RFC 7296
Internet Key Exchange Protocol Version 2 (IKEv2)
Pages: 142
Internet Standard: 79
→ Errata
Obsoletes: 5996
Updated by: 7427 7670 8247 8983 9370
Internet Standard: 79
→ Errata
Obsoletes: 5996
Updated by: 7427 7670 8247 8983 9370
Part 6 of 6 – Pages 124 to 142
5. Security Considerations
While this protocol is designed to minimize disclosure of configuration information to unauthenticated peers, some such disclosure is unavoidable. One peer or the other must identify itself first and prove its identity first. To avoid probing, the initiator of an exchange is required to identify itself first, and usually is required to authenticate itself first. The initiator can, however, learn that the responder supports IKE and what cryptographic protocols it supports. The responder (or someone impersonating the responder) not only can probe the initiator for its identity but may, by using CERTREQ payloads, be able to determine what certificates the initiator is willing to use. Use of EAP authentication changes the probing possibilities somewhat. When EAP authentication is used, the responder proves its identity before the initiator does, so an initiator that knew the name of a valid initiator could probe the responder for both its name and certificates. Repeated rekeying using CREATE_CHILD_SA without additional Diffie- Hellman exchanges leaves all SAs vulnerable to cryptanalysis of a single key. Implementers should take note of this fact and set a limit on CREATE_CHILD_SA exchanges between exponentiations. This document does not prescribe such a limit. The strength of a key derived from a Diffie-Hellman exchange using any of the groups defined here depends on the inherent strength of the group, the size of the exponent used, and the entropy provided by the random number generator used. Due to these inputs, it is difficult to determine the strength of a key for any of the defined groups. Diffie-Hellman group number two, when used with a strong random number generator and an exponent no less than 200 bits, is common for use with 3DES. Group five provides greater security than group two. Group one is for historic purposes only and does not provide sufficient strength except for use with DES, which is also for historic use only. Implementations should make note of these estimates when establishing policy and negotiating security parameters. Note that these limitations are on the Diffie-Hellman groups themselves. There is nothing in IKE that prohibits using stronger groups nor is there anything that will dilute the strength obtained from stronger groups (limited by the strength of the other algorithms
negotiated including the PRF). In fact, the extensible framework of IKE encourages the definition of more groups; use of elliptic curve groups may greatly increase strength using much smaller numbers. It is assumed that all Diffie-Hellman exponents are erased from memory after use. The IKE_SA_INIT and IKE_AUTH exchanges happen before the initiator has been authenticated. As a result, an implementation of this protocol needs to be completely robust when deployed on any insecure network. Implementation vulnerabilities, particularly DoS attacks, can be exploited by unauthenticated peers. This issue is particularly worrisome because of the unlimited number of messages in EAP-based authentication. The strength of all keys is limited by the size of the output of the negotiated PRF. For this reason, a PRF whose output is less than 128 bits (e.g., 3DES-CBC) MUST NOT be used with this protocol. The security of this protocol is critically dependent on the randomness of the randomly chosen parameters. These should be generated by a strong random or properly seeded pseudorandom source (see [RANDOMNESS]). Implementers should take care to ensure that use of random numbers for both keys and nonces is engineered in a fashion that does not undermine the security of the keys. For information on the rationale of many of the cryptographic design choices in this protocol, see [SIGMA] and [SKEME]. Though the security of negotiated Child SAs does not depend on the strength of the encryption and integrity protection negotiated in the IKE SA, implementations MUST NOT negotiate NONE as the IKE integrity protection algorithm or ENCR_NULL as the IKE encryption algorithm. When using pre-shared keys, a critical consideration is how to assure the randomness of these secrets. The strongest practice is to ensure that any pre-shared key contain as much randomness as the strongest key being negotiated. Deriving a shared secret from a password, name, or other low-entropy source is not secure. These sources are subject to dictionary and social-engineering attacks, among others. The NAT_DETECTION_*_IP notifications contain a hash of the addresses and ports in an attempt to hide internal IP addresses behind a NAT. Since the IPv4 address space is only 32 bits, and it is usually very sparse, it would be possible for an attacker to find out the internal address used behind the NAT box by trying all possible IP addresses and trying to find the matching hash. The port numbers are normally fixed to 500, and the SPIs can be extracted from the packet. This reduces the number of hash calculations to 2^32. With an educated
