--- 1/draft-ietf-ipsecme-qr-ikev2-01.txt 2018-02-27 11:13:34.817354905 -0800 +++ 2/draft-ietf-ipsecme-qr-ikev2-02.txt 2018-02-27 11:13:34.857355848 -0800 @@ -1,21 +1,21 @@ Internet Engineering Task Force S. Fluhrer Internet-Draft D. McGrew Intended status: Standards Track P. Kampanakis -Expires: June 23, 2018 Cisco Systems +Expires: August 31, 2018 Cisco Systems V. Smyslov ELVIS-PLUS - December 20, 2017 + February 27, 2018 Postquantum Preshared Keys for IKEv2 - draft-ietf-ipsecme-qr-ikev2-01 + draft-ietf-ipsecme-qr-ikev2-02 Abstract The possibility of Quantum Computers pose a serious challenge to cryptography algorithms deployed widely today. IKEv2 is one example of a cryptosystem that could be broken; someone storing VPN communications today could decrypt them at a later time when a Quantum Computer is available. It is anticipated that IKEv2 will be extended to support quantum secure key exchange algorithms; however that is not likely to happen in the near term. To address this @@ -31,25 +31,25 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on June 23, 2018. + This Internet-Draft will expire on August 31, 2018. Copyright Notice - Copyright (c) 2017 IETF Trust and the persons identified as the + Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as @@ -58,32 +58,32 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Changes . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 5 2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Exchanges . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Upgrade procedure . . . . . . . . . . . . . . . . . . . . . . 10 5. PPK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1. PPK_ID format . . . . . . . . . . . . . . . . . . . . . . 11 - 5.2. Operational Considerations . . . . . . . . . . . . . . . 11 + 5.2. Operational Considerations . . . . . . . . . . . . . . . 12 5.2.1. PPK Distribution . . . . . . . . . . . . . . . . . . 12 5.2.2. Group PPK . . . . . . . . . . . . . . . . . . . . . . 12 - 5.2.3. PPK-only Authentication . . . . . . . . . . . . . . . 12 + 5.2.3. PPK-only Authentication . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 15 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 16 8.2. Informational References . . . . . . . . . . . . . . . . 16 - Appendix A. Discussion and Rationale . . . . . . . . . . . . . . 16 + Appendix A. Discussion and Rationale . . . . . . . . . . . . . . 17 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 17 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 1. Introduction It is an open question whether or not it is feasible to build a Quantum Computer (and if so, when one might be implemented), but if it is, many of the cryptographic algorithms and protocols currently in use would be insecure. A Quantum Computer would be able to solve DH and ECDH problems in polynomial time [I-D.hoffman-c2pq], and this would imply that the security of existing IKEv2 [RFC7296] systems would be compromised. IKEv1 [RFC2409], when used with strong @@ -116,29 +116,43 @@ authentication if configured). This document does not replace the authentication checks that the protocol does; instead, it is done as a parallel check. 1.1. Changes RFC EDITOR PLEASE DELETE THIS SECTION. Changes in this draft in each version iterations. + draft-ietf-ipsecme-qr-ikev2-02 + + o Added note that the PPK is stirred in the initial IKE SA setup + only. + + o Added note about the initiator ignoring any content in the + PPK_IDENTITY notification from the responder. + + o fixed Tero's suggestions from 2/6/1028 + + o Added IANA assigned message types where necessary. + + o fixed minor text nits + draft-ietf-ipsecme-qr-ikev2-01 o Nits and minor fixes. o prf is replaced with prf+ for the SK_d and SK_pi/r calculations. o Clarified using PPK in case of EAP authentication. - o PPK_SUUPORT notification is changed to USE_PPK to better reflect + o PPK_SUPPORT notification is changed to USE_PPK to better reflect its purpose. draft-ietf-ipsecme-qr-ikev2-00 o Migrated from draft-fluhrer-qr-ikev2-05 to draft-ietf-ipsecme-qr- ikev2-00 that is a WG item. draft-fluhrer-qr-ikev2-05 o Nits and editorial fixes. @@ -222,21 +235,21 @@ If the initiator is configured to use a postquantum preshared key with the responder (whether or not the use of the PPK is mandatory), then he will include a notification USE_PPK in the IKE_SA_INIT request message as follows: Initiator Responder ------------------------------------------------------------------ HDR, SAi1, KEi, Ni, N(USE_PPK) ---> - N(USE_PPK) is a status notification payload with the type [TBA]; it + N(USE_PPK) is a status notification payload with the type 16435; it has a protocol ID of 0, no SPI and no notification data associated with it. If the initiator needs to resend this initial message with a cookie (because the responder response included a COOKIE notification), then the resend would include the USE_PPK notification if the original message did. If the responder does not support this specification or