Internet Draft R. Gellens
Document: draft-gellens-pop-err-00.txt QUALCOMM
Expires: 28 August 2000 28 February 2000

The SYS and AUTH POP Response Codes

Status of this Memo:

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.

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Table of Contents

1. Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in this Document . . . . . . . . . . . . . . 2
3. Comments . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
5. The SYS Response Code . . . . . . . . . . . . . . . . . . . 3
6. The AUTH Response Code . . . . . . . . . . . . . . . . . . . 3
7. The AUTH-RESP-CODE Capability . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 5
10. Security Considerations . . . . . . . . . . . . . . . . . . . 5
11. Author's Address . . . . . . . . . . . . . . . . . . . . . . 5
12. Full Copyright Statement . . . . . . . . . . . . . . . . . . 5

1. Abstract

RFC 2449 [POP-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. Comments

Public comments should be sent to the IETF POP3 Extensions mailing
list, <ietf-pop3ext@imc.org>. To subscribe, send a message
containing SUBSCRIBE to <ietf-pop3ext-request@imc.org>. Private
comments should be sent to the author.

4. Background

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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.

5. 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.

6. 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.

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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.

7. 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.

8. References

[KEYWORDS] Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March 1997.
<ftp://ftp.isi.edu/in-notes/rfc2119.txt>

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[POP3] Myers, Rose, "Post Office Protocol -- Version 3", RFC 1939,
Carnegie Mellon, Dover Beach Consulting, Inc., May 1996.
<ftp://ftp.isi.edu/in-notes/rfc1939.txt>

[POP-EXT] Gellens, Newman, Lundblade, "POP3 Extension Mechanism",
RFC 2449, Qualcomm, Innosoft, Qualcomm, November 1998.
<ftp://ftp.isi.edu/in-notes/rfc2449.txt>

9. IANA Considerations

IANA is requested to add the AUTH-RESP-CODE capability to the list
of POP3 capabilities (established by RFC 2449 [POP3-EXT]).

IANA is also requested to add the SYS and AUTH response codes to the
list of POP3 response codes (also established by RFC 2449
[POP3-EXT]).

10. Security Considerations

Section 3, The AUTH Response Code, discusses the security issues
related to use of the AUTH response code with the USER command.

11. Author's Address

Randall Gellens +1 858 651 5115
QUALCOMM Incorporated randy@qualcomm.com
5775 Morehouse Drive
San Diego, CA 92121-2779
U.S.A.

12. Full Copyright Statement

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.

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The limited permissions granted above are perpetual and will not be
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This document and the information contained herein is provided on an
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