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Security fix, CVE-2017-14495, OOM in DNS response creation.

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Fix out-of-memory Dos vulnerability. An attacker which can
send malicious DNS queries to dnsmasq can trigger memory
allocations in the add_pseudoheader function
The allocated memory is never freed which leads to a DoS
through memory exhaustion. dnsmasq is vulnerable only
if one of the following option is specified:
--add-mac, --add-cpe-id or --add-subnet.
This commit is contained in:
Simon Kelley
2017-09-25 20:16:50 +01:00
parent 897c113fda
commit 51eadb692a
2 changed files with 19 additions and 1 deletions
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12
CHANGELOG
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@@ -70,6 +70,18 @@ version 2.78
Credit to Felix Wilhelm, Fermin J. Serna, Gabriel Campana
and Kevin Hamacher of the Google Security Team for
finding this.
Fix out-of-memory Dos vulnerability. An attacker which can
send malicious DNS queries to dnsmasq can trigger memory
allocations in the add_pseudoheader function
The allocated memory is never freed which leads to a DoS
through memory exhaustion. dnsmasq is vulnerable only
if one of the following option is specified:
--add-mac, --add-cpe-id or --add-subnet.
CVE-2017-14495 applies.
Credit to Felix Wilhelm, Fermin J. Serna, Gabriel Campana
and Kevin Hamacher of the Google Security Team for
finding this.
version 2.77

8
src/edns0.c
View File

@@ -192,9 +192,15 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
!(p = skip_section(p,
ntohs(header->ancount) + ntohs(header->nscount) + ntohs(header->arcount),
header, plen)))
{
free(buff);
return plen;
}
if (p + 11 > limit)
return plen; /* Too big */
{
free(buff);
return plen; /* Too big */
}
*p++ = 0; /* empty name */
PUTSHORT(T_OPT, p);
PUTSHORT(udp_sz, p); /* max packet length, 512 if not given in EDNS0 header */