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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2898 (Obsoleted by RFC 8018) == Outdated reference: A later version (-06) exists of draft-jennings-vipr-overview-00 ** Downref: Normative reference to an Informational draft: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 'VIPR-OVERVIEW') == Outdated reference: A later version (-02) exists of draft-jennings-vipr-vap-00 Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 dispatch J. Rosenberg 3 Internet-Draft jdrosen.net 4 Intended status: Standards Track C. Jennings 5 Expires: October 3, 2011 Cisco 6 M. Petit-Huguenin 7 Stonyfish 8 April 1, 2011 10 Session Initiation Protocol (SIP) Extensions for Blocking VoIP Spam 11 Using PSTN Validation 12 draft-petithuguenin-vipr-sip-antispam-00 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 October 3, 2011. 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 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 79 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 80 9.1. Normative References . . . . . . . . . . . . . . . . . . . 8 81 9.2. Informative References . . . . . . . . . . . . . . . . . . 8 82 Appendix A. Release notes . . . . . . . . . . . . . . . . . . . . 8 83 A.1. Modifications between vipr-00 and dispatch-03 . . . . . . . 8 84 A.2. Modifications between dispatch-03 and dispatch-02 . . . . . 9 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 87 1. Introduction 89 The anti-spam tickets described in this specification are the key 90 security mechanism in ViPR for mitigation of SPAM. The domain 91 originating a call inserts a ticket in the SIP INVITE sent to the 92 other domain. The Border Element in the domain receiving the call 93 (see Figure 1) can check the ticket to ensure that this originating 94 domain has been authorized by the terminating domain. This document 95 relies heavily on the concepts and terminology defined in 96 [VIPR-OVERVIEW] and will not make sense if you have not read that 97 document first. 99 +-+ +-+ 100 | | | | +------+ 101 | | +-----| |---|Enroll| 102 | | | | | +------+ 103 |I| | |I| 104 |n| +-----+ |n| 105 VAP |t| | ViPR| |t| 106 +----------|r|---|Srvr |--|e|----------------- 107 | |a| | | |r| P2P-Validation 108 | |n| +-----+ |n| 109 | |e| |e| 110 | |t| |t| 111 +-----+ SIP | | +-----+ | | 112 | CA |-------|F|---| |--|F| --------------- 113 +-----+ |i| | | |i| SIP/TLS 114 . |r| | . | |r| 115 SIP/ . |e| | | |e| 116 MGCP/ . |w| | BE | |w| 117 TDM . |a| | | |a| 118 . |l| | | |l| 119 +-----+ |l| | | |l| 120 | UA |-------| |---| |--| |----------------- 121 +-----+ | | +-----+ | | SRTP 122 | | | | 123 +-+ +-+ 124 | | 125 +--------------------+-----------------+ 126 | 127 Single administrative domain 129 Figure 1: Architecture 131 2. Terminology 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in [RFC2119]. 137 3. Terminating Side Procedures 139 The Border Element will receive the TLS ClientHello which begins the 140 TLS handshake. The Border Element will present its own configured 141 cert. Once TLS handshaking is complete, the Border Element notes the 142 domain from the SubjectAltName on the other side of the TLS 143 connection, and associates it with that connection. 145 Next, the Border Element will receive an INVITE. This INVITE will 146 contain a ticket in the X-Cisco-ViPR-Ticket header field value. The 147 Border Element extracts this header field. This call flow assumes it 148 is present. The Border Element parses it, and obtains the epoch 149 value encoded in the ticket. This is matched against the current 150 epoch value for the configured password. If they match, processing 151 continues. The Border Element verifies the signature is correct. 152 Next, it examines the start and stop time of the validity. If the 153 current time is between the start and stop times, the check is 154 passed. Next, the Border Element checks the granted-to domain in the 155 ticket. It compares that domain against the domain name in the 156 SubjectAltName of the peer on the other side of the TLS connection, 157 as noted above. Next, it takes the Request-URI of the SIP INVITE. 158 That will be of the form sip:+number@domain. If it is not in that 159 form, and if the number does not begin with a plus, the request is 160 dropped. The value, including the plus, is then compared to the 161 number in the ticket. If it is equal, the check has passed. The 162 Border Element leaves the header field in the request, but forwards 163 to the Call Agent. 165 In addition, the Border Element will typically be configured to apply 166 its SIP message validation logic, and enforce restrictions on the 167 sizes of various SIP header fields. This provides an additional 168 layer of security in case malicious SIP messages are sent. 170 The Border Element will also apply port forwarding in the case of 171 NAT, so that the incoming request is forwarded to the appropriate 172 Call Agent node. 174 The Call Agent will receive incoming SIP INVITEs. The Request-URI of 175 the INVITE will contain an E.164 number as indicated by a leading 176 plus. If the Request-URI is not an E.164, the request must be 177 rejected with a 403. Only E.164 numbers can be accepted on a ViPR 178 trunk. 180 4. Originating Side Procedures 182 The routes stored to other domains in the Call Agent will each store 183 a ticket to utilize with calls to that route. The Call Agent learns 184 about these routes and the information needed to construct the ticket 185 from the VAP protocol [VIPR-VAP]. When sending a SIP request to one 186 of these domains, the Call Agent MUST include the ticket in any 187 dialog forming request or request that is not in an existing dialog. 