Network Working Group R. Earhart Internet Draft: URL-SMTP Carnegie Mellon Document: draft-earhart-url-smtp-00.txt December 1997 Expires June 1997 An SMTP URL Interface Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months. and may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress". To learn the current status of any Internet-Draft, please check the 1id-abstracts.txt listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). This document suggests a proposed protocol for the Internet community, and requests discussion and suggestions for improvements. Distribution of this draft is unlimited. The protocol discussed in this document is experimental and subject to change. Persons planning on either implementing or using this protocol are STRONGLY URGED to get in touch with the author before embarking on such a project. Abstract It is occasionally useful to be able to reference a generic server to be used for message submission. URLs provide a good mechanism for refering to arbitrary network resources. The SMTP URL scheme allows a URL to specify an SMTP server, thus allowing other protocols to use a general ''URL to be used for message delivery'' in place of an explicit reference to SMTP. Earhart [Page 1]
Internet DRAFT An SMTP URL Interface December 15, 1997 1. Conventions Used in this Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [KEYWORDS]. 2. SMTP URL Scheme The SMTP URL follows the common Internet scheme syntax as defined in [BASIC-URL] except that plaintext passwords are not permitted. If :<port> is omitted, the port defaults to 25. The specified server should not be assumed to have any services available other than SMTP. Other than authentication, no protocol actions are implied by an SMTP URL; an SMTP URL only specifies the location of an SMTP service, not what to do with it (common actions are to use the SMTP server to verify an address, and to submit Internet mail). An SMTP URL has the following general form: url-smtp = "smtp://" url-server "smtp" refers to the URL scheme; "://" is used to indicate a reference to an Internet host address. The <url-server> element includes the hostname, and optional user name, authentication mechanism and port number. Note that unsafe or reserved characters such as " " or "?" MUST be hex encoded as described in the URL specification [BASIC-URL]. Hex encoded octets are interpreted according to UTF-8 [UTF8]. 3. SMTP URL User Name and Authentication Mechanism A user name and/or authentication mechanism may be supplied. They are used to perform SASL [SASL] authentication after making the connection to the SMTP server. If no user name or authentication mechanism is supplied, then the SASL ANONYMOUS [SASL-ANON] mechanism is used by default. If an authentication mechanism is supplied without a user name, then one SHOULD be obtained from the specified mechanism or requested from the user as appropriate. If a user name is supplied without an authentication mechanism then ";AUTH=*" is assumed. The ";AUTH=" authentication parameter is interpreted as described in the IMAP URL Scheme [IMAP-URL]. Earhart [Page 2]
Internet DRAFT An SMTP URL Interface December 15, 1997 Note that if unsafe or reserved characters such as " " or ";" are present in the user name or authentication mechanism, they MUST be encoded as described in the URL specification [BASIC-URL]. 4. Formal Syntax The following syntax specification uses the augmented Backus-Naur Form (BNF) notation as specified in [ABNF]. This uses the ABNF core rules as specified in Appendix A of the ABNF specification [ABNF]. Except as noted otherwise, all alphabetic characters are case- insensitive. The use of upper or lower case characters to define token strings is for editorial clarity only. Implementations MUST accept these strings in a case-insensitive fashion. url-auth = ";AUTH=" ("*" / url-enc-auth) url-achar = uchar / "&" / "=" / "~" ;; See [BASIC-URL] for definition of "uchar" url-enc-auth = 1*url-achar ;; encoded version of auth-type-name above url-enc-user = *url-achar ;; encoded version of login userid url-server = [url-enc-user [url-auth] "@"] hostport ;; See [BASIC-URL] for definition of "hostport" url-smtp = "smtp://" url-server 5. Security Considerations SMTP URLs have the same security considerations as IMAP URLs [IMAP- URL]. Clients SHOULD make the SMTP URL being used obvious to the user, as using an undesireable server may compromise the security of the user's message. Earhart [Page 3]
Internet DRAFT An SMTP URL Interface December 15, 1997 6. Copyright Copyright (C) The Internet Society 1997. All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 7. References [ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. <url:ftp://ds.internic.net/rfc/rfc2234.txt> [BASIC-URL] Berners-Lee, Masinter, McCahill, "Uniform Resource Locators (URL)", RFC 1738, December 1994. <url:ftp://ds.internic.net/rfc/rfc1738.txt> [IMAP-URL] Newman, "IMAP URL Scheme", RFC 2192, July 1997. <url:ftp://ds.internic.net/rfc/rfc2192.txt> Earhart [Page 4]
Internet DRAFT An SMTP URL Interface December 15, 1997 [KEYWORDS] Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. <url:ftp://ds.internic.net/rfc/rfc2119.txt> [SASL] Myers, "Simple Authentication and Security Layer (SASL)", RFC 2222, October 1997. <url:ftp://ds.internic.net/rfc/rfc2222.txt> [SASL-ANON] Newman, "Anonymous SASL Mechanism", RFC 2245, November 1997. <url:ftp://ds.internic.net/rfc/rfc2245.txt> [UTF8] Yergeau, "UTF-8, a transformation format of Unicode and ISO 10646", RFC 2044, October 1996. <url:ftp://ds.internic.net/rfc/rfc2044.txt> 8. Author's Address Robert H. Earhart Carnegie Mellon 5000 Forbes Ave. Pittsburgh PA, 15213-3890 Email: earhart+@cmu.edu Expires June 1997 Earhart [Page 5]