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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 draft-ietf-sieve-managesieve

Sieve Working Group                                     A. Melnikov, Ed.
Internet-Draft                                             Isode Limited
Intended status: Standards Track                               T. Martin
Expires: March 17, 2009                             BeThereBeSquare Inc.
                                                      September 13, 2008


             A Protocol for Remotely Managing Sieve Scripts
                      draft-martin-managesieve-12

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on March 17, 2009.

Abstract

   Sieve scripts allow users to filter incoming email.  Message stores
   are commonly sealed servers so users cannot log into them, yet users
   must be able to update their scripts on them.  This document
   describes a protocol "ManageSieve" for securely managing Sieve
   scripts on a remote server.  This protocol allows a user to have
   multiple scripts, and also alerts a user to syntactically flawed
   scripts.

Changes since draft-martin-managesieve-09





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   o  TBD.


Table of Contents

   1.      Introduction . . . . . . . . . . . . . . . . . . . . . . .  4
   1.1.    Conventions used in this document  . . . . . . . . . . . .  4
   1.2.    Syntax . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.3.    Response Codes . . . . . . . . . . . . . . . . . . . . . .  4
   1.4.    Active Script  . . . . . . . . . . . . . . . . . . . . . .  7
   1.5.    Quotas . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   1.6.    Script Names . . . . . . . . . . . . . . . . . . . . . . .  7
   1.7.    Capabilities . . . . . . . . . . . . . . . . . . . . . . .  8
   1.8.    Link Level . . . . . . . . . . . . . . . . . . . . . . . .  9

   2.      Commands . . . . . . . . . . . . . . . . . . . . . . . . . 10
   2.1.    AUTHENTICATE Command . . . . . . . . . . . . . . . . . . . 10
   2.1.1.  Use of SASL PLAIN mechanism over TLS . . . . . . . . . . . 14
   2.2.    STARTTLS Command . . . . . . . . . . . . . . . . . . . . . 15
   2.2.1.  Server Identity Check  . . . . . . . . . . . . . . . . . . 15
   2.3.    LOGOUT Command . . . . . . . . . . . . . . . . . . . . . . 18
   2.4.    CAPABILITY Command . . . . . . . . . . . . . . . . . . . . 18
   2.5.    HAVESPACE Command  . . . . . . . . . . . . . . . . . . . . 18
   2.6.    PUTSCRIPT Command  . . . . . . . . . . . . . . . . . . . . 19
   2.7.    LISTSCRIPTS Command  . . . . . . . . . . . . . . . . . . . 20
   2.8.    SETACTIVE Command  . . . . . . . . . . . . . . . . . . . . 21
   2.9.    GETSCRIPT Command  . . . . . . . . . . . . . . . . . . . . 21
   2.10.   DELETESCRIPT Command . . . . . . . . . . . . . . . . . . . 22
   2.11.   Recommended extensions . . . . . . . . . . . . . . . . . . 22
   2.11.1. RENAMESCRIPT Command . . . . . . . . . . . . . . . . . . . 23
   2.11.2. NOOP Command . . . . . . . . . . . . . . . . . . . . . . . 24
   2.11.3. UNAUTHENTICATE Command . . . . . . . . . . . . . . . . . . 24

   3.      Sieve URL Scheme . . . . . . . . . . . . . . . . . . . . . 24

   4.      Formal Syntax  . . . . . . . . . . . . . . . . . . . . . . 26

   5.      Security Considerations  . . . . . . . . . . . . . . . . . 31

   6.      IANA Considerations  . . . . . . . . . . . . . . . . . . . 32
   6.1.    Manage Sieve Capability Registration Template  . . . . . . 32
   6.2.    Registration of Initial Manage Sieve capabilities  . . . . 33
   6.3.    Manage Sieve Response Code Registration Template . . . . . 35
   6.4.    Registration of Initial Manage Sieve Response Codes  . . . 35

   7.      Acknowledgements . . . . . . . . . . . . . . . . . . . . . 38

   8.      References . . . . . . . . . . . . . . . . . . . . . . . . 38



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   8.1.    Normative References . . . . . . . . . . . . . . . . . . . 38
   8.2.    Informative References . . . . . . . . . . . . . . . . . . 40

           Authors' Addresses . . . . . . . . . . . . . . . . . . . . 40
           Intellectual Property and Copyright Statements . . . . . . 42














































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1.  Introduction

1.1.  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 [KEYWORDS].

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.  Line breaks that do not start a new "C:" or
   "S:" exist for editorial reasons.

1.2.  Syntax

   This a line oriented protocol much like [IMAP4rev1] or [ACAP].  There
   are three data types: atoms, numbers and strings.  Strings may be
   quoted or literal.  See [ACAP] for detailed descriptions of these
   types.

   Each command consists of an atom (the command name) followed by zero
   or more strings and numbers terminated by CRLF.

   All client queries are replied to with either an OK, NO, or BYE
   response.  Each response may be followed by a response code (see
   Section 1.3) and by a string consisting of human readable text in the
   local language, encoded in [UTF-8].  The contents of the string
   SHOULD be shown to the user and implementations MUST NOT attempt to
   parse the message for meaning.

   The BYE response SHOULD be used if the server wishes to close the
   connection.  A server may wish to do this because the client was idle
   for too long or there were too many failed authentication attempts.
   This response can be issued at any time and should be immediately
   followed by a server hang-up of the connection.  If a server has an
   inactivity timeout resulting in client autologout it MUST be no less
   than 30 minutes after successful authentication.  The inactivity
   timeout MAY be less before authentication.

1.3.  Response Codes

   An OK, NO, or BYE response from the server MAY contain a response
   code to describe the event in a more detailed machine parsable
   fashion.  A response code consists of data inside parentheses in the
   form of an atom, possibly followed by a space and arguments.
   Response codes are defined when there is a specific action that a
   client can take based upon the additional information.  In order to
   support future extension, the response code is represented as a
   slash-separated (Solidus, %x2F) hierarchy with each level of



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   hierarchy representing increasing detail about the error.  Response
   codes MUST NOT start with the Solidus character.  Clients MUST
   tolerate additional hierarchical response code detail which they
   don't understand.  For example, if the client supports the "QUOTA"
   response code, but doesn't understand the "QUOTA/MAXSCRIPTS" response
   code, it should treat "QUOTA/MAXSCRIPTS" as "QUOTA".

   Client implementations MUST tolerate (ignore) response codes that
   they do not recognize.

   The currently defined response codes are:

   AUTH-TOO-WEAK

   This response code is returned in the NO response from an
   AUTHENTICATE command.  It indicates that site security policy forbids
   the use of the requested mechanism for the specified authentication
   identity.

   ENCRYPT-NEEDED

   This response code is returned in the NO response from an
   AUTHENTICATE command.  It indicates that site security policy
   requires the use of a strong encryption mechanism for the specified
   authentication identity and mechanism.

   QUOTA

   If this response code is returned in the NO/BYE response, it means
   that the command would have placed the user above the site-defined
   quota constraints.  If this response code is returned in the OK
   response, it can mean that the user's storage is near its quota, or
   it can mean that the account exceeded its quota but that that
   condition is being allowed by the server (the server supports so
   called "soft quotas").

   REFERRAL

   This response code may be returned with a BYE result from any
   command, and includes a mandatory parameter that indicates what
   server to access to manage this user's sieve scripts.  The server
   will be specified by a Sieve URL (see Section 3).  The scriptname
   portion of the URL MUST NOT be specified.  The client should
   authenticate to the specified server and use it for all further
   commands in the current session.

   SASL




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   This response code can occur in the OK response to a successful
   AUTHENTICATE command and includes the optional final server response
   data from the server as specified by [SASL].