189 5. Tickets 191 This ticket is a sequence of characters. These MUST be placed into a 192 X-Cisco-ViPR-Ticket SIP header field value. Consequently the format 193 for this header field is: 194 Ticket = "X-Cisco-ViPR-Ticket" HCOLON ticket-val 195 ticket-val = 1*(alphanum / "-" / "_" / ".") 197 This header field MUST be utilized in all dialog forming requests and 198 all out-of-dialog requests. It is not utilized in responses. The 199 ticket-value is a modified base64 encoded version of an object that 200 is composed of a series of TLVs. Each TLV is a 16 bit type, a 16 bit 201 length, and a variable length value. The length field refers to the 202 length of the value portion of the TLV, measured in bytes. The 203 following TLV types are defined: 205 1. Ticket Unique ID: This TLV has a type of 0x0001. It contains a 206 128 bit ID that has a unique identifier for this ticket. The 207 value MUST contain a 128 bit UUID defined by [RFC4122]. This TLV 208 MUST be present. However at this time it is used for diagnostic 209 purposes only. 210 2. Salt: This TLV has a type of 0x0002. It contains a value which 211 MUST be at least 32 bits, and contains a random number. Its 212 presence ensures that each ticket contains sufficient randomness. 213 This TLV MUST be present. 214 3. Validity: This TLV has a type of 0x0003. It contains two 64 bit 215 NTP times. The first is the start of the validity of the ticket, 216 the next is the end time for the validity of the ticket. This 217 TLV MUST be present. 218 4. Number: This TLV has a type of 0x0004. It contains a string 219 which has an E.164 number, included the "+", which may be called 220 using this ticket. The TLV has variable length. This TLV MUST 221 be present. 223 5. Granting Node: This TLV has a type of 0x0005. It contains a 128 224 bit value which is the Node-ID of the node which granted the 225 ticket. This TLV MUST be present. 226 6. Granting Domain: This TLV has a type of 0x0006. The domain 227 which granted the ticket. A string, up to 256 characters, each 228 of which must be a valid domain name character. The TLV has 229 variable length. This TLV MUST be present. 230 7. Granted-To Domain: This TLV has a type of 0x0007. The domain to 231 which the ticket is granted. A string, up to 256 characters, 232 each of which must be a valid domain name character. The TLV has 233 a variable length. This TLV MUST be present. 234 8. Epoch: This TLV has a type of 0x0008. It contains a 32 bit 235 epoch value. It is used to select a key. This TLV MUST be 236 present. 237 9. Integrity: This TLV has a type of 0x0009. It contains a 160 bit 238 integrity value, computed using HMAC-SHA1. This TLV MUST be 239 present and MUST be the last TLV in the object. 241 The base64 encoding uses the base64url encoding from RFC4648 242 [RFC4648], with the exception of the pad character, which is a "." 243 instead of an "=". This ensures that the output is a valid SIP 244 token. 246 To compute the MAC, the following is done. First, the key is 247 obtained. The key is actually a 128 bit key, configured into the 248 system. The key, P, is then used to compute Km: 250 Km = HMAC-SHA1(P, S | Epoch) 252 Based on PBKDF2 from PKCS #5 [RFC2898] with HMAC-SHA1 as PRF and 253 iteration count of 1. Where S is the 32 bit salt and Epoch is the 32 254 bit Epoch, from the ticket. This produces a 160 bit Km. The MAC is 255 then computed as another HMAC-SHA1, over the entire ticket up to but 256 not including the Integrity itself, using Km as the key. This 257 produces the 160 bit MAC. 259 6. Security Considerations 261 TBD 263 7. IANA Considerations 265 TBD - Register SIP Header 267 TBD - Form IANA registry for Ticket TLVs 269 8. Acknowledgements 271 Thanks to Patrice Bruno for his comments, suggestions and questions 272 that helped to improve this document. 274 9. References 276 9.1. Normative References 278 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 279 Requirement Levels", BCP 14, RFC 2119, March 1997. 281 [RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography 282 Specification Version 2.0", RFC 2898, September 2000. 284 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 285 Unique IDentifier (UUID) URN Namespace", RFC 4122, 286 July 2005. 288 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 289 Encodings", RFC 4648, October 2006. 291 [VIPR-OVERVIEW] 292 Rosenberg, J., Jennings, C., and M. Petit-Huguenin, 293 "Verification Involving PSTN Reachability: Requirements 294 and Architecture Overview", 295 draft-jennings-vipr-overview-00 (work in progress), 296 April 2011. 298 9.2. Informative References 300 [VIPR-VAP] 301 Rosenberg, J., Jennings, C., and M. Petit-Huguenin, 302 "Verification Involving PSTN Reachability: The ViPR Access 303 Protocol (VAP)", draft-jennings-vipr-vap-00 (work in 304 progress), April 2011. 306 Appendix A. Release notes 308 This section must be removed before publication as an RFC. 310 A.1. Modifications between vipr-00 and dispatch-03 312 o Moved to new Working Group. 314 A.2. Modifications between dispatch-03 and dispatch-02 316 o Added terminology section. 317 o Nits 318 o Shorter I-Ds references. 319 o Changed issued-to to granted-to. 320 o Fixed the ABNF. 321 o The tickets is used in all dialog forming requests, not only 322 INVITE. 323 o The Number TLV has a variable length. 324 o The Integrity TLV MUST be the last in the object. 325 o Fixed a discrepancy in the epoch length. 327 Authors' Addresses 329 Jonathan Rosenberg 330 jdrosen.net 331 Monmouth, NJ 332 US 334 Email: jdrosen@jdrosen.net 335 URI: http://www.jdrosen.net 337 Cullen Jennings 338 Cisco 339 170 West Tasman Drive 340 MS: SJC-21/2 341 San Jose, CA 95134 342 USA 344 Phone: +1 408 421-9990 345 Email: fluffy@cisco.com 347 Marc Petit-Huguenin 348 Stonyfish 350 Email: marc@stonyfish.com