust do not share RDMA Read Request Queue resources. If the issue is a bug in the Remote Peer’sPeerÆs implementation, andbut not a malicious attack, the issue can be solved by requiring the Remote Peer’sPeerÆs RNIC to throttle RDMA Read Requests. By properly configuring the Stream at the Remote Peer through a trusted 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 Peer. If the Stream is correctly configured, and if the Remote Peer submits more requests than the Local Peer’sPeerÆs RDMA Read Request Queue can handle, the requests would be queued at the Remote Peer’sPeerÆs RNIC until previous requests complete. If the Remote Peer’sPeerÆs Stream is not configured correctly, the RDMAP Stream is terminated when more RDMA Read Requests arrive at the Local Peer than the Local Peer can handle (assuming the prior paragraph’sparagraphÆs recommendation is implemented). Thus an RNIC implementation SHOULD provide a mechanism to cap the number of outstanding RDMA Read Requests. The configuration of this limit is outside the scope of this specification.document. 7.5.3 Resource Consumption by Idle ULPs 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 Local Peer, and request dedicated resources then do no actual work. This allows the Remote Peer to be very light weight (i.e. only negotiate resources, but do no data transfer) and consumes a disproportionate amount of resources inat the server.Local Peer. A general countermeasure for this style of attack is to monitor active RDMAP Streams and if resources are getting low, reap the resources from RDMAP Streams that are not transferring data and possibly terminate the Stream. This would presumably be under administrative control. Refer to Section 7.5.1 for the analysis and countermeasures for this style of attack on the following RNIC resources: Stream Context Memory, Page Translation Tables and STag namespace. Note that some RNIC resources are not at risk of this type of attack from a Remote Peer because an attack requires the Remote Peer to send messages in order to consume the resource. Receive Data Buffers, Completion Queue, and RDMA Read Request Queue resources are examples. These resources are, however, at risk from a Local Peerlocal ULP that attempts to allocate resources, then goes idle. This could also be created if the ULP negotiates the resource levels with the Remote Peer, which causes the Local Peer to consume resources, however the Remote Peer never sends data to consume them. The general countermeasure described in this section can be used to free resources allocated by an idle Local Peer. 7.5.4 Exercise of non-optimal code paths Another form of DOS attack is to attempt to exercise data paths that can consume a disproportionate amount of resources. An example might be if error cases are handled on a "slow path" (consuming either host or RNIC computational resources), and an attacker generates excessive numbers of errors in an attempt to consume these resources. Note that for most RDMAP or DDP errors, the attacking Stream will simply be torn down. Thus for this form of attack to be effective, the Remote Peer needs to exercise data paths which do not cause the Stream to be torn down. If an RNIC implementation contains "slow paths" which do not result in the tear down of the Stream, it is recommended that an implementation provide the ability to detect the above condition and allow an administrator to act, including potentially administratively tearing down the RDMAP Stream associated with the Stream exercising data paths consuming a disproportionate amount of resources. 7.5.5 Remote Invalidate an STag Shared on Multiple Streams If a Local Peer has enabled an STag for remote access, the Remote Peer could attempt to remote invalidate the STag by using the RDMAP Send with Invalidate or Send with SE and Invalidate 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 STag; thus there are no security issues. If the STag is valid across multiple Streams, then the Remote Peer can prevent other Streams from using that STag by using the remote invalidate functionality. Thus if RDDP Streams do not share Partial Mutual Trust (i.e. the Remote Peer may attempt to remote invalidate the STag prematurely), the ULP MUST NOT enable an STag which would be valid across multiple Streams. 