The Threat Analysis and Requirements for Cryptographic Authentication of Routing Protocols' Transports
draft-ietf-karp-threats-reqs-01

Abstract

Different routing protocols exist and each employs its own mechanism for securing the protocol packets on the wire. While most already have some method for accomplishing cryptographic message authentication, in many cases the existing methods are dated, vulnerable to attack, and employ cryptographic algorithms that have been deprecated. The "Keying and Authentication for Routing Protocols" (KARP) effort aims to overhaul and improve these mechanisms.

This document has two main parts - the first describes the threat analysis for attacks against routing protocols' transports and the second enumerates the requirements for addressing the described threats. This document, along with the KARP design guide and KARP framework documents, will be used by KARP design teams for specific protocol review and overhaul. This document reflects the input of both the IETF's Security Area and Routing Area in order to form a jointly agreed upon guidance.

Status of this Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on April 12, 2011.

Copyright Notice

Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

1.  Introduction
    1.1.  Terminology
    1.2.  Requirements Language
    1.3.  Scope
    1.4.  Incremental Approach
    1.5.  Goals
    1.6.  Non-Goals
    1.7.  Audience

2.  Threats
    2.1.  Threats In Scope
    2.2.  Threats Out of Scope

3.  Requirements for Phase 1 of a Routing Protocol Transport's Security Update

4.  Security Considerations

5.  IANA Considerations

6.  Acknowledgements

7.  Change History (RFC Editor: Delete Before Publishing)

8.  References
    8.1.  Normative References
    8.2.  Informative References

§  Authors' Addresses

1.  Introduction

In March 2006 the Internet Architecture Board (IAB) held a workshop on the topic of "Unwanted Internet Traffic". The report from that workshop is documented in RFC 4948 [RFC4948] (Andersson, L., Davies, E., and L. Zhang, “Report from the IAB workshop on Unwanted Traffic March 9-10, 2006,” August 2007.). Section 8.1 of that document states "A simple risk analysis would suggest that an ideal attack target of minimal cost but maximal disruption is the core routing infrastructure." Section 8.2 calls for "[t]ightening the security of the core routing infrastructure." Four main steps were identified for that tightening:

• More secure mechanisms and practices for operating routers. This work is being addressed in the OPSEC Working Group.
• Cleaning up the Internet Routing Registry repository [IRR], and securing both the database and the access, so that it can be used for routing verifications. This work should be addressed through liaisons with those running the IRR's globally.
• Specifications for cryptographic validation of routing message content. This work will likely be addressed in the SIDR Working Group.
• Securing the routing protocols' packets on the wire

This document addresses the last item in the list above, securing the the transmission of routing protocol packets on the wire, or rather securing routing protocol transport. This effort is referred to as Keying and Authentication for Routing Protocols, or "KARP". This document specifically addresses the threat analysis for per packet routing protocol transport authentication, and the requirements for protocols to mitigate those threats.

This document is one of three that together form the guidance and instructions for KARP design teams working to overhaul routing protocol transport security. The other two are the KARP Design Guide [I‑D.ietf‑karp‑design‑guide] (Lebovitz, G. and M. Bhatia, “Keying and Authentication for Routing Protocols (KARP) Design Guidelines,” September 2010.) and the KARP Framework [I‑D.ietf‑karp‑framework] (Atwood, W. and G. Lebovitz, “Framework for Cryptographic Authentication of Routing Protocol Packets on the Wire,” February 2010.).

1.1.  Terminology

Within the scope of this document, the following words, when beginning with a capital letter, or spelled in all capitals, hold the meanings described to the right of each term. If the same word is used uncapitalized, then it is intended to have its common english definition.

PSK (Pre-Shared Key)

A key used by both peers in a secure configuration. Usually exchanged out-of-band prior to a first connection.

Routing Protocol

When used with capital "R" and "P" in this document the term refers the Routing Protocol for which work is being done to provide or enhance its peer authentication mechanisms.

PRF

In cryptography, a pseudorandom function family, abbreviated PRF, is a collection of efficiently-computable functions which emulate a random oracle in the following way: No efficient algorithm can distinguish (with significant advantage) between a function chosen randomly from the PRF family and a random oracle (a function whose outputs are fixed completely at random). Informally, a PRF takes a secret key and a set of input values and produces random-seeming output values for each input value.