   TRANSITION-NEEDED

   This response code occurs in a NO response of an AUTHENTICATE
   command.  It indicates that the user name is valid, but the entry in
   the authentication database needs to be updated in order to permit
   authentication with the specified mechanism.  This is typically done
   by establishing a secure channel using TLS, verifying server identity
   as specified in Section 2.2.1, and finally authenticating once using
   the [PLAIN] authentication mechanism.  The selected mechanism SHOULD
   then work for authentications in subsequent sessions.

   This condition can happen if a user has an entry in a system
   authentication database such as Unix /etc/passwd, but does not have
   credentials suitable for use by the specified mechanism.

   TRYLATER

   A command failed due to a temporary server failure.  The client MAY
   continue using local information and try the command later.  This
   response code only makes sense when returned in a NO/BYE response.

   ACTIVE

   A command failed because it is not allowed on the active script.  For
   example DELETESCRIPT on the active script.  This response code only
   makes sense when returned in a NO/BYE response.

   NONEXISTENT

   A command failed because the references script name doesn't exist.
   This response code only makes sense when returned in a NO/BYE
   response.

   ALREADYEXISTS

   A command failed because the references script name already exists.
   This response code only makes sense when returned in a NO/BYE
   response.

   TAG

   This response code name is followed by a string specified in the
   command.  See Section 2.11.2 for a possible use case.




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1.4.  Active Script

   A user may have multiple Sieve scripts on the server, yet only one
   script may be used for filtering of incoming messages.  This is the
   active script.  Users may have zero or one active scripts and MUST
   use the SETACTIVE command described below for changing the active
   script or disabling Sieve processing.  For example, a user may have
   an everyday script they normally use and a special script they use
   when they go on vacation.  Users can change which script is being
   used without having to download and upload a script stored somewhere
   else.

1.5.  Quotas

   Servers SHOULD impose quotas to prevent malicious users from
   overflowing available storage.  If a command would place a user over
   a quota setting, servers that impose such quotas MUST reply with a NO
   response containing the QUOTA response code.  Client implementations
   MUST be able to handle commands failing because of quota
   restrictions.

1.6.  Script Names

   A Sieve script name is a sequence of Unicode characters encoded in
   UTF-8 [UTF-8].  A script name MUST comply with Net-Unicode Definition
   (Sectio 2 of [NET-UNICODE]), with the following additional
   restrictions:

   o  0000-001F; [CONTROL CHARACTERS]

   o  007F; DELETE

   o  0080-009F; [CONTROL CHARACTERS]

   o  2028; LINE SEPARATOR

   o  2029; PARAGRAPH SEPARATOR

   Sieve script names MUST be at least one octet (and hense Unicode
   character) long.  Zero octets script name has a special meaning (see
   Section 2.8).  Servers MUST allow names of up to 128 Unicode
   characters in length (which can take up to 512 bytes when encoded in
   UTF-8, not counting the terminating NUL), and MAY allow longer names.
   A server that receives a script name longer than its internal limit
   MUST rejects the corresponding operation, in particular it MUST NOT
   truncate the script name.





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1.7.  Capabilities

   Server capabilities are sent automatically by the server upon a
   client connection, or after successful STARTTLS and AUTHENTICATE
   (which establishes a SASL security layer) commands.  Capabilities may
   change immediately after a successfully completed STARTTLS command
   and/or immediately after a successfully completed AUTHENTICATE
   command.  Capabilities MUST remain static at all other times.

   Clients MAY request the capabilities at a later time by issuing the
   CAPABILITY command described later.  The capabilities consist of a
   series of lines each with one or two strings.  The first string is
   the name of the capability, which is case-insensitive.  The second
   optional string is the value associated with that capability.  Order
   of capabilities is arbitrary, but each capability name can appear at
   most once.

   The following capabilities are defined in this document:

   IMPLEMENTATION - Name of implementation and version.

   SASL - List of SASL mechanisms supported by the server, each
   separated by a space.  This list can be empty if and only if STARTTLS
   is also advertised.  This means that the client must negotiate TLS
   encryption with STARTTLS first, at which point the SASL capability
   will list a non empty list of SASL mechanisms.

   SIEVE - List of space separated Sieve extensions (as listed in Sieve
   "require" action [SIEVE]) supported by the Sieve engine.

   STARTTLS - If TLS [TLS] is supported by this implementation.  Before
   advertising this capability a server MUST verify to the best of its
   ability that TLS can be successfully negotiated by a client with
   common cipher suites.  Specifically, a server should verify that a
   server certificate has be installed and that the TLS subsystem has
   successfully initialized.

   NOTIFY - A space separated list of URI schema parts for supported
   notification methods.  This capability MUST be specified if the Sieve
   implementation supports the "enotify" extension [NOTIFY].

   LANGUAGE - The language (<Language-Tag> from [RFC4646]) currently
   used for human readable error messages.  If this capability is not
   returned, the "i-default" [RFC2277] language is assumed.  Note that
   the current language MAY be per-user configurable (i.e. it MAY change
   after authentication).

   Section 2.11 defines some additional ManageSieve extensions and their



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   respective capabilities.

   A server implementation MUST return SIEVE and IMPLEMENTATION
   capabilities.

   A client implementation MUST ignore any listed capabilities that it
   does not understand.

       Example:

       S: "IMPlemENTATION" "Example1 ManageSieved v001"
       S: "SASl" "DIGEST-MD5 GSSAPI"
       S: "SIeVE" "fileinto vacation"
       S: "StaRTTLS"
       S: "NOTIFY" "xmpp mailto"
       S: OK

1.8.  Link Level

   The ManageSieve protocol assumes a reliable data stream such as that
   provided by TCP.  When TCP is used, a ManageSieve server typically
   listens on port 2000. [[anchor6: IANA registration of port 2000 is
   pending.]]

   Before opening the TCP connection, the ManageSieve client first MUST
   resolve the Domain Name System (DNS) hostname associated with the
   receiving entity and determine the appropriate TCP port for
   communication with the receiving entity.  The process is as follows:

   1.  Attempt to resolve the hostname using a [DNS-SRV] Service of
       "sieve" and a Proto of "tcp" for the target domain (e.g.
       "example.net"), resulting in resource records such as
       "_sieve._tcp.example.net.".  The result of the SRV lookup, if
       successful, will be one or more combinations of a port and
       hostname; the ManageSieve client MUST resolve the returned
       hostnames to IPv4/IPv6 addresses according to returned SRV record
       weight.  IP addresses from the first successfully resolved
       hostname (with the corresponding port number returned by SRV
       lookup) are used to connect to the server.  If connection using
       one of the IP addresses fails, the next resolved IP address is
       used to connect.  If connection to all resolved IP addresses
       fails, then the resolution/connect is repeated for the next
       hostname returned by SRV lookup.

   2.  If the SRV lookup fails, the fallback SHOULD be a normal IPv4 or
       IPv6 address record resolution to determine the IP address, where
       the port used is the default ManageSieve port of 2000.




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2.  Commands

   This section and its subsections describes valid ManageSieve
   commands.  Upon initial connection to the server the client's session
   is in non-authenticated state.  Prior to successful authentication
   only the AUTHENTICATE, CAPABILITY, STARTTLS, LOGOUT and NOOP (see
   Section 2.11.2) commands are valid.  ManageSieve extensions MAY
   define other commands which are valid in non-authenticated state.
   Servers MUST reject all other commands with a NO response.  Clients
   may pipeline commands (send more than one command at a time without
   waiting for completion of the first command ).  However, a group of
   commands sent together MUST NOT have an AUTHENTICATE (*), a STARTTLS
   or a HAVESPACE command anywhere but the last command in the list.

   (*) - The only exception to this rule is when the AUTHENTICATE
   command contains an initial response for a SASL mechanism that allows
   clients to send data first, the mechanism is known to complete in one
   round-trip and the mechanism doesn't negotiate a SASL security layer.
   Two examples of such SASL mechanisms are PLAIN [PLAIN] and EXTERNAL
   [SASL].