guess of the use of private address space, the number of hash calculations is much smaller. Designers should therefore not assume that use of IKE will not leak internal address information. When using an EAP authentication method that does not generate a shared key for protecting a subsequent AUTH payload, certain man-in- the-middle and server-impersonation attacks are possible [EAPMITM]. These vulnerabilities occur when EAP is also used in protocols that are not protected with a secure tunnel. Since EAP is a general- purpose authentication protocol, which is often used to provide single-signon facilities, a deployed IPsec solution that relies on an EAP authentication method that does not generate a shared key (also known as a non-key-generating EAP method) can become compromised due to the deployment of an entirely unrelated application that also happens to use the same non-key-generating EAP method, but in an unprotected fashion. Note that this vulnerability is not limited to just EAP, but can occur in other scenarios where an authentication infrastructure is reused. For example, if the EAP mechanism used by IKEv2 utilizes a token authenticator, a man-in-the-middle attacker could impersonate the web server, intercept the token authentication exchange, and use it to initiate an IKEv2 connection. For this reason, use of non-key-generating EAP methods SHOULD be avoided where possible. Where they are used, it is extremely important that all usages of these EAP methods SHOULD utilize a protected tunnel, where the initiator validates the responder's certificate before initiating the EAP authentication. Implementers should describe the vulnerabilities of using non-key-generating EAP methods in the documentation of their implementations so that the administrators deploying IPsec solutions are aware of these dangers. An implementation using EAP MUST also use a public-key-based authentication of the server to the client before the EAP authentication begins, even if the EAP method offers mutual authentication. This avoids having additional IKEv2 protocol variations and protects the EAP data from active attackers. If the messages of IKEv2 are long enough that IP-level fragmentation is necessary, it is possible that attackers could prevent the exchange from completing by exhausting the reassembly buffers. The chances of this can be minimized by using the Hash and URL encodings instead of sending certificates (see Section 3.6). Additional mitigations are discussed in [DOSUDPPROT]. Admission control is critical to the security of the protocol. For example, trust anchors used for identifying IKE peers should probably be different than those used for other forms of trust, such as those used to identify public web servers. Moreover, although IKE provides a great deal of leeway in defining the security policy for a trusted
peer's identity, credentials, and the correlation between them, having such security policy defined explicitly is essential to a secure implementation.5.1. Traffic Selector Authorization
IKEv2 relies on information in the Peer Authorization Database (PAD) when determining what kind of Child SAs a peer is allowed to create. This process is described in Section 4.4.3 of [IPSECARCH]. When a peer requests the creation of a Child SA with some Traffic Selectors, the PAD must contain "Child SA Authorization Data" linking the identity authenticated by IKEv2 and the addresses permitted for Traffic Selectors. For example, the PAD might be configured so that authenticated identity "sgw23.example.com" is allowed to create Child SAs for 192.0.2.0/24, meaning this security gateway is a valid "representative" for these addresses. Host-to-host IPsec requires similar entries, linking, for example, "fooserver4.example.com" with 198.51.100.66/32, meaning this identity is a valid "owner" or "representative" of the address in question. As noted in [IPSECARCH], "It is necessary to impose these constraints on creation of child SAs to prevent an authenticated peer from spoofing IDs associated with other, legitimate peers". In the example given above, a correct configuration of the PAD prevents sgw23 from creating Child SAs with address 198.51.100.66, and prevents fooserver4 from creating Child SAs with addresses from 192.0.2.0/24. It is important to note that simply sending IKEv2 packets using some particular address does not imply a permission to create Child SAs with that address in the Traffic Selectors. For example, even if sgw23 would be able to spoof its IP address as 198.51.100.66, it could not create Child SAs matching fooserver4's traffic. The IKEv2 specification does not specify how exactly IP address assignment using Configuration payloads interacts with the PAD. Our interpretation is that when a security gateway assigns an address using Configuration payloads, it also creates a temporary PAD entry linking the authenticated peer identity and the newly allocated inner address. It has been recognized that configuring the PAD correctly may be difficult in some environments. For instance, if IPsec is used between a pair of hosts whose addresses are allocated dynamically using DHCP, it is extremely difficult to ensure that the PAD