KDF (Key derivation function)

A KDF is a function in which an input key and other input data is used to generate (or derive) keying material that can be employed by cryptographic algorithms. The key that is input to a KDF is called a key derivation key. KDFs can be used to generate one or more keys from either (i) a uniformly random or pseudorandom seed value or (ii) a Diffie-Hellman shared secret or (iii) a non-uniform random source or (iv) a passphrase.

Identifier

The type and value used by one peer of an authenticated message exchange to signify to the other peer who they are. The Identifier is used by the receiver as a lookup index into a table containing further information about the peer that is required to continue processing the message, for example a Security Association (SA) or keys.

Identity Proof

Once the form of identity is decided, then there must be a cryptographic proof of that identity, that the peer really is who they assert themselves to be. Proof of identity can be arranged between the peers in a few ways, for example pre-shared keys, raw assymetric keys, or a more user-friendly representation of assymetric keys, such as a certificate. Certificates can be used in a way requiring no additional supporting systems -- e.g. public keys for each peer can be maintained locally for verification upon contact. Certificate management can be made more simple and scalable with the use of minor additional supporting systems, as is the case with self-signed certificates and a flat file list of "approved thumbprints". Self-signed certificates will have somewhat lower security properties than Certificate Authority signed certificates . The use of these different identity proofs vary in ease of deployment, ease of ongoing management, startup effort, ongoing effort and management, security strength, and consequences from loss of secrets from one part of the system to the rest of the system. For example, they differ in resistance to a security breach, and the effort required to remediate the whole system in the event of such a breach. The point here is that there are options, many of which are quite simple to employ and deploy.

SA (Security Association)

The parameters and keys that together form the required information for processing secure sessions between peers. Examples of items that may exist in an SA include: Identifier, PSK, Traffic Key, cryptographic algorithms, key lifetimes.

KMP (Key Management Protocol)

A protocol used between peers for creation, distribution and maintenance of secret keys. It determines how secret keys are generated and made available to both the parties. If session or traffic keys are being used, KMP is responsible for generating them and determining when they should be renewed.

A KMP is helpful because it negotiates unique, pair wise, random keys without administrator involvement. It also negotiates as mentioned earlier several of the SA parameters required for the secure connection, including key life times. It keeps track of those lifetimes using counters, and negotiates new keys and parameters before they expire, again, without administrator interaction. Additionally, in the event of a breach, changing the KMP key will immediately cause a rekey to occur for the Traffic Key, and those new Traffic Keys will be installed and used in the current connection.

KMP Function

Any actual KMP used in the general KARP solution framework

Peer Key

Keys that are used between peers as the identity proof. These keys may or may not be connection specific, depending on how they were established, and what form of identity and identity proof is being used in the system. This would generally be given by the KMP that would later be used to derive fresh traffic keys.

Traffic Key

The actual key (or set of keys) used for protecting the routing protocol traffic. Since the traffic keys used in a particular connection are not a fixed part of a device configuration no data exists anywhere else in the operator's systems which can be stolen, e.g. in the case of a terminated or turned employee. If a server or other data store is stolen or compromised, the thieves gain no access to current traffic keys. They may gain access to key derivation material, like a PSK, but not current traffic keys in use.

Definitions of items specific to the general KARP framework are described in more detail in the KARP Framework [I‑D.ietf‑karp‑framework] (Atwood, W. and G. Lebovitz, “Framework for Cryptographic Authentication of Routing Protocol Packets on the Wire,” February 2010.) document.

1.2.  Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119 [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

When used in lower case, these words convey their typical use in common language, and are not to be interpreted as described in RFC2119 [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

1.3.  Scope

Three basic services (or techniques) may be employed in order to secure any piece of data as it is transmitted over the wire: privacy, authentication, and message integrity. The focus for this effort, and the scope for this roadmap document, will be message authentication and packet integrity only. This work explicitly excludes, at this point in time, privacy services. Non-repudiation is also excluded as a goal at this time. Since the objective of most routing protocols is to broadly advertise the routing topology, routing messages are commonly sent in the clear; confidentiality is not normally required for routing protocols. However, ensuring that routing peers truly are the trusted peers expected, and that no rogue peers or messages can compromise the stability of the routing environment is critical, and thus our focus. Privacy and non-repudiation may be addressed in future work.

