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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-16) exists of draft-yeung-g-ikev2-12 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPSECME D. Migault, Ed. 3 Internet-Draft Ericsson 4 Intended status: Standards Track T. Guggemos, Ed. 5 Expires: May 22, 2018 LMU Munich 6 Y. Nir 7 Dell EMC 8 November 18, 2017 10 Implicit IV for Counter-based Ciphers in Encapsulating Security Payload 11 (ESP) 12 draft-ietf-ipsecme-implicit-iv-00 14 Abstract 16 Encapsulating Security Payload (ESP) sends an initialization vector 17 (IV) or nonce in each packet. The size of IV depends on the applied 18 transform, being usually 8 or 16 octets for the transforms defined by 19 the time this document is written. Some algorithms such as AES-GCM, 20 AES-CCM, AES-CTR and ChaCha20-Poly1305 require a unique nonce but do 21 not require an unpredictable nonce. When using such algorithms the 22 packet counter value can be used to generate a nonce. This avoids 23 sending the nonce itself, and savec in the case of AES-GCM, AES-CCM, 24 AES-CTR and ChaCha20-Poly1305 8 octets per packet. This document 25 describes how to do this. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on May 22, 2018. 44 Copyright Notice 46 Copyright (c) 2017 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (https://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 2 62 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 4. Implicit IV . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 5. Initiator Behavior . . . . . . . . . . . . . . . . . . . . . 4 66 6. Responder Behavior . . . . . . . . . . . . . . . . . . . . . 4 67 7. Security Consideration . . . . . . . . . . . . . . . . . . . 4 68 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 69 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 70 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 10.1. Normative References . . . . . . . . . . . . . . . . . . 5 72 10.2. Informational References . . . . . . . . . . . . . . . . 6 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 75 1. Requirements notation 77 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 78 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 79 document are to be interpreted as described in [RFC2119]. 81 2. Introduction 83 Counter-based AES modes of operation such as AES-CTR ([RFC3686]), 84 AES-CCM ([RFC4309]), and AES-GCM ([RFC4106]) require the 85 specification of an nonce for each ESP packet. The same applies for 86 ChaCha20-Poly1305 ([RFC7634]. Currently this nonce is sent in each 87 ESP packet ([RFC4303]). This practice is designated in this document 88 as "explicit nonce". 90 In some context, such as IoT, it may be preferable to avoid carrying 91 the extra bytes associated to the IV and instead generate it locally 92 on each peer. The local generation of the nonce is designated in 93 this document as "implicit IV". 95 The size of this nonce depends on the specific algorithm, but all of 96 the algorithms mentioned above take an 8-octet nonce. 98 This document defines how to compute the nonce locally when it is 99 implicit. It also specifies how peers agree with the Internet Key 100 Exchange version 2 (IKEv2 - [RFC7296]) on using an implicit IV versus 101 an explicit IV. 103 This document limits its scope to the algorithms mentioned above. 104 Other algorithms with similar properties may later be defined to use 105 this extension. 107 This document does not consider AES-CBC ([RFC3602]) as AES-CBC 108 requires the IV to be unpredictable. Deriving it directly from the 109 packet counter as described below is insecure as mentioned in 110 Security Consideration of [RFC3602] and has led to real world chosen 111 plain-text attack such as BEAST [BEAST]. 113 3. Terminology 115 o IoT: Internet of Things. 117 o IV: Initialization Vector. 119 o Nonce: a fixed-size octet string used only once. This is similar 120 to IV, except that in common usage there is no implication of non- 121 predictability. 123 4. Implicit IV 125 With the algorithms listed in Section 2, the 8 byte nonce MUST NOT 126 repeat. The binding between a ESP packet and its nonce is provided 127 using the Sequence Number or the Extended Sequence Number. Figure 1 128 and Figure 2 represent the IV with a regular 4-byte Sequence Number 129 and with an 8-byte Extended Sequence Number respectively. 131 0 1 2 3 132 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 | Zero | 135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 136 | Sequence Number | 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 Figure 1: Implicit IV with a 4 byte Sequence Number 141 o Sequence Number: the 4 byte Sequence Number carried in the ESP 142 packet. 144 o Zero: a 4 byte array with all bits set to zero. 146 0 1 2 3 147 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 149 | Extended | 150 | Sequence Number | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 Figure 2: Implicit IV with an 8 byte Extended Sequence Number 155 o Extended Sequence Number: the 8 byte Extended Sequence Number of 156 the Security Association. The 4 byte low order bytes are carried 157 in the ESP packet. 