2.1.  AUTHENTICATE Command

   Arguments:  String - mechanism
               String - initial data (optional)

   The AUTHENTICATE command indicates a SASL [SASL] authentication
   mechanism to the server.  If the server supports the requested
   authentication mechanism, it performs an authentication protocol
   exchange to identify and authenticate the user.  Optionally, it also
   negotiates a security layer for subsequent protocol interactions.  If
   the requested authentication mechanism is not supported, the server
   rejects the AUTHENTICATE command by sending the NO response.

   The authentication protocol exchange consists of a series of server
   challenges and client responses that are specific to the selected
   authentication mechanism.  A server challenge consists of a string
   (quoted or literal) followed by a CRLF.  The contents of the string
   is a base-64 encoding [BASE64] of the SASL data.  A client response
   consists of a string (quoted or literal) with the base-64 encoding of
   the SASL data followed by a CRLF.  If the client wishes to cancel the
   authentication exchange, it issues a string containing a single "*".
   If the server receives such a response, it MUST reject the
   AUTHENTICATE command by sending an NO reply.

   Note that an empty challenge/response is sent as an empty string.  If
   the mechanism dictates that the final response is sent by the server
   this data MAY be placed within the data portion of the SASL response



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   code to save a round trip.

   The optional initial-response argument to the AUTHENTICATE command is
   used to save a round trip when using authentication mechanisms that
   are defined to send no data in the initial challenge.  When the
   initial-response argument is used with such a mechanism, the initial
   empty challenge is not sent to the client and the server uses the
   data in the initial-response argument as if it were sent in response
   to the empty challenge.  If the initial-response argument to the
   AUTHENTICATE command is used with a mechanism that sends data in the
   initial challenge, the server MUST reject the AUTHENTICATE command by
   sending the NO response.

   The service name specified by this protocol's profile of SASL is
   "sieve".

   Reauthentication is not supported by ManageSieve protocol's profile
   of SASL.  I.e. after a successfully completed AUTHENTICATE command,
   no more AUTHENTICATE commands may be issued in the same session.
   After a successful AUTHENTICATE command completes, a server MUST
   reject any further AUTHENTICATE commands with a NO reply.  However
   note that a server may implement UNAUTHENTICATE extension described
   in Section 2.11.3.

   If a security layer is negotiated through the SASL authentication
   exchange, it takes effect immediately following the CRLF that
   concludes the successful authentication exchange for the client, and
   the CRLF of the OK response for the server.

   When a security layer takes effect, the ManageSieve protocol is reset
   to the initial state (the state in ManageSieve after a client has
   connected to the server).  The server MUST discard any knowledge
   obtained from the client which was not obtained from the SASL (or
   TLS) negotiation itself.  Likewise, the client MUST discard any
   knowledge obtained from the server, such as the list of ManageSieve
   extensions, which was not obtained from the SASL (or TLS) negotiation
   itself.  (Note that a client MAY compare the advertised SASL
   mechanisms before and after authentication in order to detect an
   active down-negotiation attack.  See below.)

   Once a SASL security layer is established, the server MUST re-issue
   the capability results, followed by an OK response.  This is
   necessary to protect against man-in-the-middle attacks which alter
   the capabilities list prior to SASL negotiation.  The capability
   results MUST include all SASL mechanisms the server was capable of
   negotiating with that client.  This is done in order to allow client
   to detect active down-negotiation attack.




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   When both [TLS] and SASL security layers are in effect, the TLS
   encoding MUST be applied (when sending data) after the SASL encoding,
   regardless of the order in which the layers were negotiated.

   Server implementations SHOULD support SASL proxy authentication so
   that an administrator can administer a user's scripts.  Proxy
   authentication is when a user authenticates as herself/himself but
   requests the server to act (authorize) as another user.

   The authorization identity generated by this [SASL] exchange is a
   "simple username" (in the sense defined in [SASLprep]), and both
   client and server MUST use the [SASLprep] profile of the [StringPrep]
   algorithm to prepare these names for transmission or comparison.  If
   preparation of the authorization identity fails or results in an
   empty string (unless it was transmitted as the empty string), the
   server MUST fail the authentication.

   If an AUTHENTICATE command fails with a NO response, the client MAY
   try another authentication mechanism by issuing another AUTHENTICATE
   command.  In other words, the client may request authentication types
   in decreasing order of preference.

   Note that a failed (NO) response to the AUTHENTICATE command may
   contain one of the following response codes: AUTH-TOO-WEAK, ENCRYPT-
   NEEDED or TRANSITION-NEEDED.  See Section 1.3 for detailed
   description of the relevant conditions.

   To ensure interoperability, client and server implementations of this
   extension MUST implement the [SCRAM] SASL mechanism.

   Implementations MAY advertise the ANONYMOUS SASL mechanism
   [SASL-ANON].  This indicates that the server supports ANONYMOUS SIEVE
   script syntax verification.  Only the CAPABILITY, PUTSCRIPT and
   LOGOUT commands are available to the anonymous user.  All other
   commands MUST give NO responses.  Furthermore the PUTSCRIPT command
   MUST NOT persistently store any data.  In this mode a positive
   response to the PUTSCRIPT command indicates that the given script
   does not have any syntax errors.

   Examples (Note that long lines are folded for readability and are not
   part of protocol exchange):










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       S: "IMPLEMENTATION" "Example1 ManageSieved v001"
       S: "SASL" "DIGEST-MD5 GSSAPI"
       S: "SIEVE" "fileinto vacation"
       S: "STARTTLS"
       S: OK
       C: Authenticate "DIGEST-MD5"
       S: "cmVhbG09ImVsd29vZC5pbm5vc29mdC5jb20iLG5vbmNlPSJPQTZNRzl0
           RVFHbTJoaCIscW9wPSJhdXRoIixhbGdvcml0aG09bWQ1LXNlc3MsY2hh
           cnNldD11dGYtOA=="
       C: "Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
           QuaW5ub3NvZnQuY29tIixub25jZT0iT0E2TUc5dEVRR20yaGgiLG5jPTAw
           MDAwMDAxLGNub25jZT0iT0E2TUhYaDZWcVRyUmsiLGRpZ2VzdC11cmk9Im
           ltYXAvZWx3b29kLmlubm9zb2Z0LmNvbSIscmVzcG9uc2U9ZDM4OGRhZDkw
           ZDRiYmQ3NjBhMTUyMzIxZjIxNDNhZjcscW9wPWF1dGg="
       S: OK (SASL "cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZ
           mZmZA==")

   A slightly different variant of the same authentication exchange:

       S: "IMPLEMENTATION" "Example1 ManageSieved v001"
       S: "SASL" "DIGEST-MD5 GSSAPI"
       S: "SIEVE" "fileinto vacation"
       S: "STARTTLS"
       S: OK
       C: Authenticate "DIGEST-MD5"
       S: {128}
       S: cmVhbG09ImVsd29vZC5pbm5vc29mdC5jb20iLG5vbmNlPSJPQTZNRzl0
          RVFHbTJoaCIscW9wPSJhdXRoIixhbGdvcml0aG09bWQ1LXNlc3MsY2hh
          cnNldD11dGYtOA==
       C: {276+}
       C: Y2hhcnNldD11dGYtOCx1c2VybmFtZT0iY2hyaXMiLHJlYWxtPSJlbHdvb2
          QuaW5ub3NvZnQuY29tIixub25jZT0iT0E2TUc5dEVRR20yaGgiLG5jPTAw
          MDAwMDAxLGNub25jZT0iT0E2TUhYaDZWcVRyUmsiLGRpZ2VzdC11cmk9Im
          ltYXAvZWx3b29kLmlubm9zb2Z0LmNvbSIscmVzcG9uc2U9ZDM4OGRhZDkw
          ZDRiYmQ3NjBhMTUyMzIxZjIxNDNhZjcscW9wPWF1dGg="
       S: {56}
       S: cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZA==
       C: ""
       S: OK

