INTERNET-DRAFT Simon Butcher
Expires April 2004 Alien Internet Services
October 2003
Uniform Resource Locator Schemes for
Internet Relay Chat Servers
<draft-butcher-irc-url-00.txt>
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of Section 10 of RFC2026. Distribution of this document is
unlimited. Comments should be sent to the author.
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Abstract
This document specifies two URL (Uniform Resource Locator) schemes,
using the URI (Uniform Resource Indicator) names "irc" and "ircs",
for the location of IRC (Internet Relay Chat) servers. These URLs
allow for easy location of an IRC server, optionally also specifying
an IRC channel to join or person to contact upon connection.
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1. Introduction
Since its introduction, Internet Relay Chat (IRC) has become widely
known and used within the Internet Community as a real-time chat
medium. IRC networks are steadily growing larger, not only with
regards to the number of regular uses, but also the number of
channels and servers required to support the demand.
Due to the nature of IRC as a simple real-time chat service, it has
been known to be used for a wide variety of uses such as software
support, job interviews, and of course just for a casual chat.
While IRC is progressing, the need for an appropriate Uniform
Resource Locator (URL) scheme has become apparent. Applications for
such a scheme would range quite widely, including IRC network server
lists on a website, software support contact details, or even a
meeting location with an e-mail including a specific IRC channel.
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].
In this document, the term "client" is defined as the IRC client
software, and the term "user" is the end-user of that software.
2. URL Definition
An IRC URL begins with either the Uniform Resource Identifiers (URIs)
"irc" or "ircs", denoting normal and secured connections
respectively. Normal sessions are via the existing transport, as
defined in [RFC2812], and secured sessions are the same, only via a
secure transport layer such as [TLS] (or [SSL], the predecessor to
TLS).
The URL scheme for IRC follows the Generic URL Syntax, defined in
[RFC2396].
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2.1. ABNF Syntax
The following is the definition for an IRC URL in [ABNF] grammar:
ircURL = type "://" location "/" [ channel ] [ options ]
type = "irc" / "ircs"
location = [ authinfo "@" ] hostport
; See Section 3.2.2 of [RFC2396] for
; the definition of 'hostport'.
authinfo = [ nickname *2( ";" nickname ) ] [ ":" password ]
nickname = ALPHA / DIGIT / %x23-25 / %x2A-2F
; Further restrictions may apply upon
; connection, depending on the server.
; Some common nickname characters must be
; encoded, as per recommendations in Section
; 2.4.3 in [RFC2396].
password = ALPHA / DIGIT / %x23-24 / %x2A-2F / ";" / "=" / "?"
channel = ALPHA / DIGIT / %x23-24 / %x2A-2F
; See [RFC2811] for the definition of
; a channel.
options = "?" option *( "&" option )
option = optname [ "=" optvalue ]
optname = ALPHA
optvalue = ALPHA / DIGIT / %x23-24 / %x2A-2F / ":" / ";" / "@"
; Other characters (such as [Unicode]
; characters in [UTF-8]) must be escaped
; as per rules in Section 2.2.5 of [RFC2718].
; See also Section 4 of this document.
The use of the "%" character (%x25) is used to facilitate escaped
characters. Should the "%" character itself be needed, it must be
escaped, such as "%25". The use of spaces, escaped (%20) or
otherwise, SHOULD NOT be allowed for channel names or nicknames, as
they are currently unsupported by existing IRC protocols.
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2.2. Authentication
Multiple nicknames MAY be specified, and pending any error or lack of
availability, the IRC client software MAY request the next nickname
in the list.
Clients MUST NOT accept any more than three (3) nicknames, and any
more nicknames specified MUST be ignored to curtail potential abuse.
Clients may only attempt to use alternative nicknames given during
the one connection. Clients MUST NOT reconnect to the server to try
alternative nicknames.
Should the client run out of alternative nicknames to try, but the
server is willing to accept another attempt, the client MAY either
disconnect from the server and show the user an error message, or
prompt the user for another nickname to try.
The use of passwords is not recommended, as they present a
significant security problem. They are allowed purely for
convenience. Users of the password field must be aware of the
security issues discussed in Section 6 of this document.
2.3. Server Ports
Special consideration must be given to URLs without ports specified.
Almost all IRC servers are contactable on a variety of standard ports
as allocated by the IANA. Should an IRC URL be specified without a
port, a client SHOULD try a number of standard ports:
- For the "irc" URI, it is RECOMMENDED that the server is attempts
connection to the ports 194, 6665, 6666, 6667, 6668 and 6669.