7.5.6 Remote Peer attacking an Unshared CQ 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 the CQ to handle completions of received buffers, and the receive buffer queue is longer than the Completion Queue, then an overflow can potentially occur. The effect on the attackerÆs Stream is catastrophic. However if an RNIC does not have the proper protections in place, then an attack to overflow the CQ can also cause corruption and/or termination of an unrelated Stream. Thus an RNIC MUST ensure that if a CQ overflows, any Streams which do not use the CQ MUST remain unaffected. 7.6 Elevation of Privilege The RDMAP/DDP Security Architecture explicitly differentiates between three levels of privilege - Non-Privileged, Privileged, and the Privileged Resource Manager. If a Non-Privileged ULP is able to elevate its privilege level to a Privileged ULP, then mapping a physical address list to an STag can provide local and remote access to any physical address location on the node. If a Privileged Mode ULP is able to promote itself to be a Resource Manager, then it is possible for it to perform denial of service type attacks where substantial amounts of local resources could be consumed. In general, elevation of privilege is a local implementation specific issue and thus outside the scope of this specification. <TBD: make more general and include authentication etc>document. There is one issue worth noting, however. If the RNIC implementation, by some insecure mechanism (or implementation defect), can enable a Remote Peer or un-trusted Local Peerlocal ULP to load firmware into the RNIC Engine, it is possible to use the RNIC to attack the host. Thus, an RNIC implementation MUST NOT enable firmware to be loaded on the RNIC Engine directly from aan untrusted local ULP or Remote Peer, unless the Remote Peer isthey are properly authenticated (by a mechanism outside the scope of this specification.document. The mechanism presumably entails authenticating that the remote ULP has the right to perform the update), and the update is done via a secure protocol, such as IPsec (See Section 8 Security Services for RDMARDMAP and DDP on page 38). Further, an implementation MUST NOT allow a Non-Privileged Local Peer to update firmware in the RNIC Engine.40). 8 Security Services for RDMARDMAP and DDP RDMARDMAP and DDP are used to control, read and write data buffers over IP networks. Therefore, the control and the data packets of these protocols are vulnerable to the spoofing, tampering and information disclosure attacks listed in Section 7. Generally speaking, Stream confidentiality protects against eavesdropping. Stream and/or session authentication and integrity protection is a counter measurement against various spoofing and tampering attacks. The effectiveness of authentication and integrity against a specific attack, depend on whether the authentication is machine level authentication (as the one provided by IPsec and SSL), or ULP authentication. 8.1 Introduction to Security Options The following security services can be applied to an RDMAP/DDP Stream: 1. Session confidentiality - protects against eavesdropping (section 7.4.9). 2. Per-packet data source authentication - protects against the following spoofing attacks: network based impersonation (section 7.2.1), Stream hijacking (section 7.2.2), and man in the middle (section 7.2.3). 3. Per-packet integrity - protects against tampering done by network based modification of buffer content (section 7.3.4) 4. Packet sequencing - protects against replay attacks, which is a special case of the above tampering attack. If an RDMAP/DDP Stream may be subject to impersonation attacks, or Stream hijacking attacks, it is recommended that the Stream be authenticated, integrity protected, and protected from replay attacks; it may use confidentiality protection to protect from eavesdropping (in case the RDMAP/DDP Stream traverses a public network). Both IPsec and SSL are capable of providing the above security services for IP and TCP traffic respectively. ULP protocols are able to provide only part of the above security services. The next sections describe the different security options. 8.1.1 Introduction to IPsec IPsec is a protocol suite which is used to secure communication at the network layer between two peers. The IPsec protocol suite is specified within the IP Security Architecture [RFC2401], IKE [RFC2409], IPsec Authentication Header (AH) [RFC2402] and IPsec Encapsulating Security Payload (ESP) [RFC2406] documents. IKE is the key management protocol while AH and ESP are used to protect IP traffic. An IPsec SA is a one-way security association, uniquely identified by the 3-tuple: Security Parameter Index (SPI), protocol (ESP/AH) and destination IP address. The parameters for an IPsec security association are typically established by a key management protocol. These include the encapsulation mode, encapsulation type, session keys and SPI values. IKE is a two phase negotiation protocol based on the modular exchange of messages defined by ISAKMP [RFC2408],and the IP Security Domain of Interpretation (DOI) [RFC2407]. IKE has two phases, and accomplishes the following functions: 1. Protected cipher suite and options negotiation - using keyed MACs and encryption and anti-replay mechanisms. 