Slirc: IRC interface to Slack

27 Nov 2017 (Updated 27 Aug 2021)

Update: Ralph Rönnquist has an improved version of this script which has been updated for the most recent changes to the Slack API. You should use his version instead of the scripts linked below.

If you need to communicate with other people via Slack, but would prefer to avoid the web interface and Electron application, they offer an IRC gateway. Unfortunately, the gateway has some shortcomings that make it a fairly unsatisfactory solution:

The away status of other users is not shown in /WHOIS queries.
Channels that you are a member of (as shown in the web interface) are not joined automatically, and if you don’t join them explicitly, you won’t see messages from them. Other users who are trying to talk to you may not expect this.
Pasting is cumbersome: the normal way that web interface users will paste text snippets leads to you receiving a message containing only a URL directing you to the Slack web interface in order to view the pasted text.
If you have email notifications enabled, they will continue to come through while you’re connected, and will stack up endlessly, even if you are not marked as away. This is because messages are not marked as read until you disconnect the IRC client. The rationale given for this is that they have no way of knowing if you’ve actually seen the message in the IRC client (but then why mark them as read once when the client disconnects?).
The IRC gateway is not available for all users.

I ended up implementing my own gateway in the form of a locally-running Perl script that communicates with Slack’s RTM interface. This has numerous advantages over the official interface:

Away status is reported correctly in /WHOIS and /WHO queries.
Channels that you’re in are force-joined on connection. If you leave a channel in IRC, you leave it via the API too (making the change visible to other users).
Pasted text snippets are fetched and displayed inline as ordinary messages.
Messages are marked as read on receipt in the normal way.
It doesn’t require any intervention on the part of the workspace owner to use. It requires a Slack API key, but you can obtain a usable key on your own, in spite of what the Slack documentation claims.
Being a self-contained script, it’s easy to customize if you don’t like the way it works.

Installation and setup

Download the script here:

slirc-20190508.pl

To run it, you will first need to install the prerequisite modules from CPAN. These are:

AnyEvent
AnyEvent::HTTP
AnyEvent::Socket
AnyEvent::WebSocket::Client
URI::Encode
Data::Dumper
JSON

On most Linux systems, you will be able to install each of these with:

sudo cpan <module-list>

Make sure you have OpenSSL development headers installed before attempting to install the socket module.

You then need to create a configuration file. This should contain the following lines:

slack_token=<API key>
password=<Password for IRC server>
port=<Port for IRC server>

Save your configuration file and run the gateway with:

./slirc-20190225.pl <file.conf>

You should then be able to connect using the IRC client of your choice on the configured port using the password specified in the configuration file. The IRC server does not support TLS, and so doesn’t bind to any address other than 127.0.0.1. If you need access to it across the network, you should use a TLS proxy or a TLS-capable IRC bouncer on the same host.

Obtaining an API key

You can obtain a “legacy” API key by requesting it via the web interface from your workspace owner. However, you can also obtain one yourself, since the web interface uses the RTM API.

To do this, log in via the web interface with your web browser’s network request tracing enabled and wait. Eventually, the chat interface will be ready, and you should see a series of requests to the API. Pick any of them and look in the POST body for a parameter called token. As long as you don’t explicitly log out (clearing cookies is fine), this key will remain usable.

A simple Perl script using LWP::UserAgent automates the process of extracting API keys from non-SSO login credentials:

slack_login_key.pl

Recent changes

Release 20190225

HTML entities are now escaped/unescaped properly.
Channel IDs are translated with the correct sigil.
You can now close accumulated group chats. This is mapped to JOIN/PART (the behaviour of JOIN/PART for public channels is unaffected).
IRC-side PING checks are now more lenient, to work around bugs in some IRC clients.
Added X commands for debug dumps and dynamically switching protocol debug on/off.

Release 20180515

Since 15 May 2018, you can also listen on a Unix domain socket. To use this feature, add the following line to your config file:

unix_socket=<path>

This feature was added by Colin Watson.

Release 20190508

This release adds some changes from Neia Finch to improve interaction with Slack bots, and display information contained in attachment messages.

Using the gateway

Multiple IRC clients can be connected simultaneously. Messages from any client will be sent via the Slack API. Messages and other events received from the Slack API will be broadcast to all connected IRC clients.

If the RTM connection goes down, all IRC clients will be disconnected and will need to reconnect. IRC clients that connect before the RTM connection is available will not be sent welcome messages until the connection is up.

A ChanServ-like user called X is present on the server. It supports the following commands:

/msg X newgroup <name>: Create a new private group. Users can be invited to the group via the usual /INVITE command.
/msg X newchan <name>: Create a new public channel.
/msg X archive <name>: Archive the given group or channel.
/msg X cat <file-id>: Fetch the given file and display it inline in the form of NOTICE messages.
/msg X disconnect: Disconnect and reconnect the RTM client.

Mentions of the form <@nickname> or <#channel> will be translated and appear correctly to clients using the web interface.

Copyright

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.