RFC3206 - The SYS and AUTH POP Response Codes

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.

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

1. Introduction

RFC2449 [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 RFC2119 [KEYWORDS].

3. Background

RFC2449 [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.

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.

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.

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 RFC2449 [POP3-EXT]).

IANA has also added the SYS and AUTH response codes to the list of

POP3 response codes (also established by RFC2449 [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.

9. References

[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate

Requirement Levels", BCP 14, RFC2119, March 1997.

[POP3] Myers, J. and M. Rose, "Post Office Protocol -- Version

3", STD 53, RFC1939, May 1996.

[POP3-EXT] Gellens, R., Newman, C. and L. Lundblade, "POP3 Extension

Mechanism", RFC2449, 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

11. Full Copyright Statement

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