2. Master key generation - via Diffie-Hellman calculations. 3. Authentication of end-points (usually machine level authentication). 4. IPsec SA management (selector negotiation, options negotiation, create, delete, and rekeying). Items 1 through 3 are accomplished in IKE Phase 1, while item 4 is handled in IKE Phase 2. IKE phase 1 defines four authentication methods; three of them require both sides to have certified signature or encryption public keys; the forth requirefourth requires the side to exchange out-of-band a secret random string - called pre-shared-secret (PSS). An IKE Phase 2 negotiation is performed to establish both an inbound and an outbound IPsec SA. The traffic to be protected by an IPsec SA is determined by a selector which has been proposed by the IKE initiator and accepted by the IKE Responder. The IPsec SA selector can be a "filter" or traffic classifier, defined as the 5-tuple: <Source IP address, Destination IP address, transport protocol (e.g. UDP/SCTP/TCP), Source port, Destination port>. The successful establishment of a IKE Phase-2 SA results in the creation of two uni-directional IPsec SAs fully qualified by the tuple <Protocol (ESP/AH), destination address, SPI>. The session keys for each IPsec SA are derived from a master key, typically via a MODP Diffie-Hellman computation. Rekeying of an existing IPsec SA pair is accomplished by creating two new IPsec SAs, making them active, and then optionally deleting the older IPsec SA pair. Typically the new outbound SA is used immediately, and the old inbound SA is left active to receive packets for some locally defined time, perhaps 30 seconds or 1 minute. Optionally, rekeying can use Diffie-HelmanDiffie-Hellman for keying material generation. 8.1.2 Introduction to SSL Limitations on RDMAP SSL and TLS [RFC 2246] provide Stream authentication, integrity and confidentiality for TCP based ULPs. SSL supports one-way (server only) or mutual certificates based authentication. There are at least two limitations that make SSL underneath RDMAP less appropriate thenthan IPsec for DDP/RDMA security: 1. The maximum length supported by the TLS record layer protocol is 2^14 bytes - longer packets must be fragmented (as a comparison, the maximal length of an IPsec packet is determined by the maximum length of an IP packet). 2. SSL is a connection oriented protocol. If a stream cipher or block cipher in CBC mode is used for bulk encryption, then a packet can be decrypted only after all the packets preceding it have already arrived. If SSL is used to protect DDP/RDMA traffic, then SSL must gather all out-of-order packets before RDMAP/DDP can place them into the ULP buffer, which might cause a significant decrease in its efficiency. 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 still occur by modifying the RDMAP/DDP header to incorrectly place the data into the wrong buffer, thus effectively corrupting the data stream. 8.1.3 ULPs Which Provide Security ULPs which provide integrated security but wish to leverage lower-layer protocol security should be aware of security concerns around correlating a specific channel’schannelÆs security mechanisms to the authentication performed by the ULP. See [NFSv4CHANNEL] for additional information on a promising approach called "channel binding". From [NFSv4CHANNEL]: "The concept of channel bindings allows applications to prove that the end-points of two secure channels at different network layers are the same by binding authentication at one channel to the session protection at the other channel. The use of channel bindings allows applications to delegate session protection to lower layers, which may significantly improve performance for some applications." 