idnits 2.17.1 draft-hathcock-minger-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** It looks like you're using RFC 3978 boilerplate. You should update this to the boilerplate described in the IETF Trust License Policy document (see https://trustee.ietf.org/license-info), which is required now. -- Found old boilerplate from RFC 3978, Section 5.1 on line 14. -- Found old boilerplate from RFC 3978, Section 5.5, updated by RFC 4748 on line 356. -- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 367. -- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 374. -- Found old boilerplate from RFC 3979, Section 5, paragraph 3 on line 380. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- == The page length should not exceed 58 lines per page, but there was 1 longer page, the longest (page 2) being 108 lines == It seems as if not all pages are separated by form feeds - found 0 form feeds but 11 pages Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** There is 1 instance of too long lines in the document, the longest one being 1 character in excess of 72. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (March 6, 2007) is 6254 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- -- Obsolete informational reference (is this intentional?): RFC 1734 (Obsoleted by RFC 5034) -- Obsolete informational reference (is this intentional?): RFC 2821 (Obsoleted by RFC 5321) -- Obsolete informational reference (is this intentional?): RFC 4234 (Obsoleted by RFC 5234) Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group A. Hathcock 2 Internet-Draft J. Merkel 3 Intended Status: Informational Alt-N Technologies 4 Expires: September 6, 2007 March 6, 2007 6 The Minger Email Address Verification Protocol 7 draft-hathcock-minger-01.txt 9 Status of this Memo 11 By submitting this Internet-Draft, each author represents that any 12 applicable patent or other IPR claims of which he or she is aware 13 have been or will be disclosed, and any of which he or she becomes 14 aware will be disclosed, in accordance with Section 6 of BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on September 6, 2007. 34 Copyright Notice 36 Copyright (C) The IETF Trust (2007). 38 Abstract 40 This document describes the Minger protocol. Minger is a protocol 41 for determining whether an email address exists and, optionally, 42 retrieving some information about the user of that address. It 43 includes security in the form of a username/hashed password but can 44 also be used anonymously if desired. 46 Requirements Language 48 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 49 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 50 document are to be interpreted as described in [RFC2119]. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 55 1.1. The problem . . . . . . . . . . . . . . . . . . . . . . 3 56 1.2. Existing solutions . . . . . . . . . . . . . . . . . . . 3 57 1.3. The solution . . . . . . . . . . . . . . . . . . . . . . 3 58 2. The Minger protocol . . . . . . . . . . . . . . . . . . . . 4 59 2.1 The Minger query process . . . . . . . . . . . . . . . . 4 60 2.2 Description of query elements . . . . . . . . . . . . . . 5 61 3. Minger responses . . . . . . . . . . . . . . . . . . . . . . 5 62 3.1 Description of response elements . . . . . . . . . . . . 6 63 3.2 Example responses . . . . . . . . . . . . . . . . . . . . 6 64 4. Anonymous mode . . . . . . . . . . . . . . . . . . . . . . . 7 65 5. Security Considerations . . . . . . . . . . . . . . . . . . 8 66 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 8 67 7. Informative References . . . . . . . . . . . . . . . . . . . 9 68 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . 10 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 70 Intellectual Property and Copyright Statements . . . . . . . . . 11 72 1. Introduction 74 1.1 The problem 76 It is common for elements within a typical email handling topology 77 to be unaware of whether individual local-parts are valid for the 78 mail it accepts. For example, so-called "edge" servers which provide 79 security oriented services for downstream mail handling elements 80 often do not have an exhaustive listing of all valid local-parts for 81 a given domain. Thus, they are sometimes forced to accept messages 82 which might otherwise be rejected as "user unknown". Similarly, 83 entities offering "backup MX" mail services are rarely privy to a 84 complete local-part listing and are therefore forced to accept 85 messages which might otherwise be rejected. Finally, even within a 86 common administrative framework of several locally maintained and 87 controlled SMTP servers in a load balanced configuration, it is not 88 always possible for all servers to access a common local-part 89 database. 91 1.2 Existing solutions 93 The need to determine whether an email address contains a valid local 94 part has lead to the use of at least two existing mechanisms - Finger 95 [RFC1288] and SMTP "call-back" / "call-forward". 