   Another example demonstrating use of SASL PLAIN mechanism under TLS.
   This example also demonstrate use of SASL "initial response" (the
   second parameter to the Authenticate command):








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       S: "IMPLEMENTATION" "Example1 ManageSieved v001"
       S: "SASL" ""
       S: "SIEVE" "fileinto vacation"
       S: "STARTTLS"
       S: OK
       C: STARTTLS
       S: OK
       <TLS negotiation, further commands are under TLS layer>
       S: "IMPLEMENTATION" "Example1 ManageSieved v001"
       S: "SASL" "PLAIN"
       S: "SIEVE" "fileinto vacation"
       S: OK
       C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xu"
       S: NO
       C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xz"
       S: NO
       C: Authenticate "PLAIN" "QJIrweAPyo6Q1T9xy"
       S: BYE "Too many failed authentication attempts"
       <Server closes connection>

   The following example demonstrates use of SASL "initial response".
   It also demonstrates that an empty response can be sent as a literal:

       C: AUTHENTICATE "GSSAPI" {1488+}
       C: YIIE[...1480 octets here ...]dA==
       S: {208}
       S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKic
          [...114 octets here ...]
          /yzpAy9p+Y0LanLskOTvMc0MnjgAa4YEr3eJ6
       C: {0+}
       C:
       S: {44}
       S: BQQF/wAMAAwAAAAAYRGFAo6W0vIHti8i1UXODgEAEAA=
       C: {44+}
       C: BQQE/wAMAAwAAAAAIsT1iv9UkZApw471iXt6cwEAAAE=
       S: OK

2.1.1.  Use of SASL PLAIN mechanism over TLS

   This section is normative for ManageSieve client implementations that
   support SASL [PLAIN] over [TLS].

   If a ManageSieve client is willing to use SASL PLAIN over TLS to
   authenticate to the ManageSieve server, the client MUST verify the
   server identity (see Section 2.2.1).  If the server identity can't be
   verified (e.g. the server has not provided any certificate, or if the
   certificate verification fails) the client MUST NOT attempt to
   authenticate using the SASL PLAIN mechanism.



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2.2.  STARTTLS Command

   Support for STARTTLS command in servers is optional.  Its
   availability is advertised with "STARTTLS" capability as described in
   Section 1.7.

   The STARTTLS command requests commencement of a TLS [TLS]
   negotiation.  The negotiation begins immediately after the CRLF in
   the OK response.  After a client issues a STARTTLS command, it MUST
   NOT issue further commands until a server response is seen and the
   TLS negotiation is complete.

   The STARTTLS command is only valid in non-authenticated state.  The
   server remains in non-authenticated state, even if client credentials
   are supplied during the TLS negotiation.  The SASL [SASL] EXTERNAL
   mechanism MAY be used to authenticate once TLS client credentials are
   successfully exchanged, but servers supporting the STARTTLS command
   are not required to support the EXTERNAL mechanism.

   After the TLS layer is established, the server MUST re-issue the
   capability results, followed by an OK response.  This is necessary to
   protect against man-in-the-middle attacks which alter the
   capabilities list prior to STARTTLS.  This capability result MUST NOT
   include the STARTTLS capability.

   The client MUST discard cached capability information and replace it
   with the new information.  The server MAY advertise different
   capabilities after STARTTLS.

       Example:

       C: StartTls
       S: oK
       <TLS negotiation, further commands are under TLS layer>
       S: "IMPLEMENTATION" "Example1 ManageSieved v001"
       S: "SASL" "PLAIN DIGEST-MD5 GSSAPI"
       S: "SIEVE" "fileinto vacation"
       S: "LANGUAGE" "fr"
       S: ok

2.2.1.  Server Identity Check

   During the TLS negotiation, the ManageSieve client MUST check its
   understanding of the server hostname/IP address against the server's
   identity as presented in the server Certificate message, in order to
   prevent man-in-the-middle attacks.  In this section, the client's
   understanding of the server's identity is called the "reference
   identity".



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   Checking is performed according to the following rules:

   o  If the reference identity is a hostname:

      1.  If a subjectAltName extension of the SRVName [X509-SRV],
          dNSName [X509] (in that order of preference) type is present
          in the server's certificate, than it SHOULD be used as the
          source of the server's identity.  Matching is performed as
          described in Section 2.2.1.1, with the exception that no
          wildcard matching is allowed for SRVName type.  If the
          certificate contains multiple names (e.g., more than one
          dNSName field), then a match with any one of the fields is
          considered acceptable.

      2.  The client MAY use other types of subjectAltName for
          performing comparison.

      3.  The server's identity MAY also be verified by comparing the
          reference identity to the Common Name (CN) [RFC4519] value in
          the leaf Relative Distinguished Name (RDN) of the subjectName
          field of the server's certificate.  This comparison is
          performed using the rules for comparison of DNS names in
          Section 2.2.1.1, below, with the exception that no wildcard
          matching is allowed. [[anchor8: Chris Newman says that such
          prohibition of wildcards doesn't match existing practice.]]
          Although the use of the Common Name value is existing
          practice, it is deprecated, and Certification Authorities are
          encouraged to provide subjectAltName values instead.  Note
          that the TLS implementation may represent DNs in certificates
          according to X.500 or other conventions.  For example, some
          X.500 implementations order the RDNs in a DN using a left-to-
          right (most significant to least significant) convention
          instead of LDAP's right- to-left convention.

   o  When the reference identity is an IP address, the iPAddress
      subjectAltName SHOULD be used by the client for comparison.  The
      comparison is performed as described in Section 2.2.1.2.

   o  In either case the client MAY map the reference identity to a
      different type prior to performing a comparison.  Mappings may be
      performed for all available subjectAltName types to which the
      reference identity can be mapped; however, the reference identity
      should only be mapped to types for which the mapping is either
      inherently secure (e.g., extracting the DNS hostname from a URI)
      or for which the mapping is performed in a secure manner (e.g.,
      using DNSSEC, or using user- or admin-configured host-to-address/
      address-to-host lookup tables).




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   If the server identity check fails, user-oriented clients SHOULD
   either notify the user (clients MAY give the user the opportunity to
   continue with the ManageSieve session in this case) or close the
   transport connection and indicate that the server's identity is
   suspect.  Automated clients SHOULD return or log an error indicating
   that the server's identity is suspect and/or SHOULD close the
   transport connection.  Automated clients MAY provide a configuration
   setting that disables this check, but MUST provide a setting which
   enables it.

   Beyond the server identity check described in this section, clients
   should be prepared to do further checking to ensure that the server
   is authorized to provide the service it is requested to provide.  The
   client may need to make use of local policy information in making
   this determination.

2.2.1.1.  Comparison of DNS Names

   If the reference identity is an internationalized domain name,
   conforming implementations MUST convert it to the ASCII Compatible
   Encoding (ACE) format as specified in Section 4 of RFC 3490 [RFC3490]
   before comparison with subjectAltName values of type dNSName.
   Specifically, conforming implementations MUST perform the conversion
   operation specified in Section 4 of [RFC3490] as follows:

   o  in step 1, the domain name SHALL be considered a "stored string";

   o  in step 3, set the flag called "UseSTD3ASCIIRules";

   o  in step 4, process each label with the "ToASCII" operation; and

   o  in step 5, change all label separators to U+002E (full stop).

   After performing the "to-ASCII" conversion, the DNS labels and names
   MUST be compared for equality according to the rules specified in
   Section 3 of [RFC3490], i.e. once all label separators are replaced
   with U+002E (dot) they are compared in the case-insensitive manner.

   The '*' (ASCII 42) wildcard character is allowed in subjectAltName
   values of type dNSName, and then only as the left-most (least
   significant) DNS label in that value.  This wildcard matches any
   left-most DNS label in the server name.  That is, the subject
   *.example.com matches the server names a.example.com and
   b.example.com, but does not match example.com or a.b.example.com.