8.2 Requirements for IPsec Encapsulation of DDP The IP Storage working group has spent significant time and effort to define the normative IPsec requirements for IP Storage [RFC3723]. Portions of that specification are applicable to a wide variety of protocols, including the RDDP protocol suite. In order to not replicate this effort, an RNIC implementation MUST follow the requirements defined in RFC3723 Section 2.3 and Section 5, including the associated normative references for those sections. Additionally, since IPsec acceleration hardware may only be able to handle a limited number of active IKE Phase 2 SAs, Phase 2 delete messages may be sent for idle SAs, as a means of keeping the number of active Phase 2 SAs to a minimum. The receipt of an IKE Phase 2 delete message MUST NOT be interpreted as a reason for tearing down an DDP/RDMA Stream. Rather, it is preferable 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 potential for continually bringing Streams up and down. Note that there are serious security issues if IPsec is not implemented end-to-end. For example, if IPsec is implemented as a tunnel in the middle of the network, any hosts between the peerPeer and the IPsec tunneling device can freely attack the unprotected Stream. 9 Security considerations This entire specificationdocument is focused on security considerations. 10 References 10.1 Normative References [RFC2828] Shirley, R., "Internet Security Glossary", FYI 36, RFC 2828, May 2000. [DDP] Shah, H., J. Pinkerton, R.Recio, and P. Culley, "Direct Data Placement over Reliable Transports", Internet-Draft draft-ietf-rddp-ddp-01.txt, February 2003.Work in Progress draft-ietf-rddp-ddp-04.txt, December 2004. [RDMAP] Recio, R., P. Culley, D. Garcia, J. Hilland, "An RDMA Protocol Specification", Internet-Draft draft-ietf-rddp- rdmap-01.txt, February 2003.Work in Progress draft-ietf-rddp-rdmap-03.txt, December 2004. [RFC3723] Aboba B., et al, "Securing Block Storage Protocols over IP", Internet draft (work in progress), RFC3723, April 2004. [SCTP] R. Stewart et al., "Stream Control Transmission Protocol", RFC 2960, October 2000. [TCP] Postel, J., "Transmission Control Protocol - DARPA Internet Program Protocol Specification", RFC 793, September 1981. 10.2 Informative References [IPv6-Trust] Nikander, P., J.Kempf, E. Nordmark, "IPv6 Neighbor Discovery Trust Models and threats", Internet-Draft draft- ietf-send-psreq-01.txt, January 2003.Informational RFC, RFC3756, May 2004. [NFSv4CHANNEL] Williams, N., "On the Use of Channel Bindings to Secure Channels", Internet-Draft draft-ietf-nfsv4-channel- bindings-02.txt, July 2004. 11 Appendix A: ULP Issues for RDDP Client/Server Protocols This section is a normative appendix to the specificationdocument that is focused on client/server ULP implementation requirements to ensure a secure server implementation. The prior sections outlined specific attacks and their countermeasures. This section summarizes the attacks and countermeasures that have been defined in the prior section which 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 communicate with many clients which do not necessarily have a trust relationship with each otherother, and ensure that each client can not attack another client through server interactions. Further, the server may wish to use multiple Streams to communicate with a specific client, and those Streams may share mutual trust. Note that this section assumes a compliant RNIC and Privileged Resource Manager implementation - thus it focuses specifically on ULP server (e.g. application) implementation issues. All of the prior section's details on attacks and countermeasures apply to the server.server, thus requirements which are repeated in this section use non-normative "must", "should", "may". In some cases normative SHOULD statements for the ULP infrom the main body of this document are made MUST statements for the ULP server because the operating conditions can be refined to make the motives for a SHOULD inapplicable. If a prior SHOULD is changed to a MUST in this section, it is explicitly noted.noted and it uses upper-case normative statements. The following list summarizes the releventrelevant attacks that clients can mount on the shared server, by re-stating the previous normative statements to be client/server specific: * Spoofing * Sections 7.2.1 to 7.2.3. For protection against many forms of spoofing attacks, enable IPsec. * Section 7.2.4 Using an STag on a Different Streamspecific. Note that each client/server ULP may employ explicit RDMA operations (RDMA Read, RDMA Write) in differing fashions. Therefore where appropriate, "Local ULP", "Local Peer" and "Remote Peer" are used in place of "server" or "client", in order to retain full generality of each requirement. * Spoofing * Sections 7.2.1 to 7.2.3. For protection against many forms of spoofing attacks, enable IPsec. * Section 7.2.4 Using an STag on a Different Stream on page 23.24. To ensure that one