room_cal/scripts/sieve

Sieve: SMS Extranet Code Filter

Extracts a Booking.com Extranet challenge code from an incoming email and POSTs it to the room-cal /sms/code API so the service can complete two-factor authentication automatically.

Files

File	Purpose
sms_code.sieve	Sieve rule — matches the message body and pipes to the shell script
sms_code_filter.sh	Pipe target — extracts the code and POSTs it to the API

How it works

1. Dovecot delivers an incoming email through the Sieve rule.
2. If the body contains "Extranet code:", the message is piped (:copy, so it still lands in the inbox) to sms_code_filter.sh.
3. The script greps for Extranet code: \K[0-9]{6} and POSTs {"code": "<digits>"} to ${SMS_API_URL}/sms/code with an X-SMS-Secret header.
4. The room-cal API queues the code for the next GET /sms/code long-poll.

Deployment

1. Install the Dovecot extprograms plugin

apt install dovecot-sieve   # Debian/Ubuntu — sieve_extprograms is bundled

2. Configure Dovecot (/etc/dovecot/conf.d/90-sieve.conf)

plugin {
  sieve_plugins = sieve_extprograms
  sieve_pipe_bin_dir = /etc/dovecot/sieve-pipe
}

3. Install the filter script

cp scripts/sieve/sms_code_filter.sh /etc/dovecot/sieve-pipe/
chmod +x /etc/dovecot/sieve-pipe/sms_code_filter.sh
chown root:dovecot /etc/dovecot/sieve-pipe/sms_code_filter.sh

4. Set environment variables

Edit the top of sms_code_filter.sh (or export from Dovecot's environment):

SMS_API_URL=https://your-room-cal-host      # base URL, no trailing slash
SMS_GATEWAY_SECRET=your-secret-here         # matches SMS_GATEWAY_SECRET in the API

5. Activate the Sieve rule

Per-user — copy or symlink to the user's active script:

cp scripts/sieve/sms_code.sieve /home/zib/sieve/sms_code.sieve
# then reference it from ~/.dovecot.sieve or include it in the active script

Global (applies to all users) — add to sieve_global_path or sieve_before in 90-sieve.conf:

plugin {
  sieve_before = /etc/dovecot/sieve/sms_code.sieve
}

6. Reload Dovecot

doveadm reload

Testing

Send a test message with body Extranet code: 123456 (don't share) and check that the API receives it:

curl -s -H "X-SMS-Secret: $SMS_GATEWAY_SECRET" \
  "${SMS_API_URL}/sms/code?timeout=5"
# → {"code": "123456"}

Check Dovecot logs (/var/log/mail.log) for pipe errors if nothing arrives.