OSPF, IS-IS, LDP, and RIP already have existing mechanisms for cryptographically authenticating and integrity checking the packets on the wire. Products with these mechanisms have already been produced, code has already been written and both have been optimized for the existing mechanisms. Rather than turn away from these mechanisms, this document aims to enhance them, updating them to modern and secure levels.

Therefore, the scope of this roadmap of work includes:

• Making use of existing routing protocol transport security mechanisms, where they exist, and enhancing or updating them as necessary for modern cryptographic best practices
• Developing a framework for using automatic key management in order to ease deployment, lower cost of operation, and allow for rapid responses to security breaches
• Specifying the automated key management protocol that may be combined with the bits-on-the-wire mechanisms.

This document does not contain protocol specifications. Instead, it defines the areas where protocol specification work is needed and sets a direction, a set of requirements, and a relative priority for addressing that specification work.

There are a set of threats to routing protocols that are considered in-scope for this document, and a set considered out-of- scope. These are described in detail in the Threats (Section 2) section below.

1.4.  Incremental Approach

The work also serves as an agreement between the Routing Area and the Security Area about the priorities and work plan for incrementally delivering the above work. The principle of crawl, walk, run will be in place and routing protocol authentication mechanisms may not go immediately from their current state to a state containing the best possible, most modern security practices. This point is important as there will be times when the best-security-possible will give way to vastly- improved-over-current-security-but-admittedly-not-yet-best-security- possible, in order that incremental progress toward a more secure Internet may be achieved. As such, this document will call out places where agreement has been reached on such trade offs.

Incremental steps will need to be taken for a few very practical reasons. First, there are a considerable number of deployed routing devices in operating networks that will not be able to run the most modern cryptographic mechanisms without significant and unacceptable performance penalties. The roadmap for any one routing protocol MUST allow for incremental improvements on existing operational devices. Second, current routing protocol performance on deployed devices has been achieved over the last 20 years through extensive tuning of software and hardware elements, and is a constant focus for improvement by vendors and operators alike. The introduction of new security mechanisms affects this performance balance. The performance impact of any incremental step of security improvement will need to be weighed by the community, and introduced in such a way that allows the vendor and operator community a path to adoption that upholds reasonable performance metrics. Therefore, certain specification elements may be introduced carrying the "SHOULD" guidance, with the intention that the same mechanism will carry a "MUST" in the next release of the specification.

This gives the vendors and implementors the guidance they need to tune their software and hardware appropriately over time. Last, some security mechanisms require the build out of other operational support systems, and this will take time. An example where these three reasons are at play in an incremental improvement roadmap is seen in the improvement of BGP's [RFC4271] (Rekhter, Y., Li, T., and S. Hares, “A Border Gateway Protocol 4 (BGP-4),” January 2006.) security via the update of the TCP Authentication Option (TCP-AO) [I-D.ietf-tcpm-tcp-auth-opt] effort. It would be ideal, and reflect best common security practice, to have a fully specified key management protocol for negotiating TCP-AO's authentication material, using certificates for peer authentication in the keying.

However, in the spirit of incremental deployment, we will first address issues like cryptographic algorithm agility, replay attacks, TCP session resetting in the base TCP-AO protocol before we layer key management on top of it.

1.5.  Goals

The goals and general guidance for the KARP work follow:

1. Provide authentication and integrity protection for packets on the wire of existing routing protocols
2. Deliver a path to incrementally improve security of the routing infrastructure as explained in the earlier sections.
3. The deployability of the improved security solutions on currently running routing infrastructure equipment. This begs the consideration of the current state of processing power available on routers in the network today.
4. Operational deployability - A solutions acceptability will also be measured by how deployable the solution is by common operator teams using common deployment processes and infrastructures. I.e. We will try to make these solutions fit as well as possible into current operational practices or router deployment. This will be heavily influenced by operator input, to ensure that what we specify can -- and, more importantly, will -- be deployed once specified and implemented by vendors. Deployment of incrementally more secure routing infrastructure in the Internet is the final measure of success. Measurably, we would like to see an increase in the number of surveyed respondents who report deploying the updated authentication mechanisms anywhere across their network, as well as a sharp rise in usage for the total percentage of their network's routers.
   