client can not access another client's data via use of the other client's STag, the server ULP MUSTmust either scope an STag to a single Stream or use a unique Protection Domain per client. If a single client has multiple streamsStreams that share Partial Mutual Trust, then the STag can be shared between the associated Streams by using a single Protection Domain amoungamong the associated Streams (see section 8.1.3 ULPs Which Provide Security on page 42 for additional issues). To prevent unintended sharing of STags within the associated Streams, a server ULP SHOULDshould use STags in such a fashion that it is difficult to predict the next allocated STag number. * Tampering * 7.3.2 Modifying a Buffer After Indication on page 25.26. Before the serverlocal ULP operates on a buffer that was written by the Remote Peer using an RDMA Write or RDMA Read, the serverlocal ULP MUST ensure the thebuffer can no longer be modifiedmodified, by invalidating the STag for remote access (note that this is stronger than the SHOULD in section 7.3.2). This can either be done explicitly by revoking remote access rights for the STag when the clientRemote Peer indicates the operation has completed, or by checking to make sure the clientRemote Peer Invalidated the STag through the RDMAP Invalidate capability, and if it did not, the Local Peerlocal ULP then explicitly revokesrevoking the STag remote access rights. * Information Disclosure * 7.4.2 Using RDMA Read to Access Stale Data on page 26. A27. In a general purpose server environment there is no compelling rationale to not require a buffer to be initialized before remote read is enabled (and an enormous down side of unintentionally sharing data). Thus a local ULP MUST (this is stronger than the SHOULD in section 7.4.2) ensure that no stale data is contained in a buffer before remote read access rights are granted to a clientRemote Peer (this can be done by zeroing the contents of the memory, for example). * 7.4.3 Accessing a Buffer After the Transfer on page 26.28. This mitigation is already covered by section 7.3.2 (above). * 7.4.4 Accessing Unintended Data With a Valid STag on page 26.28. The ULP server MUSTmust set the base and bounds of the buffer when the STag is initialized to expose only the data to be retrieved. * 7.4.5 RDMA Read into an RDMA Write Buffer on page 27.28. If a serverpeer only intends a buffer to be exposed for remote write access, it MUSTmust set the access rights to the buffer to only enable remote write access. * 7.4.6 Using Multiple STags Which Alias to the Same Buffer on page 27.29. The requirement in section 7.2.4 (above) mitigates this attack. A server buffer is exposed to only one client at a time to ensure that no information disclosure or information tampering occurs between peers. * 7.4.9 Network based eavesdropping on page 28. Enable IPsec30. Confidentiality services should be enabled by the ULP if this threat is a concern. * Denial of Service * 18.104.22.168 Multiple Streams Sharing Receive Buffers on page 30.31. ULP memory footprint size can be important for some server ULPs. If a server ULP is expecting significant network traffic from multiple clients, using a receive buffer queue per Stream where there is a large number of Streams can consume substantial amounts of memory. Thus a receive queue that can be shared by multiple Streams is attractive. However, because of the attacks outlined in this section, sharing a single receive queue between multiple clients MUSTmust only be done if thea mechanism is in place to ensure one client can'tcannot consume too manyreceive buffers is enabled.in excess of its limits, as defined by each ULP. For multiple Streams within a single client ULP (which presumably shared partial mutual trust)Partial Mutual Trust) this added overhead does not have tomay be enabled.avoided. * 22.214.171.124 Local ULP Attacking a Shared CQ on page 31. <TBD>The33. The normative RNIC mitigations were *require the RNIC MUST NOTto not enable sharing of a CQ across Streams that belong to different Protection Domains. * A ULP SHOULD NOT share a CQ between Streams whichif the local ULPs do not share Partial Mutual Trust. BecauseThus while the attack is a local serverULP attacking another server ULP, * 126.96.36.199 Remote Peer Attacking a Shared CQ on page 32. There are two mitigations specified inis not allowed to enable this section -feature in an unsafe mode, if the two local ULPs share Partial Tutual Trust, they must behave in the following manner: 1) The sizing of the completion queue is based on the size of the receive queue and send queues as documented in 188.8.131.52 Local or Remote Peer Attacking a Shared CQ on page 33. 