Dnsmasq does pass on the do-bit, and return DNSSEC RRs, irrespective
of of having DNSSEC validation compiled in or enabled.
The thing to understand here is that the cache does not store all the
DNSSEC RRs, and dnsmasq doesn't have the (very complex) logic required
to determine the set of DNSSEC RRs required in an answer. Therefore if
the client wants the DNSSEC RRs, the query can not be answered from
the cache. When DNSSEC validation is enabled, any query with the
do-bit set is never answered from the cache, unless the domain is
known not to be signed: the query is always forwarded. This ensures
that the DNSEC RRs are included.
The same thing should be true when DNSSEC validation is not enabled,
but there's a bug in the logic.
line 1666 of src/rfc1035.c looks like this
if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) || !do_bit || !(crecp->flags & F_DNSSECOK))
{ ...answer from cache ... }
So local stuff (hosts, DHCP, ) get answered. If the do_bit is not set
then the query is answered, and if the domain is known not to be
signed, the query is answered.
Unfortunately, if DNSSEC validation is not turned on then the
F_DNSSECOK bit is not valid, and it's always zero, so the question
always gets answered from the cache, even when the do-bit is set.
This code should look like that at line 1468, dealing with PTR queries
if ((crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG)) ||
!do_bit ||
(option_bool(OPT_DNSSEC_VALID) && !(crecp->flags & F_DNSSECOK)))
where the F_DNSSECOK bit is only used when validation is enabled.
I noticed that dnsmasq often wasn't sending any unsolicited RAs for me.
This turned out to happen when the interface (a bridge interface) wasn't
created yet at the time dnsmasq started. When dnsmasq is started after
the interface is created, it sends RAs as expected. I assume this also
extends to other types of virtual interfaces that are created after
dnsmasq starts.
Digging into the source, it seems to be caused by a missing call to
ra_start_unsolicited for non-template contexts in construct_worker from
src/dhcp6.c. The attached patch adds that call, but only if the
interface index or address changed to prevent doing fast RAs for no reason.
I tested it on my own server and it appears to work as expected. When
the interface is created and configured, dnsmasq does fast RAs for a
while and then settles into slow RAs.
If we're talking to upstream servers from a fixed port, specified by query-port
we create the fds to do this once, before dropping root, so that ports <1024 can be used.
But we call check_servers() before reading /etc/resolv.conf, so if the only servers
are in resolv.conf, at that point there will be no servers, and the fds get garbage
collected away, only to be recreated (but without root) after we read /etc/resolv.conf
Make pre-allocated server fds immortal, to avoid this problem.
If query-port is set, we create sockets bound to the wildcard address and the query port for
IPv4 and IPv6, but the IPv6 one fails, because is covers IPv4 as well, and an IPv4 socket
already exists (it gets created first). Set V6ONLY to avoid this.
I got reported bug in Fedora [1], that cname is broken in new releases.
At first I though this was false report, but there is still new
regression in cname handling.
Before, it accepted alias with trailing dot. Not it would accept only
target, but not alias.
cname=alias.,target
is no longer valid. The issue is it will count size to skip after
canonicalize. If that ignores trailing dot, next name would be "". And
that is invalid and refused, dnsmasq refuses to start.
I also think that any whitespace like tab should be possible after
comma. So this fixes also 30858e3b9b.
The way of accessing the list of available hashes on nettle was
vulnerable to breaking if the version of libnettle in use was
different to the version dnsmasq was compiled against.
Change to a new system if libnettle >= 3.4 is in use.
Older versions if nettle are still OK, once 3.4 is reached,
the ABi problem is fixed. Thanks to Petr Menšík for clues on this.
Use strlen to determine the length of the filename returned by
inotify, as in->len refers to the length of the buffer containing
the name, not the length of the name itself.
http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2018q1/011950.html
Signed-off-by: Andy Hawkins <andy@gently.org.uk>
Patch further modified by simon@thekelleys.org to avoid
out-of-bounds array access with an empty string, call strlen once,
and reverse order of filename verifcation and resolv-file test.
It's OK for NSEC records to be expanded from wildcards,
but in that case, the proof of non-existence is only valid
starting at the wildcard name, *.<domain> NOT the name expanded
from the wildcard. Without this check it's possible for an
attacker to craft an NSEC which wrongly proves non-existence
in a domain which includes a wildcard for NSEC.
RFC 4034 says:
[RFC2181] specifies that an RRset is not allowed to contain duplicate
records (multiple RRs with the same owner name, class, type, and
RDATA). Therefore, if an implementation detects duplicate RRs when
putting the RRset in canonical form, it MUST treat this as a protocol
error. If the implementation chooses to handle this protocol error
in the spirit of the robustness principle (being liberal in what it
accepts), it MUST remove all but one of the duplicate RR(s) for the
purposes of calculating the canonical form of the RRset.
We chose to handle this robustly, having found at least one recursive
server in the wild which returns duplicate NSEC records in the AUTHORITY
section of an answer generated from a wildcard record. sort_rrset() is
therefore modified to delete duplicate RRs which are detected almost
for free during the bubble-sort process.
Thanks to Toralf Förster for helping to diagnose this problem.
