rfc2192.txt

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     authentication mechanism is inherited from a base IMAP URL.

     URLs always use "/" as the hierarchy delimiter for the purpose of
     resolving paths in relative URLs.  IMAP4 permits the use of any
     hierarchy delimiter in mailbox names.  For this reason, relative
     mailbox paths will only work if the mailbox uses "/" as the
     hierarchy delimiter.  Relative URLs may be used on mailboxes which
     use other delimiters, but in that case, the entire mailbox name
     MUST be specified in the relative URL or inherited as a whole from
     the base URL.

     The base URL for a list of mailboxes or messages which was referred
     to by an IMAP URL is always the referring IMAP URL itself.  The
     base URL for a message or message part which was referred to by an
     IMAP URL may be more complicated to determine.  The program
     interpreting the relative URL will have to check the headers of the
     MIME entity and any enclosing MIME entities in order to locate the
     "Content-Base" and "Content-Location" headers.  These headers are
     used to determine the base URL as defined in [HTTP].  For example,
     if the referring IMAP URL contains a "/;SECTION=1.2" parameter,
     then the MIME headers for section 1.2, for section 1, and for the
     enclosing message itself SHOULD be checked in that order for
     "Content-Base" or "Content-Location" headers.


9. Multinational Considerations

     IMAP4 [IMAP4] section 5.1.3 includes a convention for encoding
     non-US-ASCII characters in IMAP mailbox names.  Because this
     convention is private to IMAP, it is necessary to convert IMAP's
     encoding to one that can be more easily interpreted by a URL
     display program.  For this reason, IMAP's modified UTF-7 encoding
     for mailboxes MUST be converted to UTF-8 [UTF8].  Since 8-bit
     characters are not permitted in URLs, the UTF-8 characters are



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RFC 2192                    IMAP URL Scheme               September 1997


     encoded as required by the URL specification [BASIC-URL].  Sample
     code is included in Appendix A to demonstrate this conversion.


10. Examples

     The following examples demonstrate how an IMAP4 client program
     might translate various IMAP4 URLs into a series of IMAP4 commands.
     Commands sent from the client to the server are prefixed with "C:",
     and responses sent from the server to the client are prefixed with
     "S:".

     The URL:

      <imap://minbari.org/gray-council;UIDVALIDITY=385759045/;UID=20>

     Results in the following client commands:

         <connect to minbari.org, port 143>
         C: A001 LOGIN ANONYMOUS [e-mail]
         C: A002 SELECT gray-council
         <client verifies the UIDVALIDITY matches>
         C: A003 UID FETCH 20 BODY.PEEK[]

     The URL:

      <imap://[e-mail]/users.*;type=list>

     Results in the following client commands:

       <client requests password from user>
       <connect to minbari.org imap server, activate strong encryption>
       C: A001 LOGIN MICHAEL zipper
       C: A002 LIST "" users.*

     The URL:

      <imap://psicorp.org/~peter/%E6%97%A5%E6%9C%AC%E8%AA%9E/
      %E5%8F%B0%E5%8C%97>

     Results in the following client commands:

       <connect to psicorp.org, port 143>
       C: A001 LOGIN ANONYMOUS [e-mail]
       C: A002 SELECT ~peter/&ZeVnLIqe-/&U,BTFw-
       <commands the client uses for viewing the contents of a mailbox>





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RFC 2192                    IMAP URL Scheme               September 1997


     The URL:

      <imap://;AUTH=[e-mail]/gray-council/;uid=20/
      ;section=1.2>

     Results in the following client commands:

         <connect to minbari.org, port 143>
         C: A001 AUTHENTICATE KERBEROS_V4
         <authentication exchange>
         C: A002 SELECT gray-council
         C: A003 UID FETCH 20 BODY.PEEK[1.2]

     If the following relative URL is located in that body part:

      <;section=1.4>

     This could result in the following client commands:

         C: A004 UID FETCH 20 (BODY.PEEK[1.2.MIME]
               BODY.PEEK[1.MIME]
               BODY.PEEK[HEADER.FIELDS (Content-Base Content-Location)])
         <Client looks for Content-Base or Content-Location headers in
          result.  If no such headers, then it does the following>
         C: A005 UID FETCH 20 BODY.PEEK[1.4]

     The URL:

      <imap://;AUTH=*@minbari.org/gray%20council?SUBJECT%20shadows>

     Could result in the following:

         <connect to minbari.org, port 143>
         C: A001 CAPABILITY
         S: * CAPABILITY IMAP4rev1 AUTH=GSSAPI
         S: A001 OK
         C: A002 AUTHENTICATE GSSAPI
         <authentication exchange>
         S: A002 OK user lennier authenticated
         C: A003 SELECT "gray council"
         ...
         C: A004 SEARCH SUBJECT shadows
         S: * SEARCH 8 10 13 14 15 16
         S: A004 OK SEARCH completed
         C: A005 FETCH 8,10,13:16 ALL
         ...