2) The local ULP ensures that CQ entries are reaped frequently enough to adhere to section 184.108.40.206's rules. * 220.127.116.11 Local or Remote Peer Attacking a Shared CQ on page 33. There are two mitigations specified in this section - one requires a worst-case size of the CQ, and can be implemented entirely within the Privileged Resource Manager. The second approach requires cooperation with the local ULP server (to not post too many buffers), and enables a smaller CQ to be used. In some server environments, partial trust of the server ULP (but not the clients) is acceptable, thus the smaller CQ fully mitigates the remote attacker. In other environments, the local server ULP could also contain untrusted elements which can attack the local machine (or have bugs). In those environments, the worst-case size of the CQ must be used. * 18.104.22.168 The section requires a serverÆs Privileged Resource Manager to not enableallow sharing of RDMA Read Request Queues across multiple Streams that do not share partial mutual trust.Partial Mutual Trust, for a ULP which performs RDMA Read operations to server buffers. However, because the server ULP knows best which of its Streams share partial mutual trust,Partial Mutual Trust, this requirement can be reflected back to the ULP. The ULP (i.e. server) requirement in this case is that it MUST NOT requestallow RDMA Read Request Queues to be shared between ULPs which do not have partial mutual trust.Partial Mutual Trust. * 7.5.5 Remote Invalidate an STag Shared on Multiple Streams on page 37.38. This mitigation is already covered by section 7.3.2 (above). 12 Appendix B: Summary of RNIC and ULP Implementation Requirements This appendix is informative. Below is a summary of implementation requirements for the RNIC: * 5 Trust and Resource Sharing * 7.2.4 Using an STag on a Different Stream * 7.3.1 Buffer Overrun - RDMA Write or Read Response * 7.3.2 Modifying a Buffer After Indication * 7.4.8 Controlling Access to PTT & STag Mapping * 7.5.1 RNIC Resource Consumption * 22.214.171.124 Multiple Streams Sharing Receive Buffers * 126.96.36.199 Local ULP Attacking a Shared CQ * 188.8.131.52 Local or Remote Peer Attacking a Shared CQ * 184.108.40.206 Attacking the RDMA Read Request Queue * 7.5.4 Exercise of non-optimal code paths7.5.6 Remote Peer attacking an Unshared CQ on page 38. * 7.6 Elevation of Privilege 39 * 8.2 Requirements for IPsec Encapsulation of DDP Below is a summary of implementation requirements for the ULP above the RNIC: * 7.2.4 Using an STag on a Different Stream * 7.3.2 Modifying a Buffer After Indication * 7.4.2 Using RDMA Read to Access Stale Data * 7.4.3 Accessing a Buffer After the Transfer * 7.4.4 Accessing Unintended Data With a Valid STag * 7.4.5 RDMA Read into an RDMA Write Buffer * 7.4.6 Using Multiple STags Which Alias to the Same Buffer * 7.4.9 Network based eavesdropping * 220.127.116.11 Local ULP Attacking a Shared CQ * 7.5.5 Remote Invalidate an STag Shared on Multiple Streams 13 Appendix C: Partial Trust Taxonomy This appendix is informative. Partial Trust is defined as when one party is willing to assume 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. Note that the partially trusted peer may attempt a different set of attacks. This may be appropriate for many ULPs where any adverse effects of the betrayal is easily confined and does not place other clients or ULPs at risk. The Trust Models described in this section have three primary distinguishing characteristics. The Trust Model refers to a Local Peerlocal ULP and Remote Peer, which are intended to be the local and remote ULP instances communicating via RDMA/DDP. * Local Resource Sharing (yes/no) - When local resources are shared, they are shared across a grouping of RDMAP/DDP Streams. If local resources are not shared, the resources are dedicated on a per Stream basis. Resources are defined in Section 4.2 - Resources on page 11.12. The advantage of not sharing resources between Streams is that it reduces the types of attacks that are possible. The disadvantage is that ULPs might run out of resources. * Local Partial Trust (yes/no) - Local Partial Trust is determined based on whether the local grouping of RDMAP/DDP Streams (which typically equates to one ULP or group of ULPs) mutually trust each other to not perform a specific set of attacks. * Remote Partial Trust (yes/no) - The Remote Partial Trust level is determined based on whether the Local Peerlocal ULP