From 3d4ff1ba8419546490b464418223132529514033 Mon Sep 17 00:00:00 2001

From: Simon Kelley <simon@thekelleys.org.uk>

Date: Mon, 25 Sep 2017 18:52:50 +0100

Subject: [PATCH 4/9] Security fix, CVE-2017-14493, DHCPv6 - Stack buffer

 overflow.

Fix stack overflow in DHCPv6 code. An attacker who can send

a DHCPv6 request to dnsmasq can overflow the stack frame and

crash or control dnsmasq.

---

 src/rfc3315.c | 3 +++

 1 file changed, 3 insertions(+)

diff --git a/src/rfc3315.c b/src/rfc3315.c

index 1687931..920907c 100644

--- a/src/rfc3315.c

+++ b/src/rfc3315.c

@@ -206,6 +206,9 @@ static int dhcp6_maybe_relay(struct state *state, void *inbuff, size_t sz,

   /* RFC-6939 */

   if ((opt = opt6_find(opts, end, OPTION6_CLIENT_MAC, 3)))

     {

+      if (opt6_len(opt) - 2 > DHCP_CHADDR_MAX) {

+        return 0;

+      }

       state->mac_type = opt6_uint(opt, 0, 2);

       state->mac_len = opt6_len(opt) - 2;

       memcpy(&state->mac[0], opt6_ptr(opt, 2), state->mac_len);

-- 

2.9.5