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From 5086b12a4b1269d1576b5bab01f72c6fa19c55bc Mon Sep 17 00:00:00 2001
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From: Simon Kelley <simon@thekelleys.org.uk>
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Date: Mon, 25 Sep 2017 18:52:50 +0100
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Subject: [PATCH 3/9]     Security fix, CVE-2017-14493, DHCPv6 - Stack buffer
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 overflow.
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    Fix stack overflow in DHCPv6 code. An attacker who can send
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    a DHCPv6 request to dnsmasq can overflow the stack frame and
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    crash or control dnsmasq.
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---
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 src/rfc3315.c | 3 +++
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 1 file changed, 3 insertions(+)
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diff --git a/src/rfc3315.c b/src/rfc3315.c
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index 73bdee4..8d18a28 100644
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--- a/src/rfc3315.c
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+++ b/src/rfc3315.c
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@@ -206,6 +206,9 @@ static int dhcp6_maybe_relay(struct state *state, void *inbuff, size_t sz,
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   /* RFC-6939 */
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   if ((opt = opt6_find(opts, end, OPTION6_CLIENT_MAC, 3)))
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     {
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+      if (opt6_len(opt) - 2 > DHCP_CHADDR_MAX) {
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+        return 0;
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+      }
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       state->mac_type = opt6_uint(opt, 0, 2);
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       state->mac_len = opt6_len(opt) - 2;
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       memcpy(&state->mac[0], opt6_ptr(opt, 2), state->mac_len);
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-- 
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2.9.5
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