idnits 2.17.1 draft-bhatia-moving-ah-to-historic-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (December 30, 2011) is 4501 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Bhatia 3 Internet-Draft Alcatel-Lucent 4 Intended status: Informational December 30, 2011 5 Expires: July 2, 2012 7 Moving Authentication Header (AH) to Historic 8 draft-bhatia-moving-ah-to-historic-00 10 Abstract 12 This document recommends retiring Authentication Header (AH) and 13 discusses the reasons for doing so. It recommends moving RFC 4302 to 14 Historic status. 16 Requirements Language 18 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 19 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 20 document are to be interpreted as described in RFC 2119 [RFC2119]. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on July 2, 2012. 39 Copyright Notice 41 Copyright (c) 2011 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 1. Introduction 56 IPsec uses two protocols to provide traffic security services -- 57 Authentication Header (AH) and Encapsulating Security Payload (ESP). 58 Both protocols are described in detail in their respective RFCs 59 [RFC4302] [RFC4303] 61 [RFC4301] recommends IPsec implementations to MUST support ESP and 62 MAY support AH. Support for AH was downgraded to MAY because 63 experience has shown that there are very few contexts in which ESP 64 cannot provide the requisite security services. Note that ESP can be 65 used to provide only integrity, without confidentiality, making it 66 comparable to AH in most contexts. 68 AH offers integrity and data origin authentication, with optional (at 69 the discretion of the receiver) anti-replay features. ESP, on the 70 other hand, offers the same set of services, and also additionally 71 offers confidentiality. 73 These protocols may be applied individually or in combination with 74 each other to provide IPv4 and IPv6 security services. However, most 75 security requirements can be met through the use of ESP by itself. 76 Each protocol supports two modes of use: transport mode and tunnel 77 mode. In transport mode, AH and ESP provide protection primarily for 78 next layer protocols; in tunnel mode, AH and ESP are applied to 79 tunneled IP packets. [RFC4301] describes detailed differences 80 between these two modes. 82 There is no particular security problem with using AH. It lives up 83 to its security claims. Its just that its completely redundant with 84 ESP, since ESP will NULL encryption (ESP-NULL) [RFC2410] can provide 85 the same functionality and the world can do with one less protocol. 87 Moving AH to historic doesn't mean that people have to stop using AH 88 right now. It only means that in the opinion of the community there 89 are now better alternatives. Moving AH to historic will discourage 90 new protocols to mandate the use of AH. It however, does not 91 preclude the possibility of new work to IETF that will require or 92 enhance AH. It just means that the authors will have to explain why 93 that solution is really needed and why ESP-NULL cant be used instead. 95 2. AH and ESP 97 It is alleged that AH provides more security than ESP in the 98 transport mode as AH also authenticates the IP header fields. This 99 argument is however moot as ESP in the tunnel mode can provide the 100 same level of security since the payload now includes the original IP 101 header. It is also believed by many that securing the IP header isnt 102 really very important [Schneier]. 104 It is commonly believed that AH is quite useful in securing the IPv6 105 extension headers. AH protects most of the basic IPv6 header, the 106 non-mutable extension headers after the AH, and the IP payload. 107 Protection for the IPv6 header excludes the mutable fields: DSCP, 108 ECN, Flow Label, and Hop Limit. ESP, on the other hand, doesn't 109 protect the immutable parts of the IPv6 header nor those of any 110 extension header. This can however be fixed by putting the IPv6 111 extension headers that are required to be protected after the ESP 112 header. Hop-by-Hop options are not an issue, as the intermediate 113 hops do not have keys to verify the message authentication code so 114 they cannot really be protected anyways. 116 AH breaks Network Address Translators (NATs). This is because AH 117 relies on the sanctity of the IP header so that any tamperings, even 118 by a NAT, get detected and packets get discarded. Solving this issue 119 requires another device that fixes the NAT translation back to the 120 original one (a specific case of Double NAT). ESP, on the other 121 hand, fixes this problem by encapsulating ESP packets inside UDP 122 packets for traversing NATs [RFC3948]. 124 Firewalls in the enterprise environments often require visibility 125 into packets, ranging from simple packet header inspection to deeper 126 payload examination. Routers also often need to deep inspect control 127 traffic to prioritize certain protocol packets over the others. This 128 was initially difficult with ESP since was impossible to know whether 129 an ESP packet was integrity protected or encrypted by merely 130 inspecting the packet. This was easy with AH since the payload was 131 transmitted in clear. This problem however has been solved by 132 introducing WESP [RFC5840] which defines a mechanism to provide 133 additional information in relevant IPsec packets so intermediate 134 devices can efficiently differentiate between encrypted and 135 integrity-only ESP packets. 137 ESP-NULL seems to do everything useful that can be done with AH. 138 Given this, it makes sense to move AH to Historic status so that 139 newer protocols dont mandate or propose extensions that rely on AH to 140 be supported. 142 3. Security Considerations 144 Its argued that ESP in the tunnel mode is equivalent to the AH in the 145 transport mode. It should however be noted that ESP tunnel mode SA 146 applied to an IPv6 flow results in at least 50 bytes of additional 147 overhead per packet. This additional overhead may be undesirable for 148 many bandwidth-constrained wireless and/or satellite communications 149 networks, as these types of infrastructure are not overprovisioned. 151 Packet overhead is particularly significant for traffic profiles 152 characterized by small packet payloads (e.g., various voice codecs). 153 If these small packets are afforded the security services of an IPsec 154 tunnel mode SA, the amount of per-packet overhead is increased. 156 This issue will perhaps be alleviated by header compression schemes 157 defined in [RFC5856] [RFC5857] and [RFC5858]. 159 4. IANA Considerations 161 None 163 5. References 165 5.1. Normative References 167 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 168 Requirement Levels", BCP 14, RFC 2119, March 1997. 170 [RFC2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and 171 Its Use With IPsec", RFC 2410, November 1998. 173 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 174 Internet Protocol", RFC 4301, December 2005. 176 [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, 177 December 2005. 179 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 180 RFC 4303, December 2005. 182 5.2. Informative References 184 [RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M. 185 Stenberg, "UDP Encapsulation of IPsec ESP Packets", 186 RFC 3948, January 2005. 188 [RFC5840] Grewal, K., Montenegro, G., and M. Bhatia, "Wrapped 189 Encapsulating Security Payload (ESP) for Traffic 190 Visibility", RFC 5840, April 2010. 192 [RFC5856] Ertekin, E., Jasani, R., Christou, C., and C. Bormann, 193 "Integration of Robust Header Compression over IPsec 194 Security Associations", RFC 5856, May 2010. 196 [RFC5857] Ertekin, E., Christou, C., Jasani, R., Kivinen, T., and C. 197 Bormann, "IKEv2 Extensions to Support Robust Header 198 Compression over IPsec", RFC 5857, May 2010. 200 [RFC5858] Ertekin, E., Christou, C., and C. Bormann, "IPsec 201 Extensions to Support Robust Header Compression over 202 IPsec", RFC 5858, May 2010. 204 [Schneier] 205 Ferguson, N. and B. Schneier, "A Cryptographic Evaluation 206 of IPsec", December 2003, 207 . 209 Author's Address 211 Manav Bhatia 212 Alcatel-Lucent 214 Email: manav.bhatia@alcatel-lucent.com