does not have any PPK configured, then she ignores the received notification and @@ -283,44 +296,49 @@ as the initial ones, even if the underlying prf has output size different from its key size. Note, that at the time this document was written, all prfs defined for use in IKEv2 [IKEV2-IANA-PRFS] had output size equal to the (preferred) key size. For such prfs only the first iteration of prf+ is needed: SK_d = prf (PPK, SK_d' | 0x01) SK_pi = prf (PPK, SK_pi' | 0x01) SK_pr = prf (PPK, SK_pr' | 0x01) + Note that the PPK is used in SK_d, SK_pi and SK_pr calculation only + during the initial IKE SA setup. It MUST NOT be used when these + subkeys are calculated as result of IKE SA rekey, resumption or other + similar operation. + The initiator then sends the IKE_AUTH request message, including the PPK_ID value as follows: Initiator Responder ------------------------------------------------------------------ HDR, SK {IDi, [CERT,] [CERTREQ,] [IDr,] AUTH, SAi2, - TSi, TSr, N(PPK_IDENTITY)(PPK_ID), [N(NO_PPK_AUTH)]} ---> + TSi, TSr, N(PPK_IDENTITY, PPK_ID), [N(NO_PPK_AUTH)]} ---> - PPK_IDENTITY is a status notification with the type [TBA]; it has a + PPK_IDENTITY is a status notification with the type 16436; it has a protocol ID of 0, no SPI and a notification data that consists of the identifier PPK_ID. A situation may happen when the responder has some PPKs, but doesn't have a PPK with the PPK_ID received from the initiator. In this case the responder cannot continue with PPK (in particular, she cannot authenticate the initiator), but she could be able to continue with normal IKEv2 protocol if the initiator provided its authentication data computed as in normal IKEv2, without using PPKs. For this purpose, if using PPKs for communication with this responder is optional for the initiator, then the initiator MAY include a notification NO_PPK_AUTH in the above message. - NO_PPK_AUTH is a status notification with the type [TBA]; it has a + NO_PPK_AUTH is a status notification with the type 16437; it has a protocol ID of 0 and no SPI. A notification data consists of the initiator's authentication data computed using SK_pi' (i.e. the data that computed without using PPKs and would normally be placed in the AUTH payload). Authentication Method for computing the authentication data MUST be the same as indicated in the AUTH payload and is not included in the notification. Note that if the initiator decides to include NO_PPK_AUTH notification, then it means that the initiator needs to perform authentication data computation twice that may consume substantial computation power (e.g. if digital signatures are involved). @@ -381,26 +399,27 @@ Initiator Responder ------------------------------------------------------------------ <-- HDR, SK {IDr, [CERT,] AUTH, SAr2, TSi, TSr, N(PPK_IDENTITY)} When the initiator receives the response, then he checks for the presence of the PPK_IDENTITY notification. If he receives one, he marks the SA as using the configured PPK to generate SK_d, SK_pi, - SK_pr (as shown above); if he does not receive one, he MUST either - fail the IKE SA negotiation sending the AUTHENTICATION_FAILED - notification in the Informational exchange (if the PPK was configured - as mandatory), or continue without using the PPK (if the PPK was not - configured as mandatory and the initiator included the NO_PPK_AUTH - notification in the request). + SK_pr (as shown above); the content of the received PPK_IDENTITY (if + any) MUST be ignored. If the initiator does not receive the + PPK_IDENTITY, he MUST either fail the IKE SA negotiation sending the + AUTHENTICATION_FAILED notification in the Informational exchange (if + the PPK was configured as mandatory), or continue without using the + PPK (if the PPK was not configured as mandatory and the initiator + included the NO_PPK_AUTH notification in the request). If EAP is used in the IKE_AUTH exchange, then the initiator doesn't include AUTH payload in the first request message, however the responder sends back AUTH payload in the first reply. The peers then exchange AUTH payloads after EAP is successfully completed. As a result, the responder sends AUTH payload twice - in the first IKE_AUTH reply message and in the last one, while the initiator sends AUTH payload only in the last IKE_AUTH request. See more details about EAP authentication in IKEv2 in Section 2.16 of [RFC7296]. @@ -417,21 +436,21 @@ Initiator Responder ------------------------------------------------------------------- HDR, SK {IDi, [CERTREQ,] [IDr,] SAi2, TSi, TSr} --> <-- HDR, SK {IDr, [CERT,] AUTH, EAP} HDR, SK {EAP} --> <-- HDR, SK {EAP (success)} HDR, SK {AUTH, - N(PPK_IDENTITY)(PPK_ID) + N(PPK_IDENTITY, PPK_ID) [, N(NO_PPK_AUTH)]} --> <-- HDR, SK {AUTH, SAr2, TSi, TSr [, N(PPK_IDENTITY)]} Note, that the IKE_SA_INIT exchange in case of PPK is as described above (including exchange of the USE_PPK notifications), regardless whether EAP is employed in the IKE_AUTH or not. 4. Upgrade procedure @@ -451,23 +470,23 @@ With this configuration, the node will continue to operate with nodes that have not yet been upgraded. This is due to the USE_PPK notify and the NO_PPK_AUTH notify; if the initiator has not been upgraded, he will not send the USE_PPK notify (and so the responder will know that we will not use a PPK). If the responder has not been upgraded, she will not send the USE_PPK notify (and so the initiator will know to not use a PPK). If both peers have been upgraded, but the responder isn't yet configured with the PPK for the initiator, then the responder could do standard IKEv2 protocol if the initiator sent - NO_PPK_AUTH notification. If the responder has not been upgraded and - properly configured, they will both realize it, and in that case, the - link will be quantum secure. + NO_PPK_AUTH notification. If both the responder and initiator have + been upgraded and properly configured, they will both realize it, and + in that case, the link will be quantum secure. As an optional second step, after all nodes have been upgraded, then the administrator may then go back through the nodes, and mark the use of PPK as mandatory. This will not affect the strength against a passive attacker; it would mean that an attacker with a Quantum Computer (which is sufficiently fast to be able to break the (EC)DH in real time would not be able to perform a downgrade attack). 5. PPK @@ -584,23 +603,23 @@ (assuming that the PPK was high entropy and secret, and that all the subkeys are sufficiently long). Although this protocol preserves all the security properties of IKEv2 against adversaries with conventional computers, it allows an adversary with a Quantum Computer to decrypt all traffic encrypted with the initial IKE SA. In particular, it allows the adversary to recover the identities of both sides. If there is IKE traffic other than the identities that need to be protected against such an adversary, implementations MAY rekey the initial IKE SA immediately - after negotiating it to generate a new SKEYSEED with from the - postquantum SK_d. This would reduce the amount of data available to - an attacker with a Quantum Computer. + after negotiating it to generate a new SKEYSEED from the postquantum + SK_d. This would reduce the amount of data available to an attacker + with a Quantum Computer. Alternatively, an initial IKE SA (which is used to exchange identities) can take place, perhaps by using the protocol documented in [RFC6023]. After the childless IKE SA is created, implementations would immediately create a new IKE SA (which is used to exchange everything else) by using a rekey mechanism for IKE SAs. Because the rekeyed IKE SA keys are a function of SK_d, which is a function of the PPK (among other things), traffic protected by that IKE SA is secure against Quantum capable adversaries. @@ -661,23 +680,23 @@ doesn't contain the USE_PPK notification, then the initiator doesn't abort exchange immediately, but instead waits some time for more responses (possibly retransmitting the request). If all the received responses contain no USE_PPK, then the exchange is aborted. 7. IANA Considerations This document defines three new Notify Message Types in the "Notify Message Types - Status Types" registry: - USE_PPK - PPK_IDENTITY - NO_PPK_AUTH + 16435 USE_PPK + 16436 PPK_IDENTITY + 16437 NO_PPK_AUTH This document also creates a new IANA registry for the PPK_ID types. The initial values of this registry are: PPK_ID Type Value ----------- ----- Reserved 0 PPK_ID_OPAQUE 1 PPK_ID_FIXED 2 Unassigned 3-127 @@ -757,23 +775,24 @@ trivially solved, the attacker still can't recover any key material (except for the SK_ei, SK_er, SK_ai, SK_ar values for the initial IKE exchange) unless they can find the PPK, which is too difficult if the PPK has enough entropy (for example, 256 bits). Note that we do allow an attacker with a Quantum Computer to rederive the keying material for the initial IKE SA; this was a compromise to allow the responder to select the correct PPK quickly. Another goal of this protocol is to minimize the number of changes within the IKEv2 protocol, and in particular, within the cryptography - of IKEv2. By limiting our changes to notifications, and translating - the nonces, it is hoped that this would be implementable, even on - systems that perform much of the IKEv2 processing is in hardware. + of IKEv2. By limiting our changes to notifications, and adjusting + the SK_d, SK_pi, SK_pr, it is hoped that this would be implementable, + even on systems that perform much of the IKEv2 processing is in + hardware. A third goal was to be friendly to incremental deployment in operational networks, for which we might not want to have a global shared key or quantum resistant IKEv2 is rolled out incrementally. This is why we specifically try to allow the PPK to be dependent on the peer, and why we allow the PPK to be configured as optional. A fourth goal was to avoid violating any of the security goals of IKEv2.