draft-ietf-lisp-threats-03.txt   draft-ietf-lisp-threats-04.txt 
Network Working Group D. Saucez Network Working Group D. Saucez
Internet-Draft INRIA Internet-Draft INRIA
Intended status: Informational L. Iannone Intended status: Informational L. Iannone
Expires: April 19, 2013 Telecom ParisTech Expires: August 29, 2013 Telecom ParisTech
O. Bonaventure O. Bonaventure
Universite catholique de Louvain Universite catholique de Louvain
October 16, 2012 February 25, 2013
LISP Threats Analysis LISP Threats Analysis
draft-ietf-lisp-threats-03.txt draft-ietf-lisp-threats-04.txt
Abstract Abstract
This document analyzes the threats against the security of the This document analyzes the potential threats against the security of
Locator/Identifier Separation Protocol (LISP) and proposes a set of the Locator/Identifier Separation Protocol (LISP) if deployed in the
recommendations to mitigate some of the identified security risks. Internet. This document proposes a set of recommendations to
mitigate the identified security risks and keep a security level
equivalent to what is observed in the Internet today (i.e., without
LISP). By following the recommendations of this draft a LISP
deployment can achieve a security level that is comparable to the
existing Internet architecture.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 19, 2013. This Internet-Draft will expire on August 29, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4
3. On-path Attackers . . . . . . . . . . . . . . . . . . . . . . 4 3. On-path Attackers . . . . . . . . . . . . . . . . . . . . . . 4
4. Off-Path Attackers: Reference Environment . . . . . . . . . . 4 4. Off-Path Attackers: Reference Environment . . . . . . . . . . 5
5. Data-Plane Threats . . . . . . . . . . . . . . . . . . . . . . 6 5. Data-Plane Threats . . . . . . . . . . . . . . . . . . . . . . 6
5.1. EID-to-RLOC Database Threats . . . . . . . . . . . . . . . 6 5.1. EID-to-RLOC Database Threats . . . . . . . . . . . . . . . 7
5.2. EID-to-RLOC Cache Threats . . . . . . . . . . . . . . . . 7 5.2. EID-to-RLOC Cache Threats . . . . . . . . . . . . . . . . 7
5.2.1. EID-to-RLOC Cache poisoning . . . . . . . . . . . . . 7 5.2.1. EID-to-RLOC Cache poisoning . . . . . . . . . . . . . 7
5.2.2. EID-to-RLOC Cache overflow . . . . . . . . . . . . . . 9 5.2.2. EID-to-RLOC Cache overflow . . . . . . . . . . . . . . 9
5.3. Attacks not leveraging on the LISP header . . . . . . . . 9 5.3. Attacks not leveraging on the LISP header . . . . . . . . 10
5.4. Attacks leveraging on the LISP header . . . . . . . . . . 10 5.4. Attacks leveraging on the LISP header . . . . . . . . . . 10
5.4.1. Attacks using the Locator Status Bits . . . . . . . . 10 5.4.1. Attacks using the Locator Status Bits . . . . . . . . 10
5.4.2. Attacks using the Map-Version bit . . . . . . . . . . 11 5.4.2. Attacks using the Map-Version bit . . . . . . . . . . 12
5.4.3. Attacks using the Nonce-Present and the Echo-Nonce 5.4.3. Attacks using the Nonce-Present and the Echo-Nonce
bits . . . . . . . . . . . . . . . . . . . . . . . . . 12 bits . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.4.4. Attacks using the ID Instance bits . . . . . . . . . . 13 5.4.4. Attacks using the Instance ID bits . . . . . . . . . . 14
6. Control Plane Threats . . . . . . . . . . . . . . . . . . . . 13 6. Control Plane Threats . . . . . . . . . . . . . . . . . . . . 14
6.1. Attacks with Map-Request messages . . . . . . . . . . . . 13 6.1. Attacks with Map-Request messages . . . . . . . . . . . . 14
6.2. Attacks with Map-Reply messages . . . . . . . . . . . . . 15 6.2. Attacks with Map-Reply messages . . . . . . . . . . . . . 16
6.3. Gleaning Attacks . . . . . . . . . . . . . . . . . . . . . 16 6.3. Gleaning Attacks . . . . . . . . . . . . . . . . . . . . . 17
7. Threats concerning Interworking . . . . . . . . . . . . . . . 17 7. Threats concerning Interworking . . . . . . . . . . . . . . . 18
8. Threats with Malicious xTRs . . . . . . . . . . . . . . . . . 18 8. Threats with Malicious xTRs . . . . . . . . . . . . . . . . . 19
9. Security of the Proposed Mapping Systems . . . . . . . . . . . 21 9. Security of the Proposed Mapping Systems . . . . . . . . . . . 23
9.1. LISP+ALT . . . . . . . . . . . . . . . . . . . . . . . . . 21 9.1. LISP+ALT . . . . . . . . . . . . . . . . . . . . . . . . . 23
9.2. LISP-DDT . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.2. LISP-DDT . . . . . . . . . . . . . . . . . . . . . . . . . 24
10. Threats concerning LISP-MS . . . . . . . . . . . . . . . . . . 23 10. Threats concerning LISP-MS . . . . . . . . . . . . . . . . . . 25
10.1. Map Server . . . . . . . . . . . . . . . . . . . . . . . . 23 10.1. Map Server . . . . . . . . . . . . . . . . . . . . . . . . 25
10.2. Map Resolver . . . . . . . . . . . . . . . . . . . . . . . 24 10.2. Map Resolver . . . . . . . . . . . . . . . . . . . . . . . 26
11. Suggested Recommendations . . . . . . . . . . . . . . . . . . 26 11. Security Recommendations . . . . . . . . . . . . . . . . . . . 28
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
13. Security Considerations . . . . . . . . . . . . . . . . . . . 28 13. Security Considerations . . . . . . . . . . . . . . . . . . . 30
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
15.1. Normative References . . . . . . . . . . . . . . . . . . . 28 15.1. Normative References . . . . . . . . . . . . . . . . . . . 31
15.2. Informative References . . . . . . . . . . . . . . . . . . 29 15.2. Informative References . . . . . . . . . . . . . . . . . . 31
Appendix A. Document Change Log . . . . . . . . . . . . . . . . . 30 Appendix A. Document Change Log . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction 1. Introduction
The Locator/ID Separation Protocol (LISP) is defined in The Locator/ID Separation Protocol (LISP) is defined in [RFC6830].
[I-D.ietf-lisp]. The present document aims at assessing the security The present document assesses the security level and identifies
level and identifying security threats in the LISP specification. As security threats in the LISP specification if LISP is deployed in the
a result of the performed analysis, the document also proposes some Internet (i.e., a public non-trustable environment). As a result of
recommendations aiming at improving LISP's resiliency against off- the performed analysis, the document determines the severity of the
path attackers. threats and proposes recommendations to reach the same level of
security in LISP than in Internet today (e.g., without LISP).
The document is composed of two main parts: the first discussing the The document is composed of three main parts: the first discussing
LISP data-plane; while the second discussing the LISP control-plane. the LISP data-plane; while the second discussing the LISP control-
plane. The final part summarizes the recommendations to prevent the
identified threats.
The LISP data-plane consists of LISP packet encapsulation, The LISP data-plane consists of LISP packet encapsulation,
decapsulation, and forwarding and includes the EID-to-RLOC Cache and decapsulation, and forwarding and includes the EID-to-RLOC Cache and
EID-to-RLOC Database data structures used to perform these EID-to-RLOC Database data structures used to perform these
operations. operations.
The LISP control-plane consists in the mapping distribution system, The LISP control-plane consists in the mapping distribution system,
which can be one of the mapping distribution systems proposed so far which can be one of the mapping distribution systems proposed so far
(e.g., [I-D.ietf-lisp], [I-D.fuller-lisp-ddt], [I-D.ietf-lisp-alt], (e.g., [RFC6830], [I-D.ietf-lisp-ddt], [RFC6836], [RFC6833],
[I-D.ietf-lisp-ms], [I-D.meyer-lisp-cons], and [I-D.lear-lisp-nerd]), [I-D.meyer-lisp-cons], and [RFC6837]), and the Map-Request, Map-
and the Map-Request, Map-Reply, Map-Register, and Map-Notification Reply, Map-Register, and Map-Notification messages.
messages.
This document does not consider all the possible uses of LISP as This document does not consider all the possible uses of LISP as
discussed in [I-D.ietf-lisp]. The document focuses on LISP unicast, discussed in [RFC6830]. The document focuses on LISP unicast,
including as well LISP Interworking [I-D.ietf-lisp-interworking], including as well LISP Interworking [RFC6832], LISP-MS [RFC6833],
LISP-MS [I-D.ietf-lisp-ms], LISP Map-Versioning LISP Map-Versioning [RFC6834], and briefly considering the ALT
[I-D.ietf-lisp-map-versioning], and briefly considering the ALT mapping system described in [RFC6836] and the Delegated Database Tree
mapping system described in [I-D.ietf-lisp-alt] and the Delegated mapping system described in [I-D.ietf-lisp-ddt]. The reading of
Database Tree mapping system described in [I-D.fuller-lisp-ddt]. The these documents is a prerequisite for understanding the present
reading of these documents is a prerequisite for understanding the document.
present document.
Unless otherwise stated, the document assumes a generic IP service Unless otherwise stated, the document assumes a generic IP service
and does not discuss the difference, from a security viewpoint, and does not discuss the difference, from a security viewpoint,
between using IPv4 or IPv6. between using IPv4 or IPv6.
This document has identified several threats on LISP in the case of
public deployments. However, most of the threats can be prevented
with careful deployment and configuration. Moreover, several threats
are introduced by optimization techniques that can be deactivated in
public deployments of LISP without alteration of its functioning as
these techniques are designed for LISP deployments in private
trustable environments. Finally, this document has not identified
any threats that would require a change in the LISP protocol or
architecture.
2. Definition of Terms 2. Definition of Terms
The present document does not introduce any new term, compared to the Severity level: this document specifies the severity level of every
main LISP specification. For a complete list of terms please refer identified threat. We identified four severity levels for the
to [I-D.ietf-lisp]. threats.
Level 0: the threat is not introduced by LISP and is equivalent to
what is encountered without LISP.
Level 1: the threat is introduced by LISP but can be neutralized by
configuration or deployment techniques, i.e., LISP protocol and
architecture does not need to be reconsidered for public
deployment.
Level 2: the threat is introduced by LISP but can be avoided by
deactivating the feature in public deployment.
Level 3: the threat is introduced by LISP and cannot be avoided
without changing the LISP specification or architecture.
The present document does not introduce any other new term, compared
to the main LISP specification. For a complete list of terms please
refer to [RFC6830].
3. On-path Attackers 3. On-path Attackers
On-path attackers are attackers that are able to capture and modify On-path attackers are attackers that are able to capture and modify
all the packets exchanged between an Ingress Tunnel Router (ITR) and all the packets exchanged between an Ingress Tunnel Router (ITR) and
an Egress Tunnel Router (ETR). To cope with such an attacker, an Egress Tunnel Router (ETR). To cope with such an attacker,
cryptographic techniques such as those used by IPSec ([RFC4301]) are cryptographic techniques such as those used by IPSec ([RFC4301]) are
required. We do not consider that LISP has to cope with such kind of required. As with IP, LISP relies on higher layer cryptography to
attackers. secure packet payloads from on path attacks, so we do not consider
on-path attackers in this document.
Mobile IP has also considered time-shifted attacks from on-path Mobile IP has also considered time-shifted attacks from on-path
attackers. A time-shifted attack is an attack where the attacker is attackers. A time-shifted attack is an attack where the attacker is
temporarily on the path between two communicating hosts. While it is temporarily on the path between two communicating hosts. While it is
on-path, the attacker sends specially crafted packets or modifies on-path, the attacker sends specially crafted packets or modifies
packets exchanged by the communicating hosts in order to disturb the packets exchanged by the communicating hosts in order to disturb the
packet flow (e.g., by performing a man in the middle attack). An packet flow (e.g., by performing a man in the middle attack). An
important issue for time-shifted attacks is the duration of the important issue for time-shifted attacks is the duration of the
attack once the attacker has left the path between the two attack once the attacker has left the path between the two
communicating hosts. We do not consider time-shifted attacks in this communicating hosts. We do not consider time-shifted attacks in this
skipping to change at page 6, line 7 skipping to change at page 6, line 17
assigned IP address. SA stands for Spoofing Attacker. assigned IP address. SA stands for Spoofing Attacker.