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2.2.1.2.  Comparison of IP Addresses

   When the reference identity is an IP address, the identity MUST be
   converted to the "network byte order" octet string representation
   [RFC791][RFC2460].  For IP Version 4, as specified in RFC 791, the
   octet string will contain exactly four octets.  For IP Version 6, as
   specified in RFC 2460, the octet string will contain exactly sixteen
   octets.  This octet string is then compared against subjectAltName
   values of type iPAddress.  A match occurs if the reference identity
   octet string and value octet strings are identical.

2.2.1.3.  Comparison of Other subjectName Types

   Client implementations MAY support matching against subjectAltName
   values of other types as described in other documents.

2.3.  LOGOUT Command

   The client sends the LOGOUT command when it is finished with a
   connection and wishes to terminate it.  The server MUST reply with an
   OK response and terminate the connection.  The server MUST ignore
   commands issued by the client after the LOGOUT command.

       Example:

       C: Logout
       S: Ok
       <connection terminated>

2.4.  CAPABILITY Command

   The CAPABILITY command requests the server capabilities as described
   earlier in this document.  It has no parameters.

       Example:

       C: CAPABILITY
       S: "IMPLEMENTATION" "Example1 ManageSieved v001"
       S: "SASL" "PLAIN KERBEROS_V4 GSSAPI"
       S: "SIEVE" "fileinto vacation"
       S: "STARTTLS"
       S: OK

2.5.  HAVESPACE Command







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   Arguments:  String - name
               Number - script size

   The HAVESPACE command is used to query the server for available
   space.  Clients specify the name they wish to save the script as and
   its size in octets.  Servers respond with an NO if storing a script
   with that name and size would fail or OK otherwise.  Clients SHOULD
   issue this command before attempting to place a script on the server.

   Note that the OK response from the HAVESPACE command does not
   constitute a guarantee of success as server disk space conditions
   could change between the client issuing the HAVESPACE and the client
   issuing the PUTSCRIPT commands.  A QUOTA response code (see
   Section 1.3) remains a possible (albeit unlikely) response to a
   subsequent PUTSCRIPT with the same name and size.

       Example:

       C: HAVESPACE "myscript" 999999
       S: NO (QUOTA) "Quota exceeded"

       C: HAVESPACE "foobar" 435
       S: OK

2.6.  PUTSCRIPT Command

   Arguments:  String - Script name
               String - Script content

   The PUTSCRIPT command is used by the client to submit a Sieve script
   to the server.

   If the script already exists, upon success the old script will be
   overwritten.  The old script MUST NOT be overwritten if PUTSCRIPT
   fails in any way.  A script of zero length SHOULD be disallowed.

   This command places the script on the server.  It does not affect
   whether the script is processed on incoming mail, unless it replaces
   the script which is already active.  The SETACTIVE command is used to
   mark a script as active.

   When submitting large scripts clients SHOULD use the HAVESPACE
   command beforehand to query if the server is willing to accept a
   script of that size.

   The server MUST check the submitted script for syntactic validity,
   which includes checking that all Sieve extensions mentioned in Sieve
   script "require" statement(s) are supported by the Sieve interpreter.



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   If the script fails this test the server MUST reply with a NO
   response.  Any script that fails the validity test MUST NOT be stored
   on the server.  The message given with a NO response MUST be human
   readable and SHOULD contain a specific error message giving the line
   number of the first error.  Implementors should strive to produce
   helpful error messages similar to those given by programming language
   compilers.  Client implementations should note that this may be a
   multiline literal string with more than one error message separated
   by CRLFs.  The human readable message is in the language returned in
   the latest LANGUAGE capability (or in "i-default", see Section 1.7),
   encoded in UTF-8 [UTF-8].

       Example:

       C: Putscript "foo" {31+}
       C: #comment
       C: InvalidSieveCommand
       C:
       S: NO "line 2: Syntax error"

       C: Putscript "mysievescript" {110+}
       C: require ["fileinto"];
       C:
       C: if envelope :contains "to" "tmartin+sent" {
       C:   fileinto "INBOX.sent";
       C: }
       S: OK

2.7.  LISTSCRIPTS Command

   This command lists the scripts the user has on the server.  Upon
   success a list of CRLF separated script names (each represented as a
   quoted or literal string) is returned followed by an OK response.  If
   there exists an active script the atom ACTIVE is appended to the
   corresponding script name.  The atom ACTIVE MUST NOT appear on more
   than one response line.















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       Example:

       C: Listscripts
       S: "summer_script"
       S: "vacation_script"
       S: {13}
       S: clever"script
       S: "main_script" ACTIVE
       S: OK

       C: listscripts
       S: "summer_script"
       S: "main_script" active
       S: OK

2.8.  SETACTIVE Command

   Arguments:  String - script name

   This command sets a script active.  If the script name is the empty
   string (i.e. "") then any active script is disabled.  Disabling an
   active script when there is no script active is not an error and MUST
   result in OK reply.

   If the script does not exist on the server then the server MUST reply
   with a NO response.  Such reply SHOULD contain the NONEXISTENT
   response code.

       Examples:

       C: Setactive "vacationscript"
       S: Ok

       C: Setactive ""
       S: Ok

       C: Setactive "baz"
       S: No (NONEXISTENT) "There is no script by that name"

       C: Setactive "baz"
       S: No (NONEXISTENT) {31}
       S: There is no script by that name

2.9.  GETSCRIPT Command







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   Arguments:  String - script name

   This command gets the contents of the specified script.  If the
   script does not exist the server MUST reply with a NO response.  Such
   reply SHOULD contain the NONEXISTENT response code.

   Upon success a string with the contents of the script is returned
   followed by a OK response.

       Example:

       C: Getscript "myscript"
       S: {54}
       S: #this is my wonderful script
       S: reject "I reject all";
       S:
       S: OK

2.10.  DELETESCRIPT Command

   Arguments:  String - script name

   This command is used to delete a user's Sieve script.  Servers MUST
   reply with a NO response if the script does not exist.  Such
   responses SHOULD include the NONEXISTENT response code.

   The server MUST NOT allow the client to delete an active script, so
   the server MUST reply with a NO response if attempted.  Such response
   SHOULD contain the ACTIVE response code.  If a client wishes to
   delete an active script it should use the SETACTIVE command to
   disable the script first.

       Example:

       C: Deletescript "foo"
       S: Ok

       C: Deletescript "baz"
       S: No (ACTIVE) "You may not delete an active script"

2.11.  Recommended extensions

   This Section defines several extensions support for which is
   RECOMMENDED.

   The RENAME extension (advertised as the "RENAME" capability with no
   parameters) defines a new RENAMESCRIPT command.




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   The NOOP extension (advertised as the "NOOP" capability with no
   parameters) defines a new NOOP command.

   The UNAUTHENTICATE extension (advertised as the "UNAUTHENTICATE"
   capability with no parameters) defines a new UNAUTHENTICATE command,
   which allows a client to return the server to non-authenticated
   state.

2.11.1.  RENAMESCRIPT Command

   Arguments:  String - Old Script name
               String - New Script name

   This command is used to rename a user's Sieve script.  Servers MUST
   reply with a NO response if the old script does not exist (in which
   case the NONEXISTENT response code SHOULD be included), or a script
   with the new name already exists (in which case the ALREADYEXISTS
   response code SHOULD be included).  Renaming the active script is
   allowed, the renamed script remains active.

       Example:

       C: Renamescript "foo" "bar"
       S: Ok

       C: Renamescript "baz" "bar"
       S: No "bar already exists"

   If the server doesn't support the RENAMESCRIPT command, the client
   can emulate it by performing the following steps:

   1.  List available scripts with LISTSCRIPTS.  If the script with the
       new script name exists, then the client should ask the user
       whether to abort the operation, to replace the script (by issuing
       the DELETESCRIPT <newname> after that) or to chose a different
       name.