   Interviews with operators show several points about routing security. First, over 70% of operators have deployed transport connection protection via TCP-MD5 on their EBGP [ISR2008] (McPherson, D. and C. Labovitz, “Worldwide Infrastructure Security Report,” October 2008.). Over 55% also deploy MD5 on their IBGP connections, and 50% deploy MD5 on some other IGP. The survey states that "a considerable increase was observed over previous editions of the survey for use of TCP MD5 with external peers (eBGP), internal peers (iBGP) and MD5 extensions for IGPs." Though the data is not captured in the report, the authors believe anecdotally that of those who have deployed MD5 somewhere in their network, only about 25-30% of the routers in their network are deployed with the authentication enabled. None report using IPsec to protect the routing protocol, and this was a decline from the few that reported doing so in the previous year's report. From my personal conversations with operators, of those using MD5, almost all report deploying with one single manual key throughout the entire network. These same operators report that the one single key has not been changed since it was originally installed, sometimes five or more years ago. When asked why, particularly for the case of BGP using TCP MD5, the following reasons are often given:

   A.

   Changing the keys triggers a TCP reset, and thus bounces the links/adjacencies, undermining Service Level Agreements (SLAs).

   B.

   For external peers, difficulty of coordination with the other organization is an issue. Once they find the correct contact at the other organization (not always so easy), the coordination function is serialized and on a per peer/AS basis. The coordination is very cumbersome and tedious to execute in practice.

   C.

   Keys must be changed at precisely the same time, or at least within 60 seconds (as supported by two major vendors) in order to limit connectivity outage duration. This is incredibly difficult to do, operationally, especially between different organizations.

   D.

   Relatively low priority compared to other operational issues.

   E.

   Lack of staff to implement the changes device by device.

   F.

   There are three use cases for operational peering at play here: peers and interconnection with other operators, Internal BGP and other routing sessions within a single operator, and operator-to-customer-CPE devices. All three have very different properties, and all are reported as cumbersome. One operator reported that the same key is used for all customer premise equipment. The same operator reported that if the customer mandated, a unique key could be created, although the last time this occurred it created such an operational headache that the administrators now usually tell customers that the option doesn't even exist, to avoid the difficulties. These customer-unique keys are never changed, unless the customer demands so. The main threat at play here is that a terminated employee from such an operator who had access to the one (or few) keys used for authentication in these environments could easily wage an attack -- or offer the keys to others who would wage the attack -- and bring down many of the adjacencies, causing destabilization to the routing system.

5. Whatever mechanisms we specify need to be easier than the current methods to deploy, and should provide obvious operational efficiency gains along with significantly better security and threat protection. This combination of value may be enough to drive much broader adoption.
6. Address the threats enumerated above in the "Threats" section (Section 2) for each routing protocol, along a roadmap. Not all threats may be able to be addressed in the first specification update for any one protocol. Roadmaps will be defined so that both the security area and the routing area agree on how the threats will be addressed completely over time.
7. Create a re-usable architecture, framework, and guidelines for various IETF working teams who will address these security improvements for various Routing Protocols. The crux of the KARP work is to re-use that framework as much as possible across relevant Routing Protocols. For example, designers should aim to re-use the key management protocol that will be defined for BGP's TCP-AO key establishment for as many other routing protocols as possible. This is but one example.
8. Bridge any gaps between IETF's Routing and Security Areas by recording agreements on work items, roadmaps, and guidance from the Area leads and Internet Architecture Board (IAB, www.iab.org).

1.6.  Non-Goals

The following two goals are considered out-of-scope for this effort:

• Privacy of the packets on the wire. Once this roadmap is realized, we may revisit work on privacy.
• Message content validity (routing database validity). This work is being addressed in other IETF efforts, like SIDR.

