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38 lines
1.2 KiB
Diff
38 lines
1.2 KiB
Diff
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From 38af9b1ac3242a4128e88069c495024caa565f0e Mon Sep 17 00:00:00 2001
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From: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>
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Date: Tue, 29 Aug 2017 12:35:40 +0100
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Subject: [PATCH] forward.c: fix CVE-2017-13704
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Fix SIGSEGV in rfc1035.c answer_request() line 1228 where memset()
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is called with header & limit pointing at the same address and thus
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tries to clear memory from before the buffer begins.
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answer_request() is called with an invalid edns packet size provided by
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the client. Ensure the udp_size provided by the client is bounded by
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512 and configured maximum as per RFC 6891 6.2.3 "Values lower than 512
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MUST be treated as equal to 512"
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The client that exposed the problem provided a payload udp size of 0.
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Signed-off-by: Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk>
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---
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src/forward.c | 2 ++
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1 file changed, 2 insertions(+)
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diff --git a/src/forward.c b/src/forward.c
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index f22556a..62c5a5a 100644
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--- a/src/forward.c
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+++ b/src/forward.c
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@@ -1408,6 +1408,8 @@ void receive_query(struct listener *listen, time_t now)
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defaults to 512 */
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if (udp_size > daemon->edns_pktsz)
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udp_size = daemon->edns_pktsz;
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+ if (udp_size < 512)
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+ udp_size = 512; /* RFC 6891 6.2.3 */
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}
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#ifdef HAVE_AUTH
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--
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2.7.4
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