NSA is an off-path attacker that is only able to send packets whose NSA is an off-path attacker that is only able to send packets whose
source address is its assigned IP address. NSA stands for Non source address is its assigned IP address. NSA stands for Non
Spoofing Attacker. Spoofing Attacker.
It should be noted that with LISP, packet spoofing is slightly It should be noted that with LISP, packet spoofing is slightly
different than in the current Internet. Generally the term "spoofed different than in the current Internet. Generally the term "spoofed
packet" indicates a packet containing a source IP address that is not packet" indicates a packet containing a source IP address that is not
the one of the actual originator of the packet. Since LISP uses the one of the actual originator of the packet. Since LISP uses
encapsulation, the spoofed address can be in the outer header as well encapsulation, the spoofed address could be in the outer header as
as in the inner header, this translates in two types of spoofing: well as in the inner header, this translates in two types of
spoofing:
EID Spoofing: the originator of the packet puts in it a spoofed EID. EID Spoofing: the originator of the packet puts in it a spoofed EID.
The packet will be normally encapsulated by the ITR of the site The packet will be normally encapsulated by the ITR of the site
(or a PITR if the source site is not LISP enabled). (or a PITR if the source site is not LISP enabled).
RLOC Spoofing: the originator of the packet generates directly a RLOC Spoofing: the originator of the packet generates directly a
LISP-encapsulated packet with a spoofed source RLOC. LISP-encapsulated packet with a spoofed source RLOC.
Note that the two types of spoofing are not mutually exclusive, Note that the two types of spoofing are not mutually exclusive,
rather all combinations are possible and can be used to perform rather all combinations are possible and could be used to perform
different kind of attacks. different kind of attacks.
In the reference environment, both SA and NSA attackers are capable In the reference environment, both SA and NSA attackers are capable
of sending LISP encapsulated data packets and LISP control packets. of sending LISP encapsulated data packets and LISP control packets.
This means that SA is able to perform both RLOC and EID spoofing This means that SA is able to perform both RLOC and EID spoofing
while NSA can only perform EID spoofing. They may also send other while NSA can only perform EID spoofing. They may also send other
types of IP packets such as ICMP messages. We assume that both types of IP packets such as ICMP messages. We assume that both
attackers can query the LISP mapping system (e.g., through a public attackers can query the LISP mapping system (e.g., through a public
Map Resolver) to obtain the mappings for both HA and HB. Map Resolver) to obtain the mappings for both HA and HB.
5. Data-Plane Threats 5. Data-Plane Threats
This section discusses threats and attacks related to the LISP data- This section discusses threats and attacks related to the LISP data-
plane. More precisely, we discuss the operations of encapsulation, plane. More precisely, we discuss the operations of encapsulation,
decapsulation, and forwarding as well as the content of the EID-to- decapsulation, and forwarding as well as the content of the EID-to-
RLOC Cache and EID-to-RLOC Database as specified in the original LISP RLOC Cache and EID-to-RLOC Database as specified in the original LISP
document ([I-D.ietf-lisp]). document ([RFC6830]).
We start considering the two main data structures of LISP, namely the We start considering the two main data structures of LISP, namely the
EID-to-RLOC Database and the EID-to-RLOC Cache. Then, we look at the EID-to-RLOC Database and the EID-to-RLOC Cache. Then, we look at the
data plane attacks that can be performed by a spoofing off-path data plane attacks that can be performed by a spoofing off-path
attacker (SA) and discuss how they can be mitigated by LISP xTRs. In attacker (SA) and discuss how they can be mitigated by LISP xTRs. In
this analysis, we assume that the LR1 and LR2 (resp. LR3 and LR4) this analysis, we assume that the LR1 and LR2 (resp. LR3 and LR4)
xTRs maintain an EID-to-RLOC Cache that contains the required mapping xTRs maintain an EID-to-RLOC Cache that contains the required mapping
entries to allow HA and HB to exchange packets. entries to allow HA and HB to exchange packets.
5.1. EID-to-RLOC Database Threats 5.1. EID-to-RLOC Database Threats
The EID-to-RLOC Database on each xTR maintains the set of mappings The EID-to-RLOC Database on each xTR maintains the set of mappings
related to the EID-Prefixes that are "behind" the xTR. Where related to the EID-Prefixes that are "behind" the xTR. Where
"behind" means that at least one of the xTR's globally visible IP "behind" means that at least one of the xTR's globally visible IP
addresses is a RLOC for those EID-Prefixes. addresses is a RLOC for those EID-Prefixes.
As described in [I-D.ietf-lisp], the EID-to-RLOC Database content is As described in [RFC6830], the EID-to-RLOC Database content is
determined by configuration. This means that the only way to attack determined by configuration. This means that the only way to attack
this data structure is by gaining privileged access to the xTR. As this data structure is by gaining privileged access to the xTR. As
such, it is out of the scope of LISP to propose any mechanism to such, it is out of the scope of LISP to propose any mechanism to
protect routers and, hence, it is no further analyzed in this protect routers and, hence, it is no further analyzed in this
document. document.
Severity level 0.
5.2. EID-to-RLOC Cache Threats 5.2. EID-to-RLOC Cache Threats
A key component of the overall LISP architecture is the EID-to-RLOC The EID-to-RLOC Cache (also called the Map-Cache) is the data
Cache. The EID-to-RLOC Cache is the data structure that stores the structure that stores a copy of the mappings retrieved from a remote
bindings between EID and RLOC (namely the "mappings") to be used ETR's mapping database via the LISP control plane. Attacks against
later on. Attacks against this data structure can happen either when this data structure could happen either when the mappings are first
the mappings are first installed in the cache (see also Section 6) or installed in the cache (see also Section 6) or by corrupting
by corrupting (poisoning) the mappings already present in the cache. (poisoning) the mappings already present in the cache.
Severity level 2. The severity level of EID-to-RLOC Cache Threats
depends on the attack vector as described below.
5.2.1. EID-to-RLOC Cache poisoning 5.2.1. EID-to-RLOC Cache poisoning
The content of the EID-to-RLOC Cache can be poisoned by spoofing LISP The content of the EID-to-RLOC Cache could be poisoned by spoofing
encapsulated packets. Examples of EID-to-RLOC Cache poisoning are: LISP encapsulated packets. Examples of EID-to-RLOC Cache poisoning
are:
Fake mapping: The cache contains entirely fake mappings that do not Fake mapping: The cache contains entirely fake mappings that do not
originate from an authoritative mapping server. This can be originate from an authoritative mapping server. This could be
achieved either through gleaning as described in Section 6.3 or achieved either through gleaning as described in Section 6.3 or
by attacking the control-plane as described in Section 6. by attacking the control-plane as described in Section 6.
EID Poisoning: The EID-Prefix in a specific mapping is not owned by EID Poisoning: The EID-Prefix in a specific mapping is not owned by
the originator of the entry. Similarly to the previous case, the originator of the entry. Similarly to the previous case,
this can be achieved either through gleaning as described in this could be achieved either through gleaning as described in
Section 6.3 or by attacking the control-plane as described in Section 6.3 or by attacking the control-plane as described in
Section 6. Section 6.
EID redirection/RLOC poisoning: The EID-Prefix in the mapping is not EID redirection/RLOC poisoning: The EID-Prefix in the mapping is not
bound to (located by) the set of RLOCs present in the mapping. bound to (located by) the set of RLOCs present in the mapping.
This can result in packets being redirected elsewhere, This could result in packets being redirected elsewhere,
eavesdropped, or even blackholed. Note that not necessarily eavesdropped, or even black-holed. Note that not necessarily
all RLOCs are fake/spoofed. The attack works also if only part all RLOCs are fake/spoofed. The attack works also if only part
of the RLOCs, the highest priority ones, is compromised. of the RLOCs, the highest priority ones, is compromised.
Again, this can be achieved either through the gleaning as Again, this could be achieved either through the gleaning as
described in Section 6.3 or by attacking the control-plane as described in Section 6.3 or by attacking the control-plane as
described in Section 6. described in Section 6.
Reachability poisoning: The reachability information stored in the Reachability poisoning: The reachability information stored in the
mapping could be poisoned, redirecting the packets to a subset mapping could be poisoned, redirecting the packets to a subset
of the RLOCs (or even stopping it if locator status bits are of the RLOCs (or even stopping it if locator status bits are
all set to 0). If reachability information is not verified all set to 0). If reachability information is not verified
through the control-plane this attack can be simply achieved by through the control-plane this attack could be achieved by
sending a spoofed packet with swapped or all locator status sending a spoofed packet with swapped or all locator status
bits reset. The same result can be obtained by attacking the bits reset. The same result could be obtained by attacking the
control-plane as described in Section 6. Depending on how the control-plane as described in Section 6. Depending on how the
RLOC reachability information is stored on the router, the RLOC reachability information is stored on the router, the
attack can impact only one mapping or all the mappings that attack could impact only one mapping or all the mappings that
share the same RLOC. share the same RLOC.
Traffic Engineering information poisoning: The LISP protocol defines Traffic Engineering information poisoning: The LISP protocol defines
two attributes associated to each RLOC in order to perform two attributes associated to each RLOC in order to perform
inbound Traffic Engineering (TE), namely priority and weight. inbound Traffic Engineering (TE), namely priority and weight.
By injecting fake TE attributes, the attacker is able to break By injecting fake TE attributes, the attacker is able to break
load balancing policies and concentrate all the traffic on a load balancing policies and concentrate all the traffic on a
single RLOC or put more load on a RLOC than what is expected, single RLOC or put more load on a RLOC than what is expected,
creating congestion. It is even possible to block the traffic creating congestion. It is even possible to block the traffic
if all the priorities are set to 255 (special value indicating if all the priorities are set to 255 (special value indicating
not to use the RLOC). Corrupting the TE attributes can be not to use the RLOC). Corrupting the TE attributes could be
achieved by attacking the control-plane as described in achieved by attacking the control-plane as described in
Section 6. Section 6.
Mapping TTL poisoning: The LISP protocol associates a Time-To-Live Mapping TTL poisoning: The LISP protocol associates a Time-To-Live
to each mapping that, once expired, allows to delete a mapping to each mapping that, once expired, allows to delete a mapping
from the EID-to-RLOC Cache (or forces a Map-Request/Map-Reply from the EID-to-RLOC Cache (or forces a Map-Request/Map-Reply
exchange to refresh it if still needed). By injecting fake TTL exchange to refresh it if still needed). By injecting fake TTL
values, an attacker can either shrink the EID-to-RLOC Cache values, an attacker could either shrink the EID-to-RLOC Cache
(using very short TTL), thus creating an excess of cache miss (using very short TTL), thus creating an excess of cache miss
causing a DoS on the mapping system, or it can increase the causing a DoS on the mapping system, or it could increase the
size of the cache by putting very high TTL values, up to a size of the cache by putting very high TTL values, up to a
cache overflow (see Section 5.2.2). Corrupting the TTL can be cache overflow (see Section 5.2.2). Corrupting the TTL could
achieved by attacking the control-plane as described in be achieved by attacking the control-plane as described in
Section 6. Long TTL can be use in fake mappings to increase Section 6. Long TTL could be used in fake mappings to increase
attack duration. attack duration.
Instance ID poisoning: The LISP protocol allows using a 24-bit Instance ID poisoning: The LISP protocol allows using a 24-bit
identifier to select the forwarding table to use on the identifier to select the forwarding table to use on the
decapsulating ETR to forward the decapsulated packet. By decapsulating ETR to forward the decapsulated packet. By
spoofing this attribute the attacker is able to redirect or spoofing this attribute the attacker might cause traffic to be
blackhole inbound traffic. Corrupting the Instance ID either dropped or decapsulated and then placed into the
attribute can be achieved by attacking the control-plane as incorrect VRF at the destination ETR. Corrupting the Instance
described in Section 6. ID attribute could be achieved by attacking the control-plane
as described in Section 6.
Map-Version poisoning: The LISP protocol allows associating a Map-Version poisoning: The LISP protocol offers the option to
version number to mappings ([I-D.ietf-lisp-map-versioning]). associate a version number to mappings ([RFC6834]). The LISP
The LISP header can transport source and destination map- header can transport source and destination map-versions,
versions, describing which version of the mapping have been describing which version of the mapping have been used to
used to select the source and the destination RLOCs of the LISP select the source and the destination RLOCs of the LISP
encapsulated packet. By spoofing this attribute the attacker encapsulated packet. By spoofing this attribute the attacker
is able to trigger Map-Request on the receiving ETR. is able to trigger Map-Request on the receiving ETR.
Corrupting the Map-Version attribute can be achieved either by Corrupting the Map-Version attribute could be achieved either
attacking the control-plane as described in Section 6 or by by attacking the control-plane as described in Section 6 or by
using spoofed packets as described in Section 5.4.2. using spoofed packets as described in Section 5.4.2.