1.7.  Audience

The audience for this document includes:

• Routing Area working group chairs and participants - These people are charged with updates to the Routing Protocol specifications. Any and all cryptographic authentication work on these specifications will occur in Routing Area working groups, with close partnership with the Security Area. Co- advisors from Security Area may often be named for these partnership efforts.
• Security Area reviewers of routing area documents - These people are delegated by the Security Area Directors to perform reviews on routing protocol specifications as they pass through working group last call or IESG review. They will pay particular attention to the use of cryptographic authentication and corresponding security mechanisms for the routing protocols. They will ensure that incremental security improvements are being made, in line with this roadmap.
• Security Area engineers - These people partner with routing area authors/designers on the security mechanisms in routing protocol specifications. Some of these security area engineers will be assigned by the Security Area Directors, while others will be interested parties in the relevant working groups.
• Operators - The operators are a key audience for this work, as the work is considered to have succeeded if the operators deploy the technology, presumably due to a perception of significantly improved security value coupled with relative similarity to deployment complexity and cost. Conversely, the work will be considered a failure if the operators do not care to deploy it, either due to lack of value or perceived (or real) over- complexity of operations. And as such, the GROW and OPSEC WGs should be kept squarely in the loop as well.

2.  Threats

In RFC4949 [RFC4949] (Shirey, R., “Internet Security Glossary, Version 2,” August 2007.), a threat is defined as a potential for violation of security, which exists when there is a circumstance, capability, action, or event that could breach security and cause harm. This section defines the threats that are in scope for this roadmap, and those that are explicitly out of scope. This document leverages the "Generic Threats to Routing Protocols" model, RFC 4593 [RFC4593] (Barbir, A., Murphy, S., and Y. Yang, “Generic Threats to Routing Protocols,” October 2006.), capitalizes terms from that document, and offers a terse definition of those terms. (More thorough description of routing protocol threats sources, motivations, consequences and actions can be found in RFC 4593 [RFC4593] (Barbir, A., Murphy, S., and Y. Yang, “Generic Threats to Routing Protocols,” October 2006.) itself). The threat listings below expand upon these threat definitions.

2.1.  Threats In Scope

The threats that will be addressed in this roadmap are those from OUTSIDERS, attackers that may reside anywhere in the Internet, have the ability to send IP traffic to the router, may be able to observe the router's replies, and may even control the path for a legitimate peer's traffic. These are not legitimate participants in the routing protocol. Message authentication and integrity protection specifically aims to identify messages originating from OUTSIDERS.

The concept of OUTSIDERS can be further refined to include attackers who are terminated employees, and those sitting on-path.

• On-Path - attackers with control of a network resource or a tap along the path of packets between two routers. An on-path outsider can attempt a man-in-the-middle attack, in addition to several other attack classes. A man-in-the-middle (MitM) attack occurs when an attacker who has access to packets flowing between two peers tampers with those packets in such a way that both peers think they are talking to each other directly, when in fact they are actually talking to the attacker only. Protocols conforming to this roadmap will use cryptographic mechanisms to prevent a man-in-the-middle attacker from situating himself undetected.
• Terminated Employees - in this context, those who had access router configuration that included keys or keying material like pre-shared keys used in securing the routing protocol. Using this material, the attacker could send properly MAC'd spoofed packets appearing to come from router A to router B, and thus impersonate an authorized peer. The attacker could then send false traffic that changes the network behavior from its operator's design. The goal of addressing this source specifically is to call out the case where new keys or keying material becomes necessary very quickly, with little operational expense, upon the termination of such an employee. This grouping could also refer to any attacker who somehow managed to gain access to keying material, and said access had been detected by the operators such that the operators have an opportunity to move to new keys in order to prevent an attack.

These attack actions are in scope for this roadmap:

• Spoofing - when an unauthorized device assumes the identity of an authorized one. Spoofing can be used, for example, to inject malicious routing information that causes the disruption of network services. Spoofing can also be used to cause a neighbor relationship to form that subsequently denies the formation of the relationship with the legitimate router.
• Falsification - an action whereby an attacker sends false routing information. To falsify the routing information, an attacker has to be either the originator or a forwarder of the routing information. Falsification may occur by an originator, or a forwarder, and may involve overclaiming, misclaiming, or mistatement of network resource reachability. We must be careful to remember that in this work we are only targeting falsification from outsiders as may occur from tampering with packets in flight. Falsification from BYZANTINES (see the Threats Out of Scope section (Section 2.2) below) are not addressed by the KARP effort.
• Interference - when an attacker inhibits the exchanges by legitimate routers. The types of interference addressed by this work include:

  A.

