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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2898 (Obsoleted by RFC 8018) == Outdated reference: A later version (-06) exists of draft-jennings-vipr-overview-01 ** Downref: Normative reference to an Informational draft: draft-jennings-vipr-overview (ref. 'VIPR-OVERVIEW') == Outdated reference: A later version (-02) exists of draft-jennings-vipr-vap-01 Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 VIPR J. Rosenberg 3 Internet-Draft jdrosen.net 4 Intended status: Standards Track C. Jennings 5 Expires: January 12, 2012 Cisco 6 M. Petit-Huguenin 7 Stonyfish 8 July 11, 2011 10 Session Initiation Protocol (SIP) Extensions for Blocking VoIP Spam 11 Using PSTN Validation 12 draft-petithuguenin-vipr-sip-antispam-02 14 Abstract 16 Verification Involving PSTN Reachability (ViPR) is a new technique 17 for inter-domain federation of SIP calls. ViPR makes use of the PSTN 18 as an introduction mechanism to verify the correctness of mappings 19 from phone numbers to domains. The PSTN introduction mechanism can 20 also be used as a technique for blocking spam - a SIP caller is only 21 authorized when its calling domain has previously called that same 22 number over the PSTN. This document describes an extension to SIP 23 which enables authorization of SIP calls based on a prior PSTN 24 introduction. 26 Legal 28 This documents and the information contained therein are provided on 29 an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE 30 REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE 31 IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL 32 WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY 33 WARRANTY THAT THE USE OF THE INFORMATION THEREIN WILL NOT INFRINGE 34 ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS 35 FOR A PARTICULAR PURPOSE. 37 Status of this Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at http://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on January 12, 2012. 54 Copyright Notice 56 Copyright (c) 2011 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (http://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 72 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 5 73 3. Terminating Side Procedures . . . . . . . . . . . . . . . . . . 5 74 4. Originating Side Procedures . . . . . . . . . . . . . . . . . . 6 75 5. Tickets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 76 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 77 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 78 7.1. IANA Registration of ViPR-Ticket Header Field . . . . . . . 7 79 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 80 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 81 9.1. Normative References . . . . . . . . . . . . . . . . . . . 8 82 9.2. Informative References . . . . . . . . . . . . . . . . . . 8 83 Appendix A. Release notes . . . . . . . . . . . . . . . . . . . . 9 84 A.1. Modifications between vipr-02 and vipr-01 . . . . . . . . . 9 85 A.2. Modifications between vipr-01 and vipr-00 . . . . . . . . . 9 86 A.3. Modifications between vipr-00 and dispatch-03 . . . . . . . 9 87 A.4. Modifications between dispatch-03 and dispatch-02 . . . . . 9 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 90 1. Introduction 92 The anti-spam tickets described in this specification are the key 93 security mechanism in ViPR for mitigation of SPAM. The domain 94 originating a call inserts a ticket in the SIP INVITE sent to the 95 other domain. The Border Element in the domain receiving the call 96 (see Figure 1) can check the ticket to ensure that this originating 97 domain has been authorized by the terminating domain. This document 98 relies heavily on the concepts and terminology defined in 99 [VIPR-OVERVIEW] and will not make sense if you have not read that 100 document first. 102 +-+ +-+ 103 | | | | +------+ 104 | | +-----| |---|Enroll| 105 | | | | | +------+ 106 |I| | |I| 107 |n| +-----+ |n| 108 VAP |t| | ViPR| |t| 109 +----------|r|---|Srvr |--|e|----------------- 110 | |a| | | |r| P2P-Validation 111 | |n| +-----+ |n| 112 | |e| |e| 113 | |t| |t| 114 +-----+ SIP | | +-----+ | | 115 | CA |-------|F|---| |--|F| --------------- 116 +-----+ |i| | | |i| SIP/TLS 117 . |r| | . | |r| 118 SIP/ . |e| | | |e| 119 MGCP/ . |w| | BE | |w| 120 TDM . |a| | | |a| 121 . |l| | | |l| 122 +-----+ |l| | | |l| 123 | UA |-------| |---| |--| |----------------- 124 +-----+ | | +-----+ | | SRTP 125 | | | | 126 +-+ +-+ 127 | | 128 +--------------------+-----------------+ 129 | 130 Single administrative domain 132 Figure 1: Architecture 134 2. Terminology 136 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 137 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 138 document are to be interpreted as described in [RFC2119]. 