159 5. Initiator Behavior 161 An initiator supporting this feature SHOULD propose implicit IV for 162 all relevant algorithms. To facilitate backward compatibility with 163 non-supporting peers the initiator SHOULD also include those same 164 algorithms without IIV. This may require extra transforms. 166 6. Responder Behavior 168 The rules of SA payload processing ensure that the responder will 169 never send an SA payload containing the IIV indicator to an initiator 170 that does not support IIV. 172 7. Security Consideration 174 Nonce generation for these algorithms has not been explicitly 175 defined. It has been left to the implementation as long as certain 176 security requirements are met. This document provides an explicit 177 and normative way to generate IVs. The mechanism described in this 178 document meets the IV security requirements of all relevant 179 algorithms. 181 As the IV MUST NOT repeat for one SPI when Counter-Mode ciphers are 182 used, Implicit IV as described in this document MUST NOT be used in 183 setups with the chance that the Sequence Number overlaps for one SPI. 184 Multicast as described in [RFC5374], [RFC6407] and 185 [I-D.yeung-g-ikev2] is a prominent example, where many senders share 186 one secret and thus one SPI. Section 3.5 of [RFC6407] explains how 187 repetition MAY BE prevented by using a prefix for each group member, 188 which could be prefixed to the Sequence Number. Otherwise, Implicit 189 IV MUST NOT be used in multicast scenarios. 191 8. IANA Considerations 193 AES-CTR, AES-CCM, AES-GCM and ChaCha20-Poly1305 are likely to 194 implement the implicit IV described in this document. This section 195 limits assignment of new code points to the recommended suites 196 provided in [RFC8221], thus the new Transform Type 1 - Encryption 197 Algorithm Transform IDs [IANA] are as defined below: 199 - ENCR_AES_CCM_8_IIV 201 - ENCR_AES_GCM_16_IIV 203 - ENCR_CHACHA20_POLY1305_IIV 205 These algorithms should be added with this document as ESP Reference 206 and "Not Allowed" for IKEv2 Reference. 208 9. Acknowledgements 210 We woudl like to thanks people Valery Smyslov for their valuable 211 comments as well as the ipseceme chairs Tero Kivinen and David 212 Waltermire for moving this work forward. 214 10. References 216 10.1. Normative References 218 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 219 Requirement Levels", BCP 14, RFC 2119, 220 DOI 10.17487/RFC2119, March 1997, 221 . 223 [RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher 224 Algorithm and Its Use with IPsec", RFC 3602, 225 DOI 10.17487/RFC3602, September 2003, 226 . 228 [RFC3686] Housley, R., "Using Advanced Encryption Standard (AES) 229 Counter Mode With IPsec Encapsulating Security Payload 230 (ESP)", RFC 3686, DOI 10.17487/RFC3686, January 2004, 231 . 233 [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode 234 (GCM) in IPsec Encapsulating Security Payload (ESP)", 235 RFC 4106, DOI 10.17487/RFC4106, June 2005, 236 . 238 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 239 RFC 4303, DOI 10.17487/RFC4303, December 2005, 240 . 242 [RFC4309] Housley, R., "Using Advanced Encryption Standard (AES) CCM 243 Mode with IPsec Encapsulating Security Payload (ESP)", 244 RFC 4309, DOI 10.17487/RFC4309, December 2005, 245 . 247 [RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast 248 Extensions to the Security Architecture for the Internet 249 Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008, 250 . 252 [RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain 253 of Interpretation", RFC 6407, DOI 10.17487/RFC6407, 254 October 2011, . 256 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 257 Kivinen, "Internet Key Exchange Protocol Version 2 258 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 259 2014, . 261 [RFC7634] Nir, Y., "ChaCha20, Poly1305, and Their Use in the 262 Internet Key Exchange Protocol (IKE) and IPsec", RFC 7634, 263 DOI 10.17487/RFC7634, August 2015, 264 . 266 [RFC8221] Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T. 267 Kivinen, "Cryptographic Algorithm Implementation 268 Requirements and Usage Guidance for Encapsulating Security 269 Payload (ESP) and Authentication Header (AH)", RFC 8221, 270 DOI 10.17487/RFC8221, October 2017, 271 . 273 10.2. Informational References 275 [BEAST] Thai, T. and J. Juliano, "Here Come The xor Ninjas", , 276 May 2011, . 279 [I-D.yeung-g-ikev2] 280 Weis, B., Nir, Y., and V. Smyslov, "Group Key Management 281 using IKEv2", draft-yeung-g-ikev2-12 (work in progress), 282 October 2017. 284 [IANA] "IANA IKEv2 Parameter - Type 1 - Encryption Algorithm 285 Transform IDs", . 288 Authors' Addresses 290 Daniel Migault (editor) 291 Ericsson 292 8400 boulevard Decarie 293 Montreal, QC H4P 2N2 294 Canada 296 Email: daniel.migault@ericsson.com 298 Tobias Guggemos (editor) 299 LMU Munich 300 Oettingenstr. 67 301 80538 Munich, Bavaria 302 Germany 304 Email: guggemos@mnm-team.org 305 URI: http://mnm-team.org/~guggemos 307 Yoav Nir 308 Dell EMC 309 9 Andrei Sakharov St 310 Haifa 3190500 311 Israel 313 Email: ynir.ietf@gmail.com