of a specific RDMAP/DDP Stream partially trusts the Remote Peer of the Stream (see the definition of Partial Trust in Section 3 Introduction). Not all of the combinations of the trust characteristics are expected to be used by ULPs. This paperdocument specifically analyzes five ULP Trust Models that are expected to be in common use. The Trust Models are as follows: * NS-NT - Non-Shared Local Resources, no Local Trust, no Remote Trust - typically a server ULP that wants to run in the safest mode possible. All attack mitigations are in place to ensure robust operation. * NS-RT - Non-Shared Local Resources, no Local Trust, Remote Partial Trust - typically a peer-to-peer ULP, which has, by some method outside of the scope of this specification,document, authenticated the Remote Peer. Note that unless some form of key based authentication is used on a per RDMA/DDP Stream basis, it may not be possible be possible for man-in-the-middle attacks to occur. See section 8, Security Services for RDMARDMAP and DDP on page 38.40. * S-NT - Shared Local Resources, no Local Trust, no Remote Trust - typically a server ULP that runs in an untrusted environment where the amount of resources required is either too large or too dynamic to dedicate for each RDMAP/DDP Stream. * S-LT - Shared Local Resources, Local Partial Trust, no Remote Trust - typically a ULP, which provides a session layer and uses multiple Streams, to provide additional throughput or fail-over capabilities. All of the Streams within the local ULP partially trust each other, but do not trust the Remote Peer. This trust model may be appropriate for embedded environments. * S-T - Shared Local Resources, Local Partial Trust, Remote Partial Trust - typically a distributed application, such as a distributed database application or a High Performance Computer (HPC) application, which is intended to run on a cluster. Due to extreme resource and performance requirements, the application typically authenticates with all of its peers and then runs in a highly trusted environment. The application peers are all in a single application fault domain and depend on one another to be well-behaved when accessing data structures. If a trusted Remote Peer has an implementation defect that results in poor behavior, the entire application could be corrupted. Models NS-NT and S-NT above are typical for Internet networking - neither Local Peerslocal ULPs nor the Remote Peer is trusted. Sometimes optimizations can be done that enable sharing of Page Translation Tables across multiple Local Peers,local ULPs, thus Model S-LT can be advantageous. Model S-T is typically used when resource scaling across a large parallel ULP makes it infeasible to use any other model. Resource scaling issues can either be due to performance around scaling or because there simply are not enough resources. Model NS-RT is probably the least likely model to be used, but is presented for completeness. 14 Author’sAuthorÆs Addresses James Pinkerton Microsoft Corporation One Microsoft Way Redmond, WA. 98052 USA Phone: +1 (425) 705-5442 Email: firstname.lastname@example.org Ellen Deleganes Intel Corporation MS JF5-355 2111 NE 25th Ave. Hillsboro, OR 97124 USA Phone: +1 (503) 712-4173 Email: email@example.com Sara Bitan Microsoft Corporation Email: firstname.lastname@example.org 15 Acknowledgments Allyn Romanow Cisco Systems 170 W Tasman Drive San Jose, CA 95134 USA Phone: +1 408 525 8836 Email: email@example.com Catherine Meadows Naval Research Laboratory Code 5543 Washington, DC 20375 Email: firstname.lastname@example.org Patricia Thaler Agilent Technologies, Inc. 1101 Creekside Ridge Drive, #100 M/S-RG10 Roseville, CA 95678 Phone: +1-916-788-5662 email: email@example.com James Livingston NEC Solutions (America), Inc. 7525 166th Ave. N.E., Suite D210 Redmond, WA 98052-7811 Phone: +1 (425) 897-2033 Email: firstname.lastname@example.org John Carrier Adaptec, Inc. 691 S. Milpitas Blvd. Milpitas, CA 95035 USA Phone: +1 (360) 378-8526 Email: email@example.com Caitlin Bestler Email: firstname.lastname@example.org Bernard Aboba Microsoft Corporation One Microsoft Way Redmond, WA. 98052 USA Phone: +1 (425) 706-6606 Email: email@example.com 16 Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved.(2004). This document and translations of it may be copied and furnishedis subject to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided thatthe above copyright notice and this paragraph are included on all such copiesrights, licenses and derivative works. 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