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Versions: 00 01 02 RFC 2086

Network Working Group                                           J. Myers
Internet Draft                                           Carnegie Mellon
Document: draft-myers-imap-acl-00.txt                      December 1995


                          IMAP4 ACL extension

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.  Internet Drafts may be updated, replaced, or obsoleted by
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   Drafts as reference material or to cite them other than as a
   ``working draft'' or ``work in progress''.

   To learn the current status of any Internet-Draft, please check the
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   Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
   munnari.oz.au.

   A revised version of this draft document will be submitted to the RFC
   editor as a Proposed Standard for the Internet Community.  Discussion
   and suggestions for improvement are requested.  This document will
   expire before April 1996.  Distribution of this draft is unlimited.






















J. Myers                                                        [Page i]


Internet DRAFT                    ACL                  December 14, 1995


1.   Abstract

   The ACL extension of the Internet Message Access Protocol [IMAP4]
   permits access control lists to be manipulated through the IMAP
   protocol.

2.   Conventions Used in this Document

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.

3.   Introduction and Overview

   The ACL extension is present in any IMAP4 implementation which
   returns "ACL" as one of the supported capabilities to the CAPABILITY
   command.

   An access control list is a set of <identifier,rights> pairs.

   Identifier is an ASCII string with implementation-defined semantics.
   Possible variations of identifier interpretation include, but are not
   limited to:

   * User names, as specified in the LOGIN command.

   * Named groups of users, presumably managed by some
     authorization service.

   * Only allowing identifiers supported by the operating system
     (e.g. ``user'', ``group'', and ``other'' for the Unix filesystem)

   * A prefix to the identifier specifying an "authentication
     type".

     As an example, an implementation may control posting to a group
     based on the contents of the From: header:

     from$user             p

   * Whether the union of rights for matching identifiers are granted
     to a user or whether the rights for the most specific matching
     identifier is granted.

     As an example, for a mailbox with the following ACL:

     user                  lrsa
     group-user-is-in      lrsw




J. Myers                                                        [Page 2]


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     One implementation may grant the user 'lrswa' rights, another
     may only grant the user 'lrsa' rights.

   * A prefix to an identifier name specifying the listed rights
     are to be removed from users who match the prefixed identifier.

     As an example, for a mailbox with the following ACL:

     group-user-is-in      lrsw
     -user                 w

     An implementation may grant the user 'lrs' rights.

   Rights is a string listing a (possibly empty) set of alphanumeric
   characters, each character listing a set of operations which is being
   controlled.  Letters are reserved for ``standard'' rights, listed
   below.  Digits are reserved for implementation or site defined
   rights.  The standard rights are:

   l - lookup (mailbox is visible to LIST/LSUB commands)
   r - read (SELECT the mailbox, perform CHECK, FETCH, PARTIAL,
       SEARCH, COPY from mailbox)
   s - keep seen/unseen information across sessions (STORE \SEEN flag)
   w - write (STORE flags other than \SEEN and \DELETED)
   i - insert (perform APPEND, COPY into mailbox)
   p - post (send mail to submission address for mailbox,
       not enforced by IMAP4 itself)
   c - create (CREATE new sub-mailboxes in any implementation-defined
       hierarchy)
   d - delete (STORE \DELETED flag, perform EXPUNGE)
   a - administer (perform SETACL)

   An implementation may tie rights together or may force rights to
   always or never be granted.  For example, in an implementation that
   uses unix mode bits, the rights "wisd" are tied, the "a" right is
   always granted to the owner and is never granted to another user.  If
   rights are tied in an implementation, it should be conservative in
   granting rights in response to SETACL commands--unless all rights in
   a tied set are specified, none should be used.  Numeric rights may
   not be tied.











J. Myers                                                        [Page 3]


Internet DRAFT                    ACL                  December 14, 1995


4.   Commands


4.1. SETACL MAILBOX

   Arguments:  mailbox name
               authentication identifier
               access rights

   Data:       no specific data for this command

   Result:     OK - setacl mailbox completed
               NO - setacl mailbox failure: can't set acl
               BAD - command unknown or arguments invalid

      The SETACL MAILBOX command changes the access control list on the
      specified mailbox so that the specified identifier is granted the
      permissions enumerated in rights.


