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From f2ad2cecb55825f7e4409222de1688b9ceebceda 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 20:16:50 +0100
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Subject: [PATCH 6/9] Security fix, CVE-2017-14495, OOM in DNS response
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creation.
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Fix out-of-memory Dos vulnerability. An attacker which can
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send malicious DNS queries to dnsmasq can trigger memory
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allocations in the add_pseudoheader function
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The allocated memory is never freed which leads to a DoS
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through memory exhaustion. dnsmasq is vulnerable only
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if one of the following option is specified:
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--add-mac, --add-cpe-id or --add-subnet.
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---
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src/edns0.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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diff --git a/src/edns0.c b/src/edns0.c
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index eed135e..5bdc133 100644
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--- a/src/edns0.c
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+++ b/src/edns0.c
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@@ -192,9 +192,15 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
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!(p = skip_section(p,
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ntohs(header->ancount) + ntohs(header->nscount) + ntohs(header->arcount),
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header, plen)))
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+ {
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+ free(buff);
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return plen;
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+ }
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if (p + 11 > limit)
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- return plen; /* Too big */
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+ {
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+ free(buff);
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+ return plen; /* Too big */
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+ }
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*p++ = 0; /* empty name */
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PUTSHORT(T_OPT, p);
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PUTSHORT(udp_sz, p); /* max packet length, 512 if not given in EDNS0 header */
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--
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2.9.5
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