   2.  Download the old script with GETSCRIPT <oldname>.

   3.  Upload the old script with the new name: PUTSCRIPT <newname>.

   4.  If the old script was active (as reported by LISTSCRIPTS in step
       1), then make the new script active: SETACTIVE <newname>

   5.  Delete the old script: DELETESCRIPT <oldname>

   Note that these steps don't describe how to handle various other
   error conditions (for example NO response containing QUOTA response



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   code in step 3).  Error handling is left as an excercise for the
   reader.

2.11.2.  NOOP Command

   Arguments:  String - tag to echo back (optional)

   The NOOP command does nothing, beyond returning a response to the
   client.  It may be used by clients for protocol re-synchronisation or
   to reset any inactivity auto-logout timer on the server.

   The response to the NOOP command is always OK, followed by the TAG
   response code together with the supplied string; if no string was
   supplied in the NOOP command, the TAG response code MUST NOT be
   included.

   Older servers may not understand the NOOP client and robust clients
   SHOULD be prepared to receive a NO response.

       Examples:

       C: NOOP
       S: OK "NOOP completed"

       C: NOOP "STARTTLS-SYNC-42"
       S: OK (TAG {16}
       S: STARTTLS-SYNC-42) "Done"

2.11.3.  UNAUTHENTICATE Command

   The UNAUTHENTICATE command returns the server to the non-
   authenticated state.  It doesn't affect any previously established
   TLS [TLS] or SASL (Section 2.1) security layer.

   The UNAUTHENTICATE command is only valid in authenticated state.  If
   issued in a wrong state, the server MUST reject it with a NO
   response.

   The UNAUTHENTICATE command has no parameters.

   When issued in the authenticated state, the UNAUTHENTICATE command
   MUST NOT fail (i.e. it must never return anything other than OK or
   BYE)


3.  Sieve URL Scheme

   URI scheme name: sieve



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   Status: permanent

   URI scheme syntax:

         Described using ABNF [ABNF] and ABNF entities from [URI-GEN].

         sieveurl = sieveurl-server / sieveurl-list-scripts /
                    sieveurl-script

         sieveurl-server = "sieve://" authority

         sieveurl-list-scripts = "sieve://" [ authority ] ["/"]

         sieveurl-script = "sieve://" [ authority ] "/" scriptname

         scriptname = 1*pchar

   URI scheme semantics:

      A Sieve URL identifies a Sieve server or a Sieve script on a Sieve
      server.  The latter form is associated with the application/sieve
      MIME type defined in [SIEVE].  There is no MIME type associated
      with the former form of Sieve URI.

      The server form is used in the REFERRAL response code in order to
      designate another server where the client should perform its
      operations.

      The script form allows to retrieve (GETSCRIPT), update
      (PUTSCRIPT), delete (DELETESCRIPT) or activate (SETACTIVE) the
      named script, however the most typical action would be to retrieve
      the script.  If the script name is empty (omitted), the URI
      requests that the client lists available scripts using the
      LISTSCRIPTS command.

   Encoding considerations: The script name, if present, is in UTF-8.
   Non-US-ASCII UTF-8 octets MUST be percent-encoded as described in
   [URI-GEN].

      The user name (in the "authority" part), if present, is in UTF-8.
      Non-US-ASCII UTF-8 octets MUST be percent-encoded as described in
      [URI-GEN].

   Applications/protocols that use this URI scheme name:
   ManageSieve [RFC XXXX] clients and servers.  Clients that can store
   user preferences in protocols such as [LDAP] or [ACAP].

   Interoperability considerations: None.



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   Security considerations:
   The <scriptname> part of a ManageSieve URL might potentially disclose
   some confidential information about the author of the script or,
   depending on a ManageSieve implementation, about configuration of the
   mail server.  The latter might be used to prepare for a more complex
   attack on the mail system.

   Clients resolving ManageSieve URLs that wish to achieve data
   confidentiality and/or integrity SHOULD use the STARTTLS command (if
   supported by the server) before starting authentication, or use a
   SASL mechanism, such as GSSAPI, that provides a confidentiality
   security layer.

   Contact: Alexey Melnikov <alexey.melnikov@isode.com>

   Author/Change controller: IESG.

   References: This document and RFC 5228 [SIEVE].


4.  Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) notation as specified in [ABNF].  This uses the ABNF core
   rules as specified in Appendix A of the ABNF specification [ABNF].
   "UTF8-2", "UTF8-3" and "UTF8-4" non-terminal are defined in [UTF-8].

   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.

    SAFE-CHAR             = %x01-09 / %x0B-0C / %x0E-21 / %x23-5B /
                            %x5D-7F
                            ;; any TEXT-CHAR except QUOTED-SPECIALS

    QUOTED-CHAR           = SAFE-UTF8-CHAR / DQUOTE QUOTED-SPECIALS

    QUOTED-SPECIALS       = DQUOTE / "\"

    SAFE-UTF8-CHAR        = SAFE-CHAR / UTF8-2 / UTF8-3 / UTF8-4
                            ;; <UTF8-2>, <UTF8-3> and <UTF8-4>
                            ;; are defined in [UTF-8]

    ATOM-CHAR             = "!" / %x23-27 / %x2A-5B / %x5D-7A / %x7C-7E
                            ;; Any CHAR except ATOM-SPECIALS

    ATOM-SPECIALS         = "(" / ")" / "{" / SP / CTL /



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                             QUOTED-SPECIALS

    QUOTED-SPECIALS       = <"> / "\"

    atom                  = 1*1024ATOM-CHAR

    iana-token            = atom
                            ;; MUST be registered with IANA

    auth-type             = DQUOTE auth-type-name DQUOTE

    auth-type-name        = iana-token
                            ;; as defined in SASL [SASL]

    command               = (command-any / command-auth /
                             command-nonauth) CRLF
                            ;; Modal based on state

    command-any           = command-capability / command-logout /
                            command-noop
                            ;; Valid in all states

    command-auth          = command-getscript / command-setactive /
                            command-listscripts / command-deletescript /
                            command-putscript /
                            command-havespace /  /
                            command-renamescript /
                            command-unauthenticate
                            ;; Valid only in Authenticated state

    command-nonauth       = command-authenticate / command-starttls
                            ;; Valid only when in Non-Authenticated
                            ;; state

    command-authenticate  = "AUTHENTICATE" SP auth-type [SP string]
                            *(CRLF string)

    command-capability    = "CAPABILITY"

    command-deletescript  = "DELETESCRIPT" SP sieve-name

    command-getscript     = "GETSCRIPT" SP sieve-name

    command-havespace     = "HAVESPACE" SP sieve-name SP number

    command-listscripts   = "LISTSCRIPTS"

    command-noop          = "NOOP" [SP string]



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    command-logout        = "LOGOUT"

    command-putscript     = "PUTSCRIPT" SP sieve-name SP sieve-script

    sieve-script          = string

    command-renamescript  = "RENAMESCRIPT" SP old-sieve-name SP
                            new-sieve-name

    old-sieve-name        = sieve-name

    new-sieve-name        = sieve-name

    command-setactive     = "SETACTIVE" SP sieve-name

    command-starttls      = "STARTTLS"

    command-unauthenticate= "UNAUTHENTICATE"

    extend-token          = atom
                            ;; MUST be defined by a standards track or
                            ;; IESG approved experimental protocol
                            ;; extension

    extension-data        = extension-item *(SP extension-item)

    extension-item        = extend-token / string / number /
                            "(" [extension-data] ")"

    literal-c2s           = "{" number  "+}" CRLF *OCTET
                            ;; The number represents the number of
                            ;; octets.
                            ;; This type of literal can only be sent
                            ;; from the client to the server.

    literal-s2c           = "{" number  "}" CRLF *OCTET
                            ;; Almost identical to literal-c2s,
                            ;; but with no '+' character.
                            ;; The number represents the number of
                            ;; octets.
                            ;; This type of literal can only be sent
                            ;; from the server to the client.