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RFC 2192                    IMAP URL Scheme               September 1997


     NOTE: In this final example, the client has implementation
     dependent choices.  The authentication mechanism could be anything,
     including PREAUTH.  And the final FETCH command could fetch more or
     less information about the messages, depending on what it wishes to
     display to the user.


11. Security Considerations

     Security considerations discussed in the IMAP specification [IMAP4]
     and the URL specification [BASIC-URL] are relevant.  Security
     considerations related to authenticated URLs are discussed in
     section 3 of this document.

     Many email clients store the plain text password for later use
     after logging into an IMAP server.  Such clients MUST NOT use a
     stored password in response to an IMAP URL without explicit
     permission from the user to supply that password to the specified
     host name.


12. ABNF for IMAP URL scheme

     This uses ABNF as defined in RFC 822 [IMAIL].  Terminals from the
     BNF for IMAP [IMAP4] and URLs [BASIC-URL] are also used.  Strings
     are not case sensitive and free insertion of linear-white-space is
     not permitted.

     achar            = uchar / "&" / "=" / "~"
                             ; see [BASIC-URL] for "uchar" definition

     bchar            = achar / ":" / "@" / "/"

     enc_auth_type    = 1*achar
                           ; encoded version of [IMAP-AUTH] "auth_type"

     enc_list_mailbox = 1*bchar
                             ; encoded version of [IMAP4] "list_mailbox"

     enc_mailbox      = 1*bchar
                             ; encoded version of [IMAP4] "mailbox"

     enc_search       = 1*bchar
                             ; encoded version of search_program below

     enc_section      = 1*bchar
                             ; encoded version of section below




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RFC 2192                    IMAP URL Scheme               September 1997


     enc_user         = 1*achar
                             ; encoded version of [IMAP4] "userid"

     imapurl          = "imap://" iserver "/" [ icommand ]

     iauth            = ";AUTH=" ( "*" / enc_auth_type )

     icommand         = imailboxlist / imessagelist / imessagepart

     imailboxlist     = [enc_list_mailbox] ";TYPE=" list_type

     imessagelist     = enc_mailbox [ "?" enc_search ] [uidvalidity]

     imessagepart     = enc_mailbox [uidvalidity] iuid [isection]

     isection         = "/;SECTION=" enc_section

     iserver          = [iuserauth "@"] hostport
                             ; See [BASIC-URL] for "hostport" definition

     iuid             = "/;UID=" nz_number
                             ; See [IMAP4] for "nz_number" definition

     iuserauth        = enc_user [iauth] / [enc_user] iauth

     list_type        = "LIST" / "LSUB"

     search_program   = ["CHARSET" SPACE astring SPACE]
                        search_key *(SPACE search_key)
                           ; IMAP4 literals may not be used
                           ; See [IMAP4] for "astring" and "search_key"

     section          = section_text / (nz_number *["." nz_number]
                         ["." (section_text / "MIME")])
                        ; See [IMAP4] for "section_text" and "nz_number"

     uidvalidity      = ";UIDVALIDITY=" nz_number
                             ; See [IMAP4] for "nz_number" definition

13. References

     [BASIC-URL] Berners-Lee, Masinter, McCahill, "Uniform Resource
     Locators (URL)", RFC 1738, CERN, Xerox Corporation, University of
     Minnesota, December 1994.

         <ftp://ds.internic.net/rfc/rfc1738.txt>





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RFC 2192                    IMAP URL Scheme               September 1997


     [IMAP4] Crispin, M., "Internet Message Access Protocol - Version
     4rev1", RFC 2060, University of Washington, December 1996.

         <ftp://ds.internic.net/rfc/rfc2060.txt>

     [IMAP-AUTH] Myers, J., "IMAP4 Authentication Mechanism", RFC 1731,
     Carnegie-Mellon University, December 1994.

         <ftp://ds.internic.net/rfc/rfc1731.txt>

     [HTTP] Fielding, Gettys, Mogul, Frystyk, Berners-Lee, "Hypertext
     Transfer Protocol -- HTTP/1.1", RFC 2068, UC Irvine, DEC, MIT/LCS,
     January 1997.

         <ftp://ds.internic.net/rfc/rfc2068.txt>

     [IMAIL] Crocker, "Standard for the Format of ARPA Internet Text
     Messages", STD 11, RFC 822, University of Delaware, August 1982.

         <ftp://ds.internic.net/rfc/rfc822.txt>

     [KEYWORDS] Bradner, "Key words for use in RFCs to Indicate
     Requirement Levels", RFC 2119, Harvard University, March 1997.

         <ftp://ds.internic.net/rfc/rfc2119.txt>

     [MIME] Freed, N., Borenstein, N., "Multipurpose Internet Mail
     Extensions", RFC 2045, Innosoft, First Virtual, November 1996.

        <ftp://ds.internic.net/rfc/rfc2045.txt>

     [REL-URL] Fielding, "Relative Uniform Resource Locators", RFC 1808,
     UC Irvine, June 1995.