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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (January 13, 2016) is 2320 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DIME H. Tschofenig 3 Internet-Draft ARM Limited 4 Intended status: Informational J. Korhonen, Ed. 5 Expires: July 16, 2016 Broadcom Corporation 6 G. Zorn 7 Network Zen 8 K. Pillay 9 Oracle Communications 10 January 13, 2016 12 Diameter AVP Level Security End-to-End Security: Scenarios and 13 Requirements 14 draft-ietf-dime-e2e-sec-req-04.txt 16 Abstract 18 This specification discusses requirements for providing Diameter 19 security at the level of individual Attribute-Value Pairs. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on July 16, 2016. 38 Copyright Notice 40 Copyright (c) 2016 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 3. Security Threats . . . . . . . . . . . . . . . . . . . . . . 3 58 4. Scenarios for Diameter AVP-Level Protection . . . . . . . . . 5 59 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7 60 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 61 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 62 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 63 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 64 9.1. Normative References . . . . . . . . . . . . . . . . . . 8 65 9.2. Informative References . . . . . . . . . . . . . . . . . 9 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 68 1. Introduction 70 The Diameter base protocol specification [2] offers security 71 protection between neighboring Diameter peers and mandates that peer 72 connections must be protected by TLS (for TCP), DTLS (for SCTP) or 73 alternative security mechanisms independent of Diameter (e.g., IPsec) 74 is used. These security protocols offer a wide range of security 75 properties, including entity authentication, data-origin 76 authentication, integrity, confidentiality protection and replay 77 protection. They also support a large number of cryptographic 78 algorithms, algorithm negotiation, and different types of 79 credentials. It should be understood that TLS/DTLS/IPsec in Diameter 80 context does not provide end-to-end security unless the Diameter 81 nodes are direct peers i.e., neighboring Diameter nodes. The current 82 Diameter security is realized hop-by-hop. 84 The need to also offer additional security protection of AVPs between 85 non-neighboring Diameter nodes was recognized very early in the work 86 on Diameter. This led to work on Diameter security using the 87 Cryptographic Message Syntax (CMS) [3]. Due to lack of deployment 88 interest at that time (and the complexity of the developed solution) 89 the specification was, however, never completed. 91 In the meanwhile Diameter had received a lot of deployment interest 92 from the cellular operator community and because of the 93 sophistication of those deployments the need for protecting Diameter 94 AVPs between non-neighboring nodes re-surfaced. Since early 2000 95 (when the work on [3] was discontinued) the Internet community had 96 seen advances in cryptographic algorithms (for example, authenticated 97 encryption algorithms) and new security building blocks were 98 developed. 100 This document collects requirements for developing a solution to 101 protect Diameter AVPs. 103 2. Terminology 105 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 106 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this 107 documents are to be interpreted as described in RFC 2119 [1]. 109 This document re-uses terminology from the Diameter base 110 specification [2]. 112 In the figures below we use the symbols 'AVP' and '{AVP}k'. AVP 113 refers to an unprotected AVP and {AVP}k refers to an AVP that 114 experiences security protection (using key "k") without further 115 distinguishing between integrity and confidentiality protection. 117 3. Security Threats 119 The following description aims to illustrate various security threats 120 that raise the need for protecting Diameter Attribute-Value Pairs 121 (AVPs). Figure 1 illustrates an example of Diameter based roaming 122 architecture in which Diameter clients within the visited networks 123 need to interact with Diameter servers in the home domain. AAA 124 domains are interconnected using a Diameter-based AAA interconnection 125 network labeled as AAA Broker. 127 +oooooooooooooooooo+ +====================+ 128 | Example.net | | | 129 | | | | 130 +--------+ +--------+ +--------+ +--------+ 131 |Diameter| |Diameter+--------+Diameter| |Diameter| 132 |Client 1+------+Proxy A1| +------+Proxy B +--------+Proxy C |----+ 133 +--------+ +--------+ | +--------+ +--------+ | 134 | | | | | | 135 | Visited Domain 1 | | | AAA Broker | | 136 +oooooooooooooooooo+ | +====================+ | 137 | | 138 | | 139 | | 140 | +\\\\\\\\\\\\\\\\\\\\+ | 141 | +--------+ Example.com | | 142 | |Diameter| | | 143 +oooooooooooooooooo+ | |Server X+--+ +--------+ | 144 | Example.org | | +--------+ | |Diameter| | 145 | | | +--------+ +---------+Proxy D |-+ 146 +--------+ +--------+ | |Diameter| | +--------+ 147 |Diameter| |Diameter| | |Server Y+--+ | 148 |Client 2+------+Proxy A2+-+ +--------+ Home Domain | 149 +--------+ +--------+ +////////////////////+ 150 | | 151 | Visited Domain 2 | 152 +oooooooooooooooooo+ 154 Figure 1: Example Diameter Deployment. 