specifies the correct "owner" for each IP address. This would require a mechanism to securely convey address assignments from the DHCP server, and link them to identities authenticated using IKEv2. Due to this limitation, some vendors have been known to configure their PADs to allow an authenticated peer to create Child SAs with Traffic Selectors containing the same address that was used for the IKEv2 packets. In environments where IP spoofing is possible (i.e., almost everywhere) this essentially allows any peer to create Child SAs with any Traffic Selectors. This is not an appropriate or secure configuration in most circumstances. See [H2HIPSEC] for an extensive discussion about this issue, and the limitations of host-to-host IPsec in general.6. IANA Considerations
[IKEV2] defined many field types and values. IANA has already registered those types and values in [IKEV2IANA], so they are not listed here again. One item has been deprecated from the "IKEv2 Certificate Encodings" registry: "Raw RSA Key". IANA has updated all references to RFC 5996 to point to this document.7. References
7.1. Normative References
[ADDGROUP] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) Diffie-Hellman groups for Internet Key Exchange (IKE)", RFC 3526, May 2003, <http://www.rfc-editor.org/info/rfc3526>. [ADDRIPV6] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006, <http://www.rfc-editor.org/info/rfc4291>. [AEAD] Black, D. and D. McGrew, "Using Authenticated Encryption Algorithms with the Encrypted Payload of the Internet Key Exchange version 2 (IKEv2) Protocol", RFC 5282, August 2008, <http://www.rfc-editor.org/info/rfc5282>.
[AESCMACPRF128] Song, J., Poovendran, R., Lee, J., and T. Iwata, "The Advanced Encryption Standard-Cipher-based Message Authentication Code-Pseudo-Random Function-128 (AES-CMAC- PRF-128) Algorithm for the Internet Key Exchange Protocol (IKE)", RFC 4615, August 2006, <http://www.rfc-editor.org/info/rfc4615>. [AESXCBCPRF128] Hoffman, P., "The AES-XCBC-PRF-128 Algorithm for the Internet Key Exchange Protocol (IKE)", RFC 4434, February 2006, <http://www.rfc-editor.org/info/rfc4434>. [EAP] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748, June 2004, <http://www.rfc-editor.org/info/rfc3748>. [ECN] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001, <http://www.rfc-editor.org/info/rfc3168>. [ESPCBC] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher Algorithms", RFC 2451, November 1998, <http://www.rfc-editor.org/info/rfc2451>. [IKEV2IANA] IANA, "Internet Key Exchange Version 2 (IKEv2) Parameters", <http://www.iana.org/assignments/ikev2-parameters/>. [IPSECARCH] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005, <http://www.rfc-editor.org/info/rfc4301>. [MUSTSHOULD] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [PKCS1] Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1", RFC 3447, February 2003, <http://www.rfc-editor.org/info/rfc3447>.
[PKIX] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008, <http://www.rfc-editor.org/info/rfc5280>. [RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the Internet Key Exchange Version 2 (IKEv2)", RFC 4307, December 2005, <http://www.rfc-editor.org/info/rfc4307>. [UDPENCAPS] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M. Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC 3948, January 2005, <http://www.rfc-editor.org/info/rfc3948>. [URLS] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005, <http://www.rfc-editor.org/info/rfc3986>.7.2. Informative References
[AH] Kent, S., "IP Authentication Header", RFC 4302, December 2005, <http://www.rfc-editor.org/info/rfc4302>. [ARCHGUIDEPHIL] Bush, R. and D. Meyer, "Some Internet Architectural Guidelines and Philosophy", RFC 3439, December 2002, <http://www.rfc-editor.org/info/rfc3439>. [ARCHPRINC] Carpenter, B., "Architectural Principles of the Internet", RFC 1958, June 1996, <http://www.rfc-editor.org/info/rfc1958>. [Clarif] Eronen, P. and P. Hoffman, "IKEv2 Clarifications and Implementation Guidelines", RFC 4718, October 2006, <http://www.rfc-editor.org/info/rfc4718>. [DES] American National Standards Institute, "American National Standard for Information Systems-Data Link Encryption", ANSI X3.106, 1983. [DH] Diffie, W. and M. Hellman, "New Directions in Cryptography", IEEE Transactions on Information Theory, V.IT-22 n. 6, June 1977.