If the above listed attacks succeed, the attacker has the means of If the ITR's map-cache is compromised (likely via compromising the
controlling the traffic. LISP control-plane) it is possible that traffic in the data-plane may
be redirected (encapsulated to the wrong destination) a or dropped by
the ITR.
If data-plane redirection is of a critical concern, then deploying
some sort of IPSEC or TLS based security on a layer above LISP (just
like you would on top of IP) is recommended.
5.2.2. EID-to-RLOC Cache overflow 5.2.2. EID-to-RLOC Cache overflow
Depending on how the EID-to-RLOC Cache is managed (e.g., Least Depending on how the EID-to-RLOC Cache is managed (e.g., Least
Recently Used - LRU vs. Least Frequently Used - LFU) and depending on Recently Used - LRU vs. Least Frequently Used - LFU) and depending on
its size, an attacker can try to fill the cache with fake mappings. its size, an attacker could try to fill the cache with fake mappings.
Once the cache is full, some mappings will be replaced by new fake Once the cache is full, some mappings will be replaced by new fake
ones, causing traffic disruption. ones, causing traffic disruption.
This can be achieved either through gleaning as described in This could be achieved either through gleaning as described in
Section 6.3 or by attacking the control-plane as described in Section 6.3 or by attacking the control-plane as described in
Section 6. Section 6.
Another way to generate an EID-to-RLOC Cache overflow is by injecting Another way to generate an EID-to-RLOC Cache overflow is by injecting
mapping with a fake and very large TTL value. In this case the cache mapping with a fake and very large TTL value. In this case the cache
will keep a large amount of mappings ending with a completely full will keep a large amount of mappings ending with a completely full
cache. This type of attack can also be performed through the cache. This type of attack could also be performed through the
control-plane. control-plane.
5.3. Attacks not leveraging on the LISP header 5.3. Attacks not leveraging on the LISP header
We first consider an attacker that sends packets without exploiting We first consider an attacker that sends packets without exploiting
the LISP header, i.e., with the N, L, E, V, and I bits reset the LISP header, i.e., with the N, L, E, V, and I bits reset
([I-D.ietf-lisp]). ([RFC6830]).
To inject a packet in the HA-HB flow, a spoofing off-path attacker To inject a packet in the HA-HB flow, a spoofing off-path attacker
(SA) can send a LISP encapsulated packet whose source is set to LR1 (SA) could send a LISP encapsulated packet whose source is set to LR1
or LR2 and destination LR3 or LR4. The packet will reach HB as if or LR2 and destination LR3 or LR4. The packet will reach HB as if
the packet was sent by host HA. This is not different from today's the packet was sent by host HA. This is not different from today's
Internet where a spoofing off-path attacker may inject data packets Internet where a spoofing off-path attacker may inject data packets
in any flow. Several existing techniques can be used by hosts to in any flow. Several existing techniques could be used by hosts to
prevent such attacks from affecting established flows, e.g., prevent such attacks from affecting established flows, e.g.,
[RFC4301] and [I-D.ietf-tcpm-tcp-security]. [RFC4301] and [I-D.ietf-tcpm-tcp-security].
On the other hand, a non-spoofing off-path attacker (NSA) can only On the other hand, a non-spoofing off-path attacker (NSA) could only
send a packet whose source address is set to its assigned IP address. send a packet whose source address is set to its assigned IP address.
The destination address of the encapsulated packet can be LR3 or LR4. The destination address of the encapsulated packet could be LR3 or
When the LISP ETR that serves HB receives the encapsulated packet, it LR4. When the LISP ETR that serves HB receives the encapsulated
can consult its EID-to-RLOC Cache and verify that NSA is not a valid packet, it can consult its EID-to-RLOC Cache and verify that NSA is
source address for LISP encapsulated packets containing a packet sent not a valid source address for LISP encapsulated packets containing a
by HA. This verification is only possible if the ETR already has a packet sent by HA. This verification is only possible if the ETR
valid mapping for HA. Otherwise, and to avoid such data packet already has a valid mapping for HA. Otherwise, and to avoid such
injection attacks, the LISP ETR should reject the packet and possibly data packet injection attacks, the LISP ETR should reject the packet
query the mapping system to obtain a mapping for the encapsulated and possibly query the mapping system to obtain a mapping for the
source EID (HA). encapsulated source EID (HA).
Severity level 1: use well known anti-spoofing techniques and
configure ETRs to verify the that RLOCs and EIDs are consistent with
the entries in the EID-to-RLOC Cache.
5.4. Attacks leveraging on the LISP header 5.4. Attacks leveraging on the LISP header
The main LISP document [I-D.ietf-lisp] defines several flags that The main LISP document [RFC6830] defines several flags that modify
modify the interpretation of the LISP header in data packets. In the interpretation of the LISP header in data packets. In this
this section, we discuss how an off-path attacker could exploit this section, we discuss how an off-path attacker could exploit this LISP
LISP header. header.
Severity level 2. The severity level of attacks leveraging on the
LISP header depends on the attack vector as described below.
5.4.1. Attacks using the Locator Status Bits 5.4.1. Attacks using the Locator Status Bits
When the L bit is set to 1, it indicates that the second 32-bits When the L bit is set to 1, it indicates that the second 32-bits
longword of the LISP header contains the Locator Status Bits. In longword of the LISP header contains the Locator Status Bits. In
this field, each bit position reflects the status of one of the RLOCs this field, each bit position reflects the status of one of the RLOCs
mapped to the source EID found in the encapsulated packet. In mapped to the source EID found in the encapsulated packet. In
particular, a packet with the L bit set and all Locator Status Bits particular, a packet with the L bit set and all Locator Status Bits
set to zero indicates that none of the locators of the encapsulated set to zero indicates that none of the locators of the encapsulated
source EID are reachable. The reaction of a LISP ETR that receives source EID are reachable. The reaction of a LISP ETR that receives
such a packet is not clearly described in [I-D.ietf-lisp]. such a packet is not clearly described in [RFC6830].
A spoofing off-path attacker (SA) can send a data packet with the L A spoofing off-path attacker (SA) could send a data packet with the L
bit set to 1, all Locator Status Bits set to zero, a spoofed source bit set to 1, all Locator Status Bits set to zero, a spoofed source
RLOC (e.g. LR1), destination LR3, and containing an encapsulated RLOC (e.g. LR1), destination LR3, and containing an encapsulated
packet whose source is HA. If LR3 blindly trusts the Locator Status packet whose source is HA. If LR3 blindly trusts the Locator Status
Bits of the received packet it will set LR1 and LR2 as unreachable, Bits of the received packet it will set LR1 and LR2 as unreachable,
possibly disrupting ongoing communication. possibly disrupting ongoing communication.
Locator Status Bits can be blindly trusted only in secure Locator Status Bits could be blindly trusted only in secure
environments. In the general unsecured Internet environment, the environments. In the general unsecured Internet environment, the
safest practice for xTRs is to confirm the reachability change safest practice for xTRs is to confirm the reachability change
through the control plane (e.g., RLOC probing). In the above through the control plane (e.g., RLOC probing). In the above
example, LR3 should note that something has changed in the Locator example, LR3 should note that something has changed in the Locator
Status Bits and query the mapping system (assuming it is trusted) in Status Bits and query the mapping system (assuming it is trusted) in
order to confirm status of the RLOCs of the source EID. order to confirm status of the RLOCs of the source EID.
A similar attack could occur by setting only one Locator Status Bit A similar attack could occur by setting only one Locator Status Bit
to 1, e.g., the one that corresponds to the source RLOC of the to 1, e.g., the one that corresponds to the source RLOC of the
packet. packet.
skipping to change at page 11, line 8 skipping to change at page 11, line 40
in Section 5.3, if the xTR accepts the packet without checking the in Section 5.3, if the xTR accepts the packet without checking the
EID-to-RLOC Cache for a mapping that binds the source EID and the EID-to-RLOC Cache for a mapping that binds the source EID and the
source RLOC of the received packet, then the same observation like source RLOC of the received packet, then the same observation like
for the spoofing attacker (SA) apply with the difference that instead for the spoofing attacker (SA) apply with the difference that instead
of complete disruption, the traffic will flow through only one RLOC, of complete disruption, the traffic will flow through only one RLOC,
possibly resulting in a DoS attack. possibly resulting in a DoS attack.
Otherwise, if the xTR does make the check through the EID-to-RLOC Otherwise, if the xTR does make the check through the EID-to-RLOC
Cache, it should reject the packet because its source address is not Cache, it should reject the packet because its source address is not
one of the addresses listed as RLOCs for the source EID. one of the addresses listed as RLOCs for the source EID.
Nevertheless, in this case a Map-Request should be sent, which can be Nevertheless, in this case a Map-Request should be sent, which could
used to perform Denial of Service attacks. Indeed an attacker can be used to perform Denial of Service attacks. Indeed an attacker
frequently change the Locator Status Bits in order to trigger a large could frequently change the Locator Status Bits in order to trigger a
amount of Map-Requests. Rate limitation, as described in large amount of Map-Requests. Rate limitation, as described in
[I-D.ietf-lisp], does not allow sending high number of such a [RFC6830], if implemented in a very simple way a single bucket for
request, resulting in the attacker saturating the rate with these all triggered control plane messages, does not allow sending high
spoofed packets. number of such a request, resulting in the attacker saturating the
rate with these spoofed packets.
Severity level 2: to avoid any risk, Locator Status Bits should be
deactivated in public deployments of LISP. Deactivating LSB does not
reduce LISP functionality.
5.4.2. Attacks using the Map-Version bit 5.4.2. Attacks using the Map-Version bit
The Map-Version bit is used to indicate whether the low-order 24 bits The optional Map-Version bit is used to indicate whether the low-
of the first 32 bits longword of the LISP header contain a Source and order 24 bits of the first 32 bits longword of the LISP header
Destination Map-Version. When a LISP ETR receives a LISP contain a Source and Destination Map-Version. When a LISP ETR
encapsulated packet with the Map-Version bit set to 1, the following receives a LISP encapsulated packet with the Map-Version bit set to
actions are taken: 1, the following actions are taken:
o It compares the Destination Map-Version found in the header with o It compares the Destination Map-Version found in the header with
the current version of its own mapping, in the EID-to-RLOC the current version of its own mapping, in the EID-to-RLOC
Database, for the destination EID found in the encapsulated Database, for the destination EID found in the encapsulated
packet. If the received Destination Map-Version is smaller (i.e., packet. If the received Destination Map-Version is smaller (i.e.,
older) than the current version, the ETR should apply the SMR older) than the current version, the ETR should apply the SMR
procedure described in [I-D.ietf-lisp] and send a Map-Request with procedure described in [RFC6830] and send a Map-Request with the
the SMR bit set. SMR bit set.
o If a mapping exists in the EID-to-RLOC Cache for the source EID, o If a mapping exists in the EID-to-RLOC Cache for the source EID,
then it compares the Map-Version of that entry with the Source then it compares the Map-Version of that entry with the Source
Map-Version found in the header of the packet. If the stored Map-Version found in the header of the packet. If the stored
mapping is older (i.e., the Map-Version is smaller) than the mapping is older (i.e., the Map-Version is smaller) than the
source version of the LISP encapsulated packet, the xTR should source version of the LISP encapsulated packet, the xTR should
send a Map-Request for the source EID. send a Map-Request for the source EID.
A spoofing off-path attacker (SA) could use the Map-Version bit to A spoofing off-path attacker (SA) could use the Map-Version bit to
force an ETR to send Map-Request messages. The attacker can retrieve force an ETR to send Map-Request messages. The attacker could
the current source and destination Map-Version for both HA and HB. retrieve the current source and destination Map-Version for both HA
Based on this information, it can send a spoofed packet with an older and HB. Based on this information, it could send a spoofed packet
Source Map-Version or Destination Map-Version. If the size of the with an older Source Map-Version or Destination Map-Version. If the
Map-Request message is larger than the size of the smallest LISP- size of the Map-Request message is larger than the size of the
encapsulated packet that could trigger such a message, this could smallest LISP-encapsulated packet that could trigger such a message,
lead to amplification attacks (see Section 6.1). However, this could lead to amplification attacks (see Section 6.1). However,
[I-D.ietf-lisp] recommends to rate limit the Map-Request messages [RFC6830] recommends to rate limit the Map-Request messages that are
that are sent by an xTR. This prevents the amplification attack, but sent by an xTR. This prevents the amplification attack, but there is
there is a risk of Denial of Service attack if an attacker sends a risk of Denial of Service attack if an attacker sends packets with
packets with Source and Destination Map-Versions that frequently Source and Destination Map-Versions that frequently change. In this
change. In this case, the ETR could consume its entire rate by case, and depending on the implementation of the rate limitation
sending Map-Request messages in response to these spoofed packets. policy, the ETR might consume its entire rate by sending Map-Request
messages in response to these spoofed packets.
