Internet Engineering Task Force (IETF) K. Murchison Request for Comments: 8440 B. Gondwana Category: Standards Track FastMail ISSN: 2070-1721 August 2018IMAP4 Extension for Returning MYRIGHTS Information in Extended LIST
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RFC 8440 IMAP LIST-MYRIGHTS August 2018
Table of Contents
1. Introduction
IMAP [RFC3501] clients typically fetch the set of rights granted on mailboxes so they can expose the allowed functionality to the logged- in user. In order to do that, the client is forced to issue a LIST or LSUB command to list all available mailboxes, followed by a MYRIGHTS command for each mailbox found. This document defines an extension to the to IMAP LIST command that is identified by the capability string "LIST-MYRIGHTS". The LIST-MYRIGHTS extension allows the client to request the set of rights that the logged-in user has been granted on mailboxes, along with other information typically returned by the LIST command.
2. Conventions Used in This Document
In examples, "C:" indicates lines sent by a client that is connected to a server. "S:" indicates lines sent by the server to the client.
3. MYRIGHTS Return Option to LIST Command
[RFC4314] defines the MYRIGHTS command, which is used by an IMAP client to determine the set of rights that the logged-in user has been granted on a given mailbox. Frequently, a client will have to look up the rights for some or all of the mailboxes returned by the LIST command. Doing so in multiple MYRIGHTS commands wastes bandwidth and can degrade performance if the client does not pipeline the requests.
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RFC 8440 IMAP LIST-MYRIGHTS August 2018
This document extends the LIST command with a new "MYRIGHTS" return option [RFC5258] that allows the client to request all of the desired information in a single command. For each listable mailbox matching the list pattern and selection options, the server MUST return an untagged LIST response and SHOULD also return an untagged MYRIGHTS response containing the set of rights granted to the logged-in user. The ordering of the responses is significant only in that the server MUST NOT send a MYRIGHTS response for a given mailbox before it sends the LIST response for that mailbox.
4. Examples
In this example, the "bar" mailbox doesn't exist, so it has no MYRIGHTS reply.
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RFC 8440 IMAP LIST-MYRIGHTS August 2018 5. Formal SyntaxThe following syntax specification uses the augmented Backus-Naur Form (BNF) as described in [RFC5234]. Terms not defined here are taken from [RFC5258].
6. Security Considerations
In addition to the security considerations described in [RFC4314], this extension makes it a bit easier for clients to overload the server by requesting MYRIGHTS information for a large number of mailboxes. However, as noted in the introduction, existing clients already try to do that by generating a large number of MYRIGHTS commands for each mailbox in which they are interested. While performing MYRIGHTS information retrieval for big lists of mailboxes, a server implementation needs to make sure that it can still serve other IMAP connections and yield execution to other connections, when necessary.
7. Privacy Considerations
This specification does not introduce any additional privacy concerns beyond those described in [RFC4314].8. IANA Considerations 8.1. Registration of IMAP Capability LIST-MYRIGHTSThis document defines the "LIST-MYRIGHTS" IMAP capability that has been added to the "IMAP Capabilities" registry [CAPABILITIES].
8.2. Registration of LIST-EXTENDED Option MYRIGHTS
This section registers the "MYRIGHTS" option that has been added to the "LIST-EXTENDED options" registry [EXTENDED].
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RFC 8440 IMAP LIST-MYRIGHTS August 2018
Person and email address to contact for further information:9. References 9.1. Normative References[CAPABILITIES]
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RFC 8440 IMAP LIST-MYRIGHTS August 2018 9.2. Informative References[RFC5819] Melnikov, A. and T. Sirainen, "IMAP4 Extension for