[DIFFSERVARCH] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998, <http://www.rfc-editor.org/info/rfc2475>. [DIFFSERVFIELD] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998, <http://www.rfc-editor.org/info/rfc2474>. [DIFFTUNNEL] Black, D., "Differentiated Services and Tunnels", RFC 2983, October 2000, <http://www.rfc-editor.org/info/rfc2983>. [DOI] Piper, D., "The Internet IP Security Domain of Interpretation for ISAKMP", RFC 2407, November 1998, <http://www.rfc-editor.org/info/rfc2407>. [DOSUDPPROT] Kaufman, C., Perlman, R., and B. Sommerfeld, "DoS protection for UDP-based protocols", ACM Conference on Computer and Communications Security, October 2003. [DSS] National Institute of Standards and Technology, U.S. Department of Commerce, "Digital Signature Standard (DSS)", FIPS 186-4, July 2013, <http://nvlpubs.nist.gov/nistpubs/FIPS/ NIST.FIPS.186-4.pdf>. [EAI] Yang, A., Steele, S., and N. Freed, "Internationalized Email Headers", RFC 6532, February 2012, <http://www.rfc-editor.org/info/rfc6532>. [EAP-IANA] IANA, "Extensible Authentication Protocol (EAP) Registry: Method Types", <http://http://www.iana.org/assignments/eap-eke/>. [EAPMITM] Asokan, N., Niemi, V., and K. Nyberg, "Man-in-the-Middle in Tunneled Authentication Protocols", November 2002, <http://eprint.iacr.org/2002/163>. [ESP] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005, <http://www.rfc-editor.org/info/rfc4303>.
[EXCHANGEANALYSIS] Perlman, R. and C. Kaufman, "Analysis of the IPsec key exchange Standard", WET-ICE Security Conference, MIT, 2001, <http://www.computer.org/csdl/proceedings/ wetice/2001/1269/00/12690150.pdf>. [FIPS.180-4.2012] National Institute of Standards and Technology, U.S. Department of Commerce, "Secure Hash Standard (SHS)", FIPS 180-4, March 2012, <http://csrc.nist.gov/publications/fips/fips180-4/ fips-180-4.pdf>. [H2HIPSEC] Aura, T., Roe, M., and A. Mohammed, "Experiences with Host-to-Host IPsec", 13th International Workshop on Security Protocols, Cambridge, UK, April 2005. [HMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- Hashing for Message Authentication", RFC 2104, February 1997, <http://www.rfc-editor.org/info/rfc2104>. [IDEA] Lai, X., "On the Design and Security of Block Ciphers", ETH Series in Information Processing, v. 1, Konstanz: Hartung-Gorre Verlag, 1992. [IDNA] Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, August 2010, <http://www.rfc-editor.org/info/rfc5890>. [IKEV1] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, November 1998, <http://www.rfc-editor.org/info/rfc2409>. [IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005, <http://www.rfc-editor.org/info/rfc4306>. [IP] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981, <http://www.rfc-editor.org/info/rfc791>. [IP-COMP] Shacham, A., Monsour, B., Pereira, R., and M. Thomas, "IP Payload Compression Protocol (IPComp)", RFC 3173, September 2001, <http://www.rfc-editor.org/info/rfc3173>.
[IPSECARCH-OLD] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998, <http://www.rfc-editor.org/info/rfc2401>. [IPV6CONFIG] Eronen, P., Laganier, J., and C. Madson, "IPv6 Configuration in Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5739, February 2010, <http://www.rfc-editor.org/info/rfc5739>. [ISAKMP] Maughan, D., Schneider, M., and M. Schertler, "Internet Security Association and Key Management Protocol (ISAKMP)", RFC 2408, November 1998, <http://www.rfc-editor.org/info/rfc2408>. [MAILFORMAT] Resnick, P., Ed., "Internet Message Format", RFC 5322, October 2008, <http://www.rfc-editor.org/info/rfc5322>. [MD5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April 1992, <http://www.rfc-editor.org/info/rfc1321>. [MIPV6] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support in IPv6", RFC 6275, July 2011, <http://www.rfc-editor.org/info/rfc6275>. [MLDV2] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004, <http://www.rfc-editor.org/info/rfc3810>. [MOBIKE] Eronen, P., "IKEv2 Mobility and Multihoming Protocol (MOBIKE)", RFC 4555, June 2006, <http://www.rfc-editor.org/info/rfc4555>. [MODES] Dworkin, M., "Recommendation for Block Cipher Modes of Operation", National Institute of Standards and Technology, NIST Special Publication 800-38A 2001 Edition, December 2001. [NAI] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The Network Access Identifier", RFC 4282, December 2005, <http://www.rfc-editor.org/info/rfc4282>. [NATREQ] Aboba, B. and W. Dixon, "IPsec-Network Address Translation (NAT) Compatibility Requirements", RFC 3715, March 2004, <http://www.rfc-editor.org/info/rfc3715>.
[OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol", RFC 2412, November 1998, <http://www.rfc-editor.org/info/rfc2412>. [PFKEY] McDonald, D., Metz, C., and B. Phan, "PF_KEY Key Management API, Version 2", RFC 2367, July 1998, <http://www.rfc-editor.org/info/rfc2367>. [PHOTURIS] Karn, P. and W. Simpson, "Photuris: Session-Key Management Protocol", RFC 2522, March 1999, <http://www.rfc-editor.org/info/rfc2522>. [RANDOMNESS] Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005, <http://www.rfc-editor.org/info/rfc4086>. [REAUTH] Nir, Y., "Repeated Authentication in Internet Key Exchange (IKEv2) Protocol", RFC 4478, April 2006, <http://www.rfc-editor.org/info/rfc4478>. [REUSE] Menezes, A. and B. Ustaoglu, "On Reusing Ephemeral Keys In Diffie-Hellman Key Agreement Protocols", December 2008, <http://www.cacr.math.uwaterloo.ca/techreports/2008/ cacr2008-24.pdf>. [RFC4945] Korver, B., "The Internet IP Security PKI Profile of IKEv1/ISAKMP, IKEv2, and PKIX", RFC 4945, August 2007, <http://www.rfc-editor.org/info/rfc4945>. [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010, <http://www.rfc-editor.org/info/rfc5996>. [RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman Tests for the Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 6989, July 2013, <http://www.rfc-editor.org/info/rfc6989>. [ROHCV2] Ertekin, E., Christou, C., Jasani, R., Kivinen, T., and C. Bormann, "IKEv2 Extensions to Support Robust Header Compression over IPsec", RFC 5857, May 2010, <http://www.rfc-editor.org/info/rfc5857>.
[SIGMA] Krawczyk, H., "SIGMA: the 'SIGn-and-MAc' Approach to Authenticated Diffie-Hellman and its Use in the IKE Protocols", Advances in Cryptography - CRYPTO 2003 Proceedings LNCS 2729, 2003, <http://www.informatik.uni-trier.de/~ley/db/conf/crypto/ crypto2003.html>. [SKEME] Krawczyk, H., "SKEME: A Versatile Secure Key Exchange Mechanism for Internet", IEEE Proceedings of the 1996 Symposium on Network and Distributed Systems Security, 1996. [TRANSPARENCY] Carpenter, B., "Internet Transparency", RFC 2775, February 2000, <http://www.rfc-editor.org/info/rfc2775>.
Appendix A. Summary of Changes from IKEv1
The goals of this revision to IKE are: 1. To define the entire IKE protocol in a single document, replacing RFCs 2407, 2408, and 2409 and incorporating subsequent changes to support NAT traversal, Extensible Authentication, and Remote Address acquisition; 2. To simplify IKE by replacing the eight different initial exchanges with a single four-message exchange (with changes in authentication mechanisms affecting only a single AUTH payload rather than restructuring the entire exchange) see [EXCHANGEANALYSIS]; 3. To remove the Domain of Interpretation (DOI), Situation (SIT), and Labeled Domain Identifier fields, and the Commit and Authentication only bits; 4. To decrease IKE's latency in the common case by making the initial exchange be 2 round trips (4 messages), and allowing the ability to piggyback setup of a Child SA on that exchange; 5. To replace the cryptographic syntax for protecting the IKE messages themselves with one based closely on ESP to simplify implementation and security analysis; 6. To reduce the number of possible error states by making the protocol reliable (all messages are acknowledged) and sequenced. This allows shortening CREATE_CHILD_SA exchanges from 3 messages to 2; 7. To increase robustness by allowing the responder to not do significant processing until it receives a message proving that the initiator can receive messages at its claimed IP address; 8. To fix cryptographic weaknesses such as the problem with symmetries in hashes used for authentication (documented by Tero Kivinen); 9. To specify Traffic Selectors in their own payloads type rather than overloading ID payloads, and making more flexible the Traffic Selectors that may be specified; 10. To specify required behavior under certain error conditions or when data that is not understood is received in order to make it easier to make future revisions in a way that does not break backward compatibility;
11. To simplify and clarify how shared state is maintained in the
presence of network failures and DoS attacks; and
12. To maintain existing syntax and magic numbers to the extent
possible to make it likely that implementations of IKEv1 can be
enhanced to support IKEv2 with minimum effort.
