app_rpt can call a script with dtmf using cmd. In the [functions] stanza, add a dtmf function like so:
xxxx = cmd, /etc/asterisk/local/shutdown.sh
Of course xxxx is a unique dtmf sequence.
Then create your script /etc/asterisk/local/shutdown.sh
#! /usr/bin/bash
/usr/sbin/shutdown -h now
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