4.2. DELETEACL MAILBOX

   Arguments:  mailbox name
               authentication identifier

   Data:       no specific data for this command

   Result:     OK - deleteacl mailbox completed
               NO - deleteacl mailbox failure: can't delete acl
               BAD - command unknown or arguments invalid

      Removes any portion of the access control list for mailbox for the
      specified identifier.


4.3. GETACL MAILBOX

   Arguments:  mailbox name

   Data:       untagged responses: ACL MAILBOX

   Result:     OK - getacl mailbox completed
               NO - getacl mailbox failure: can't get acl
               BAD - command unknown or arguments invalid

      The GETACL MAILBOX command returns the access control list for
      mailbox in some set of untagged ACL replies.  There may not be




J. Myers                                                        [Page 4]


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      more than one ACL reply specifying any given identifier.

   Example:    C: A002 GETACL MAILBOX INBOX
               S: * ACL MAILBOX INBOX Fred rwipslda
               S: A002 Ok Getacl complete


4.4. MYRIGHTS MAILBOX

   Arguments:  mailbox name

   Data:       untagged responses: MYRIGHTS MAILBOX

   Result:     OK - myrights mailbox completed
               NO - myrights mailbox failure: can't get rights
               BAD - command unknown or arguments invalid

      The MYRIGHTS MAILBOX command returns the set of rights that the
      user has to mailbox in an untagged MYRIGHTS reply.

5.   Responses


5.1. ACL MAILBOX

   Data:       mailbox name
               identifier
               rights

      The ACL MAILBOX response occurs as a result of a GETACL MAILBOX
      command.  The first string is the mailbox name for which this ACL
      entry applies.  The second string is the identifier for which this
      entry applies.  The third string is the set of rights that the
      identifier has.


5.2. MYRIGHTS MAILBOX

   Data:       mailbox name
               rights

      The MYRIGHTS MAILBOX response occurs as a result of a MYRIGHTS
      MAILBOX command.  The first string is the mailbox name for which
      this ACL entry applies.  The second string is the set of rights
      that the client has.






J. Myers                                                        [Page 5]


Internet DRAFT                    ACL                  December 14, 1995


6.   Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) notation as specified in [RFC-822] with one exception; the
   delimiter used with the "#" construct is a single space (SPACE) and
   not one or more commas.

   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.

   acl_data        ::= "ACL" SPACE acl_option SPACE astring SPACE astring
                       SPACE astring

   acl_option      ::= "MAILBOX"

   deleteacl       ::= "DELETEACL" SPACE acl_option SPACE astring SPACE astring

   getacl          ::= "GETACL" SPACE acl_option SPACE astring

   myrights        ::= "MYRIGHTS" SPACE acl_option SPACE astring

   myrights_data   ::= "MYRIGHTS" acl_option SPACE astring SPACE astring

   setacl          ::= "SETACL" SPACE acl_option SPACE astring SPACE astring
                       SPACE astring

7.   References

   [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
   RFC 1730, University of Washington, December 1994.

   [RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
   Messages", STD 11, RFC 822.

8.   Security Considerations

   An implementation must make sure the ACL commands themselves do not
   give information about mailboxes with appropriately restricted ACL's.
   For example, a GETACL command on a mailbox for which the user has
   insufficient rights should not admit the mailbox exists, much less
   return the mailbox's ACL.








J. Myers                                                        [Page 6]


Internet DRAFT                    ACL                  December 14, 1995


9.   Author's Address

   John G. Myers
   Carnegie-Mellon University
   5000 Forbes Ave.
   Pittsburgh PA, 15213-3890

   Email: jgm+@cmu.edu











































J. Myers                                                        [Page 7]


Internet DRAFT                    ACL                  December 14, 1995





                           Table of Contents



Status of this Memo ...............................................    i
1.   Abstract .....................................................    2
2.   Conventions Used in this Document ............................    2
3.   Introduction and Overview ....................................    2
4.   Commands .....................................................    4
4.1. SETACL MAILBOX ...............................................    4
4.2. DELETEACL MAILBOX ............................................    4
4.3. GETACL MAILBOX ...............................................    4
4.4. MYRIGHTS MAILBOX .............................................    5
5.   Responses ....................................................    5
5.1. ACL MAILBOX ..................................................    5
5.2. MYRIGHTS MAILBOX .............................................    5
6.   Formal Syntax ................................................    6
7.   References ...................................................    6
8.   Security Considerations ......................................    6
9.   Author's Address .............................................    7




























J. Myers                                                       [Page ii]


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