Appendix B. Diffie-Hellman Groups
There are two Diffie-Hellman groups defined here for use in IKE.
These groups were generated by Richard Schroeppel at the University
of Arizona. Properties of these primes are described in [OAKLEY].
The strength supplied by group 1 may not be sufficient for typical
uses and is here for historic reasons.
Additional Diffie-Hellman groups have been defined in [ADDGROUP].
B.1. Group 1 - 768-bit MODP
This group is assigned ID 1 (one).
The prime is: 2^768 - 2 ^704 - 1 + 2^64 * { [2^638 pi] + 149686 }
Its hexadecimal value is:
FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
E485B576 625E7EC6 F44C42E9 A63A3620 FFFFFFFF FFFFFFFF
The generator is 2.
B.2. Group 2 - 1024-bit MODP
This group is assigned ID 2 (two).
The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
Its hexadecimal value is:
FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381
FFFFFFFF FFFFFFFF
The generator is 2.
Appendix C. Exchanges and Payloads
This appendix contains a short summary of the IKEv2 exchanges, and what payloads can appear in which message. This appendix is purely informative; if it disagrees with the body of this document, the other text is considered correct. Vendor ID (V) payloads may be included in any place in any message. This sequence here shows what are the most logical places for them.C.1. IKE_SA_INIT Exchange
request --> [N(COOKIE),] SA, KE, Ni, [N(NAT_DETECTION_SOURCE_IP)+, N(NAT_DETECTION_DESTINATION_IP),] [V+][N+] normal response <-- SA, KE, Nr, (no cookie) [N(NAT_DETECTION_SOURCE_IP), N(NAT_DETECTION_DESTINATION_IP),] [[N(HTTP_CERT_LOOKUP_SUPPORTED),] CERTREQ+,] [V+][N+] cookie response <-- N(COOKIE), [V+][N+] different Diffie- <-- N(INVALID_KE_PAYLOAD), Hellman group [V+][N+] wantedC.2. IKE_AUTH Exchange without EAP
request --> IDi, [CERT+,] [N(INITIAL_CONTACT),] [[N(HTTP_CERT_LOOKUP_SUPPORTED),] CERTREQ+,] [IDr,] AUTH, [CP(CFG_REQUEST),] [N(IPCOMP_SUPPORTED)+,] [N(USE_TRANSPORT_MODE),] [N(ESP_TFC_PADDING_NOT_SUPPORTED),] [N(NON_FIRST_FRAGMENTS_ALSO),] SA, TSi, TSr, [V+][N+]
response <-- IDr, [CERT+,]
AUTH,
[CP(CFG_REPLY),]
[N(IPCOMP_SUPPORTED),]
[N(USE_TRANSPORT_MODE),]
[N(ESP_TFC_PADDING_NOT_SUPPORTED),]
[N(NON_FIRST_FRAGMENTS_ALSO),]
SA, TSi, TSr,
[N(ADDITIONAL_TS_POSSIBLE),]
[V+][N+]
error in Child SA <-- IDr, [CERT+,]
creation AUTH,
N(error),
[V+][N+]
C.3. IKE_AUTH Exchange with EAP
first request --> IDi,
[N(INITIAL_CONTACT),]
[[N(HTTP_CERT_LOOKUP_SUPPORTED),] CERTREQ+,]
[IDr,]
[CP(CFG_REQUEST),]
[N(IPCOMP_SUPPORTED)+,]
[N(USE_TRANSPORT_MODE),]
[N(ESP_TFC_PADDING_NOT_SUPPORTED),]
[N(NON_FIRST_FRAGMENTS_ALSO),]
SA, TSi, TSr,
[V+][N+]
first response <-- IDr, [CERT+,] AUTH,
EAP,
[V+][N+]
/ --> EAP
repeat 1..N times |
