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Fix rrfilter bug leading to malformed replies.

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Bug tickled by Nominum upstream when DNSSEC enabled, due to
unusual order of RRs in reply from upstream server.
This commit is contained in:
Simon Kelley
2017-01-26 18:02:54 +00:00
parent 903df07bcb
commit 0740e43e20
2 changed files with 17 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
CHANGELOG
View File

@@ -1,6 +1,6 @@
version 2.77
Generate an error when configured with a CNAME loop,
rather than a crash. Thnaks to George Metz for
rather than a crash. Thanks to George Metz for
spotting this problem.
Calculate the length of TFTP error reply packet
@@ -51,6 +51,13 @@ version 2.77
Add DNSMASQ_REQUESTED_OPTIONS environment variable to the
lease-change script. Thanks to ZHAO Yu for the patch.
Fix foobar in rrfilter code, that could cause misformed
replies, especially when DNSSEC validation on, and
the upstream server returns answer with the RRs in a
particular order. The only DNS server known to tickle
this is Nominum's. Thanks to Dave Täht for spotting the
bug and assisting in the fix.
version 2.76
Include 0.0.0.0/8 in DNS rebind checks. This range

18
src/rrfilter.c
View File

@@ -239,7 +239,15 @@ size_t rrfilter(struct dns_header *header, size_t plen, int mode)
if (!check_rrs(p, header, plen, 0, rrs, rr_found))
return plen;
/* Third pass, elide records */
/* Third pass, actually fix up pointers in the records */
p = (unsigned char *)(header+1);
check_name(&p, header, plen, 1, rrs, rr_found);
p += 4; /* qclass, qtype */
check_rrs(p, header, plen, 1, rrs, rr_found);
/* Fouth pass, elide records */
for (p = rrs[0], i = 1; i < rr_found; i += 2)
{
unsigned char *start = rrs[i];
@@ -254,14 +262,6 @@ size_t rrfilter(struct dns_header *header, size_t plen, int mode)
header->nscount = htons(ntohs(header->nscount) - chop_ns);
header->arcount = htons(ntohs(header->arcount) - chop_ar);
/* Fourth pass, fix up pointers in the remaining records */
p = (unsigned char *)(header+1);
check_name(&p, header, plen, 1, rrs, rr_found);
p += 4; /* qclass, qtype */
check_rrs(p, header, plen, 1, rrs, rr_found);
return plen;
}