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From a997ca0da044719a0ce8a232d14da8b30022592b Mon Sep 17 00:00:00 2001
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From: Simon Kelley <simon@thekelleys.org.uk>
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Date: Fri, 29 Jun 2018 14:39:41 +0100
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Subject: [PATCH] Fix sometimes missing DNSSEC RRs when DNSSEC validation not
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enabled.
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Dnsmasq does pass on the do-bit, and return DNSSEC RRs, irrespective
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of of having DNSSEC validation compiled in or enabled.
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The thing to understand here is that the cache does not store all the
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DNSSEC RRs, and dnsmasq doesn't have the (very complex) logic required
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to determine the set of DNSSEC RRs required in an answer. Therefore if
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the client wants the DNSSEC RRs, the query can not be answered from
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the cache. When DNSSEC validation is enabled, any query with the
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do-bit set is never answered from the cache, unless the domain is
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known not to be signed: the query is always forwarded. This ensures
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that the DNSEC RRs are included.
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The same thing should be true when DNSSEC validation is not enabled,
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but there's a bug in the logic.
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line 1666 of src/rfc1035.c looks like this
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if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) || !do_bit || !(crecp->flags & F_DNSSECOK))
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{ ...answer from cache ... }
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So local stuff (hosts, DHCP, ) get answered. If the do_bit is not set
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then the query is answered, and if the domain is known not to be
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signed, the query is answered.
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Unfortunately, if DNSSEC validation is not turned on then the
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F_DNSSECOK bit is not valid, and it's always zero, so the question
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always gets answered from the cache, even when the do-bit is set.
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This code should look like that at line 1468, dealing with PTR queries
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if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) ||
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!do_bit ||
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(option_bool(OPT_DNSSEC_VALID) && !(crecp->flags & F_DNSSECOK)))
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where the F_DNSSECOK bit is only used when validation is enabled.
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---
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src/rfc1035.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/src/rfc1035.c b/src/rfc1035.c
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index ebb1f36..580f5ef 100644
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--- a/src/rfc1035.c
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+++ b/src/rfc1035.c
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@@ -1663,7 +1663,9 @@ size_t answer_request(struct dns_header *header, char *limit, size_t qlen,
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}
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/* If the client asked for DNSSEC don't use cached data. */
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- if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) || !do_bit || !(crecp->flags & F_DNSSECOK))
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+ if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) ||
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+ !do_bit ||
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+ (option_bool(OPT_DNSSEC_VALID) && !(crecp->flags & F_DNSSECOK)))
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do
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{
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/* don't answer wildcard queries with data not from /etc/hosts
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@@ -1747,7 +1749,7 @@ size_t answer_request(struct dns_header *header, char *limit, size_t qlen,
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{
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if ((crecp = cache_find_by_name(NULL, name, now, F_CNAME | (dryrun ? F_NO_RR : 0))) &&
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(qtype == T_CNAME || (crecp->flags & F_CONFIG)) &&
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- ((crecp->flags & F_CONFIG) || !do_bit || !(crecp->flags & F_DNSSECOK)))
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+ ((crecp->flags & F_CONFIG) || !do_bit || (option_bool(OPT_DNSSEC_VALID) && !(crecp->flags & F_DNSSECOK))))
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{
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if (!(crecp->flags & F_DNSSECOK))
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sec_data = 0;
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--
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2.14.4
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