\ <-- EAP
last request --> AUTH
last response <-- AUTH,
[CP(CFG_REPLY),]
[N(IPCOMP_SUPPORTED),]
[N(USE_TRANSPORT_MODE),]
[N(ESP_TFC_PADDING_NOT_SUPPORTED),]
[N(NON_FIRST_FRAGMENTS_ALSO),]
SA, TSi, TSr,
[N(ADDITIONAL_TS_POSSIBLE),]
[V+][N+]
C.4. CREATE_CHILD_SA Exchange for Creating or Rekeying Child SAs
request --> [N(REKEY_SA),]
[CP(CFG_REQUEST),]
[N(IPCOMP_SUPPORTED)+,]
[N(USE_TRANSPORT_MODE),]
[N(ESP_TFC_PADDING_NOT_SUPPORTED),]
[N(NON_FIRST_FRAGMENTS_ALSO),]
SA, Ni, [KEi,] TSi, TSr,
[V+][N+]
normal <-- [CP(CFG_REPLY),]
response [N(IPCOMP_SUPPORTED),]
[N(USE_TRANSPORT_MODE),]
[N(ESP_TFC_PADDING_NOT_SUPPORTED),]
[N(NON_FIRST_FRAGMENTS_ALSO),]
SA, Nr, [KEr,] TSi, TSr,
[N(ADDITIONAL_TS_POSSIBLE),]
[V+][N+]
error case <-- N(error)
different Diffie- <-- N(INVALID_KE_PAYLOAD),
Hellman group [V+][N+]
wanted
C.5. CREATE_CHILD_SA Exchange for Rekeying the IKE SA
request --> SA, Ni, KEi,
[V+][N+]
response <-- SA, Nr, KEr,
[V+][N+]
C.6. INFORMATIONAL Exchange
request --> [N+,] [D+,] [CP(CFG_REQUEST)] response <-- [N+,] [D+,] [CP(CFG_REPLY)]Acknowledgements
Many individuals in the IPsecME Working Group were very helpful in contributing ideas and text for this document, as well as in reviewing the clarifications suggested by others. The acknowledgements from the IKEv2 document were: This document is a collaborative effort of the entire IPsec WG. If there were no limit to the number of authors that could appear on an RFC, the following, in alphabetical order, would have been listed: Bill Aiello, Stephane Beaulieu, Steve Bellovin, Sara Bitan, Matt Blaze, Ran Canetti, Darren Dukes, Dan Harkins, Paul Hoffman, John Ioannidis, Charlie Kaufman, Steve Kent, Angelos Keromytis, Tero Kivinen, Hugo Krawczyk, Andrew Krywaniuk, Radia Perlman, Omer Reingold, and Michael Richardson. Many other people contributed to the design. It is an evolution of IKEv1, ISAKMP, and the IPsec DOI, each of which has its own list of authors. Hugh Daniel suggested the feature of having the initiator, in message 3, specify a name for the responder, and gave the feature the cute name "You Tarzan, Me Jane". David Faucher and Valery Smyslov helped refine the design of the Traffic Selector negotiation.
Authors' Addresses
Charlie Kaufman Microsoft 1 Microsoft Way Redmond, WA 98052 United States EMail: charliekaufman@outlook.com Paul Hoffman VPN Consortium 127 Segre Place Santa Cruz, CA 95060 United States Phone: 1-831-426-9827 EMail: paul.hoffman@vpnc.org Yoav Nir Check Point Software Technologies Ltd. 5 Hasolelim St. Tel Aviv 6789735 Israel EMail: ynir.ietf@gmail.com Pasi Eronen Independent EMail: pe@iki.fi Tero Kivinen INSIDE Secure Eerikinkatu 28 HELSINKI FI-00180 Finland EMail: kivinen@iki.fi