Internet DRAFT - draft-oakley-irc-ctcp
draft-oakley-irc-ctcp
Network Working Group M. Mikulenas
Internet-Draft Independent
Updates: 1459, 2812 (if approved) D. Oakley
Intended status: Informational ircdocs
Expires: July 13, 2018 January 09, 2018
Internet Relay Chat: Client-to-Client Protocol (CTCP)
draft-oakley-irc-ctcp-02
Abstract
This document describes the Client-to-Client Protocol (CTCP), which
lets Internet Relay Chat (IRC) clients send each other messages that
get displayed or responded to in special ways. CTCP has been widely
implemented, with most clients supporting it natively. This document
outlines how to implement CTCP and the most common messages used.
It updates RFC 1459 and RFC 2812.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on July 13, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Message Syntax . . . . . . . . . . . . . . . . . . . . . . . 3
3. Message Types . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Extended formatting . . . . . . . . . . . . . . . . . . . 4
3.2. Metadata Query . . . . . . . . . . . . . . . . . . . . . 4
3.3. Extended Query . . . . . . . . . . . . . . . . . . . . . 4
4. Messages . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Message List . . . . . . . . . . . . . . . . . . . . 6
A.1. ACTION . . . . . . . . . . . . . . . . . . . . . . . . . 6
A.2. CLIENTINFO . . . . . . . . . . . . . . . . . . . . . . . 7
A.3. DCC . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
A.4. FINGER . . . . . . . . . . . . . . . . . . . . . . . . . 8
A.5. PING . . . . . . . . . . . . . . . . . . . . . . . . . . 8
A.6. SOURCE . . . . . . . . . . . . . . . . . . . . . . . . . 8
A.7. TIME . . . . . . . . . . . . . . . . . . . . . . . . . . 9
A.8. VERSION . . . . . . . . . . . . . . . . . . . . . . . . . 9
A.9. USERINFO . . . . . . . . . . . . . . . . . . . . . . . . 10
Appendix B. Change History [RFC Editor: Please remove this
section] . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The core Internet Relay Chat (IRC) protocol as described in [RFC1459]
and [RFC2812] only has a single command for regular user messages,
and does not provide a way for clients to exchange information
directly. Client-to-Client Protocol (CTCP) messages let clients
exchange messages that get displayed or responded to in special ways.
Some examples of how CTCP is used is to request special formatting on
messages, query other clients for metadata, and help initiate file
transfers with other clients.
This document goes over the subset of CTCP which is commonly
implemented, and is compatible with clients implementing CTCP as
described by older documents.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. Message Syntax
CTCP queries are sent with the PRIVMSG IRC command, and CTCP replies
are sent with NOTICE command. To indicate a CTCP query or reply, the
body of the message (the second parameter) begins with the CTCP
delimiter. The ABNF [RFC5234] for this message body is as follows:
delim = %x01
command = 1*( %x02-09 / %x0B-0C / %x0E-1F / %x21-FF )
; any octet except NUL, delim, CR, LF, and " "
params = 1*( %x02-09 / %x0B-0C / %x0E-FF )
; any octet except NUL, delim, CR, and LF
body = delim command [ SPACE params ] [ delim ]
Commands are case-insensitive. When creating new CTCP commands,
authors SHOULD use only alphanumeric characters for ease of
implementation.
The final CTCP delimiter SHOULD be sent on outgoing messages for
compatibility reasons, and software MUST accept incoming messages
which lack it. This is due to how servers implement message
truncation and certain clients implement message splitting.
Queries MAY be sent to channels. When these queries are responded
to, the responses are sent to the querying client rather than the
channel which the query was originally sent to.
Many servers implement optional filtering so that only the ACTION
CTCP message can be sent to channels. When this is done, it can
typically be enabled or disabled by channel operators with a channel
mode.
Here are two examples of CTCP queries and replies:
:alice!a@localhost PRIVMSG bob :\x01VERSION\x01
:bob!b@localhost NOTICE alice :\x01VERSION Snak for Mac 4.13\x01
:alice!a@localhost PRIVMSG #ircv3 :\x01PING 1473523796 918320\x01
:bob!b@localhost NOTICE alice :\x01PING 1473523796 918320\x01
3. Message Types
CTCP messages generally take on one of these types. These message
types are defined here to simplify understanding, and aren't
differentiated by the protocol itself.
