bin/get_catalog: use dnspython

1 files changed, 54 insertions, 41 deletions

diff --git a/bin/get_catalog b/bin/get_catalog
index d9e744b..772d5b4 100755
--- a/bin/get_catalog
+++ b/bin/get_catalog
@@ -1,41 +1,54 @@
-#! /bin/sh
-#
-# Fetch the catalog zone '$1' from the server '$2' and print a list of zones.
-
-set -e
-
-catalog="$1"
-server="$2"
-
-tempfile="$(mktemp -t catalog)"
-trap 'rm $tempfile' 0
-
-if ! dig "$catalog" axfr @"$server" +noall +answer >"$tempfile"; then
-	printf >&2 '%s: query failed\n' "$0"
-	exit 1
-fi
-
-# Make sure the result has an SOA, otherwise the query failed.
-if ! awk <"$tempfile" "
-BEGIN {
-	exitcode=1
-}
-
-\$1 == \"$catalog.\" && \$4 == \"SOA\" {
-	exitcode=0
-}
-
-END {
-	exit exitcode
-}
-"; then
-	printf >&2 '%s: no SOA found in zone; transfer failed?\n' "$0"
-	exit 1
-fi
-
-awk <"$tempfile" "
-\$1 ~ /zones.$catalog/ && \$4 == \"PTR\" {
-	zone = \$5
-	sub(/\\.$/, \"\", zone)
-	print zone
-}"
+#! /usr/bin/env python3
+# vim:set noet sw=8 ts=8 sts=8:
+
+import sys, socket
+import dns.query
+import dns.zone
+import dns.rdatatype
+
+def resolve(hostname):
+	try:
+		addrs = socket.getaddrinfo(
+				hostname, 53, proto=socket.IPPROTO_UDP)
+		return list(dict.fromkeys([addr[4][0] for addr in addrs]))
+	except Exception as e:
+		raise (Exception(f"resolving {hostname}: {e}"))
+
+def axfr(zone, hostname):
+	addrs = resolve(hostname)
+	last_exc = None
+
+	for addr in addrs:
+		try:
+			return dns.zone.from_xfr(dns.query.xfr(addr, zone))
+		except Exception as e:
+			last_exc = e
+	raise (Exception(str(last_exc)))
+
+def print_catalog(zone):
+	for name, node in zone.nodes.items():
+		for rdata in node.rdatasets:
+			if rdata.rdtype == dns.rdatatype.PTR:
+				for ptr in rdata:
+					print(str(ptr.target).rstrip('.'))
+
+
+def main():
+	if len(sys.argv) != 3:
+		print(f"Usage: {sys.argv[0]} <zone> <server>")
+		return 1
+
+	zone_name = sys.argv[1]
+	server = sys.argv[2]
+
+	try:
+		zone = axfr(zone_name, server)
+		print_catalog(zone)
+	except Exception as e:
+		print(f"Zone transfer failed: {e}")
+		return 1
+
+	return 0
+
+if __name__ == "__main__":
+	sys.exit(main())