Network Working Group R. Gellens
Request for Comments: 3206 QUALCOMM
Category: Standards Track February 2002
The SYS and AUTH POP Response Codes
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This memo proposes two response codes: SYS and AUTH, which enable
clients to unambiguously determine an optimal response to an
authentication failure. In addition, a new capability (AUTH-RESP-
CODE) is defined.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in this Document . . . . . . . . . . . . . . 2
3. Background . . . . . . . . . . . . . . . . . . . . . . . . 2
4. The SYS Response Code . . . . . . . . . . . . . . . . . . . 3
5. The AUTH Response Code . . . . . . . . . . . . . . . . . . 3
6. The AUTH-RESP-CODE Capability . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 4
8. Security Considerations . . . . . . . . . . . . . . . . . . 4
9. References . . . . . . . . . . . . . . . . . . . . . . . . 5
10. Author's Address . . . . . . . . . . . . . . . . . . . . . . 5
11. Full Copyright Statement . . . . . . . . . . . . . . . . . 6
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1. Introduction
RFC 2449 [POP3-EXT] defined extended [POP3] response codes, to give
clients more information about errors so clients can respond more
appropriately. In addition to the mechanism, two initial response
codes were defined (IN-USE and LOGIN-DELAY), in an attempt to
differentiate between authentication failures related to user
credentials, and other errors.
In practice, these two response codes, while helpful, do not go far
enough. This memo proposes two additional response codes: SYS and
AUTH, which enable clients to unambiguously determine an optimal
response to an authentication failure.
In addition, a new capability (AUTH-RESP-CODE) is defined.
2. 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 RFC 2119 [KEYWORDS].
3. Background
RFC 2449 [POP3-EXT] introduced the IN-USE and LOGIN-DELAY response
codes. The intent is to allow clients to clearly determine the
underlying cause of a failure in order to respond. For example,
clients need to know if the user should be asked for new credentials,
or if the POP3 session should simply be tried again later. (Some
deployed POP3 clients attempt to parse the text of authentication
failure errors, looking for strings known to be issued by various
servers which indicate the mailbox is locked.)
IN-USE indicates that an exclusive lock could not be obtained for the
user's mailbox, probably because another POP3 session is in progress.
LOGIN-DELAY informs the client that the user has not waited long
enough before authenticating again.
However, there are other error conditions which do not require new
credentials, some of which should be brought to the user's attention.
Despite the IN-USE and LOGIN-DELAY responses, clients cannot be sure
if any other error requires new user credentials.
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RFC 3206 The SYS and AUTH POP Response Codes February 2002
4. The SYS Response Code
The SYS response code announces that a failure is due to a system
error, as opposed to the user's credentials or an external condition.
It is hierarchical, with two possible second-level codes: TEMP and
PERM. (Case is not significant at any level of the hierarchy.)
SYS/TEMP indicates a problem which is likely to be temporary in
nature, and therefore there is no need to alarm the user, unless the
failure persists. Examples might include a central resource which is
currently locked or otherwise temporarily unavailable, insufficient
free disk or memory, etc.
SYS/PERM is used for problems which are unlikely to be resolved
without intervention. It is appropriate to alert the user and
suggest that the organization's support or assistance personnel be
contacted. Examples include corrupted mailboxes, system
configuration errors, etc.
The SYS response code is valid with an -ERR response to any command.
5. The AUTH Response Code
The AUTH response code informs the client that there is a problem
with the user's credentials. This might be an incorrect password, an
unknown user name, an expired account, an attempt to authenticate in
violation of policy (such as from an invalid location or during an
unauthorized time), or some other problem.
The AUTH response code is valid with an -ERR response to any
authentication command including AUTH, USER (see note), PASS, or
APOP.
Servers which include the AUTH response code with any authentication
failure SHOULD support the CAPA command [POP3-EXT] and SHOULD include
the AUTH-RESP-CODE capability in the CAPA response. AUTH-RESP-CODE
assures the client that only errors with the AUTH code are caused by
credential problems.
NOTE: Returning the AUTH response code to the USER command
reveals to the client that the specified user exists. It is
strongly RECOMMENDED that the server not issue this response code
to the USER command.
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6. The AUTH-RESP-CODE Capability
CAPA tag:
AUTH-RESP-CODE
Arguments:
none
Added commands:
none
Standard commands affected:
none
Announced states / possible differences:
both / no
Commands valid in states:
n/a
Specification reference:
this document
Discussion:
The AUTH-RESP-CODE capability indicates that the server includes
the AUTH response code with any authentication error caused by a
problem with the user's credentials.
7. IANA Considerations
IANA has added the AUTH-RESP-CODE capability to the list of POP3
capabilities (established by RFC 2449 [POP3-EXT]).
IANA has also added the SYS and AUTH response codes to the list of
POP3 response codes (also established by RFC 2449 [POP3-EXT]).
8. Security Considerations
Section 5, The AUTH Response Code, discusses the security issues
related to use of the AUTH response code with the USER command.
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9. References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[POP3] Myers, J. and M. Rose, "Post Office Protocol -- Version
3", STD 53, RFC 1939, May 1996.
[POP3-EXT] Gellens, R., Newman, C. and L. Lundblade, "POP3 Extension
Mechanism", RFC 2449, November 1998.
10. Author's Address
Randall Gellens
QUALCOMM Incorporated
5775 Morehouse Drive
San Diego, CA 92121-2779
U.S.A.
Phone: +1 858 651 5115
EMail: randy@qualcomm.com
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11. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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