From b04cb88462863d762093760ffcfe1946200e30f5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Thu, 7 Jan 2021 10:44:46 +0100
Subject: [PATCH] Fix off-by-one bug in ISC SPNEGO implementation

The ISC SPNEGO implementation is based on mod_auth_kerb code.  When
CVE-2006-5989 was disclosed, the relevant fix was not applied to the
BIND 9 codebase, making the latter vulnerable to the aforementioned flaw
when "tkey-gssapi-keytab" or "tkey-gssapi-credential" is set in
named.conf.

The original description of CVE-2006-5989 was:

    Off-by-one error in the der_get_oid function in mod_auth_kerb 5.0
    allows remote attackers to cause a denial of service (crash) via a
    crafted Kerberos message that triggers a heap-based buffer overflow
    in the component array.

Later research revealed that this flaw also theoretically enables remote
code execution, though achieving the latter in real-world conditions is
currently deemed very difficult.

This vulnerability was responsibly reported as ZDI-CAN-12302 ("ISC BIND
TKEY Query Heap-based Buffer Overflow Remote Code Execution
Vulnerability") by Trend Micro Zero Day Initiative.
---
 lib/dns/spnego.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dns/spnego.c b/lib/dns/spnego.c
index e61d1c600f..753dc8049f 100644
--- a/lib/dns/spnego.c
+++ b/lib/dns/spnego.c
@@ -848,7 +848,7 @@ der_get_oid(const unsigned char *p, size_t len, oid *data, size_t *size) {
 		return (ASN1_OVERRUN);
 	}
 
-	data->components = malloc(len * sizeof(*data->components));
+	data->components = malloc((len + 1) * sizeof(*data->components));
 	if (data->components == NULL) {
 		return (ENOMEM);
 	}
-- 
2.26.2