156 Eavesdropping: Some Diameter applications carry information that is 157 only intended for consumption by end points, either by the 158 Diameter client or by the Diameter server but not by 159 intermediaries. As an example, consider the Diameter EAP 160 application [4] that allows the transport of keying material 161 between the Diameter server to the Diameter client (using the EAP- 162 Master-Session-Key AVP) for the protection of air interface 163 between the end device and the network access server. The content 164 of the EAP-Master-Session-Key AVP should benefit from protection 165 against eavesdropping by intermediaries. Other AVPs, for example 166 those listed in Section 13.3 of [2], might also carry sensitive 167 personal data that, when collected by intermediaries, allow for 168 traffic analysis. 170 In context of the deployment shown in Figure 1 the adversary 171 could, for example, be in the AAA broker network. 173 Injection and Manipulation: The Diameter base protocol specification 174 mandates security protection between neighboring nodes but 175 Diameter agents may be compromised or misconfigured and inject/ 176 manipulate AVPs. To detect such actions additional security 177 protection needs to be applied at the Diameter layer. 179 Nodes that could launch such an attack are any Diameter agents 180 along the end-to-end communication path. 182 Impersonation: Imagine a case where a Diameter message from 183 Example.net contains information claiming to be from Example.org. 184 This would either require strict verification at the edge of the 185 AAA broker network or cryptographic assurance at the Diameter 186 layer to prevent a successful impersonation attack. 188 Any Diameter realm could launch such an attack aiming for 189 financial benefits or to disrupt service availability. 191 4. Scenarios for Diameter AVP-Level Protection 193 This scenario outlines a number of cases for deploying security 194 protection of individual Diameter AVPs. 196 In the first scenario, shown in Figure 2, end-to-end security 197 protection is provided between the Diameter client and the Diameter 198 server with any number of intermediate Diameter agents. Diameter 199 AVPs exchanged between these two Diameter nodes may be protected end- 200 to-end (notation '{AVP}k') or unprotected (notation 'AVP'). 202 +--------+ +--------+ 203 |Diameter| AVP, {AVP}k |Diameter| 204 |Client +-----------------........... -------------------+Server | 205 +--------+ +--------+ 207 Figure 2: End-to-End Diameter AVP Security Protection. 209 In the second scenario, shown in Figure 3, a Diameter proxy acts on 210 behalf of the Diameter client with regard to security protection. It 211 applies security protection to outgoing Diameter AVPs and verifies 212 incoming AVPs. Typically, the proxy enforcing the security 213 protection belongs to the same domain as the Diameter client/server 214 without end-to-end security features. 216 +--------+ +--------+ +--------+ 217 |Diameter| AVP |Diameter| AVP, {AVP}k |Diameter| 218 |Client +-----+Proxy A +---------- .......... -----------+Server | 219 +--------+ +--------+ +--------+ 221 Figure 3: Middle-to-End Diameter AVP Security Protection. 223 In the third scenario shown in Figure 4 a Diameter proxy acts on 224 behalf of the Diameter server. 226 +--------+ +--------+ +--------+ 227 |Diameter| AVP, {AVP}k |Diameter| AVP |Diameter| 228 |Client +-----------------........... ----+Proxy D +-----+Server | 229 +--------+ +--------+ +--------+ 231 Figure 4: End-to-Middle Diameter AVP Security Protection. 233 The fourth and the final scenario (see Figure 5) is a combination of 234 the end-to-middle and the middle-to-end scenario shown in Figure 4 235 and in Figure 3. From a deployment point of view this scenario is 236 easier to accomplish for two reasons: First, Diameter clients and 237 Diameter servers remain unmodified. This ensures that no 238 modifications are needed to the installed Diameter infrastructure. 239 Second, key management is also simplified since fewer number of keys 240 need to be negotiated and provisioned. 242 +--------+ +--------+ +--------+ +--------+ 243 |Diameter| AVP |Diameter| AVP, {AVP}k |Diameter| AVP |Diameter| 244 |Client +-----+Proxy A +-- .......... ----+Proxy D +-----+Server | 245 +--------+ +--------+ +--------+ +--------+ 247 Figure 5: Middle-to-Middle Diameter AVP Security Protection. 249 Various security threats are mitigated by selectively applying 250 security protection for individual Diameter AVPs. Without protection 251 there is the possibility for password sniffing, confidentiality 252 violation, AVP insertion, deletion or modification. Additionally, 253 applying digital signature offers non-repudiation capabilities; a 254 feature not yet available in today's Diameter deployment. 