140 3. Terminating Side Procedures 142 The Border Element will receive the TLS ClientHello which begins the 143 TLS handshake. The Border Element will present its own configured 144 cert. Once TLS handshaking is complete, the Border Element notes the 145 domain from the SubjectAltName on the other side of the TLS 146 connection, and associates it with that connection. 148 Next, the Border Element will receive an INVITE. This INVITE will 149 contain a ticket in the ViPR-Ticket header field value. The Border 150 Element extracts this header field. This call flow assumes it is 151 present. The Border Element parses it, and obtains the epoch value 152 encoded in the ticket. This is matched against the current epoch 153 value for the configured password. If they match, processing 154 continues. The Border Element verifies the signature is correct. 155 Next, it examines the start and stop time of the validity. If the 156 current time is between the start and stop times, the check is 157 passed. Next, the Border Element checks the granted-to domain in the 158 ticket. It compares that domain against the domain name in the 159 SubjectAltName of the peer on the other side of the TLS connection, 160 as noted above. Next, it takes the Request-URI of the SIP INVITE. 161 That will be of the form sip:+number@domain. If it is not in that 162 form, and if the number does not begin with a plus, the request is 163 dropped. The value, including the plus, is then compared to the 164 number in the ticket. If it is equal, the check has passed. The 165 Border Element leaves the header field in the request, but forwards 166 to the Call Agent. 168 In addition, the Border Element will typically be configured to apply 169 its SIP message validation logic, and enforce restrictions on the 170 sizes of various SIP header fields. This provides an additional 171 layer of security in case malicious SIP messages are sent. 173 The Border Element will also apply port forwarding in the case of 174 NAT, so that the incoming request is forwarded to the appropriate 175 Call Agent node. 177 The Call Agent will receive incoming SIP INVITEs. The Request-URI of 178 the INVITE will contain an E.164 number as indicated by a leading 179 plus. If the Request-URI is not an E.164, the request must be 180 rejected with a 403. Only E.164 numbers can be accepted on a ViPR 181 trunk. 183 4. Originating Side Procedures 185 The routes stored to other domains in the Call Agent will each store 186 a ticket to utilize with calls to that route. The Call Agent learns 187 about these routes and the information needed to construct the ticket 188 from the VAP protocol [VIPR-VAP]. When sending a SIP request to one 189 of these domains, the Call Agent MUST include the ticket in any 190 dialog forming request or request that is not in an existing dialog. 192 5. Tickets 194 This ticket is a sequence of characters. These MUST be placed into a 195 ViPR-Ticket SIP header field value. Consequently the format for this 196 header field is: 197 Ticket = "ViPR-Ticket" HCOLON ticket-val 198 ticket-val = 1*(alphanum / "-" / "_" / ".") 200 This header field MUST be utilized in all dialog forming requests and 201 all out-of-dialog requests. It is not utilized in responses. The 202 ticket-value is a modified base64 encoded version of an object that 203 is composed of a series of TLVs. Each TLV is a 16 bit type, a 16 bit 204 length, and a variable length value. The length field refers to the 205 length of the value portion of the TLV, measured in bytes. The 206 following TLV types are defined: 208 1. Ticket Unique ID: This TLV has a type of 0x0001. It contains a 209 128 bit ID that has a unique identifier for this ticket. The 210 value MUST contain a 128 bit UUID defined by [RFC4122]. This TLV 211 MUST be present. However at this time it is used for diagnostic 212 purposes only. 213 2. Salt: This TLV has a type of 0x0002. It contains a value which 214 MUST be at least 32 bits, and contains a random number. Its 215 presence ensures that each ticket contains sufficient randomness. 216 This TLV MUST be present. 217 3. Validity: This TLV has a type of 0x0003. It contains two 64 bit 218 NTP times. The first is the start of the validity of the ticket, 219 the next is the end time for the validity of the ticket. This 220 TLV MUST be present. 221 4. Number: This TLV has a type of 0x0004. It contains a string 222 which has an E.164 number, included the "+", which may be called 223 using this ticket. The TLV has variable length. This TLV MUST 224 be present. 