    number                = 1*DIGIT
                            ;; A 32-bit unsigned number.
                            ;; (0 <= n < 4,294,967,296)

    quoted                = DQUOTE *1024QUOTED-CHAR DQUOTE



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                            ;; limited to 1024 octets between the <">s

    resp-code             = "AUTH-TOO-WEAK" / "ENCRYPT-NEEDED" /
                            "QUOTA" / resp-code-sasl /
                            resp-code-referral /
                            "TRANSITION-NEEDED" / "TRYLATER" /
                            "ACTIVE" / "NONEXISTENT" /
                            "ALREADYEXISTS" /
                            "TAG" SP string /
                            resp-code-ext

    resp-code-referral    = "REFERRAL" SP sieveurl

    resp-code-sasl        = "SASL" SP string

    resp-code-name        = iana-token
                            ;; The response code name is hierarchical,
                            ;; separated by '/'.
                            ;; The response code name MUST NOT start
                            ;; with '/'.

    resp-code-ext         = resp-code-name [SP extension-data]
                            ;; unknown response codes MUST be tolerated
                            ;; by the client.

    response              = response-authenticate /
                            response-logout /
                            response-getscript /
                            response-setactive /
                            response-listscripts /
                            response-deletescript /
                            response-putscript /
                            response-capability /
                            response-havespace /
                            response-starttls /
                            response-renamescript /
                            response-noop /
                            response-unauthenticate

    response-authenticate = *(string CRLF)
                            ((response-ok [response-capability]) /
                             response-nobye)
                            ;; <response-capability> is REQUIRED if a
                            ;; SASL security layer was negotiated and
                            ;; MUST be omitted otherwise.

    response-capability   = *(single-capability) response-oknobye




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    single-capability     = capability-name [SP string] CRLF

    capability-name       = string
                            ;; Note that literal-s2c is allowed.

    initial-capabilities  = DQUOTE "IMPLEMENTATION" DQUOTE SP string /
                            DQUOTE "SASL" DQUOTE SP sasl-mechs /
                            DQUOTE "SIEVE" DQUOTE SP sieve-extensions /
                            DQUOTE "NOTIFY" DQUOTE SP notify-mechs /
                            DQUOTE "STARTTLS" DQUOTE /
                            DQUOTE "LANGUAGE" DQUOTE SP language /
                            DQUOTE "RENAME" DQUOTE /
                            DQUOTE "NOOP" DQUOTE
                            ;; Each capability conforms to
                            ;; the syntax for single-capability.
                            ;; Also note that the capability name
                            ;; can be returned as either literal-s2c
                            ;; or quoted, even though only "quoted"
                            ;; string is shown above.

    sasl-mechs = string
                 ; space separated list of SASL mechanisms,
                 ; each SASL mechanism name complies with rules
                 ; specified in [SASL].
                 ; Can be empty.

    sieve-extensions = string
                 ; space separated list of supported SIEVE extensions,
                 ; can be empty.

    language     = string
                 ; Contains <Language-Tag> from [RFC4646].

    notify-mechs = string
                 ; space separated list of URI schema parts
                 ; for supported notification [NOTIFY] methods.
                 ; MUST NOT be empty.

    response-deletescript = response-oknobye

    response-getscript    = (sieve-script CRLF response-ok) /
                            response-nobye

    response-havespace    = response-oknobye

    response-listscripts  = *(sieve-name [SP "ACTIVE"] CRLF)
                            response-oknobye
                            ;; ACTIVE may only occur with one sieve-name



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    response-logout       = response-oknobye

    response-unauthenticate= response-oknobye
                             ;; "NO" response can only be returned when
                             ;; the command is issued in a wrong state
                             ;; or has a wrong number of parameters

    response-ok           = "OK" [SP "(" resp-code ")"]
                            [SP string] CRLF
                            ;; The string contains human readable text
                            ;; encoded as UTF-8.

    response-nobye        = ("NO" / "BYE") [SP "(" resp-code ")"]
                            [SP string] CRLF
                            ;; The string contains human readable text
                            ;; encoded as UTF-8.

    response-oknobye      = response-ok / response-nobye

    response-noop         = response-ok

    response-putscript    = response-oknobye

    response-renamescript = response-oknobye

    response-setactive    = response-oknobye

    response-starttls     = (response-ok response-capability) /
                            response-nobye

    sieve-name            = string
                            ;; See Section 1.6 for the full list of
                            ;; prohibited characters.

    string                = quoted / literal-c2s / literal-s2c
                            ;; literal-c2s is only allowed when sent
                            ;; from the client to the server.
                            ;; literal-s2c is only allowed when sent
                            ;; from the server to the client.
                            ;; quoted is allowed in either direction.


5.  Security Considerations

   The AUTHENTICATE command uses SASL [SASL] to provide authentication
   and authorization services.  Integrity and privacy services can be
   provided by [SASL] and/or [TLS].  When a SASL mechanism is used the
   security considerations for that mechanism apply.



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   This protocol's transactions are susceptible to passive observers or
   man in the middle attacks which alter the data, unless the optional
   encryption and integrity services of the SASL (via the AUTHENTICATE
   command) and/or [TLS] (via the STARTTLS command) are enabled, or an
   external security mechanism is used for protection.  It may be useful
   to allow configuration of both clients and servers to refuse to
   transfer sensitive information in the absence of strong encryption.

   If an implementation supports SASL mechanisms that are vulnerable to
   passive eavesdropping attacks (such as [PLAIN]), then the
   implementation MUST support at least one configuration where these
   SASL mechanisms are not advertised or used without the presence of an
   external security layer such as [TLS].

   Some response codes returned on failed AUTHENTICATE command may
   disclose whether or not the username is valid, so server
   implementations SHOULD provide the ability to disable these features
   (or make them not conditional on a per-user basis) for sites
   concerned about such disclosure.  In the case of ENCRYPT-NEEDED, if
   it is applied to all identities then no extra information is
   disclosed, but if it is applied on a per-user basis it can disclose
   information.


6.  IANA Considerations

   IANA is requested to reserve TCP port number 2000 for use with the
   Manage Sieve protocol described in this document.

   IANA is requested to register the "sieve" URI scheme defined in
   Section 3 of this document.

   IANA is requested to create a new registry for Manage Sieve
   capabilities.  The registration template for Manage Sieve
   capabilities is specified in Section 6.1.  Manage Sieve protocol
   capabilities MUST be specified in a standards track or IESG approved
   experimental RFC.

   IANA is requested to create a new registry for Manage Sieve response
   codes.  The registration template for Manage Sieve response codes is
   specified in Section 6.3.  Manage Sieve protocol response codes MUST
   be specified in a standards track or IESG approved experimental RFC.

6.1.  Manage Sieve Capability Registration Template

   To: iana@iana.org
   Subject: Manage Sieve Capability Registration
   Please register the following Manage Sieve Capability:



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   Capability name:
   Description:
   Relevant publications:
   Person & email address to contact for further information:
   Author/Change controller:

6.2.  Registration of Initial Manage Sieve capabilities

   To: iana@iana.org
   Subject: Manage Sieve Capability Registration
   Please register the following Manage Sieve Capabilities:

      Capability name: IMPLEMENTATION

      Description: Its value contains name of server implementation and
      its version.

      Relevant publications: this RFC, Section 1.7.

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Capability name: SASL

      Description: Its value contains a space separated list of SASL
      mechanisms supported by server.

      Relevant publications: this RFC, Section 1.7 and Section 2.1.

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Capability name: SIEVE

      Description: Its value contains a space separated list of
      supported SIEVE extensions

      Relevant publications: this RFC, Section 1.7.  Also [SIEVE].

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.




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      Capability name: STARTTLS

      Description: This capability is returned if server supports TLS
      (STARTTLS command).

      Relevant publications: this RFC, Section 1.7 and Section 2.2.