97 Finger [RFC1288] describes a protocol for the exchange of user 98 information. In theory, Finger could be used to determine whether an 99 account exists by careful examination of the results of a Finger 100 query. However, Finger suffers from a lack of security which makes 101 its modern day use problematic. For example, it is possible for 102 attackers to obtain information about the users of an email system 103 which they can then sell or use as targets for spam and viruses. 104 Also, Finger requires the use of TCP rather than UDP which seems ill 105 suited to a simple verification scheme. 107 SMTP "call-back" and "call-forward" are terms describing a widespread 108 practice whereby SMTP servers place an incoming SMTP session on hold 109 while they attempt to use an outbound SMTP session to determine 110 whether or not a given email address is valid. The theory behind this 111 is as follows: if an SMTP server responds positively to an SMTP RCPT 112 or MAIL command [RFC2821] with a given email address then this 113 potentially means that the address local part is valid. One problem 114 with such a scheme is the lack of efficiency inherent in the need to 115 tear-up and tear-down an SMTP session over TCP. Also, because these 116 types of SMTP sessions are not purposed to deliver mail, they 117 typically drop connection after the RCPT command is processed. This 118 leads to a large number of SMTP sessions which appear in logs to have 119 simply failed for no reason. 121 SMTP includes a VRFY command which can be used to determine whether 122 an email address exits. It is routinely disabled for the same 123 reasons described above in the discussion on Finger. 125 1.3 The solution 127 What's needed is a UDP based protocol which is secure, has little 128 overhead, and can be easily invoked to determine whether a given 129 email address is valid or not. Minger fulfills this need. 131 2. The Minger protocol 133 Minger is a UDP protocol that operates on port 4069. 135 Syntax descriptions use the form described in Augmented Backus-Naur 136 Form for Syntax Specifications (ABNF) [RFC4234]. 138 2.1 The Minger query process 140 A Minger client constructs a query string comprised of either two or 141 four elements and transmits it over UDP to a Minger server. The 142 format of the query is as follows: 144 ABNF: 146 Query-string = id SP mailbox [SP credentials] 148 id = 1*50(VCHAR) ; used to match a query to a 149 ; response 151 mailbox = Local-part "@" Domain ; as defined in [RFC2821] 153 credentials = username SP digest ; authentication credentials 155 username = 1*50(VCHAR) ; username credential 157 password = 1*50(VCHAR) ; password credential 159 digest-text = username ":" password ; input text for digest 161 digest = base64 ; digest for security 162 ; base64 defined in [RFC1734] 164 2.2 Description of query elements 166 id 168 This is an identifier assigned by the program that generates the 169 query. This same value will be echoed back in the response 170 returned by the Minger server and can therefore be used to match 171 a response to the proper query. 173 mailbox 175 This is the email address for which verification of 176 existence is desired. 178 credentials 180 These values are pre-arranged elements determined and 181 configured in advance so that Minger servers provide service only 182 to authorized clients. When not provided, Minger is operating in 183 anonymous mode. 185 digest 187 This is the base64 encoding of the MD5 [RFC1321] hash of 188 Digest-text. Digest-text is constructed, the MD5 hash of that 189 is computed, and that result is base64 encoded. 191 3. Minger responses 193 Minger servers return responses in a simple XML format. The XML 194 format returned by the Minger server has certain required elements 195 but can include additional optional elements as desired by particular 196 implementations. 198 [W3C-XML] DTD: 200 202 205 206 207 ]> 209 3.1 Description of response elements 211 id 213 Queries submit an identifier. That value is copied into the 214 id field within responses. This allows clients to match up 215 responses to the proper queries. 217 status 219 The following status codes are defined: 221 0 - invalid request (for example, malformed query string) 222 1 - access denied (for example, query from unauthorized IP) 223 2 - bad or missing credentials (returned when anonymous 224 mode is disabled and no credentials were provided in the 225 query string or when the credentials themselves are 226 invalid) 227 3 - email address does not exist 228 4 - email address exists but can not receive mail (for example, 229 the account associated with the email address has exceeded 230 local storage constraints or it is otherwise disabled due 231 to local policy) 232 5 - email address exists and is active (able to receive mail) 234 name and email 236 Optional full name and email address associated with the query 237 result. The value returned in the "email" element might differ 238 from the email address used in the actual query itself. For 239 example, if the query specifies an email address alias then the 240 minger result might contain the actual email address in the 241 "email" element. 