A non-spoofing off-path attacker (NSA) cannot success in such an A non-spoofing off-path attacker (NSA) could not success in such an
attack if the destination xTR rejects the LISP encapsulated packets attack if the destination xTR rejects the LISP encapsulated packets
that are not sent by one of the RLOCs mapped to the included source that are not sent by one of the RLOCs mapped to the included source
EID. If it is not the case, the attacker can be able to perform EID. If it is not the case, the attacker could be able to perform
attacks concerning the Destination Map Version number as for the attacks concerning the Destination Map Version number as for the
spoofing off-path attacker (SA). spoofing off-path attacker (SA).
Severity level 1: the correct deployment of anti-spoofing and rate
limitation techniques prevents the attacks leveraging on the Map-
Version.
5.4.3. Attacks using the Nonce-Present and the Echo-Nonce bits 5.4.3. Attacks using the Nonce-Present and the Echo-Nonce bits
The Nonce-Present and Echo-Nonce bits are used when verifying the The Nonce-Present and Echo-Nonce bits are used when verifying the
reachability of a remote ETR. Assume that LR3 wants to verify that reachability of a remote ETR. Assume that LR3 wants to verify that
LR1 receives the packets that it sends. LR3 can set the Echo-Nonce LR1 receives the packets that it sends. LR3 can set the Echo-Nonce
and the Nonce-Present bits in LISP data encapsulated packets and and the Nonce-Present bits in LISP data encapsulated packets and
include a random nonce in these packets. Upon reception of these include a random nonce in these packets. Upon reception of these
packets, LR1 will store the nonce sent by LR3 and echo it when it packets, LR1 will store the nonce sent by LR3 and echo it when it
returns LISP encapsulated data packets to LR3. returns LISP encapsulated data packets to LR3.
skipping to change at page 13, line 14 skipping to change at page 14, line 9
will consider the ETR not reachable. The success of this test will will consider the ETR not reachable. The success of this test will
of course depend on the ratio between the amount of packets sent by of course depend on the ratio between the amount of packets sent by
the legitimate ITR and the spoofing off-path attacker (SA). the legitimate ITR and the spoofing off-path attacker (SA).
Packets sent by a non-spoofing off-path attacker (NSA) can cause Packets sent by a non-spoofing off-path attacker (NSA) can cause
similar problem if no check is done with the EID-to-RLOC Cache (see similar problem if no check is done with the EID-to-RLOC Cache (see
Section 5.3 for the EID-to-RLOC Cache check). Otherwise, if the Section 5.3 for the EID-to-RLOC Cache check). Otherwise, if the
check is performed the packets will be rejected by the ETR that check is performed the packets will be rejected by the ETR that
receives them and cannot cause problems. receives them and cannot cause problems.
5.4.4. Attacks using the ID Instance bits Severity level 2: to avoid any problem, echo nonce should be
deactivated. Deactivating echo-nonce does not reduce LISP
functionality as it is an optimization for symmetric data flow path
and because other techniques exist to test the reachability of a
RLOC.
5.4.4. Attacks using the Instance ID bits
LISP allows to carry in its header a 24-bits value called "Instance LISP allows to carry in its header a 24-bits value called "Instance
ID" and used on the ITR to indicate which private Instance ID has ID" and used on the ITR to indicate which private Instance ID has
been used for encapsulation, while on the ETR can be used to select been used for encapsulation, while on the ETR can be used to select
the forwarding table used for forwarding the decapsulated packet. the forwarding table used for forwarding the decapsulated packet.
Even if an off-path attacker could randomly guess a valid Instance ID Even if an off-path attacker could randomly guess a valid Instance ID
value, there is no LISP specific problem. Obviously the attacker value, there is no LISP specific problem. Obviously the attacker
could be now able to reach hosts that are only reachable through the could be now able to reach hosts that are only reachable through the
routing table identified by the attacked Instance ID, however, end- routing table identified by the attacked Instance ID, however, end-
system security is out of the scope of this document. Nevertheless, system security is out of the scope of this document. Nevertheless,
access lists can be configured to protect the network from Instance access lists can be configured to protect the network from Instance
ID based attacks. ID based attacks.
Severity level 1: the correct deployment of access control lists and
firewalls prevent the attacks leveraging on the Instance ID.
6. Control Plane Threats 6. Control Plane Threats
In this section, we discuss the different types of attacks that can In this section, we discuss the different types of attacks that could
occur when an off-path attacker sends control plane packets. We occur when an off-path attacker sends control plane packets. We
focus on the packets that are sent directly to the ETR and do not focus on the packets that are sent directly to the ETR and do not
analyze the particularities of a LISP mapping system. The LISP+ALT analyze the particularities of a LISP mapping system. The LISP+ALT
and LISP-DDT mapping systems are discussed in Section 9. and LISP-DDT mapping systems are discussed in Section 9.
Severity level 2. The severity level of attacks on the LISP control-
plane depends on the attack vector as described below.
6.1. Attacks with Map-Request messages 6.1. Attacks with Map-Request messages
An off-path attacker could send Map-Request packets to a victim ETR. An off-path attacker could send Map-Request packets to a victim ETR.
In theory, a Map-Request packet is only used to solicit an answer and In theory, a Map-Request packet is only used to solicit an answer and
as such it should not lead to security problems. However, the LISP as such it should not lead to security problems. However, the LISP
specification [I-D.ietf-lisp] contains several particularities that specification [RFC6830] contains several particularities that could
could be exploited by an off-path attacker. be exploited by an off-path attacker.
The first possible exploitation is the P bit. The P bit is used to The first possible exploitation is the P bit. The P bit is used to
probe the reachability of remote ETRs in the control plane. In our probe the reachability of remote ETRs. In our reference environment,
reference environment, LR3 could probe the reachability of LR1 by LR3 could probe the reachability of LR1 by sending a Map-Request with
sending a Map-Request with the P bit set. LR1 would reply by sending the P bit set. LR1 would reply by sending a Map-Reply message with
a Map-Reply message with the P bit set and the same nonce as in the the P bit set and the same nonce as in the Map-Request message.
Map-Request message.
A spoofing off-path attacker (SA) could use the P bit to force a A spoofing off-path attacker (SA) could use the P bit to force a
victim ETR to send a Map-Reply to the spoofed source address of the victim ETR to send a Map-Reply to the spoofed source address of the
Map-Request message. As the Map-Reply can be larger than the Map- Map-Request message. As the Map-Reply can be larger than the Map-
Request message, there is a risk of amplification attack. Request message, there is a risk of amplification attack.
Considering only IPv6 addresses, a Map-Request can be as small as 40 Considering only IPv6 addresses, a Map-Request can be as small as 40
bytes, considering one single ITR address and no Mapping Protocol bytes, considering one single ITR address and no Mapping Protocol
Data. The Map-Reply instead has a size of O(12 + (R * (28 + N * Data. The Map-Reply instead has a size of O(12 + (R * (28 + N *
24))) bytes, where N is the maximum number of RLOCs in a mapping and 24))) bytes, where N is the maximum number of RLOCs in a mapping and
R the maximum number of records in a Map-Reply. Since up to 255 R the maximum number of records in a Map-Reply. Since up to 255
skipping to change at page 15, line 7 skipping to change at page 16, line 13
of a Map-Request message with the SMR bit, an ETR must return to the of a Map-Request message with the SMR bit, an ETR must return to the
source of the Map-Request message a Map-Request message to retrieve source of the Map-Request message a Map-Request message to retrieve
the corresponding mapping. This raises similar problems as the P bit the corresponding mapping. This raises similar problems as the P bit
discussed above except that as the Map-Request messages are smaller discussed above except that as the Map-Request messages are smaller
than Map-Reply messages, the risk of amplification attacks is than Map-Reply messages, the risk of amplification attacks is
reduced. This is not true anymore if the ETR append to the Map- reduced. This is not true anymore if the ETR append to the Map-
Request messages its own Map-Records. This mechanism is meant to Request messages its own Map-Records. This mechanism is meant to
reduce the delay in mapping distribution since mapping information is reduce the delay in mapping distribution since mapping information is
provided in the Map-Request message. provided in the Map-Request message.
Severity level 1: the correct deployment of anti-spoofing and rate
limitation techniques prevents the attacks leveraging the Map-Request
message.
Furthermore, appending Map-Records to Map-Request messages represents Furthermore, appending Map-Records to Map-Request messages represents
a major security risk since an off-path attacker could generate a a major security risk since an off-path attacker could generate a
(spoofed or not) Map-Request message and include in the Map-Reply (spoofed or not) Map-Request message and include in the Map-Reply
portion of the message mapping for EID prefixes that it does not portion of the message mapping for EID prefixes that it does not
serve. This could lead to various types of redirection and denial of serve. This could lead to various types of redirection and denial of
service attacks. An xTR should not process the Map-Records service attacks. An xTR should not process the Map-Records
information that it receives in a Map-Request message. information that it receives in a Map-Request message. As it is a
performance optimization, we recommend to deactivate this
functionality in public LISP deployments.
Severity level 2: to avoid any risk, appending Map-Records to Map-
Request messages should be deactivated in public deployments of LISP.
Deactivating appending Map-Records to Map-Request messages does not
reduce LISP functionality.
6.2. Attacks with Map-Reply messages 6.2. Attacks with Map-Reply messages
In this section we analyze the attacks that could occur when an off- In this section we analyze the attacks that could occur when an off-
path attacker sends directly Map-Reply messages to ETRs without using path attacker sends directly Map-Reply messages to ETRs without using
one of the proposed LISP mapping systems. one of the proposed LISP mapping systems.
There are two different types of Map-Reply messages: There are two different types of Map-Reply messages:
Positive Map-Reply: These messages contain a Map-Record binding an Positive Map-Reply: These messages contain a Map-Record binding an
EID-Prefix to one or more RLOCs. EID-Prefix to one or more RLOCs.
Negative Map-Reply: These messages contain a Map-Record for an EID- Negative Map-Reply: These messages contain a Map-Record for an EID-
Prefix with an empty locator-set and specifying an action, Prefix with an empty locator-set and specifying an action,
which may be either Drop, Natively forward, or Send Map- which may be either Drop, natively forward, or Send Map-
Request. Request.
Positive Map-Reply messages are used to map EID-Prefixes onto RLOCs. Positive Map-Reply messages are used to map EID-Prefixes onto RLOCs.
Negative Map-Reply messages are used to support PTR and interconnect Negative map-reply messages are used to indicate non-lisp prefixes.
the LISP Internet with the legacy Internet. ITRs can, if needed, be configured to send all traffic destined for
non-lisp prefixes to a Proxy-ETR.
Most of the security of the Map-Reply messages depends on the 64 bits Most of the security of the Map-Reply messages depends on the 64 bits
nonce that is included in a Map-Request and returned in the Map- nonce that is included in a Map-Request and returned in the Map-
Reply. An ETR must never accept a Map-Reply message whose nonce does Reply. An ETR must never accept a Map-Reply message whose nonce does
not match one of the pending Map-Request messages. If an ETR does not match one of the pending Map-Request messages. If an ETR does
not accept Map-Reply messages with an invalid nonce, the risk of not accept Map-Reply messages with an invalid nonce, the risk of
attack is acceptable given the size of the nonce (64 bits). attack is acceptable given the size of the nonce (64 bits).
Note, however, that the nonce only confirms that the Map-Reply was The nonce only confirms that the map-reply received was sent in
sent by the ETR that received the Map-Request. It does not validate response to a map-request sent, it does not validate the contents of
the content of the Map-Reply message. that map-reply.
In addition, an attacker can perform EID-to-RLOC Cache overflow In addition, an attacker could perform EID-to-RLOC Cache overflow
attack by de-aggregating (i.e., splitting an EID prefix into attack by de-aggregating (i.e., splitting an EID prefix into
artificially smaller EID prefixes) either positive or negative artificially smaller EID prefixes) either positive or negative
mappings. mappings.
Severity level 1: the correct deployment of anti-spoofing techniques
prevents attacks leveraging the Map-Reply message.