  Adding noise

  B.

  Replaying out-dated packets

  C.

  Inserting messages

  D.

  Corrupting messages

  E.

  Breaking synchronization

  F.

  Changing message content

• DoS attacks on transport sub-systems - This includes any other DoS attacks specifically based on the above attack types. This is when an attacker sends spoofed packets aimed at halting or preventing the underlying protocol over which the routing protocol runs, for example halting a BGP session by sending a TCP FIN or RST packet. Since this attack depends on spoofing, operators are encouraged to deploy proper authentication mechanisms to prevent such attacks.
• DoS attacks using the authentication mechanism - This includes an attacker sending packets which confuse or overwhelm a security mechanism itself. An example is initiating an overwhelming load of spoofed authenticated route messages so that the receiver needs to process the MAC check, only to discard the packet, sending CPU levels rising. Another example is when an attacker sends an overwhelming load of keying protocol initiations from bogus sources. All other possible DoS attacks are out of scope (see next section).
• Brute Force Attacks Against Password/Keys - This includes either online or offline attacks where attempts are made repeatedly using different keys/passwords until a match is found. While it is impossible to make brute force attacks on keys completely unsuccessful, proper design can make such attacks much harder to succeed. For example, the key length should be sufficiently long so that covering the entire space of possible keys is improbable using computational power expected to be available 10 years out or more. Using per session keys is another widely used method for reducing the number of brute force attacks as this would make it difficult to guess the keys.

2.2.  Threats Out of Scope

Threats from BYZANTINE sources -- faulty, misconfigured, or subverted routers, i.e., legitimate participants in the routing protocol -- are out of scope for this roadmap. Any of the attacks described in the above section (Section 2.1) that may be levied by a BYZANTINE source are therefore also out of scope.

In addition, these other attack actions are out of scope for this work:

• Sniffing - passive observation of route message contents in flight
• Falsification by Byzantine sources - unauthorized message content by a legitimate authorized source.
• Interference due to:

  A.

  Not forwarding packets - cannot be prevented with cryptographic authentication

  B.

  Delaying messages - cannot be prevented with cryptographic authentication

  C.

  Denial of receipt - cannot be prevented with cryptographic authentication

  D.

  Unauthorized message content - the work of the IETF's SIDR working group (http://www.ietf.org/html.charters/sidr-charter.html).

  E.

  Any other type of DoS attack. For example, a flood of traffic that fills the link ahead of the router, so that the router is rendered unusable and unreachable by valid packets is NOT an attack that this work will address. Many other such examples could be contrived.

3.  Requirements for Phase 1 of a Routing Protocol Transport's Security Update

The following list of requirements SHOULD be addressed by a KARP Work Phase 1 security update to any Routing Protocol (according to section 4.1 of the KARP Design Guide [I‑D.ietf‑karp‑design‑guide] (Lebovitz, G. and M. Bhatia, “Keying and Authentication for Routing Protocols (KARP) Design Guidelines,” September 2010.) document). IT IS RECOMMENDED that any Phase 1 security update to a Rouing Protocol contain a section of the specification document that describes how each of these requirements are met. It is further RECOMMENDED that textual justification be presented for any requirements that are NOT addressed.