243 Note: Minger servers MAY supply one or more additional XML elements 244 to provide additional data not specified by this document. 246 3.2 Example responses 248 Minger response returned when the queried email address does 249 not exist: 251 253 Minger response returned for invalid credentials: 255 257 Minger response returned when the queried email address exists: 259 261 Minger response returning optional name and email elements: 263 264 Arvel Hathcock 265 arvel@altn.com 266 268 4. Anonymous mode 270 Minger clients MAY attempt anonymous queries; that is, queries which 271 do not contain authentication credentials within the query string. 272 Minger servers SHOULD respond to anonymous queries in the same way 273 they respond to authenticated queries. However, Minger servers MAY 274 be configured to refuse anonymous queries. If so, they MUST respond 275 with a status of "2". Additionally, Minger servers MAY respond to 276 anonymous queries with a sub-set or none of any optional user data 277 that may otherwise be provided. 279 5. Security Considerations 281 Minger is used to obtain information about the validity of an email 282 address. It may also be used to retrieve additional implementation 283 specific data about the user of an email address. Minger also 284 supports an anonymous mode concept in which use of authentication 285 credentials is not required. Extreme care must therefore be taken 286 to ensure that sensitive data is not transmitted unless appropriate. 287 To reduce the likelihood of abuse, Minger servers should require 288 authentication and secure access with IP-based ACLs. 290 With using authentication credentials, the original password is 291 safe because only a hash is sent. However, since the hash does 292 not depend on the message, it is subject to replay abuse. 294 6. IANA Considerations 296 IANA has assigned tcp & upd port 4069 for Minger. 298 7. Informative References 300 [RFC1288] Zimmerman, D., "The Finger User Information Protocol", 301 RFC 1288, December 1991. 303 [RFC1734] Myers, J., "POP3 Authentication Command", RFC 1734, 304 December 1994. 306 [RFC2821] Klensin, J., Editor, "Simple Mail Transfer Protocol", RFC 307 2821, March 2001. 309 [RFC4234] Crocker, D., Ed. And P. Overell, "Augmented BNF for Syntax 310 Specifications: ABNF", RFC 4234, October 2005. 312 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 313 Requirement Levels", BCP 14, RFC 2119, March 1997. 315 [RFC1321] Rivest, R., "The MD5 Message Digest Algorithm", RFC 1321, 316 MIT Laboratory for Computer Science and RSA Data Security, 317 Inc., April 1992. 319 [W3C-XML] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, 320 "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C 321 REC-xml, October 2000, . 323 Appendix A. Acknowledgements 325 We wish to thank the members of the MDaemon Beta Community 326 (md-beta-subscribe@altn.com) for their ideas and help. 328 Authors' Addresses 330 Arvel Hathcock 331 Alt-N Technologies 332 http://www.altn.com 334 Email: arvel.hathcock@altn.com 336 Jonathan Merkel 337 Alt-N Technologies 338 http://www.altn.com 340 Email: jon.merkel@altn.com 342 Full Copyright Statement 344 Copyright (C) The IETF Trust (2007). 346 This document is subject to the rights, licenses and restrictions 347 contained in BCP 78, and except as set forth therein, the authors 348 retain all their rights. 350 This document and the information contained herein are provided on an 351 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 352 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 353 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 354 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 355 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 356 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 358 Intellectual Property 360 The IETF takes no position regarding the validity or scope of any 361 Intellectual Property Rights or other rights that might be claimed to 362 pertain to the implementation or use of the technology described in 363 this document or the extent to which any license under such rights 364 might or might not be available; nor does it represent that it has 365 made any independent effort to identify any such rights. Information 366 on the procedures with respect to rights in RFC documents can be 367 found in BCP 78 and BCP 79. 369 Copies of IPR disclosures made to the IETF Secretariat and any 370 assurances of licenses to be made available, or the result of an 371 attempt made to obtain a general license or permission for the use of 372 such proprietary rights by implementers or users of this 373 specification can be obtained from the IETF on-line IPR repository at 374 http://www.ietf.org/ipr. 376 The IETF invites any interested party to bring to its attention any 377 copyrights, patents or patent applications, or other proprietary 378 rights that may cover technology that may be required to implement 379 this standard. Please address the information to the IETF at 380 ietf-ipr@ietf.org. 382 Acknowledgment 384 Funding for the RFC Editor function is provided by the IETF 385 Administrative Support Activity (IASA).