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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-16) exists of draft-yeung-g-ikev2-13 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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: September 24, 2018 LMU Munich 6 Y. Nir 7 Dell EMC 8 March 23, 2018 10 Implicit IV for Counter-based Ciphers in Encapsulating Security Payload 11 (ESP) 12 draft-ietf-ipsecme-implicit-iv-01 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 September 24, 2018. 44 Copyright Notice 46 Copyright (c) 2018 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 IIV: Implicit Initialization Vector. 121 o Nonce: a fixed-size octet string used only once. This is similar 122 to IV, except that in common usage there is no implication of non- 123 predictability. 125 4. Implicit IV 127 With the algorithms listed in Section 2, the 8 byte nonce MUST NOT 128 repeat. The binding between a ESP packet and its nonce is provided 129 using the Sequence Number or the Extended Sequence Number. Figure 1 130 and Figure 2 represent the IV with a regular 4-byte Sequence Number 131 and with an 8-byte Extended Sequence Number respectively. 133 0 1 2 3 134 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 1 135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 136 | Zero | 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 | Sequence Number | 139 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 141 Figure 1: Implicit IV with a 4 byte Sequence Number 143 o Sequence Number: the 4 byte Sequence Number carried in the ESP 144 packet. 146 o Zero: a 4 byte array with all bits set to zero. 148 0 1 2 3 149 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 1 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | Extended | 152 | Sequence Number | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 155 Figure 2: Implicit IV with an 8 byte Extended Sequence Number 157 o Extended Sequence Number: the 8 byte Extended Sequence Number of 158 the Security Association. The 4 byte low order bytes are carried 159 in the ESP packet. 161 As the IV MUST NOT repeat for one SPI when Counter-Mode ciphers are 162 used, Implicit IV as described in this document MUST NOT be used in 163 setups with the chance that the Sequence Number overlaps for one SPI. 164 Multicast as described in [RFC5374], [RFC6407] and 165 [I-D.yeung-g-ikev2] is a prominent example, where many senders share 166 one secret and thus one SPI. Section 3.5 of [RFC6407] explains how 167 repetition MAY BE prevented by using a prefix for each group member, 168 which could be prefixed to the Sequence Number. Otherwise, Implicit 169 IV MUST NOT be used in multicast scenarios. 171 5. Initiator Behavior 173 An initiator supporting this feature SHOULD propose implicit IV for 174 all relevant algorithms. To facilitate backward compatibility with 175 non-supporting peers the initiator SHOULD also include those same 176 algorithms without Implicit IV (IIV). This may require extra 177 transforms. 179 6. Responder Behavior 181 The rules of SA payload processing ensure that the responder will 182 never send an SA payload containing the IIV indicator to an initiator 183 that does not support IIV. 185 7. Security Consideration 187 Nonce generation for these algorithms has not been explicitly 188 defined. It has been left to the implementation as long as certain 189 security requirements are met. Typically, for AES-GCM, AES-CCM, AES- 190 CTR and ChaCha20-Poly1305, the IV is not allowed being repeated for 191 one particular key. This document provides an explicit and normative 192 way to generate IVs. The mechanism described in this document meets 193 the IV security requirements of all relevant algorithms. 195 8. IANA Considerations 197 AES-CTR, AES-CCM, AES-GCM and ChaCha20-Poly1305 are likely to 198 implement the implicit IV described in this document. This section 199 limits assignment of new code points to the recommended suites 200 provided in [RFC8221], thus the new Transform Type 1 - Encryption 201 Algorithm Transform IDs [IANA] are as defined below: 203 - ENCR_AES_CCM_8_IIV 205 - ENCR_AES_GCM_16_IIV 207 - ENCR_CHACHA20_POLY1305_IIV 209 These algorithms should be added with this document as ESP Reference 210 and "Not Allowed" for IKEv2 Reference. 212 9. Acknowledgements 214 We would like to thanks people Valery Smyslov for their valuable 215 comments, David Schinazi for its implementation, as well as the 216 ipseceme chairs Tero Kivinen and David Waltermire for moving this 217 work forward. 219 10. References 221 10.1. Normative References 223 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 224 Requirement Levels", BCP 14, RFC 2119, 225 DOI 10.17487/RFC2119, March 1997, 226 . 228 [RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher 229 Algorithm and Its Use with IPsec", RFC 3602, 230 DOI 10.17487/RFC3602, September 2003, 231 . 233 [RFC3686] Housley, R., "Using Advanced Encryption Standard (AES) 234 Counter Mode With IPsec Encapsulating Security Payload 235 (ESP)", RFC 3686, DOI 10.17487/RFC3686, January 2004, 236 . 238 [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode 239 (GCM) in IPsec Encapsulating Security Payload (ESP)", 240 RFC 4106, DOI 10.17487/RFC4106, June 2005, 241 . 243 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 244 RFC 4303, DOI 10.17487/RFC4303, December 2005, 245 . 247 [RFC4309] Housley, R., "Using Advanced Encryption Standard (AES) CCM 248 Mode with IPsec Encapsulating Security Payload (ESP)", 249 RFC 4309, DOI 10.17487/RFC4309, December 2005, 250 . 252 [RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast 253 Extensions to the Security Architecture for the Internet 254 Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008, 255 . 257 [RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain 258 of Interpretation", RFC 6407, DOI 10.17487/RFC6407, 259 October 2011, . 261 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 262 Kivinen, "Internet Key Exchange Protocol Version 2 263 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 264 2014, . 266 [RFC7634] Nir, Y., "ChaCha20, Poly1305, and Their Use in the 267 Internet Key Exchange Protocol (IKE) and IPsec", RFC 7634, 268 DOI 10.17487/RFC7634, August 2015, 269 . 271 [RFC8221] Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T. 272 Kivinen, "Cryptographic Algorithm Implementation 273 Requirements and Usage Guidance for Encapsulating Security 274 Payload (ESP) and Authentication Header (AH)", RFC 8221, 275 DOI 10.17487/RFC8221, October 2017, 276 . 278 10.2. Informational References 280 [BEAST] Thai, T. and J. Juliano, "Here Come The xor Ninjas", , 281 May 2011, . 284 [I-D.yeung-g-ikev2] 285 Weis, B., Nir, Y., and V. Smyslov, "Group Key Management 286 using IKEv2", draft-yeung-g-ikev2-13 (work in progress), 287 March 2018. 289 [IANA] "IANA IKEv2 Parameter - Type 1 - Encryption Algorithm 290 Transform IDs", . 293 Authors' Addresses 295 Daniel Migault (editor) 296 Ericsson 297 8400 boulevard Decarie 298 Montreal, QC H4P 2N2 299 Canada 301 Email: daniel.migault@ericsson.com 303 Tobias Guggemos (editor) 304 LMU Munich 305 Oettingenstr. 67 306 80538 Munich, Bavaria 307 Germany 309 Email: guggemos@mnm-team.org 310 URI: http://mnm-team.org/~guggemos 312 Yoav Nir 313 Dell EMC 314 9 Andrei Sakharov St 315 Haifa 3190500 316 Israel 318 Email: ynir.ietf@gmail.com