6.3. Gleaning Attacks 6.3. Gleaning Attacks
A third type of attack involves the gleaning mechanism proposed in A third type of attack involves the gleaning mechanism proposed in
[I-D.ietf-lisp] and discussed in [Saucez09]. In order to reduce the [RFC6830] and discussed in [Saucez09]. In order to reduce the time
time required to obtain a mapping, [I-D.ietf-lisp] allows an ITR to required to obtain a mapping, [RFC6830] allows an ITR to learn a
learn a mapping from the LISP data encapsulated packets and the Map- mapping from the LISP data encapsulated packets and the Map-Request
Request packets that it receives. LISP data encapsulated packet packets that it receives. LISP data encapsulated packet contains a
contains a source RLOC, destination RLOC, source EID and destination source RLOC, destination RLOC, source EID and destination EID. When
EID. When an ITR receives a data encapsulated packet coming from a an ITR receives a data encapsulated packet coming from a source EID
source EID for which it does not already know a mapping, it may for which it does not already know a mapping, it may insert the
insert the mapping between the source RLOC and the source EID in its mapping between the source RLOC and the source EID in its EID-to-RLOC
EID-to-RLOC Cache. Gleaning can also be used when an ITR receives a Cache. Gleaning could also be used when an ITR receives a Map-
Map-Request as the Map-Request also contains a source EID address and Request as the Map-Request also contains a source EID address and a
a source RLOC. Once a gleaned entry has been added to the EID-to- source RLOC. Once a gleaned entry has been added to the EID-to-RLOC
RLOC cache, the LISP ITR sends a Map-Request to retrieve the mapping cache, the LISP ITR sends a Map-Request to retrieve the mapping for
for the gleaned EID from the mapping system. [I-D.ietf-lisp] the gleaned EID from the mapping system. [RFC6830] recommends
recommends storing the gleaned entries for only a few seconds. storing the gleaned entries for only a few seconds.
The first risk of gleaning is the ability to temporarily hijack an The first risk of gleaning is the ability to temporarily hijack an
identity. Consider an off-path attacker that wants to temporarily identity. Consider an off-path attacker that wants to temporarily
hijack host HA's identity and send packets to host HB with host HA's hijack host HA's identity and send packets to host HB with host HA's
identity. If the xTRs that serve host HB do not store a mapping for identity. If the xTRs that serve host HB do not store a mapping for
host HA, a non-spoofing off-path attacker (NSA) could send a LISP host HA, a non-spoofing off-path attacker (NSA) could send a LISP
encapsulated data packet to LR3 or LR4. The ETR will store the encapsulated data packet to LR3 or LR4. The ETR will store the
gleaned entry and use it to return the packets sent by host HB to the gleaned entry and use it to return the packets sent by host HB to the
attacker. In parallel, the ETR will send a Map-Request to retrieve attacker. In parallel, the ETR will send a Map-Request to retrieve
the mapping for HA. During a few seconds or until the reception of the mapping for HA. During a few seconds or until the reception of
skipping to change at page 17, line 14 skipping to change at page 18, line 33
control plane rate limit. This will extend the duration of the control plane rate limit. This will extend the duration of the
gleaned entry. If host HA establishes a flow with host HB at that gleaned entry. If host HA establishes a flow with host HB at that
time, the packets that they exchange will first pass through the time, the packets that they exchange will first pass through the
attacker. attacker.
In both cases, the attack only lasts for a few seconds (unless the In both cases, the attack only lasts for a few seconds (unless the
attacker is able to exhaust the rate limitation). However it should attacker is able to exhaust the rate limitation). However it should
be noted that today a large amount of packets might be exchanged be noted that today a large amount of packets might be exchanged
during even a small fraction of time. during even a small fraction of time.
Severity level 2: to avoid any risk, gleaning should be deactivated
in public deployments of LISP. Deactivating gleaning does not reduce
LISP functionality.
7. Threats concerning Interworking 7. Threats concerning Interworking
[I-D.ietf-lisp-interworking] defines two network elements to allow [RFC6832] defines two network elements to allow LISP and non-LISP
LISP and non-LISP sites to communicate, namely the Proxy-ITR and the sites to communicate, namely the Proxy-ITR and the Proxy-ETR. The
Proxy-ETR. The Proxy-ITR encapsulates traffic from non-LISP sites in Proxy-ITR encapsulates traffic from non-LISP sites in order to
order to forward it toward LISP sites, while the Proxy-ETR forward it toward LISP sites, while the Proxy-ETR decapsulates
decapsulates traffic arriving from LISP sites in order to forward it traffic arriving from LISP sites in order to forward it toward non-
toward non-LISP sites. For these elements some of the attack based LISP sites. For these elements some of the attack based on the LISP
on the LISP specific header are not possible, for the simple reason specific header are not possible, for the simple reason that some of
that some of the fields cannot be used due to the unidirectional the fields cannot be used due to the unidirectional nature of the
nature of the traffic. traffic.
The Proxy-ITR has functionalities similar to the ITR, however, its The Proxy-ITR has functionality similar to the ITR, however, its main
main purpose is to encapsulate packets arriving from the DFZ in order purpose is to encapsulate packets arriving from the DFZ in order to
to reach LISP sites. This means that it is no bound to any reach LISP sites. This means that it is no bound to any particular
particular EID-Prefix, hence no mapping exists and no mapping can be EID-Prefix, hence no mapping exists and no mapping can be configured
configured in the EID-to-RLOC Database. This means that the Proxy- in the EID-to-RLOC Database. This means that the Proxy-ITR element
ITR element itself is not able to check whether or not the arriving itself is not able to check whether or not the arriving traffic has
traffic has the right to be encapsulated or not. To limit such an the right to be encapsulated or not. To limit Proxy-ITRs being used
issue it is recommended to use the current practice based on as relays for attacks, Proxy-ITRs operators are encouraged to
firewalls and ACLs on the machine running the Proxy-ITR service. On implement best practices for data plane access control on the Proxy-
the other side, the Proxy-ITR is meant to encapsulate only packets ITRs and the border of the network, that is the edge of the scope of
that are destined to one of the LISP sites it is serving. This is the Proxy-ITR's announcement of the EID-Prefix. On the other side,
the case for instance for a service provider selling Proxy-ITR the Proxy-ITR is meant to encapsulate only packets that are destined
services. For this purpose a static EID-to-RLOC Cache can be to one of the LISP sites it is serving. This is the case for
configured in order to encapsulate only valid packets. In case of a instance for a service provider selling Proxy-ITR services. For this
cache-miss no Map-Request needs to be sent and the packet can be purpose a static EID-to-RLOC Cache can be configured in order to
silently dropped. encapsulate only valid packets. In case of a cache-miss no Map-
Request needs to be sent and the packet can be silently dropped.
The Proxy-ETR has functionalities similar to the ETR, however, its The Proxy-ETR has functionality similar to the ETR, however, its main
main purpose is to inject un-encapsulated packet in the DFZ in order purpose is to inject un-encapsulated packet in the DFZ in order to
to reach non-LISP-Sites. This means that since there is no specific reach non-LISP-Sites. This means that since there is no specific
EID-Prefix downstream, it has no EID-to-RLOC Database that can be EID-Prefix downstream, it has no EID-to-RLOC Database that can be
used to check whether or not the destination EID is part of its used to check whether or not the destination EID is part of its
domain. In order to avoid for the Proxy-ETR to be used as relay in a domain. In order to avoid for the Proxy-ETR to be used as relay in a
DoS attack it is preferable to configure the EID-to-RLOC Cache with DoS attack it is preferable to configure the EID-to-RLOC Cache with
static entries used to check if an encapsulated packet coming from a static entries used to check if an encapsulated packet coming from a
specific RLOC and having a specific source EID is actually allowed to specific RLOC and having a specific source EID is actually allowed to
transit through the Proxy-ETR. This is also important for services transit through the Proxy-ETR. This is also important for services
provider selling Proxy-ETR service to actually process only packets provider selling Proxy-ETR service to actually process only packets
arriving from its customers. However, in case of cache-miss no Map- arriving from its customers. However, in case of cache-miss no Map-
Request needs to be sent, rather the packet can be silently dropped Request needs to be sent, rather the packet can be silently dropped
since it is not originating from a valid site. The same drop policy since it is not originating from a valid site. The same drop policy
should be used for packets with an invalid source RLOC or a valid should be used for packets with an invalid source RLOC or a valid
source RLOC but an invalid EID. source RLOC but an invalid EID.
As it is the case without LISP, the addition of public proxies offers
opportunities to attackers to commit attacks. LISP interworking does
not open new threats compared to other interworking techniques based
on public proxies.
Severity level 0: the careful configuration of PETR and PITR combined
with the deployment of anti-spoofing techniques mitigates the attacks
leveraging interworking and provides the same level of severity as
interworking techniques in the Internet.
8. Threats with Malicious xTRs 8. Threats with Malicious xTRs
In this section, we discuss the threats that could be caused by In this section, we discuss the threats that could be caused by
malicious xTRs. We consider the reference environment below where malicious xTRs. We consider the reference environment below where
EL1 is a malicious or compromised xTR. This malicious xTR serves a EL1 is a malicious or compromised xTR. This malicious xTR serves a
set of hosts that includes HC. The other xTRs and hosts in this set of hosts that includes HC. The other xTRs and hosts in this
network play the same role as in the reference environment described network play the same role as in the reference environment described
in Section 4. in Section 4.
+-----+ +-----+
skipping to change at page 19, line 42 skipping to change at page 20, line 46
| | | |
------------------- -------------------
| |
| EID: HB | EID: HB
+-----+ +-----+
| HB | | HB |
+-----+ +-----+
Figure 2: Malicious xTRs' Reference Environment Figure 2: Malicious xTRs' Reference Environment
Malicious xTRs are probably the most serious threat to the LISP Since xTRs are cornerstone in the LISP architecture, malicious xTRs
control plane from a security viewpoint. To understand the problem, are probably the most serious threat to the LISP control plane from a
let us consider the following scenario. Host HC and HB exchange security viewpoint. Indeed, the impact of compromised LISP Control
packets with host HA. As all these hosts reside in LISP sites, LR1 Plane can be severe, and the most effective way to attack any multi-
and LR2 store mappings for HB and HC. Thus, these xTRs may need to organizational control plane is from within the system itself. To
exchange LISP control plane packets with EL1, e.g., to perform understand the problem, let us consider the following scenario. Host
reachability tests or to refresh expired mappings (e.g., if HC's HC and HB exchange packets with host HA. As all these hosts reside
mapping has a small TTL). in LISP sites, LR1 and LR2 store mappings for HB and HC. Thus, these
xTRs may need to exchange LISP control plane packets with EL1, e.g.,
to perform reachability tests or to refresh expired mappings (e.g.,
if HC's mapping has a small TTL).
A first threat against the LISP control plane is when EL1 replies to A first threat against the LISP control plane is when EL1 replies to
a legitimate Map-Request message sent by LR1 or LR2 with a Map-Reply a legitimate Map-Request message sent by LR1 or LR2 with a Map-Reply
message that contains an EID-Prefix that is larger than the prefix message that contains an EID-Prefix that is larger than the prefix
owned by the site attached to EL1. For instance if the prefix owned owned by the site attached to EL1. For instance if the prefix owned
by EL1 is 192.0.2.0/25 but the Map-Reply contain a mapping for by EL1 is 192.0.2.0/25 but the Map-Reply contain a mapping for
192.0.2.0/24. This could allow EL1 to attract packets destined to 192.0.2.0/24. This could allow EL1 to attract packets destined to
other EIDs than the EIDs that are attached to EL1. This attack is other EIDs than the EIDs that are attached to EL1. This attack is
called an "overclaiming" attack. called an "overclaiming" attack.
Overclaiming attack can be combined with de-aggregation to succeed a A malicious ETR might fragment its eid-to-rloc database and then
LISP Cache poisoning attack and prefix hijacking. For example, if instigate traffic to its site, therefore creating state on the
corresponding ITR's map-cache. This attack is called de-aggregation
attack.
