Hermod Signal - IRC - Telegram Gateway

Hermod, or Hermóðr is a figure in Norse mythology, often considered the messenger of the gods

These scripts act as a gateway between a telegram group a signal group and an irc channel. The first thing to do is to register a telegram bot with the botfather. Then you can add the bot to the admins of the telegram channel you want to share with IRC. Note the telegram API token and find the telegram group chat_id.

Reference: Telegram Bot API

Configuration

Make a copy of the file hermod.json.example to /etc/hermod.json and change values appropriately

{       
    "signal": {
        "phone": "+316xxxxxxxxxx",
        "gid": "XXXXXXXXXXXXXXXXXXXXX==",
        "cli": "/home/hermod/bin/signal-cli",
        "infile": "/home/hermod/log/tosignal.log",
        "db": "/home/hermod/var/signal.db",
        "debug": "/home/hermod/log/signal.debug",
        "anon": "Anonymous",
        "attachment_path": "/var/www/html/signal",
        "url": "https://hermod.example.com/signal"
    },  
    "telegram": {
        "token":  "999999999:xxxxxxxxxxxxxx-xxxxxxxxxxxxxxxxxxxx",
        "chat_id": "-19999999",
        "file": "/home/hermod/log/telegram.log",
        "debug": "/home/hermod/log/telegram.debug",
        "attachments": "/var/www/html/telegram",
        "url": "https://hermod.example.com/telegram"
    },  
    "irc": {
        "ircnode": "irc.freenode.net",
        "channel": "#channel",
        "port"   : 6697,
        "UseSSL" : 1,
        "nick"   : "gateway",
        "password": "xxxxxxxx",
    }
}

signal->phone is the phone number used by signal-cli. It has to be added to the group (signal->gid). signal->anon is a string used to partly anonymize telephone numbers when relaying messages to the other channels. Then the phone number has to be registered with signal-cli

Refer to the Telegram Bot API for details about telegram->token and telegram->chat_id

irc->node, irc->channel, irc->port, irc->nick and irc->password relate to... IRC. Any value for irc->UseSSL other than 0 will cause the connection to be SSL enabled.

irc->infile is the connection between the telegram webhook, the signalpoller and the IRC bot. Can be any file, as long as it is writeable by the webhook and signalpoller and readable by the bot.

The IRC bot and the webhook write to signal->infile. The poller will read it and send new content to the signal group

Setting up the hook

The gateway consists of three parts: two daemon parts and a webhook. Place the webhook in an executable place of a webserver (like https://webserver/cgi-bin/telegramhook)

Next thing is to register the webhook:

curl -F "url=https://webserver/cgi-bin/telegramhook" https://api.telegram.org/bot$TOKEN/setWebhook

Make sure the telegram bot you are using has privacy mode disabled (or is admin in the telegram group). If not, the bot won't see any group messages by other users. You can review the telegram->debug file to get the chat_id of the telegram group.

Setting up Signal

To connect with Signal, you'll need to install signal-cli

To register the signal phone number you need to run these commands:

$ signal-cli -u +316xxxxxxxxxx register
$ signal-cli -u +316xxxxxxxxxx verify XXX-XXX

The XXX-XXX code you wil get in an SMS text message so you'll have to actually install the simcard in some telephone. This is the only time it's needed.

Next is to add a phone number you control into a signal group. You can start signalpoller and look at its output; when something is said in the signal group you will see output like this:

{"envelope":{"source":"+316xxxxxxxx","sourceDevice":1,"relay":null,"timestamp":1566735523785,"isReceipt":false,"dataMessage":{"timestamp":1566735523785,"message":"Hello","expiresInSeconds":3600,"attachments":[],"groupInfo":{"groupId":"XXXXXXXXXXXXXXXXXXXXXX==","members":null,"name":null,"type":"DELIVER"}},"syncMessage":null,"callMessage":null}}

Update signal->gid in hermod.json with the groupId in this output. Set signal->phone to the number you registered with signal-cli

The signal poller does not see usernames, only telephone numbers. It would be kind of rude to relay these telephone numbers to Telegram or IRC, so the telephone numbers are anonymized as "Anonymous-XXXX", where XXXX are the last 4 numbers of the telephone number.

The bot keeps a small sqlite database signal->db, used for mapping signal telephone numbers (in the signal group) to nicknames. Members of the signal group can set their nick by issuing the command:

!setnick nickname

In the signal group. The bot will update the mapping in the database and confirm this by saying:

anonymous-XXXX is now known as nickname

In all channels.

You need to create an sqlite database file:

create table alias (phone text unique not null, nick text);

Directories for attachments and urls

The photo's and attachments send by people in telegram and signal groups are downloaded and placed in suitable directories. For Telegram, use the telegram->attachments configuration option. Make sure this directory is shared over a HTTP webserver like apache and it is writeable by the webserver. Configure telegram->url to point to this same directory.

The signal-cli program by default saves all attachments in a directory ~/.local/share/signal-cli/attachments. The easiest way to handle this is to move this entire directory to somewhere below the documentroot of the webserver and symlink it.

Start the IRC bot

Verify the bot will be receiving messages in the telegram group by checking the telegram->file. Then you can start the IRC part:

$ ./hermod
Establishing connection to [irc.freenode.net]
:weber.freenode.net NOTICE * :*** Looking up your hostname...
:weber.freenode.net NOTICE * :*** Checking Ident
:weber.freenode.net NOTICE * :*** Couldn't look up your hostname
:weber.freenode.net NOTICE * :*** No Ident response
:weber.freenode.net 001 telegram_gateway :Welcome to the freenode Internet Relay Chat Network telegram_gateway
...
...

that's all. You will see messages scrolling showing the login proces on IRC. You probably want to run these in screen(1) from cron

@reboot screen -S hermod -d -m /home/hermod/bin/hermod
@reboot screen -S poller -d -m /home/hermod/bin/signalpoller