deep-query.sh

#!/usr/bin/env bash

# Query pi-hole's domain lists, but follow CNAMEs. Useful for debugging why
# a site is being blocked if CNAME_DEEP_INSPECT=true is set (which it is by
# default on version 5.0)

# Nameserver for looking for CNAMES. Needs to be different from pihole itself;
# or, pihole's group management needs to exclude localhost from blocking. (If
# we use pihole to look for CNAMES but the domain is blocked, we won't find
# any even if they exist.)
NS="1.1.1.1"

# For a given domain name, return a list containing itself and all cnames
# down the "chain" from it.
# Usage: get_all_cnames example.com some.name.server
get_all_cnames()
{
        local query
        local ns
        local cnames
        query="$1"
        ns="$2"

        # Drop trailing period from query, if any
        query=${query%.}

        # All cnames for this query returned by dig
        cnames=$(dig @$ns CNAME $query +short)

        # Echo this query, then recursively call this function for
        # all cnames. Traverses depth-first through CNAME chains. Supports
        # cases when multiple cnames are returned by dig; even though that
        # shouldn't happen it does sometimes.
        echo -n $query
        for cn in $cnames; do
                echo -n " "
                echo -n $(get_all_cnames $cn $ns)
        done
}

# Echo usage to command line
usage()
{
        echo 'Usage:'
        echo '$0 [options] domain'
        echo ''
        echo 'Behaves the same way as pihole -q except it will also search'
        echo 'for any domains which are CNAMES of the supplied domain. (i.e.'
        echo 'it does "deep CNAME inspection")'
        echo ''
        echo 'For available options, see pihole -q --help'
}

# Parse arguments
if [ $# -lt 1 ]; then
        usage
        exit 1
fi
QUERY=${!#}
PHQARGS=${@:1:$#-1} # All but the last argument

# Call 'pihole -q' on the original domain and all cnames
for name in $(get_all_cnames $QUERY $NS); do
        if [ $name = $QUERY ]; then
                echo "Checking $name ..."
        else
                echo "Checking CNAME $name ..."
        fi
        pihole -q $PHQARGS $name
done