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3.1. Extended formatting
This type of CTCP requests special formatting of a user-visible
message. That is, to send a user-visible message that should be
displayed differently from regular messages - e.g. as an action, a
whisper, an announcement.
Extended formatting messages are sent as a PRIVMSG, and are expected
to be used in channels as well as between clients. There is no
automatic response to this message type, as it is not a query nor
reply.
These messages are sent as a PRIVMSG and can have parameters, but
generate no reply.
Example:
:dan!u@localhost PRIVMSG #ircv3 :\x01ACTION writes some specs!\x01
3.2. Metadata Query
This type of CTCP provides relatively static information about the
target client, user or connection.
This CTCP takes the form of a query and a response (as a PRIVMSG and
NOTICE, respectively). Due to how bouncers interact with multiple
clients, there may sometimes be multiple responses to queries.
Metadata queries MUST NOT require the recipient to implement any side
effects (beyond sending the reply itself); if a CTCP message causes
side effects by design, it should be categorized as an extended query
instead.
Metadata queries do not have any parameters, but expect a reply with
parameters as the response data.
Example:
:alice!a@localhost PRIVMSG bob :\x01VERSION\x01
:bob!b@localhost NOTICE alice :\x01VERSION SaberChat 27.5\x01
3.3. Extended Query
This type of CTCP provides dynamic information or invoke actions from
the client.
This CTCP takes the form of a query and a response (as a PRIVMSG and
NOTICE, respectively).
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Queries sent to a channel always generate private replies.
Extended queries and replies may have parameters.
Example:
:alice!a@localhost PRIVMSG bob :\x01PING 1473523796 918320\x01
:bob!b@localhost NOTICE alice :\x01PING 1473523796 918320\x01
4. Messages
CTCP messages themselves are not standardised. Clients that receive
either unexpected messages or known messages with unexpected values
SHOULD ignore them and produce no response to the sending user.
Clients MAY receive more than one response per user for a query they
send, due to multiple clients being connected behind an IRC bouncer.
5. Acknowledgements
Thanks to the IRCv3 group for giving feedback on this specification,
and to Khaled for advice on client flood protection.
Thanks to Michael Sandrof for creating CTCP, Troy Rollo for creating
the related DCC protocol, as well as Klaus Zeuge and Ben Mesander who
wrote and revised related specifications.
Special thanks to dequis, Sadie and James Wheare for help with this
and related work.
6. Security Considerations
CTCP messages are completely untrusted data, and clients MUST NOT
assume that they are well-formed or complete.
Older CTCP specifications describe quoting methods which are complex
and not widely implemented. Implementations SHOULD NOT implement
"low-level quoting" or "CTCP-level quoting" when parsing messages.
Older CTCP specifications describe including more than one CTCP
message inside a single PRIVMSG or NOTICE command. Implementations
SHOULD NOT implement this form of CTCP parsing as it is not widely-
implemented and may result in an implementation that can be more
easily flooded off the server they are connected to.
CTCP requests can be abused to flood clients off the server they are
connected to. Clients may ignore or delay excessive incoming
requests to protect against this.
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7. IANA Considerations
This document has no actions for IANA.
8. Normative References
[RFC1459] Oikarinen, J. and D. Reed, "Internet Relay Chat Protocol",
RFC 1459, DOI 10.17487/RFC1459, May 1993,
<https://www.rfc-editor.org/info/rfc1459>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[RFC2812] Kalt, C., "Internet Relay Chat: Client Protocol",
RFC 2812, DOI 10.17487/RFC2812, April 2000,
<https://www.rfc-editor.org/info/rfc2812>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008, <https://www.rfc-
editor.org/info/rfc5234>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008, <https://www.rfc-
editor.org/info/rfc5322>.
Appendix A. Message List
This section is not exhaustive, and only lists those CTCP messages
which are widely implemented across the IRC ecosystem.
The reply and parameter lines below use a simplified syntax that
represents variables by surrounding them with angle brackets.
A.1. ACTION
Type: Extended Formatting
Params: ACTION <text>
This extended formatting message shows that <text> should be
displayed as a third-person action or emote; in clients, it's
generally activated with the command "/me".
If <text> is empty, clients SHOULD still include a single space after
"ACTION" (i.e. an empty params section) to help compatibility.
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Clients SHOULD correctly parse incoming ACTION messages with or
without the params section.
ACTION is universally implemented and very commonly used. Clients
MUST implement this CTCP message to effectively use IRC.