226 5. Granting Node: This TLV has a type of 0x0005. It contains a 128 227 bit value which is the Node-ID of the node which granted the 228 ticket. This TLV MUST be present. 229 6. Granting Domain: This TLV has a type of 0x0006. The domain 230 which granted the ticket. A string, up to 256 characters, each 231 of which must be a valid domain name character. The TLV has 232 variable length. This TLV MUST be present. 233 7. Granted-To Domain: This TLV has a type of 0x0007. The domain to 234 which the ticket is granted. A string, up to 256 characters, 235 each of which must be a valid domain name character. The TLV has 236 a variable length. This TLV MUST be present. 237 8. Epoch: This TLV has a type of 0x0008. It contains a 32 bit 238 epoch value. It is used to select a key. This TLV MUST be 239 present. 240 9. Integrity: This TLV has a type of 0x0009. It contains a 160 bit 241 integrity value, computed using HMAC-SHA1. This TLV MUST be 242 present and MUST be the last TLV in the object. 244 The base64 encoding uses the base64url encoding from RFC4648 245 [RFC4648], with the exception of the pad character, which is a "." 246 instead of an "=". This ensures that the output is a valid SIP 247 token. 249 To compute the MAC, the following is done. First, the key is 250 obtained. The key is actually a 128 bit key, configured into the 251 system. The key, P, is then used to compute Km: 253 Km = HMAC-SHA1(P, S | Epoch) 255 Based on PBKDF2 from PKCS #5 [RFC2898] with HMAC-SHA1 as PRF and 256 iteration count of 1. Where S is the 32 bit salt and Epoch is the 32 257 bit Epoch, from the ticket. This produces a 160 bit Km. The MAC is 258 then computed as another HMAC-SHA1, over the entire ticket up to but 259 not including the Integrity itself, using Km as the key. This 260 produces the 160 bit MAC. 262 6. Security Considerations 264 TBD 266 7. IANA Considerations 268 7.1. IANA Registration of ViPR-Ticket Header Field 270 This document defines a new SIP header field: ViPR-Ticket. Its 271 syntax is defined in Section 5. This header field must be registered 272 by IANA in the SIP Parameters registry under the Header Fields 273 subregistry with the following information: 275 Header Name: ViPR-Ticket 276 Compact Form: none 278 8. Acknowledgements 280 Thanks to Patrice Bruno for his comments, suggestions and questions 281 that helped to improve this document. 283 9. References 285 9.1. Normative References 287 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 288 Requirement Levels", BCP 14, RFC 2119, March 1997. 290 [RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography 291 Specification Version 2.0", RFC 2898, September 2000. 293 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 294 Unique IDentifier (UUID) URN Namespace", RFC 4122, 295 July 2005. 297 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 298 Encodings", RFC 4648, October 2006. 300 [VIPR-OVERVIEW] 301 Jennings, C., Rosenberg, J., and M. Petit-Huguenin, 302 "Verification Involving PSTN Reachability: Requirements 303 and Architecture Overview", 304 draft-jennings-vipr-overview-01 (work in progress), 305 July 2011. 307 9.2. Informative References 309 [VIPR-VAP] 310 Jennings, C., Rosenberg, J., and M. Petit-Huguenin, 311 "Verification Involving PSTN Reachability: The ViPR Access 312 Protocol (VAP)", draft-jennings-vipr-vap-01 (work in 313 progress), July 2011. 315 Appendix A. Release notes 317 This section must be removed before publication as an RFC. 319 A.1. Modifications between vipr-02 and vipr-01 321 o Renamed Ticket to ViPR-Ticket to synchronize with -overview. 323 A.2. Modifications between vipr-01 and vipr-00 325 o Renamed X-Cisco-ViPR-Ticket to Ticket and filled the IANA section. 327 A.3. Modifications between vipr-00 and dispatch-03 329 o Moved to new Working Group. 331 A.4. Modifications between dispatch-03 and dispatch-02 333 o Added terminology section. 334 o Nits 335 o Shorter I-Ds references. 336 o Changed issued-to to granted-to. 337 o Fixed the ABNF. 338 o The tickets is used in all dialog forming requests, not only 339 INVITE. 340 o The Number TLV has a variable length. 341 o The Integrity TLV MUST be the last in the object. 342 o Fixed a discrepancy in the epoch length. 344 Authors' Addresses 346 Jonathan Rosenberg 347 jdrosen.net 348 Monmouth, NJ 349 US 351 Email: jdrosen@jdrosen.net 352 URI: http://www.jdrosen.net 353 Cullen Jennings 354 Cisco 355 170 West Tasman Drive 356 MS: SJC-21/2 357 San Jose, CA 95134 358 USA 360 Phone: +1 408 421-9990 361 Email: fluffy@cisco.com 363 Marc Petit-Huguenin 364 Stonyfish 366 Email: marc@stonyfish.com