debvm-waitssh: error out if port number is not a positive integer

1 files changed, 13 insertions, 0 deletions

diff --git a/debvm-waitssh b/debvm-waitssh
index bde1a93..a35c783 100755
--- a/debvm-waitssh
+++ b/debvm-waitssh
@@ -142,6 +142,19 @@ case "$1" in
 	;;
 esac
 
+# Guard against strings containing anything but digits, strings starting with
+# zero and empty strings as the port number.
+#
+# We cannot use [!0-9] because that matches on any character (or possibly
+# multi-character collation element) that sorts in between 0 and 9.
+case "$PORT" in *[!0123456789]*|0?*|""|??????*)
+	if [ "$VERBOSITY" -ge 1 ]; then
+		echo "$0: port '$PORT' is not a positive integer between 1 and 99999" >&2
+	fi
+	exit 1
+	;;
+esac
+
 now=$(date +%s)
 deadline=$((now + TOTALTIMEOUT))
 while test "$now" -lt "$deadline"; do