rfc4616.txt

广泛使用的邮件服务器！同时

   The second example shows how the PLAIN mechanism might be used to
   attempt to assume the identity of another user.  In this example, the
   server rejects the request.  Also, this example makes use of the
   protocol optional initial response capability to eliminate a round-
   trip.

   S: * ACAP (SASL "CRAM-MD5") (STARTTLS)
   C: a001 STARTTLS
   S: a001 OK "Begin TLS negotiation now"
   <TLS negotiation, further commands are under TLS layer>
   S: * ACAP (SASL "CRAM-MD5" "PLAIN")
   C: a002 AUTHENTICATE "PLAIN" {20+}
   C: Ursel<NUL>Kurt<NUL>xipj3plmq
   S: a002 NO "Not authorized to requested authorization identity"

5.  Security Considerations

   As the PLAIN mechanism itself provided no integrity or
   confidentiality protections, it should not be used without adequate
   external data security protection, such as TLS services provided by
   many application-layer protocols.  By default, implementations SHOULD
   NOT advertise and SHOULD NOT make use of the PLAIN mechanism unless
   adequate data security services are in place.



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RFC 4616                The PLAIN SASL Mechanism             August 2006


   When the PLAIN mechanism is used, the server gains the ability to
   impersonate the user to all services with the same password
   regardless of any encryption provided by TLS or other confidentiality
   protection mechanisms.  Whereas many other authentication mechanisms
   have similar weaknesses, stronger SASL mechanisms address this issue.
   Clients are encouraged to have an operational mode where all
   mechanisms that are likely to reveal the user's password to the
   server are disabled.

   General [SASL] security considerations apply to this mechanism.

   Unicode, [UTF-8], and [StringPrep] security considerations also
   apply.

6.  IANA Considerations

   The SASL Mechanism registry [IANA-SASL] entry for the PLAIN mechanism
   has been updated by the IANA to reflect that this document now
   provides its technical specification.

   To: [e-mail]
   Subject: Updated Registration of SASL mechanism PLAIN

   SASL mechanism name: PLAIN
   Security considerations: See RFC 4616.
   Published specification (optional, recommended): RFC 4616
   Person & email address to contact for further information:
        Kurt Zeilenga <[e-mail]>
        IETF SASL WG <[e-mail]>
   Intended usage: COMMON
   Author/Change controller: IESG <[e-mail]>
   Note: Updates existing entry for PLAIN

7.  Acknowledgements

   This document is a revision of RFC 2595 by Chris Newman.  Portions of
   the grammar defined in Section 2 were borrowed from [UTF-8] by
   Francois Yergeau.

   This document is a product of the IETF Simple Authentication and
   Security Layer (SASL) Working Group.










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RFC 4616                The PLAIN SASL Mechanism             August 2006


8.  Normative References

   [ABNF]        Crocker, D., Ed. and P. Overell, "Augmented BNF for
                 Syntax Specifications: ABNF", RFC 4234, October 2005.

   [Keywords]    Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

   [SASL]        Melnikov, A., Ed., and K. Zeilenga, Ed., "Simple
                 Authentication and Security Layer (SASL)", RFC 4422,
                 June 2006.

   [SASLPrep]    Zeilenga, K., "SASLprep: Stringprep Profile for User
                 Names and Passwords", RFC 4013, February 2005.

   [StringPrep]  Hoffman, P. and M. Blanchet, "Preparation of
                 Internationalized Strings ("stringprep")", RFC 3454,
                 December 2002.

   [Unicode]     The Unicode Consortium, "The Unicode Standard, Version
                 3.2.0" is defined by "The Unicode Standard, Version
                 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
                 61633-5), as amended by the "Unicode Standard Annex
                 #27: Unicode 3.1"
                 (http://www.unicode.org/reports/tr27/) and by the
                 "Unicode Standard Annex #28: Unicode 3.2"
                 (http://www.unicode.org/reports/tr28/).

   [UTF-8]       Yergeau, F., "UTF-8, a transformation format of ISO
                 10646", STD 63, RFC 3629, November 2003.

   [TLS]         Dierks, T. and E. Rescorla, "The Transport Layer
                 Security (TLS) Protocol Version 1.1", RFC 4346, April
                 2006.

9.  Informative References

   [ACAP]        Newman, C. and J. Myers, "ACAP -- Application
                 Configuration Access Protocol", RFC 2244, November
                 1997.

   [CRAM-MD5]    Nerenberg, L., Ed., "The CRAM-MD5 SASL Mechanism", Work
                 in Progress, June 2006.

   [DIGEST-MD5]  Melnikov, A., Ed., "Using Digest Authentication as a
                 SASL Mechanism", Work in Progress, June 2006.





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   [IANA-SASL]   IANA, "SIMPLE AUTHENTICATION AND SECURITY LAYER (SASL)
                 MECHANISMS",
                 <http://www.iana.org/assignments/sasl-mechanisms>.

   [SMTP-AUTH]   Myers, J., "SMTP Service Extension for Authentication",
                 RFC 2554, March 1999.













































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RFC 4616                The PLAIN SASL Mechanism             August 2006


Appendix A.  Changes since RFC 2595

   This appendix is non-normative.

   This document replaces Section 6 of RFC 2595.

   The specification details how the server is to compare client-
   provided character strings with stored character strings.

   The ABNF grammar was updated.  In particular, the grammar now allows
   LINE FEED (U+000A) and CARRIAGE RETURN (U+000D) characters in the
   authzid, authcid, passwd productions.  However, whether these control
   characters may be used depends on the string preparation rules
   applicable to the production.  For passwd and authcid productions,
   control characters are prohibited.  For authzid, one must consult the
   application-level SASL profile.  This change allows PLAIN to carry
   all possible authorization identity strings allowed in SASL.

   Pseudo-code was added.

   The example section was expanded to illustrate more features of the
   PLAIN mechanism.

Editor's Address

   Kurt D. Zeilenga
   OpenLDAP Foundation

   EMail: [e-mail]






















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RFC 4616                The PLAIN SASL Mechanism             August 2006


Full Copyright Statement

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