- For the "ircs" URI, it is RECOMMENDED that the default port used
is 994. User-space ports (those above port 1023) may have
questionable authenticity, and SHOULD NOT be used unless
explicitly specified.
Port numbers shown here are in decimal, and have been assigned by the
IANA.
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2.4. Channels
For compatibility with older implementations, and to allow
simplification of the specification, channels MAY be specified
without the use of the "channel" option detailed in Section 2.5.1.
Only one channel can be specified, and this facility has the same
functionality as the "channel" option. See Section 3 of this
document for examples of the equivalence between this and the
"channel" option in Section 2.5.1.
2.5. Additional Options
Additional options may be added to control what action the client
software MAY take following connection to the IRC server.
Unsupported options should simply be ignored.
These options listed here may be expanded on at a later date by
updated RFC's.
2.5.1. The "channel" Option
This instructs the client to join the specified channel, allowing the
user to participate in discussions within the channel.
The value given with the channel option is a channel name, and
optionally a "key" (see Section 4.2.10 of [RFC2811]). Its value can
be defined in [ABNF] as follows:
optvalue = name [ "," key ]
See Section 2.1 of this document for information on acceptable
characters. The "," character is not allowed in either the channel
name, or key, unless it is escaped ("%x2C").
The number of channels which can be joined at once is normally
restricted by the server, but no hard-limit is given by this
specification as this is a matter of individual server policy. As
such, multiple "channel" options may be given.
An automated message MUST NOT be sent to the channel upon joining it.
It is NOT RECOMMENDED to use the channel key feature. Please see
Section 6 of this document. If a key is required to join a channel,
and one is not given, the IRC client MAY wish to prompt the user for
the key.
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2.5.2. The "query" Option
For each "query" option, the client is requested to open some
interface where by users may type a message to the given query
target. For example, the client may open up a window where messages
may be typed to, and received from the target.
Some clients may not have the ability to open up a specific window or
dialogue box. These clients MAY prompt the user for a message to be
sent to the target, or otherwise this option MAY be ignored and hence
unsupported.
The option value is the same as the message target value specified in
Section 3.3.1 of [RFC2812], except that the client MUST only accept
one target. Multiple targets per "query" option MUST NOT be
accepted, and the entire query MUST be considered invalid and
ignored.
A message MUST NOT be automatically sent to the target, simply an
interface created to allow the user to send a message to the target.
The IRC client software MAY wish to check the availability of the
target prior to opening the interface if inclined to do so, however
any method of testing the availability MUST NOT generate any
automatic message being sent to the target.
Multiple targets MAY be referenced with multiple query options,
however in order to reduce the potential for abuse, it is RECOMMENDED
that additional query options are ignored. There are valid reasons
for having multiple targets, and abuse is minimal as no messages are
sent to the targets.
3. Examples
While examples of every situation cannot be shown here because of
space considerations, the following examples provide a rough overview
of how the IRC URL can be used.
<irc://irc.undernet.org/>
In its simplest form, the above complete URL can be used to direct a
client to a specific IRC server, which in this case is
"irc.undernet.org". The client should presume to use default port
settings.
<irc://pickle@irc.efnet.org:6667/>
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The above URL specifies that the IRC client should try to connect to
"irc.efnet.org" on the port 6667, rather than use whatever is
considered the default. It also tells the IRC client it should try
to use a nickname of "pickle", if it is available.
<irc://%C4%B0dil;idil@irc.austnet.org/>
This shows a properly [UTF-8] encoded URL, specifying the nickname
Idil (with the first character being a Turkish Latin capital letter
"I" with a dot above it, [Unicode] codepoint U+0130). Failing that,
the second nickname, "idil", may be used if the first one is
rejected, perhaps by an older IRC server.
<irc://pickle:secret@172.16.0.12:194/>
The above URL will instruct the IRC client to connect to a server
with the address 172.16.0.12, which is an IRC server that is
presumably password protected. The client should request to use the
nickname "pickle", with the password "secret" to authenticate the
session to the remote server. This URL also enforces the standard IRC
port, 194, and will stop IRC clients from hunting for ports.
<irc://irc.ircnet.net/#worldchat>
<irc://irc.ircnet.net/%23worldchat>
<irc://irc.ircnet.net/?channel=%23worldchat>
All three of these URLs connects to the IRCnet network, and will join
the client to the channel "#worldchat" upon connection.
<irc://irc.alien.net.au/?query=pickle&channel=%2Bprivate,foo>
This will connect to the server "irc.alien.net.au" and will provoke
the client to open up a window (or similar) associated with sending
messages to the nickname 'pickle'. It will also join the channel
"+private" using the channel key "foo".