Examples:
Raw: :dan!user@host PRIVMSG #ircv3 :\x01ACTION does it!\x01
Formatted: * dan does it!
Raw: :dan!user@host PRIVMSG #ircv3 :\x01ACTION \x01
Raw: :dan!user@host PRIVMSG #ircv3 :\x01ACTION\x01
Raw: :dan!user@host PRIVMSG #ircv3 :\x01ACTION
Formatted: * dan
A.2. CLIENTINFO
Type: Extended Query
Reply: CLIENTINFO <tokens>
This extended query returns a list of the CTCP messages that this
client supports and implements, delimited by a single ASCII space.
CLIENTINFO is widely implemented. Clients SHOULD implement this CTCP
message.
Example:
Query: CLIENTINFO
Response: CLIENTINFO ACTION DCC CLIENTINFO PING TIME VERSION
A.3. DCC
Type: Extended Query
Params: DCC <type> <argument> <host> <port>
This extended query sets up and controls connections that go directly
between clients, bypassing the IRC server. This is typically used
for features that require a large amount of traffic between clients
or simply wish to bypass the server itself such as file transfer and
direct chat.
The Direct Client-to-Client (DCC) Protocol requires its own
specification, and is not described in-depth here.
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DCC is widely implemented. Clients MAY implement this CTCP message.
A.4. FINGER
Type: Metadata Query
Reply: FINGER <info>
This metadata query returns miscellaneous info about the user,
typically the same information that's held in their realname field.
However, some implementations return the client name and version
instead.
FINGER is largely obsolete. Clients MAY implement this CTCP message.
Example:
Query: FINGER
Response: FINGER WeeChat 1.8-dev
A.5. PING
Type: Extended Query
Params: PING <info>
This extended query confirms reachability and latency to the target
client. When receiving a CTCP PING, the reply MUST contain exactly
the same parameters as the original query.
PING is universally implemented. Clients SHOULD implement this CTCP
message.
Example:
Query: PING 1473523721 662865
Response: PING 1473523721 662865
Query: PING foo bar baz
Response: PING foo bar baz
A.6. SOURCE
Type: Metadata Query
Reply: SOURCE <info>
This metadata query returns the location of the source code for the
client.
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SOURCE is rarely implemented. Clients MAY implement this CTCP
message.
Example:
Query: SOURCE
Response: SOURCE https://weechat.org/download
A.7. TIME
Type: Extended Query
Params: TIME <timestring>
This extended query returns the client's local time in an unspecified
human-readable format. In practice, both the format output by
ctime() and the format described in Section 3.3 of [RFC5322] are
common. Earlier specifications recommended prefixing the time string
with a colon, but this is no longer recommended.
New implementations MAY default to UTC time for privacy reasons.
TIME is almost universally implemented. Clients MAY implement this
CTCP message.
Example:
Query: TIME
Response: TIME Mon, 08 May 2017 09:15:29 GMT
A.8. VERSION
Type: Metadata Query
Reply: VERSION <verstring>
This metadata query returns the name and version of the client
software in use. There is no specified format for the version
string.
Clients may allow users to customise the response value for this
query.
VERSION is universally implemented. Clients SHOULD implement this
CTCP message.
Example:
Query: VERSION
Response: VERSION WeeChat 1.8-dev (git: v1.7-329-g22f2fd03a)
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A.9. USERINFO
Type: Metadata Query
Reply: USERINFO <info>
This metadata query returns miscellaneous info about the user,
typically the same information that's held in their realname field.
However, some implementations return "<nickname> (<realname>)"
instead.
USERINFO is largely obsolete. Clients MAY implement this CTCP
message.
Example:
Query: USERINFO
Response: USERINFO fred (Fred Foobar)
Appendix B. Change History [RFC Editor: Please remove this section]
Changes from draft 1 (July 18, 2017)
o General editing, fixed mistypes.
o Simplified some of the examples.
Changes from draft 0 (May 29, 2017)
o Added note about servers truncating CTCP messages (thanks Peter).
o Fixed misspellings and added note to TIME about previously-
recommended prefix (thanks Patrick).
o Mentioned how to parse/send empty ACTION messages (thanks dequis
and the crew).
Authors' Addresses
Mantas Mikulenas
Independent
Email: grawity@gmail.com
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Daniel Oakley
ircdocs
Email: daniel@danieloaks.net
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