1. Clear definitions of which elements of the transmission (frame, packet, segment, etc.) are protected by the authentication mechanism
2. Strong algorithms, and defined and accepted by the security community, MUST be specified. The option should use algorithms considered accepted by the IETF's Security community, which are considered appropriately safe. The use of non-standard or unpublished algorithms SHOULD BE avoided.
3. Algorithm agility for the cryptographic algorithms used in the authentication MUST be specified, i.e. more than one algorithm MUST be specified and it MUST be clear how new algorithms MAY be specified and used within the protocol. This requirement exists in case one algorithm gets broken suddenly. Research to identify weakness in algorithms is constant. Breaking a cipher isn't a matter of if, but when it will occur. It's highly unlikely that two different algorithms will be broken simultaneously. So, if two are supported, and one gets broken, we can use the other until we get a new one in place. Having the ability within the protocol specification to support such an event, having algorithm agility, is essential. Mandating two algorithms provides both a redundancy, and a mechanism for enacting that redundancy when needed. Further, the mechanism MUST describe the generic interface for new cryptographic algorithms to be used, so that implementers can use algorithms other than those specified, and so that new algorithms may be specified and supported in the future.
4. Secure use of simple PSKs, offering both operational convenience as well as building something of a fence around stupidity, MUST be specified.
5. Inter-connection replay protection. Packets captured from one session MUST NOT be able to be re-sent and accepted during a later session. In OSPF parlance, or other non TCP based protocols, two routers have a session up if they are able to exchange protocol packets. In OSPF, a session between two routers is called an adjacency only if the neighbor FSM is in ExStart or a higher state. An OSPF session between two routers must go through two main stages of two-way connectivity and LSDB synchronization before an OSPF adjacency is fully established.
6. Intra-connection replay protection. Packets captured during a session MUST NOT be able to be re-sent and accepted during that same session, to deal with long-lived connections. The design teams may thus want to provide a sufficiently large sequence number space for providing intra-connection replay protection. Additionally, replay mechanisms MUST work correctly even in the presence of Routing Protocol packet prioritization by the router.
7. A change of security parameters REQUIRES, and even forces, a change of session traffic keys
8. Intra-connection re-keying which occurs without a break or interruption to the current peering session, and, if possible, without data loss, MUST be specified. Keys need to be changed periodically, for operational privacey (e.g. when an administrator who had access to the keys leaves an organization) and for entropy purposes, and a re-keying mechanism enables the deployers to execute the change without productivity loss.
9. Efficient re-keying SHOULD be provided. The specificaion SHOULD support rekeying during a connection without the need to expend undue computational resources. In particular, the specification SHOULD avoid the need to try/compute multiple keys on a given packet.
10. Prevent DoS attacks as those described as in-scope in the threats section Section 2.1 above.
11. Default mechanisms and algorithms specified and defined are REQUIRED for all implementations.
12. For backward compatibilty reasons manual keying MUST be supported.
13. Architecture of the specification SHOULD consider and allow for future use of a KMP.
14. The authentication mechanism in the Routing Protocol MUST be decoupled from the key management system used. It MUST be obvious how the keying material was obtained, and the process for obtaining the keying material MUST exist outside of the Routing Protocol. This will allow for the various key generation methods, like manual keys and KMPs, to be used with the same Routing Protocol mechanism.
15. Convergence times of the Routing Protocols SHOULD NOT be materially affected. Materially here is defined as anything greater than a 5% convergence time increase. Note that convergence is different than boot time. Also note that convergence time has a lot to do with the speed of processors used on individual routing peers, and this processing power increases by Moore's law over time, meaning that the same route calculations and table population routines will decrease in duration over time. Therefore, this requirement should be considered only in terms of total number of messages that must be exchanged, and less for the computational intensity of processing any one message. Alternatively this can be simplified by saying that the new mechanisms should only result in a minimal increase in the number of routing protocol messages passed between the peers.
16. The changes or addition of security mechanisms SHOULD NOT cause a refresh of route updates or cause additional route updates to be generated.
17. Router implementations provide prioritized treatment to certain protocol packets. For example, OSPF HELLO messages and ACKs are prioritized for processing above other OSPF packets. The authentication mechanism SHOULD NOT interfere with the ability to observe and enforce such prioritization. Any effect on such priority mechanisms MUST be explicitly documented and justified.Replay mechanisms provided by the routing protocols MUST work even if certain protocol packets are offered prioritized treatment.
18. The authentication mechanism does not provide message confidentiality, but SHOULD NOT preclude the possibility of confidentiality support being added in the future.
19. Routing protocols MUST only send minimal information regarding the authentication mechanisms and the parameters in its protocol packets to avoid exposing the information to parties on the path.
20. In most routing protocols (OSPF, ISIS, BFD, RIP, etc), all speakers share the same key on a broadcast segment. Possession of the key itself is used for identity validation and no other identity check is used. This opens a window for an attack where the sender can masquerade as some other neighbor. Routing protocols SHOULD thus use some other information besides the key to validate a neighbor. One could look at [I‑D.ietf‑opsec‑routing‑protocols‑crypto‑issues] (Jaeggli, J., Hares, S., Bhatia, M., Manral, V., and R. White, “Issues with existing Cryptographic Protection Methods for Routing Protocols,” August 2010.) for details on such attacks.
21. Routing protocols that rely on the IP header (or information beyond the routing protocol payload) to identify the neighbor which originated the packet must either protect the IP header or provide some other means to identify the neighbor. [I‑D.ietf‑opsec‑routing‑protocols‑crypto‑issues] (Jaeggli, J., Hares, S., Bhatia, M., Manral, V., and R. White, “Issues with existing Cryptographic Protection Methods for Routing Protocols,” August 2010.) describes some attacks that are based on this.
22. The new security and authentication mechanisms MUST support incremental deployment. It will not be feasible to deploy a new Routing Protocol authentication mechanism throughout the network instantaneously. It also may not be possible to deploy such a mechanism to all routers in a large autonomous system (AS) at one time. Proposed solutions SHOULD support an incremental deployment method that provides some benefit for those who participate. Because of this, there are several requirements that any proposed KARP mechanism should consider.