<irc://irc.austnet.org/%23melbourne?channel=%23sydney>
This will connect to AUSTnet and join two channels, "#melbourne" and
"#sydney".
<irc://irc.undernet.org/?query=pickle%25butcher.id.au>
This will open a dialogue box prepared to send a message to
"pickle%butcher.id.au". Please refer to Section 3.3.1 of [RFC2812]
for more details.
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4. Internationalisation Considerations
With the inevitable adoption of [Unicode] on IRC, and indeed the
Internet as a whole, URLs MUST be encoded using the [UTF-8] character
set, with potentially unsafe octets encoded using %HH notation (where
HH is a hexadecimal value), as per Section 2.2.5 of [RFC-2718].
For example, the word for "alias" in Japanese, using Unicode code-
points, is U+5225 U+540D. Correctly encoded, this would appear in
the URL as: "%E5%88%A5%E5%90%8D". An example of this use in action
can be found in Section 3.
5. Interoperability Considerations
Many existing implementations fail to acknowledge the correct use of
the generic URL syntax defined in [RFC2396], but continue to use the
format regardless.
Some implementations do not take into consideration the use of prefix
characters on channels names, as defined by [RFC2811], and therefore
cannot correctly reference channels appropriately. Software SHOULD
NOT guess the channel type, or hence the channel's prefix character,
unless the probability of an accurate guess is 100% (for example, the
server only supports one type of channel).
Some current implementations will need slight modification to accept
the extended format defined in this specification, however most
implementations which parse the URL in a standard form will continue
to work.
The majority of incongruities are simply caused by the problem of
developers ignoring RFC-2396.
The use of the channel name without specifying the channel option is
to both maintain compatibility with the existing implementations,
whilst providing an abbreviated form, similar to the design of the
"mailto:" scheme defined by [RFC2368].
6. Security Considerations
Security problems arise only when the authentication portion of the
URL is used, or channel keys are given. While the use of the
password/key extensions is considered to be rare, they have been
included for completeness.
As the passwords and channel keys are unfortunately in clear-text,
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any user using the IRC URL should be aware of obvious insecurities.
Furthermore, it is RECOMMENDED that user software does not
automatically initiate the connection specified by the URL without
the knowledge and consent of the user. To do so would open the
implementation up to a variety of malicious activities including, but
not limited to, the purposes of direct advertising or channel
advertising (also known as "spam") by way of pop-ups.
When connecting using a secure connection ("ircs://"), user-space
ports (those above port 1023) SHOULD NOT be used automatically, as
their authority is questionable. If a secure connection cannot be
established, the client MUST either give up, or prompt the user
before attempting an insecure ("irc://") connection.
Beyond this, there are security concerns with regards with associated
protocols, including IRC and TLS, which MUST be taken into
consideration, but are beyond the scope of this document.
7. Acknowledgments
Thanks must go to Khaled Mardam-Bey for his early implementation in
his software, "mIRC", which provided the inspiration to clarify the
specification.
I would also like to acknowledge the members of the IRC development
community who encouraged me to publish this draft, after more than 18
months of pretermission.
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8. References
[ABNF] Crocker, D., and Overell, P., "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2368] Hoffman, P., Masinter, L., Zawinski, J., "The mailto URL
scheme", RFC 2368, July 1998.
[RFC2396] Berners-Lee, T, Fielding, T., Masinter, L., "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[RFC2718] Masinter, L., Alvestrand, H., Zigmond, D., Petke, R.,
"Guidelines for new URL Schemes", RFC 2718, November 1999.
[RFC2811] Kalt, C., "Internet Relay Chat: Channel Management", RFC
2811, April 2000.
[RFC2812] Kalt, C., "Internet Relay Chat: Client Protocol", RFC 2819,
April 2000.
[SSL] Hickman, K., "The SSL Protocol", Netscape Communications
Corp., February 9, 1995.
[TLS] Dierks, T. and Allen, C., "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[Unicode] The Unicode Consortium. The Unicode Standard, Version
4.0.0, (Reading, MA, Addison-Wesley, 2003. ISBN
0-321-18578-1).
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
RFC 2279, January 1998.
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9. Author's Address
Simon Butcher
Alien Internet Services
PO Box 7041
Croydon South
VIC 3136
Australia
Phone: +61-3-9879-8052
Fax: +61-3-9893-2793
Email: simonb@alien.net.au
Document Expiration and Filename
Please note that this is a draft document and it shall expire April
2004. Its filename is draft-butcher-irc-url-00.txt
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