This adds negative trust anchor support and allows reading trust anchor
data from disk, from files
/etc/systemd/dnssec-trust-anchors.d/*.positive and
/etc/systemd/dnssec-trust-anchros.d/*.negative, as well as the matching
counterparts in /usr/lib and /run.
The positive trust anchor files are more or less compatible to normal
DNS zone files containing DNSKEY and DS RRs. The negative trust anchor
files contain only new-line separated hostnames for which to require no
signing.
By default no trust anchor files are installed, in which case the
compiled-in root domain DS RR is used, as before. As soon as at least
one positive root anchor for the root is defined via trust anchor files
this buil-in DS RR is not added though.
For NXDOMAIN, it is not sufficient to prove that the next-closest
enclosure does not exist, we must also prove that there is no
wildcard domain directly below the closest enclosure which would
synthesise the name that has been requested.
For positive responses, in addition to exact matches, we should
accept wildcard ones. In that case we must first prove that
there is no precise match (i.e., that the closest encounter
is not the record itself) and secondly that the source of
synthesis exists.
Previously, we'd use the same set of identifiers for both, but that's
actually incorrect. It didn't matter much since the only NSEC3 hash
algorithm defined (SHA-1) is mapped to code 1 which is also what it is
encoded as in DS digests, but we really should make sure to use two
distinct enumerations.
We don't implement it, and we have no intention to, but at least mention
that it exists.
(This also adds a couple of other algorithms to the algorithm string
list, where these strings were missing previously.)
When we verified a signature, fix up the RR's TTL to the original TTL
mentioned in the signature, and store the signature expiry information
in the RR, too. Then, use that when adding RRs to the cache.
This renames dns_transaction_stop() to dns_transaction_stop_timeout()
and makes it only about stopping the transaction timeout. This is safe,
as in most occasions we call dns_transaction_stop() at the same time as
dns_transaction_close_connection() anyway, which does the rest of what
dns_transaction_stop() used to do. And in the one where we don't call
it, it's implicitly called by the UDP emission or TCP connection code.
This also closes the connections as we enter the validation phase of a
transaction, so that no further messages may be received then.
This removes dnssec_algorithm_supported() and simply uses the
algorithm_to_gcrypt() result as indication whether a DNSSEC algorithm is
supported.
The patch also renames "algorithm" to "md_algorithm", in a few cases, in
order to avoid confusion between DNSSEC signature algorithms and gcrypt
message digest algorithms.
The name "features" suggests an orthogonal bitmap or suchlike, but the
variables really encode only a linear set of feature levels. The type
used is already called DnsServerFeatureLevel, hence fix up the variables
accordingly, too.
This moves management of the OPT RR out of the scope management and into
the server and packet management. There are now explicit calls for
appending and truncating the OPT RR from a packet
(dns_packet_append_opt() and dns_packet_truncate_opt()) as well as a
call to do the right thing depending on a DnsServer's feature level
(dns_server_adjust_opt()).
This also unifies the code to pick a server between the TCP and UDP code
paths, and makes sure the feature level used for the transaction is
selected at the time the server is picked, and not changed until the
next time we pick a server. The server selction code is now unified in
dns_transaction_pick_server().
This all fixes problems when changing between UDP and TCP communication
for the same server, and makes sure the UDP and TCP codepaths are more
alike. It also makes sure we never keep the UDP port open when switchung
to TCP, so that we don't have to handle incoming datagrams on the latter
we don't expect.
As the new code picks the DNS server at the time we make a connection,
we don't need to invalidate the DNS server anymore when changing to the
next one, thus dns_transaction_next_dns_server() has been removed.
This new call unifies how we shut down all connection resources, such as
UDP sockets, event sources, and TCP stream objects.
This patch just adds the basic hook-up, this function will be used more
in later commits.
On LLMNR we never want to retry stream connections (since local TCP
connections should work, and we don't want to unnecessarily delay
operation), explicitly remember whether we already tried one, instead of
deriving this from a still stored stream object. This way, we can free
the stream early, without forgetting that we tried it.