Overclaiming attack could be combined with de-aggregation to succeed
a LISP Cache poisoning attack and prefix hijacking. For example, if
the EID prefix of the attacker is 192.0.2.0/25, it cannot provide a the EID prefix of the attacker is 192.0.2.0/25, it cannot provide a
mapping for the EID prefix 192.0.2.128/25 (i.e., it cannot hijack the mapping for the EID prefix 192.0.2.128/25 (i.e., it cannot hijack the
prefix). However, since a Map-Reply can contain several map records, prefix). However, since a Map-Reply can contain several map records,
it is possible to hijack such a prefix by providing as well a mapping it is possible to hijack such a prefix by providing as well a mapping
for it. To this end, the attacker can send a Map-Reply with an EID for it. To this end, the attacker could send a Map-Reply with an EID
prefix that covers at the same time the requested EID and the prefix that covers at the same time the requested EID and the
hijacked target prefix. Continuing the previous example, if the hijacked target prefix. Continuing the previous example, if the
requested mapping is for EID 192.0.2.1, and the target hijack prefix requested mapping is for EID 192.0.2.1, and the target hijack prefix
is 192.0.2.128/25, the Map-Reply will contain a map record for is 192.0.2.128/25, the Map-Reply will contain a map record for
192.0.2.0/24 and a map record for 192.0.2.128/25. Such a reply is 192.0.2.0/24 and a map record for 192.0.2.128/25. Such a reply is
considered legitimate according to the requested EID, while the map considered legitimate according to the requested EID, while the map
record of the hijacked prefix may lead to traffic redirection/ record of the hijacked prefix may lead to traffic redirection/
disruption and ITR's Cache poisoning. disruption and ITR's Cache poisoning.
Another variant of the overclaiming attack is a Denial of Service Another variant of the overclaiming attack is a Denial of Service
attack by sending a Negative Map-Reply message for a larger prefix attack by sending a Negative Map-Reply message for a larger prefix
without any locator and with the Drop action. Such a Negative Map- without any locator and with the Drop action. Such a Negative Map-
Reply indicates that the ETR that receives it should discard all Reply indicates that the ETR that receives it should discard all
packets. packets.
The current LISP specification briefly discusses the overclaiming By enabling [I-D.ietf-lisp-sec], overclaiming attacks are mitigated
problem [I-D.ietf-lisp], but does not propose any specific solution under the assumption that the mapping system can be trusted. This
to solve the problem. Nevertheless, [I-D.ietf-lisp-sec] proposes a assumption is equivalent to the general assumption that the control-
solution to protect LISP against overclaiming attacks under the plane is trustable in BGP meaning that the threat is not more severe
assumption that the mapping system can be trusted. than what is observed today. In addition, at the time of the writing
all Map Server implementations are configured with the minimal prefix
allowed to be register by their customers such that a customer cannot
register an overclaimed attack. Therefore, if mappings are always
retrieved via the mapping system with LISP-Sec activated and if Map-
Registers are cryptographically protected as recommended in the
specifications, overclaiming attack is not possible.
Another concern with malicious xTRs is the possibility of Denial of Another concern with malicious xTRs is the possibility of Denial of
Service attacks. A first attack is the flooding attack that was Service attacks. A first attack is the flooding attack that was
described in [I-D.bagnulo-lisp-threat]. This attack allows a described in [I-D.bagnulo-lisp-threat]. This attack allows a
malicious xTR to redirect traffic to a victim. The malicious xTR malicious xTR to redirect traffic to a victim. The malicious xTR
first defines a mapping for HC with two RLOCs: its own RLOC (EL1) and first defines a mapping for HC with two RLOCs: its own RLOC (EL1) and
the RLOC of the victim (e.g., LR3). The victim's RLOC is set as the RLOC of the victim (e.g., LR3). The victim's RLOC is set as
unreachable in the mapping. HC starts a large download from host HA. unreachable in the mapping. HC starts a large download from host HA.
Once the download starts, the malicious xTR updates its Locator Once the download starts, the malicious xTR updates its Locator
Status Bits, changes the mapping's version number or sets the SMR bit Status Bits, changes the mapping's version number or sets the SMR bit
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An important point to note about this flooding attack is that it An important point to note about this flooding attack is that it
reveals a limitation of the LISP architecture. A LISP ITR relies on reveals a limitation of the LISP architecture. A LISP ITR relies on
the received mapping and possible reachability information to select the received mapping and possible reachability information to select
the RLOC of the ETR that it uses to reach a given EID or block of the RLOC of the ETR that it uses to reach a given EID or block of
EIDs. However, if the ITR made a mistake, e.g., due to EIDs. However, if the ITR made a mistake, e.g., due to
misconfiguration, wrong implementation, or other types of errors and misconfiguration, wrong implementation, or other types of errors and
has chosen a RLOC that does not serve the destination EID, there is has chosen a RLOC that does not serve the destination EID, there is
no easy way for the LISP ETR to inform the ITR of its mistake. A no easy way for the LISP ETR to inform the ITR of its mistake. A
possible solution is to enforce an ETR to perform a reachability test possible solution is to enforce an ETR to perform a reachability test
with the selected ITR as soon as there is LISP encapsulated traffic with the selected ITR as soon as there is LISP encapsulated traffic
between the two. between the two. We recommend to never use reachability information
without verifying them first.
Note that the attacks discussed in this section are for documentation Note that the attacks discussed in this section are for documentation
purpose only. Malicious xTRs are either somehow directly deployed by purpose only. Malicious xTRs are either somehow directly deployed by
attackers or the result of attackers gaining privileged access to attackers or the result of attackers gaining privileged access to
existing xTRs. As such, it is out of the scope of LISP to propose existing xTRs. As such, it is out of the scope of LISP to propose
any mechanism to protect routers or to avoid their deployments with any mechanism to protect routers or to avoid their deployments with
malicious intentions. malicious intentions.
Severity level 2: the correct deployment of anti-spoofing and rate
limiting techniques combined with LISP-Sec and Map-Register
authentication prevents threats caused by malicious xTRs, as long as
mappings are always retrieved via a trustable mapping system. In
addition reachability information should never been used without
being verified first.
9. Security of the Proposed Mapping Systems 9. Security of the Proposed Mapping Systems
9.1. LISP+ALT 9.1. LISP+ALT
One of the assumptions in [I-D.ietf-lisp] is that the mapping system One of the assumptions in [RFC6830] is that the mapping system is
is more secure than sending Map-Request and Map-Reply messages more secure than sending Map-Request and Map-Reply messages directly.
directly. We analyze this assumption in this section by analyzing We analyze this assumption in this section by analyzing the security
the security of the ALT mapping system. of the ALT mapping system.
The ALT mapping system is basically a manually configured overlay of The ALT mapping system is basically a manually configured overlay of
GRE tunnels between ALT routers. BGP sessions are established GRE tunnels between ALT routers. BGP sessions are established
between ALT routers that are connected through such tunnels. An ALT between ALT routers that are connected through such tunnels. An ALT
router advertises the EID prefixes that it serves over its BGP router advertises the EID prefixes that it serves over its BGP
sessions with neighboring ALT routers and the EID-Prefixes that it sessions with neighboring ALT routers and the EID-Prefixes that it
has learned from neighboring ALT routers. has learned from neighboring ALT routers.
The ALT mapping system is in fact a discovery system that allows any The ALT mapping system is in fact a discovery system that allows any
ALT router to discover the ALT router that is responsible for a given ALT router to discover the ALT router that is responsible for a given
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This ALT router then replies directly by sending a Map-Reply to the This ALT router then replies directly by sending a Map-Reply to the
RLOC of the requesting ITR. RLOC of the requesting ITR.
The security of the ALT mapping system depends on many factors, The security of the ALT mapping system depends on many factors,
including: including:
o The security of the intermediate ALT routers. o The security of the intermediate ALT routers.
o The validity of the BGP advertisements sent on the ALT overlay. o The validity of the BGP advertisements sent on the ALT overlay.
Unfortunately, experience with BGP on the global Internet has shown ALT routers are interconnected with tunnels, the usage of secured
that BGP is subject to various types of misconfiguration problems and tunnels prevents BGP advertisements to be altered, dropped, or added
security attacks. The SIDR working group is developing a more secure by on-path or off path attackers. If a high level of security is
inter-domain routing architecture to solve this problem ([RFC6480]). required, works in the SIDR working group that develop security
solutions for BGP ([RFC6480]) could be applied to LISP+ALT.
The security of the intermediate ALT routers is another concern. A The security of the intermediate ALT routers is another concern. A
malicious intermediate ALT router could manipulate the received BGP malicious intermediate ALT router could manipulate the received BGP
advertisements and also answer to received Map-Requests without advertisements and also answer to received Map-Requests without
forwarding them to their final destination on the overlay. This forwarding them to their final destination on the overlay. This
could lead to various types of redirection attacks. Note that in could lead to various types of redirection attacks. Note that in
contrast with a regular IP router that could also manipulate in contrast with a regular IP router that could also manipulate in
transit packets, when a malicious or compromised ALT router replies transit packets, when a malicious or compromised ALT router replies
to a Map-Request, it can redirect legitimate traffic for a long to a Map-Request, it can redirect legitimate traffic for a long
period of time by sending an invalid Map-Reply message. Thus, the period of time by sending an invalid Map-Reply message. Thus, the
impact of a malicious ALT router could be much more severe than a impact of a malicious ALT router could be more severe than a
malicious router in today's Internet. malicious router in today's Internet. BGP is also weak in case of a
router involved in the BGP topology is compromised.
Severity level 1: configuring correctly the Map Servers, Map
Revolvers, and ALT routers with filters corresponding to their
customer cones provides the same security level as in BGP. If more
security is necessary, cryptography must be used to validate the
mappings themselves.
9.2. LISP-DDT 9.2. LISP-DDT
The LISP Delegated Database Tree (LISP-DDT) mapping system is The LISP Delegated Database Tree (LISP-DDT) mapping system is
proposed as an alternative for LISP+ALT [I-D.fuller-lisp-ddt]. LISP- proposed as an alternative for LISP+ALT [I-D.ietf-lisp-ddt]. LISP-
DDT is a hierarchical distributed database for EID-to-RLOC mappings. DDT is a hierarchical distributed database for EID-to-RLOC mappings.
Each DDT node is configured with an EID prefix it is authoritative Each DDT node is configured with an EID prefix it is authoritative
for, as well as the RLOC addresses and EID prefixes of the LISP-DDT for, as well as the RLOC addresses and EID prefixes of the LISP-DDT
nodes that are authoritative for more specific EID prefix. In LISP- nodes that are authoritative for more specific EID prefix. In LISP-
DDT, mappings are retrieved iteratively. A Map Resolver that needs DDT, mappings are retrieved iterative. A Map Resolver that needs to
to locate a mapping traverses the tree of DDT nodes contacting them locate a mapping traverses the tree of DDT nodes contacting them one
one after another until the leaf of the DDT tree that is after another until the leaf of the DDT tree that is authoritative
authoritative for the longest matching EID prefix for the mapping's for the longest matching EID prefix for the mapping's EID is reached.
EID is reached. The Map Resolver traverses the hierarchy of LISP-DDT The Map Resolver traverses the hierarchy of LISP-DDT nodes by sending
nodes by sending Map-Requests, with the LISP-DDT-originated bit set, Map-Requests, with the LISP-DDT-originated bit set, to LISP-DDT
to LISP-DDT nodes. The Map Resolver first contacts the root of the nodes. The Map Resolver first contacts the root of the hierarchy.
hierarchy. When a LISP-DDT node receives a Map-Request, it replies When a LISP-DDT node receives a Map-Request, it replies to the Map
to the Map Resolver with a Map-Referral that contains the list of the Resolver with a Map-Referral that contains the list of the locators
locators of its children that are authoritative of a prefix that of its children that are authoritative of a prefix that covers the
covers the EID in the Map-Request. The Map Resolver then contacts EID in the Map-Request. The Map Resolver then contacts one of these
one of these children that will return, at its turn, a Map-Referral. children that will return, at its turn, a Map-Referral. This
This procedure is iteratively executed until a Map-Referral marked procedure is iteratively executed until a Map-Referral marked with
with the done flag is received. The locators that appear in a the done flag is received. The locators that appear in a referral
referral with the done flag are those of the authoritative ETRs for with the done flag are those of the authoritative ETRs for the EID in
the EID in the Map-Request. At that moment, the Map Resolver falls the Map-Request. At that moment, the Map Resolver falls back to its
back to its normal behavior and sends a Map-Request to the ETR in normal behavior and sends a Map-Request to the ETR in order for the
order for the ITR to obtain the mapping. It is worth to mention that ITR to obtain the mapping. It is worth to mention that the Map
the Map Resolver can cache the referrals to avoid traversing all the Resolver can cache the referrals to avoid traversing all the whole
whole hierarchy for all mapping retrievals. hierarchy for all mapping retrievals.
The operation in LISP-DDT is different from ALT and thus it does not The operation in LISP-DDT is different from ALT and thus it does not
present the same threats as LISP+ALT. As a first difference, LISP- present the same threats as LISP+ALT. As a first difference, LISP-
DDT natively includes security specification providing data origin DDT natively includes security specification providing data origin
authentication, data integrity protection and secure EID prefix authentication, data integrity protection and secure EID prefix
delegation. Hence, these aspects are no further explored in this delegation. Hence, these aspects are no further explored in this
document. document.
