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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-16) exists of draft-yeung-g-ikev2-13 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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 3 Internet-Draft Ericsson 4 Intended status: Standards Track T. Guggemos 5 Expires: September 27, 2018 LMU Munich 6 Y. Nir 7 Dell EMC 8 March 26, 2018 10 Implicit IV for Counter-based Ciphers in Encapsulating Security Payload 11 (ESP) 12 draft-ietf-ipsecme-implicit-iv-02 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 27, 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 . . . . . . . . . . . . . . . . . . . 5 68 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 69 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 70 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 10.1. Normative References . . . . . . . . . . . . . . . . . . 5 72 10.2. Informational References . . . . . . . . . . . . . . . . 7 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] provides a 167 mechanism that MAY be used to prevent IV collisions when the same key 168 is used by multiple users. The mechanism consists in partitioning 169 the IV space between users by assigning the most significant byte to 170 a user. When implicit IV transforms are used, such mechanism cannot 171 be applied as the IV is not sent, but instead it is derived from the 172 Sequence Number. A similar mechanism could be used by associating 173 the most significant byte of the Sequence Number to a sender, while 174 the 3 remaining bytes will be used to carry the counter value. Such 175 mechanism prevents the use of Extended Sequence Number and limits the 176 number of packet to be sent to 2** 24 = 16777216, that is 16 M. 178 Unless some mechanism are provided to avoid collision between 179 Sequence Number, ( and so IV ), Implicit IV MUST NOT be used. 181 5. Initiator Behavior 183 An initiator supporting this feature SHOULD propose implicit IV for 184 all relevant algorithms. To facilitate backward compatibility with 185 non-supporting peers the initiator SHOULD also include those same 186 algorithms without Implicit IV (IIV). This may require extra 187 transforms. 189 6. Responder Behavior 191 The rules of SA payload processing ensure that the responder will 192 never send an SA payload containing the IIV transform to an initiator 193 that does not support IIV. 195 7. Security Consideration 197 Nonce generation for these algorithms has not been explicitly 198 defined. It has been left to the implementation as long as certain 199 security requirements are met. Typically, for AES-GCM, AES-CCM, AES- 200 CTR and ChaCha20-Poly1305, the IV is not allowed being repeated for 201 one particular key. This document provides an explicit and normative 202 way to generate IVs. The mechanism described in this document meets 203 the IV security requirements of all relevant algorithms. 205 8. IANA Considerations 207 AES-CCM, AES-GCM and ChaCha20-Poly1305 are likely to implement the 208 implicit IV described in this document. This section limits 209 assignment of new code points to the recommended suites provided in 210 [RFC8221], thus the new Transform Type 1 - Encryption Algorithm 211 Transform IDs [IANA] are as defined below: 213 - ENCR_AES_CCM_8_IIV 215 - ENCR_AES_GCM_16_IIV 217 - ENCR_CHACHA20_POLY1305_IIV 219 These algorithms should be added with this document as ESP Reference 220 and "Not Allowed" for IKEv2 Reference. 222 9. Acknowledgements 224 We would like to thanks people Valery Smyslov for their valuable 225 comments, David Schinazi for its implementation, as well as the 226 ipseceme chairs Tero Kivinen and David Waltermire for moving this 227 work forward. 229 10. References 231 10.1. Normative References 233 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 234 Requirement Levels", BCP 14, RFC 2119, 235 DOI 10.17487/RFC2119, March 1997, 236 . 238 [RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher 239 Algorithm and Its Use with IPsec", RFC 3602, 240 DOI 10.17487/RFC3602, September 2003, 241 . 243 [RFC3686] Housley, R., "Using Advanced Encryption Standard (AES) 244 Counter Mode With IPsec Encapsulating Security Payload 245 (ESP)", RFC 3686, DOI 10.17487/RFC3686, January 2004, 246 . 248 [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode 249 (GCM) in IPsec Encapsulating Security Payload (ESP)", 250 RFC 4106, DOI 10.17487/RFC4106, June 2005, 251 . 253 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 254 RFC 4303, DOI 10.17487/RFC4303, December 2005, 255 . 257 [RFC4309] Housley, R., "Using Advanced Encryption Standard (AES) CCM 258 Mode with IPsec Encapsulating Security Payload (ESP)", 259 RFC 4309, DOI 10.17487/RFC4309, December 2005, 260 . 262 [RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast 263 Extensions to the Security Architecture for the Internet 264 Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008, 265 . 267 [RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain 268 of Interpretation", RFC 6407, DOI 10.17487/RFC6407, 269 October 2011, . 271 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 272 Kivinen, "Internet Key Exchange Protocol Version 2 273 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 274 2014, . 276 [RFC7634] Nir, Y., "ChaCha20, Poly1305, and Their Use in the 277 Internet Key Exchange Protocol (IKE) and IPsec", RFC 7634, 278 DOI 10.17487/RFC7634, August 2015, 279 . 281 [RFC8221] Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T. 282 Kivinen, "Cryptographic Algorithm Implementation 283 Requirements and Usage Guidance for Encapsulating Security 284 Payload (ESP) and Authentication Header (AH)", RFC 8221, 285 DOI 10.17487/RFC8221, October 2017, 286 . 288 10.2. Informational References 290 [BEAST] Thai, T. and J. Juliano, "Here Come The xor Ninjas", , 291 May 2011, . 294 [I-D.yeung-g-ikev2] 295 Weis, B., Nir, Y., and V. Smyslov, "Group Key Management 296 using IKEv2", draft-yeung-g-ikev2-13 (work in progress), 297 March 2018. 299 [IANA] "IANA IKEv2 Parameter - Type 1 - Encryption Algorithm 300 Transform IDs", . 303 Authors' Addresses 305 Daniel Migault 306 Ericsson 307 8275 Trans Canada Route 308 Saint Laurent, QC H4S 0B6 309 Canada 311 Email: daniel.migault@ericsson.com 313 Tobias Guggemos 314 LMU Munich 315 Oettingenstr. 67 316 80538 Munich, Bavaria 317 Germany 319 Email: guggemos@mnm-team.org 320 URI: http://mnm-team.org/~guggemos 322 Yoav Nir 323 Dell EMC 324 9 Andrei Sakharov St 325 Haifa 3190500 326 Israel 328 Email: ynir.ietf@gmail.com