CVE-2017-12999/IS-IS: Add a missing length check.

This fixes a buffer over-read discovered by Forcepoint's security
researchers Otto Airamo & Antti Levomäki.

Add tests using the capture files supplied by the reporter(s).

diff --git a/print-isoclns.c b/print-isoclns.c
index 95339a0adc0ca5d48a2847553fab33beefe8ce39..9d66d0f7bb047968333f108683408660007a790c 100644 (file)
--- a/print-isoclns.c
+++ b/print-isoclns.c
@@ -2532,6 +2532,7 @@ isis_print(netdissect_options *ndo,
            ND_TCHECK2(*tptr, 1);
            alen = *tptr++;
            while (tmp && alen < tmp) {
+               N