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Capability name: NOTIFY

      Description: This capability is returned if server supports
      'enotify' [NOTIFY] Sieve extension.

      Relevant publications: this RFC, Section 1.7.

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Capability name: RENAME

      Description: This capability is returned if the server supports
      the RENAMESCRIPT command.

      Relevant publications: this RFC, Section 2.11.1.

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Capability name: NOOP

      Description: This capability is returned if the server supports
      the NOOP command.

      Relevant publications: this RFC, Section 2.11.2.

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.




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6.3.  Manage Sieve Response Code Registration Template

   To: iana@iana.org
   Subject: Manage Sieve Response Code Registration
   Please register the following Manage Sieve Response Code:

      Response Code:

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified):

      Purpose:

      Published Specification(s):

      Person & email address to contact for further information:

      Author/Change controller:

6.4.  Registration of Initial Manage Sieve Response Codes

   To: iana@iana.org
   Subject: Manage Sieve Response Code Registration
   Please register the following Manage Sieve Response Codes:

      Response Code: AUTH-TOO-WEAK

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified): NONE

      Purpose: This response code is returned in the NO response from an
      AUTHENTICATE command.  It indicates that site security policy
      forbids the use of the requested mechanism for the specified
      authentication identity.

      Published Specification(s): [RFCXXXX]

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Response Code: ENCRYPT-NEEDED

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified): NONE





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      Purpose: This response code is returned in the NO response from an
      AUTHENTICATE command.  It indicates that site security policy
      requires the use of a strong encryption mechanism for the
      specified authentication identity and mechanism.

      Published Specification(s): [RFCXXXX]

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Response Code: QUOTA

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified): NONE

      Purpose: If this response code is returned in the NO/BYE response,
      it means that the command would have placed the user above the
      site-defined quota constraints.  If this response code is returned
      in the OK response, it can mean that the user is near its quota or
      that the user exceeded its quota, but the server supports soft
      quotas.

      Published Specification(s): [RFCXXXX]

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Response Code: REFERRAL

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified): <sieveurl>

      Purpose: This response code may be returned with a BYE result from
      any command, and includes a mandatory parameter that indicates
      what server to access to manage this user's sieve scripts.  The
      server will be specified by a Sieve URL (see Section 3).  The
      scriptname portion of the URL MUST NOT be specified.  The client
      should authenticate to the specified server and use it for all
      further commands in the current session.

      Published Specification(s): [RFCXXXX]

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>



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      Author/Change controller: IESG.

      Response Code: SASL

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified): <string>

      Purpose: This response code can occur in the OK response to a
      successful AUTHENTICATE command and includes the optional final
      server response data from the server as specified by [SASL].

      Published Specification(s): [RFCXXXX]

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Response Code: TRANSITION-NEEDED

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified): NONE

      Purpose: This response code occurs in a NO response of an
      AUTHENTICATE command.  It indicates that the user name is valid,
      but the entry in the authentication database needs to be updated
      in order to permit authentication with the specified mechanism.
      This is typically done by establishing a secure channel using TLS,
      followed by authenticating once using the [PLAIN] authentication
      mechanism.  The selected mechanism SHOULD then work for
      authentications in subsequent sessions.

      Published Specification(s): [RFCXXXX]

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.

      Response Code: TRYLATER

      Arguments (use ABNF to specify syntax, or the word NONE if none
      can be specified): NONE

      Purpose: A command failed due to a temporary server failure.  The
      client MAY continue using local information and try the command
      later.  This response code only make sense when returned in a NO/
      BYE response.



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      Published Specification(s): [RFCXXXX]

      Person & email address to contact for further information: Alexey
      Melnikov <alexey.melnikov@isode.com>

      Author/Change controller: IESG.


7.  Acknowledgements

   Thanks to Simon Josefsson, Larry Greenfield, Allen Johnson, Chris
   Newman, Lyndon Nerenberg, Tim Showalter, Sarah Robeson, Walter Wong,
   Barry Leiba, Arnt Gulbrandsen, Stephan Bosch, Ken Murchison, Phil
   Pennock, Jeffrey Hutzelman, Mark E. Mallett, Dave Cridland and Robert
   Burrell Donkin for help with this document.  Special thank you to
   Phil Pennock for providing text for the NOOP command, as well as
   finding various bugs in the document.


8.  References

8.1.  Normative References

   [ABNF]     Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 5234, January 2008.

   [ACAP]     Newman, C. and J. Myers, "ACAP -- Application
              Configuration Access Protocol", RFC 2244, November 1997.

   [BASE64]   Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [DNS-SRV]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              February 2000.

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

   [NET-UNICODE]
              Klensin, J. and M. Padlipsky, "Unicode Format for Network
              Interchange", RFC 5198, March 2008.

   [NOTIFY]   Melnikov, A., Ed., Leiba, B., Ed., Segmuller, W., and T.
              Martin, "Sieve Extension: Notifications",
              draft-ietf-sieve-notify-12 (work in progress),
              December 2007.



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   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
              Languages", RFC 2277, January 1998.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, March 2003.

   [RFC4519]  Sciberras, A., "Lightweight Directory Access Protocol
              (LDAP): Schema for User Applications", RFC 4519,
              June 2006.

   [RFC4646]  Phillips, A. and M. Davis, "Tags for Identifying
              Languages", RFC 4646, September 2006.

   [RFC791]   Postel, J., "Internet Protocol", RFC 791, September 1981.

   [SASL]     Melnikov, A. and K. Zeilenga, "Simple Authentication and
              Security Layer (SASL)", RFC 4422, June 2006.

   [SASL-ANON]
              Zeilenga, K., "Anonymous Simple Authentication and
              Security Layer (SASL) Mechanism", RFC 4505, June 2006.

   [SASLprep]
              Zeilenga, K., "SASLprep: Stringprep Profile for User Names
              and Passwords", RFC 4013, February 2005.

   [SCRAM]    Menon-Sen, A., Ed. and C. Newman, "Salted Challenge
              Response Authentication Mechanism (SCRAM)",
              draft-newman-auth-scram-05.txt (work in progress),
              December 2007.

   [SIEVE]    Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
              Filtering Language", RFC 5228, January 2008.

   [StringPrep]
              Hoffman, P. and M. Blanchet, "Preparation of
              Internationalized Strings ("stringprep")", RFC 3454,
              December 2002.

   [TLS]      Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346, April 2006.

   [URI-GEN]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,



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              RFC 3986, January 2005.

   [UTF-8]    Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [X509]     Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
              X.509 Public Key Infrastructure Certificate and
              Certificate Revocation List (CRL) Profile", RFC 3280,
              April 2002.

   [X509-SRV]
              Santesson, S., "Internet X.509 Public Key Infrastructure
              Subject Alternative Name for Expression of Service Name",
              RFC 4985, August 2007.

8.2.  Informative References

   [DIGEST-MD5]
              Leach, P. and C. Newman, "Using Digest Authentication as a
              SASL Mechanism", RFC 2831, May 2000.

   [IANA-GUIDELINES]
              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [IMAP4rev1]
              Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
              4rev1", RFC 3501, March 2003.

   [LDAP]     Zeilenga, K., "Lightweight Directory Access Protocol
              (LDAP): Technical Specification Road Map", RFC 4510,
              June 2006.

   [PLAIN]    Zeilenga, K., "The PLAIN Simple Authentication and
              Security Layer (SASL) Mechanism", RFC 4616, August 2006.















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Authors' Addresses

   Alexey Melnikov (editor)
   Isode Limited
   5 Castle Business Village
   36 Station Road
   Hampton, Middlesex  TW12 2BX
   UK

   Email: Alexey.Melnikov@isode.com


   Tim Martin
   BeThereBeSquare Inc.
   672 Haight st.
   San Francisco, CA  94117
   US

   Phone: +1 510 260-4175
   Email: timmartin@alumni.cmu.edu































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Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.











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