However, threats exist for LISP-DDT as well. For instance, a DoS However, threats exist for LISP-DDT as well. For instance, a DoS
attack can be performed on the mapping infrastructure by asking to attack could be performed on the mapping infrastructure by asking to
retrieve a large amount of mappings at the same time, hence, the retrieve a large amount of mappings at the same time, hence, the
importance of carefully dimensioning the topology of the DDT importance of carefully dimensioning the topology of the DDT
hierarchy. hierarchy.
If an attacker manages to compromise a LISP-DDT node it can send fake If an attacker manages to compromise a LISP-DDT node it could send
referrals to the Map Resolver and then control the mappings delivered fake referrals to the Map Resolver and then control the mappings
to the ITRs. Furthermore, the effects of such an attack can be delivered to the ITRs. Furthermore, the effects of such an attack
longer than the attack itself if the Map Resolver caches the could be longer than the attack itself if the Map Resolver caches the
referrals. referrals.
Severity level 1: the correct deployment of anti-spoofing and rate
limiting techniques combined with embedded security features of LISP-
DDT prevent attacks leveraging LISP-DDT.
10. Threats concerning LISP-MS 10. Threats concerning LISP-MS
LISP-MS ([I-D.ietf-lisp-ms] specifies two network elements, namely LISP-MS ([RFC6833] specifies two network elements, namely the Map
the Map Server and the Map Resolver, that are meant to be used by Server and the Map Resolver, that are meant to be used by xTRs to
xTRs to access the mapping system. The advantage is clearly the fact access the mapping system. The advantage is clearly the fact that
that even if the mapping system changes in time xTRs do not need to even if the mapping system changes in time xTRs do not need to change
change anything since they deal only with Map Servers and Map anything since they deal only with Map Servers and Map Resolvers.
Resolvers. This includes the security aspects, since no change in This includes the security aspects, since no change in the local
the local security policies is needed. security policies is needed.
10.1. Map Server 10.1. Map Server
Map Server is used to dispatch Map-Request coming from the mapping Map Server is used to dispatch Map-Request coming from the mapping
system to ETRs that are authoritative for the EID in the request. To system to ETRs that are authoritative for the EID in the request. To
this end it is necessary that ETRs register their mappings to the Map this end it is necessary that ETRs register their mappings to the Map
Server. This allows the Map Server to know toward which ETR to Server. This allows the Map Server to know toward which ETR to
forward Map-Requests and also to announce the EID-prefixes of the forward Map-Requests and also to announce the EID-prefixes of the
registered mappings in the mapping system. registered mappings in the mapping system.
LISP uses a shared key approach in order to protect the Map Server LISP uses a shared key approach in order to protect the Map Server
and grant registration rights only to ETRs that have a valid key. and grant registration rights only to ETRs that have a valid key.
Shared key must be used to protect both the registration message and Shared key must be used to protect both the registration message and
the Map-Notify message when used. The mechanism used to share the the Map-Notify message when used. The mechanism used to share the
key between a Map Server and an ETRs must be secured to avoid that a key between a Map Server and an ETRs must be secured to avoid that a
malicious nodes catch the key and uses it to send forged Map-Register malicious nodes catch the key and uses it to send forged Map-Register
message to the Map Server. A forged Map-Register message can be use message to the Map Server. A forged Map-Register message could be
to attract Map-Request and thus provide invalid Map-Replies or the used to attract Map-Request and thus provide invalid Map-Replies or
redirect Map-Requests to a target to mount a DoS attack. the redirect Map-Requests to a target to mount a DoS attack.
More subtle attacks can be carried out only in the case of malicious More subtle attacks could be carried out only in the case of
ETRs. A malicious ETR can register an invalid RLOC to divert Map- malicious ETRs. A malicious ETR could register an invalid RLOC to
Requests to a target ETR and succeed a DoS attack on it. To avoid divert Map-Requests to a target ETR and succeed a DoS attack on it.
this kind of attack, the Map Server must check that the registered To avoid this kind of attack, the Map Server must check that the
RLOCs belong to ETRs authoritative for the registered EID prefix. registered RLOCs belong to ETRs authoritative for the registered EID
Such check can be done by sending and explicit Map-Request for the prefix. Such check can be done by sending and explicit Map-Request
EID to the ETRs in the mapping and check that replies with a Map- for the EID to the ETRs in the mapping and check that replies with a
Reply. If the ETRs return a valid Map-Reply, the RLOC belongs to an Map-Reply. If the ETRs return a valid Map-Reply, the RLOC belongs to
authoritative ETR. Note that this does not protect against malicious an authoritative ETR. Note that this does not protect against
ETRs that create forged Map-Replies. Stronger techniques for RLOC malicious ETRs that create forged Map-Replies. Stronger techniques
check are presented in [I-D.saucez-lisp-mapping-security]. for RLOC check are presented in [I-D.saucez-lisp-mapping-security].
Similarly to the previous case, a malicious ETR can register an Similarly to the previous case, a malicious ETR could register an
invalid EID-prefix to attract Map-Requests or to redirect them to a invalid EID-prefix to attract Map-Requests or to redirect them to a
target to mount a DoS attack. To avoid this kind of attack, the Map target to mount a DoS attack. To avoid this kind of attack, the Map
Server must check that the prefixes registered by an ETR belong to Server must check that the prefixes registered by an ETR belong to
that ETR. One method could be to manually configure EID-prefix that ETR. One method could be to manually configure EID-prefix
ranges that can be announced by ETRs. ranges that can be announced by ETRs.
[I-D.saucez-lisp-mapping-security] present alternative techniques to [I-D.saucez-lisp-mapping-security] present alternative techniques to
verify the prefix claimed by an ETR. verify the prefix claimed by an ETR.
Severity level 1: the correct deployment of anti-spoofing and rate
limiting techniques combined with usage of Map-Register
authentication prevents attacks leveraging the Map Server.
10.2. Map Resolver 10.2. Map Resolver
Map Resolvers receive Map-Requests, typically from ITRs, and use the Map Resolvers receive Map-Requests, typically from ITRs, and use the
mapping system to find a mapping for the EID in the Map-Request. It mapping system to find a mapping for the EID in the Map-Request. It
can work in two modes: can work in two modes:
Non-Caching Mode: The resolver just forwards the Map-Request to the Non-Caching Mode: The resolver just forwards the Map-Request to the
mapping system, which will take care of delivering the request mapping system, which will take care of delivering the request
to an authoritative ETR. The latter will send back a Map-Reply to an authoritative ETR. The latter will send back a Map-Reply
directly to the ITR that has originally issued the request. directly to the ITR that has originally issued the request.
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it to the mapping system. In this way it will receive the it to the mapping system. In this way it will receive the
corresponding reply, store a local copy in a cache, and send corresponding reply, store a local copy in a cache, and send
back a reply to the original requester. Since all requested back a reply to the original requester. Since all requested
mappings are locally cached, before actually making a request mappings are locally cached, before actually making a request
to the mapping system it performs a lookup in the local cache to the mapping system it performs a lookup in the local cache
and in case of an hit, it send back a reply without querying and in case of an hit, it send back a reply without querying
the mapping system. the mapping system.
In its basic mode, i.e., non-caching mode, the Map Resolver does not In its basic mode, i.e., non-caching mode, the Map Resolver does not
keep state, hence, the only direct form of attack is a DoS attack, keep state, hence, the only direct form of attack is a DoS attack,
where an attacker (or a group of attackers) can try to exhaust where an attacker (or a group of attackers) could try to exhaust
computational power by flooding the resolver with requests. Common computational power by flooding the resolver with requests. Common
filtering techniques and BCP against DoS attacks can be applied in filtering techniques and BCP against DoS attacks could be applied in
this case. this case.
Nonetheless, attackers can use resolvers as relay for DoS attacks Nonetheless, attackers could use resolvers as relay for DoS attacks
against xTRs. An off-path spoofing attacker can generate a high load against xTRs. An off-path spoofing attacker could generate a high
of requests to a set of resolvers, hence distributing the load in load of requests to a set of resolvers, hence distributing the load
order to avoid to be blocked. All this requests can use a specific in order to avoid to be blocked. All this requests can use a
EID that makes all the requests to be forwarded to a specific ETR, specific EID that makes all the requests to be forwarded to a
which, as a result, will be victim of a DDoS attack. Similarly, the specific ETR, which, as a result, will be victim of a DDoS attack.
attacker can use a spoofed source address making all the replies to Similarly, the attacker could use a spoofed source address making all
converge to one single ITR, which, as a result, will be victim of a the replies to converge to one single ITR, which, as a result, will
DDoS attack. Such scenarios are not specific to LISP, but rather a be victim of a DDoS attack. Such scenarios are not specific to LISP,
common problem of every query infrastructure, hence the same BCP can but rather a common problem of every query infrastructure, hence the
be applied in order to limit the attacks. same BCP can be applied in order to limit the attacks.
When functioning in caching-mode, the resolver will use the same type When functioning in caching-mode, the resolver will use the same type
of cache than ITRs. Due to its similarity with the ITRs' cache the of cache than ITRs. Due to its similarity with the ITRs' cache the
analysis provided in Section 5.2 holds also in this case. However, analysis provided in Section 5.2 holds also in this case. However,
an important difference exists: this cache is not used for packet an important difference exists: this cache is not used for packet
encapsulation but only for quick replies when new requests arrive. encapsulation but only for quick replies when new requests arrive.
Therefore, as the caching-mode is only an optimization, the attacks Therefore, as the caching-mode is only an optimization, the attacks
that aim at filling the Map Resolver cache have a less severe impact that aim at filling the Map Resolver cache have a less severe impact
on the traffic. on the traffic. The usage of LISP-Sec prevents ITR to obtain invalid
mappings. It is worth noting that caching is not used in current
implementations as it makes mapping synchronization hard for mobile
devices.
When Map Resolvers are used as front-end of the LIS-DDT mapping When Map Resolvers are used as front-end of the LIS-DDT mapping
system they may be exposed to another variant of DoS. Indeed, the system they may be exposed to another variant of DoS. Indeed, the
iterative operation of the Map Resolver on the DDT hierarchy implies iterative operation of the Map Resolver on the DDT hierarchy implies
that it has to maintain state about the ITR that requested the that it has to maintain state about the ITR that requested the
mapping, this in order to send the final Map-Request to the ETR on mapping, this in order to send the final Map-Request to the ETR on
behalf of the ITR. An attacker might leverage on this to fill the behalf of the ITR. An attacker might leverage on this to fill the
Map Resolver memory and then cause a DoS. Map Resolver memory and then cause a DoS. Rate limiting can be used
to present this attack.
The question may arise on whether a Kaminsky-like attack is possible The question may arise on whether a Kaminsky-like attack is possible
for an off-path attacker against ITRs sending requests to a certain for an off-path attacker against ITRs sending requests to a certain
resolver. The 64-bits nonce present in every message has been resolver. The 64-bits nonce present in every message has been
introduced in the LISP specification to avoid such kind of attack. introduced in the LISP specification to avoid such kind of attack.
There has been discussion within the LISP Working Group on the There has been discussion within the LISP Working Group on the
optimal size of the nonce, and it seems that 64-bits provides optimal size of the nonce, and it seems that 64-bits provides
sufficient protection. sufficient protection.
A possible way to limit the above-described attacks is to introduce A possible way to limit the above-described attacks is to introduce
strong identification in the Map-Request/Map-Reply by using the strong identification in the Map-Request/Map-Reply by using the
Encapsulated Control Message with authentication enabled. Encapsulated Control Message with authentication enabled
[I-D.ietf-lisp-sec].
11. Suggested Recommendations Severity level 1: the correct deployment of anti-spoofing and rate
limiting techniques combined with LISP-Sec and Map-Register
authentication prevent attacks leveraging Map Resolver.
To mitigate the impact of attacks against LISP, the following 11. Security Recommendations
recommendations should be followed.
Different deployments of LISP may have different security
requirements. The recommendations in this document aim at mitigating
threats in in public deployments of LISP.
To mitigate the impact of attacks against LISP in public deployments,
the following recommendations should be followed.
First, the use of some form of filtering can help in avoid or at First, the use of some form of filtering can help in avoid or at
least mitigate some types of attacks. least mitigate some types of attacks.
o On ETRs, packets should be decapsulated only if the destination o On ETRs, packets should be decapsulated only if the destination
EID is effectively part of the EID-Prefix downstream the ETR. EID is effectively part of the EID-Prefix downstream the ETR.