    A.

    The Routing Protocol security mechanism MUST enable each router to configure use of the security mechanism on a per- peer basis where the communication is one-on-one.

    B.

    The new KARP mechanism MUST provide backward compatibility in the message formatting, transmission, and processing of routing information carried through a mixed security environment. Message formatting in a fully secured environment MAY be handled in a non-backward compatible fashion though care must be taken to ensure that routing protocol packets can traverse intermediate routers which don't support the new format.

    C.

    In an environment where both secured and non-secured systems are interoperating a mechanism MUST exist for secured systems to identify whether an originator intended the information to be secured.

    D.

    In an environment where secured service is in the process of being deployed a mechanism MUST exist to support a transition free of service interruption (caused by the deployment per se).

23. The introduction of mechanisms to improve routing authentication and security may increase the processing performed by a router. Since most of the currently deployed routers do not have hardware to accelerate cryptographic operations, these operations could impose a significant processing burden under some circumstances. Thus proposed solutions should be evaluated carefully with regard to the processing burden they may impose, since deployment may be impeded if network operators perceive that a solution will impose a processing burden which either provokes substantial capital expense, or threatens to destabilize routers.
24. Given the high number of routers that would require the new authentication mechanisms in a typical ISP deployment, solutions can increase their appeal by minimizing the burden imposed on all routers in favor of confining significant work loads to a relatively small number of devices. Optional features or increased assurance that provokes more pervasive processing load MAY be made available for deployments where the additional resources are economically justifiable.
25. The new authentication and security mechanisms should not rely on systems external to the routing system (the equipment that is performing forwarding). In order to ensure the rapid initialization and/or return to service of failed nodes it is important to reduce reliance on these external systems to the greatest extent possible. Therefore, proposed solutions SHOULD NOT require connections to external systems, beyond those directly involved in peering relationships, in order to return to full service. It is however acceptable for the proposed solutions to require post initialization synchronization with external systems in order to fully synchronize the security information.

4.  Security Considerations

This document is mostly about security considerations for the KARP efforts, both threats and requirements for solving those threats. More detailed security considerations were placed in the Security Considerations section of the KARP Design Guide [I‑D.ietf‑karp‑design‑guide] (Lebovitz, G. and M. Bhatia, “Keying and Authentication for Routing Protocols (KARP) Design Guidelines,” September 2010.) document.

5.  IANA Considerations

This document has no actions for IANA.

6.  Acknowledgements

The majority of the text for version -00 of this document was taken from draft-lebovitz-karp-roadmap, authored by Gregory Lebovitz.

7.  Change History (RFC Editor: Delete Before Publishing)

[NOTE TO RFC EDITOR: this section for use during I-D stage only. Please remove before publishing as RFC.]

kmart-00-00 original rough rough rough draft for review by routing and security AD's

karp-threats-reqs-00-

o removed all the portions that will be covered in either draft-ietf-karp-design-guide or draft-ietf-karp-framework

8.  References

8.1. Normative References

8.2. Informative References

Authors' Addresses