255 Modification of certain Diameter AVPs may not necessarily be the act 256 of malicious behavior but could also be the result of 257 misconfiguration. An over-aggressively configured firewalling 258 Diameter proxy may also remove certain AVPs. In most cases data 259 origin authentication and integrity protection of AVPs will provide 260 the most benefits for existing deployments with minimal overhead and 261 (potentially) operating in a full-backwards compatible manner. 263 5. Requirements 265 Requirement #1: The solution MUST support an extensible set of 266 cryptographic algorithms. 268 Motivation: Solutions MUST be able to evolve to adapt to 269 evolving cryptographic algorithms and security requirements. 270 This may include the provision of a modular mechanism to allow 271 cryptographic algorithms to be updated without substantial 272 disruption to deployed implementations. 274 Requirement #2: The solution MUST support confidentiality, 275 integrity, and data-origin authentication. Solutions for 276 integrity protection MUST work in a backwards-compatible way with 277 existing Diameter applications. 279 Requirement #3: The solution MUST support replay protection. All 280 Diameter nodes have access to network time and thus can 281 synchronize their clocks. 283 Requirement #4: The solution MUST support the ability to delegate 284 security functionality to another entity 286 Motivation: As described in Section 4 the ability to let a 287 Diameter proxy to perform security services on behalf of all 288 clients within the same administrative domain is important for 289 incremental deployability. The same applies to the other 290 communication side where a load balancer terminates security 291 services for the servers it interfaces. 293 Requirement #5: The solution MUST be able to selectively apply their 294 cryptographic protection to certain Diameter AVPs. 296 Motivation: Some Diameter applications assume that certain AVPs 297 are added, removed, or modified by intermediaries. As such, it 298 MUST be possible to apply security protection selectively. 299 Furthermore, there are AVPs that MUST NOT be confidentiality 300 protected but MAY still be integrity protected such as those 301 required for Diameter message routing. 303 Requirement #6: The solution MUST define a mandatory-to-implement 304 cryptographic algorithm. 306 Motivation: For interoperability purposes it is beneficial to 307 have a mandatory-to-implement cryptographic algorithm specified 308 (unless profiles for specific usage environments specify 309 otherwise). 311 Requirement #7: The solution MUST support symmetric keys and 312 asymmetric keys. 314 Motivation: Symmetric and asymmetric cryptographic algorithms 315 provide different security services. Asymmetric algorithms, 316 for example, allow non-repudiation services to be offered. 318 Requirement #8: A solution for dynamic key management MUST be 319 included in the overall solution framework. 321 However, it is assumed that no "new" key management protocol 322 needs to be developed; instead existing ones are re-used, if at 323 all possible. Rekeying could be triggered by (a) management 324 actions and (b) expiring keying material. 326 6. Security Considerations 328 This entire document focused on the discussion of new functionality 329 for securing Diameter AVPs selectively between non-neighboring nodes. 331 7. IANA Considerations 333 This document does not require actions by IANA. 335 8. Acknowledgments 337 We would like to thank Guenther Horn, Martin Dolly, Steve Donovan, 338 Lionel Morand and Tom Taylor (rest in peace Tom) for their review 339 comments. 341 9. References 343 9.1. Normative References 345 [1] Bradner, S., "Key words for use in RFCs to Indicate 346 Requirement Levels", BCP 14, RFC 2119, 347 DOI 10.17487/RFC2119, March 1997, 348 . 350 [2] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn, 351 Ed., "Diameter Base Protocol", RFC 6733, 352 DOI 10.17487/RFC6733, October 2012, 353 . 355 9.2. Informative References 357 [3] Calhoun, P., Farrell, S., and W. Bulley, "Diameter CMS 358 Security Application", draft-ietf-aaa-diameter-cms-sec-04 359 (work in progress), March 2002. 361 [4] Eronen, P., Ed., Hiller, T., and G. Zorn, "Diameter 362 Extensible Authentication Protocol (EAP) Application", 363 RFC 4072, DOI 10.17487/RFC4072, August 2005, 364 . 366 Authors' Addresses 368 Hannes Tschofenig 369 ARM Limited 370 Austria 372 Email: Hannes.tschofenig@gmx.net 373 URI: http://www.tschofenig.priv.at 375 Jouni Korhonen (editor) 376 Broadcom Corporation 377 3151 Zanker Rd. 378 San Jose, CA 95134 379 USA 381 Email: jouni.nospam@gmail.com 383 Glen Zorn 384 Network Zen 385 227/358 Thanon Sanphawut 386 Bang Na Bangkok 10260 387 Thailand 389 Email: glenzorn@gmail.com 391 Kervin Pillay 392 Oracle Communications 393 100 Crosby Drive 394 Bedford, Massachusettes 01730 395 USA 397 Email: kervin.pillay@oracle.com