Further, still on ETRs, packets should be decapsulated only if a Further, still on ETRs, packets should be decapsulated only if a
mapping for the source EID is present in the EID-to-RLOC Cache and mapping for the source EID is present in the EID-to-RLOC Cache and
has been obtained through the mapping system (not gleaned). has been obtained through the mapping system (not gleaned).
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as [RFC3704] or SAVI [SAVI], it can be expected that attackers will as [RFC3704] or SAVI [SAVI], it can be expected that attackers will
become less capable of sending packets with a spoofed source address. become less capable of sending packets with a spoofed source address.
To prevent packet injection attacks from non-spoofing attackers To prevent packet injection attacks from non-spoofing attackers
(NSA), ETRs should always verify that the source RLOC of each (NSA), ETRs should always verify that the source RLOC of each
received LISP data encapsulated packet corresponds to one of the received LISP data encapsulated packet corresponds to one of the
RLOCs listed in the mappings for the source EID found in the inner RLOCs listed in the mappings for the source EID found in the inner
packet. An alternative could be to use existing IPSec techniques packet. An alternative could be to use existing IPSec techniques
[RFC4301] and when necessary including perhaps [RFC5386] to establish [RFC4301] and when necessary including perhaps [RFC5386] to establish
an authenticated tunnel between the ITR and the ETR. an authenticated tunnel between the ITR and the ETR.
[I-D.ietf-lisp] recommends to rate limit the control messages that [RFC6830] recommends to rate limit the control messages that are sent
are sent by an xTR. This limit is important to deal with denial of by an xTR. This limit is important to deal with denial of service
service attacks. However, a strict limit, e.g., implemented with a attacks. However, a strict limit, e.g., implemented with a token
token bucket, on all the Map-Request and Map-Reply messages sent by bucket, on all the Map-Request and Map-Reply messages sent by an xTR
an xTR is not sufficient. An xTR should distinguish between is not sufficient. An xTR should distinguish between different types
different types of control plane packets: of control plane packets:
1. The Map-Request messages that it sends to refresh expired mapping 1. The Map-Request messages that it sends to refresh expired mapping
information. information.
2. The Map-Request messages that it sends to obtain mapping 2. The Map-Request messages that it sends to obtain mapping
information because one of the served hosts tried to contact an information because one of the served hosts tried to contact an
external EID. external EID.
3. The Map-Request messages that it sends as reachability probes. 3. The Map-Request messages that it sends as reachability probes.
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These control plane messages are used for different purposes. Fixing These control plane messages are used for different purposes. Fixing
a global rate limit for all control plane messages increases the risk a global rate limit for all control plane messages increases the risk
of Denial of Service attacks if a single type of control plane of Denial of Service attacks if a single type of control plane
message can exceed the configured limit. This risk could be message can exceed the configured limit. This risk could be
mitigated by either specifying a rate for each of the five types of mitigated by either specifying a rate for each of the five types of
control plane messages. Another option could be to define a maximum control plane messages. Another option could be to define a maximum
rate for all control plane messages, and prioritize the control plane rate for all control plane messages, and prioritize the control plane
messages according to the list above (with the highest priority for messages according to the list above (with the highest priority for
message type 1). message type 1).
In [I-D.ietf-lisp], there is no mechanism that allows an xTR to In [RFC6830], there is no mechanism that allows an xTR to verify the
verify the validity of the content a Map-Reply message that it validity of the content a Map-Reply message that it receives.
receives. Besides the attacks discussed earlier in the document, a Besides the attacks discussed earlier in the document, a time-shifted
time-shifted attack where an attacker is able to modify the content attack where an attacker is able to modify the content of a Map-Reply
of a Map-Reply message but then needs to move off-path could also message but then needs to move off-path could also create redirection
create redirection attacks. The nonce only allows an xTR to verify attacks. The nonce only allows an xTR to verify that a Map-Reply
that a Map-Reply responds to a previously sent Map-Request message. responds to a previously sent Map-Request message. To verify the
In order to allow verifying the validity and integrity of bindings validity and integrity of bindings between EID-Prefixes and their
between EID-Prefixes and their RLOCS solutions proposed in RLOCS, solutions proposed in [I-D.saucez-lisp-mapping-security] and
[I-D.saucez-lisp-mapping-security] and [I-D.ietf-lisp-sec] should be [I-D.ietf-lisp-sec] could be deployed. Having LISP-SEC and lisp-
deployed. Having such kind of mechanisms would allow ITRs to ignore mapping-security in place would prevent all the above-mentioned
non-verified mappings, thus increasing security. threats.
Finally, there is also the risk of Denial of Service attack against Finally, there is also the risk of Denial of Service attack against
the EID-to-RLOC Cache. We have discussed these attacks when the EID-to-RLOC Cache. We have discussed these attacks when
considering external attackers with, e.g., the gleaning mechanism and considering external attackers with, e.g., the gleaning mechanism and
in Section 5.2. If an ITR has a limited EID-to-RLOC Cache, a in Section 5.2. If an ITR has a limited EID-to-RLOC Cache, a
malicious or compromised host residing in the site that it serves malicious or compromised host residing in the site that it serves
could generate packets to random destinations to force the ITR to could generate packets to random destinations to force the ITR to
issue a large number of Map-Requests whose answers could fill its issue a large number of Map-Requests whose answers could fill its
cache. Faced with such misbehaving hosts, LISP ITR should be able to cache. Faced with such misbehaving hosts, LISP ITR should be able to
limit the percent of Map-Requests that it sends for a given source limit the percent of Map-Requests that it sends for a given source
skipping to change at page 28, line 35 skipping to change at page 30, line 41
Security considerations are the core of this document and do not need Security considerations are the core of this document and do not need
to be further discussed in this section. to be further discussed in this section.
14. Acknowledgments 14. Acknowledgments
This document builds upon the draft of Marcelo Bagnulo This document builds upon the draft of Marcelo Bagnulo
([I-D.bagnulo-lisp-threat]), where the flooding attack and the ([I-D.bagnulo-lisp-threat]), where the flooding attack and the
reference environment were first described. reference environment were first described.
We would like to thank Jeff Wheeler for his comments. The authors would like to thank Vina Ermagan, Darrel Lewis, and Jeff
Wheeler for their comments.
This work has been partially supported by the INFSO-ICT-216372 This work has been partially supported by the INFSO-ICT-216372
TRILOGY Project (www.trilogy-project.org). TRILOGY Project (www.trilogy-project.org).
15. References 15. References
15.1. Normative References 15.1. Normative References
[I-D.fuller-lisp-ddt] [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Fuller, V., Lewis, D., Ermagan, V., and A. Jain, "LISP Locator/ID Separation Protocol (LISP)", RFC 6830,
Delegated Database Tree", draft-fuller-lisp-ddt-04 (work January 2013.
in progress), September 2012.
[I-D.ietf-lisp] [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller,
Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "Interworking between Locator/ID Separation Protocol
"Locator/ID Separation Protocol (LISP)", (LISP) and Non-LISP Sites", RFC 6832, January 2013.
draft-ietf-lisp-23 (work in progress), May 2012.
[I-D.ietf-lisp-alt] [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation
Fuller, V., Farinacci, D., Meyer, D., and D. Lewis, "LISP Protocol (LISP) Map-Server Interface", RFC 6833,
Alternative Topology (LISP+ALT)", draft-ietf-lisp-alt-10 January 2013.
(work in progress), December 2011.
[I-D.ietf-lisp-interworking] [RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID
Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, Separation Protocol (LISP) Map-Versioning", RFC 6834,
"Interworking LISP with IPv4 and IPv6", January 2013.
draft-ietf-lisp-interworking-06 (work in progress),
March 2012.
[I-D.ietf-lisp-map-versioning] [RFC6836] Fuller, V., Farinacci, D., Meyer, D., and D. Lewis,
Iannone, L., Saucez, D., and O. Bonaventure, "LISP Map- "Locator/ID Separation Protocol Alternative Logical
Versioning", draft-ietf-lisp-map-versioning-09 (work in Topology (LISP+ALT)", RFC 6836, January 2013.
progress), March 2012.
[I-D.ietf-lisp-ms] [RFC6837] Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to
Fuller, V. and D. Farinacci, "LISP Map Server Interface", Routing Locator (RLOC) Database", RFC 6837, January 2013.
draft-ietf-lisp-ms-16 (work in progress), March 2012.
15.2. Informative References 15.2. Informative References
[Chu] Jerry Chu, H., "Tuning TCP Parameters for the 21st [Chu] Jerry Chu, H., "Tuning TCP Parameters for the 21st
Century", 75th IETF, Stockholm, July 2009, Century", 75th IETF, Stockholm, July 2009,
<http://tools.ietf.org/wg/savi/>. <http://tools.ietf.org/wg/savi/>.
[I-D.bagnulo-lisp-threat] [I-D.bagnulo-lisp-threat]
Bagnulo, M., "Preliminary LISP Threat Analysis", Bagnulo, M., "Preliminary LISP Threat Analysis",
draft-bagnulo-lisp-threat-01 (work in progress), draft-bagnulo-lisp-threat-01 (work in progress),
July 2007. July 2007.
[I-D.ietf-lisp-ddt]
Fuller, V., Lewis, D., Ermagan, V., and A. Jain, "LISP
Delegated Database Tree", draft-ietf-lisp-ddt-00 (work in
progress), October 2012.
[I-D.ietf-lisp-sec] [I-D.ietf-lisp-sec]
Maino, F., Ermagan, V., Cabellos-Aparicio, A., Saucez, D., Maino, F., Ermagan, V., Cabellos-Aparicio, A., Saucez, D.,
and O. Bonaventure, "LISP-Security (LISP-SEC)", and O. Bonaventure, "LISP-Security (LISP-SEC)",
draft-ietf-lisp-sec-04 (work in progress), October 2012. draft-ietf-lisp-sec-04 (work in progress), October 2012.
[I-D.ietf-tcpm-tcp-security] [I-D.ietf-tcpm-tcp-security]
Gont, F., "Survey of Security Hardening Methods for Gont, F., "Survey of Security Hardening Methods for
Transmission Control Protocol (TCP) Implementations", Transmission Control Protocol (TCP) Implementations",
draft-ietf-tcpm-tcp-security-03 (work in progress), draft-ietf-tcpm-tcp-security-03 (work in progress),
March 2012. March 2012.
[I-D.lear-lisp-nerd]
Lear, E., "NERD: A Not-so-novel EID to RLOC Database",
draft-lear-lisp-nerd-09 (work in progress), April 2012.
[I-D.meyer-lisp-cons] [I-D.meyer-lisp-cons]
Brim, S., "LISP-CONS: A Content distribution Overlay Brim, S., "LISP-CONS: A Content distribution Overlay
Network Service for LISP", draft-meyer-lisp-cons-04 (work Network Service for LISP", draft-meyer-lisp-cons-04 (work
in progress), April 2008. in progress), April 2008.
[I-D.saucez-lisp-mapping-security] [I-D.saucez-lisp-mapping-security]
Saucez, D. and O. Bonaventure, "Securing LISP Mapping Saucez, D. and O. Bonaventure, "Securing LISP Mapping
replies", draft-saucez-lisp-mapping-security-00 (work in replies", draft-saucez-lisp-mapping-security-00 (work in
progress), February 2011. progress), February 2011.
skipping to change at page 30, line 40 skipping to change at page 32, line 41
[SAVI] IETF, "Source Address Validation Improvements Working [SAVI] IETF, "Source Address Validation Improvements Working
Group", <http://tools.ietf.org/wg/savi/>. Group", <http://tools.ietf.org/wg/savi/>.
[Saucez09] [Saucez09]
Saucez, D. and L. Iannone, "How to mitigate the effect of Saucez, D. and L. Iannone, "How to mitigate the effect of
scans on mapping systems", Submitted to the Trilogy scans on mapping systems", Submitted to the Trilogy
Summer School on Future Internet. Summer School on Future Internet.
Appendix A. Document Change Log Appendix A. Document Change Log
o Version 04 Posted February 2013.
* Clear statement that the document compares threats of public
LISP deployments with threats in the current Internet
architecture.
* Addition of a severity level discussion at the end of each
section.
* Addressed comments from D. Lewis' review.
* Updated References.
* Further editorial polishing.
o Version 03 Posted October 2012. o Version 03 Posted October 2012.
* Dropped Reference to RFC 2119 notation because it is not * Dropped Reference to RFC 2119 notation because it is not
actually used in the document. actually used in the document.
* Deleted future plans section. * Deleted future plans section.
* Updated References * Updated References
* Deleted/Modified sentences referring to the early status of the * Deleted/Modified sentences referring to the early status of the
 End of changes. 119 change blocks. 
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