resolved: explicitly handle case when the trust anchor is empty

Since we honour RFC5011 revoked keys it might happen we end up with an
empty trust anchor, or one where there's no entry for the root left.
With this patch the logic is changed what to do in this case.

Before this patch we'd end up requesting the root DS, which returns with
NODATA but a signed NSEC we cannot verify, since the trust anchor is
empty after all. Thus we'd return a DNSSEC result of "missing-key", as
we lack a verified version of the key.

With this patch in place, look-ups for the root DS are explicitly
recognized, and not passed on to the DNS servers. Instead, if
downgrade-ok mode is on an unsigned NODATA response is synthesized, so
that the validator code continues under the assumption the root zone was
unsigned. If downgrade-ok mode is off a new transaction failure is
generated, that makes this case recognizable.

diff --git a/src/libelogind/sd-bus/bus-common-errors.h b/src/libelogind/sd-bus/bus-common-errors.h
index 46f3877d013fb811d8e2f796ecd3d27876e5df7a..9e49725843dba547c02d6b28a628d593e590c788 100644 (file)
--- a/src/libelogind/sd-bus/bus-common-errors.h
+++ b/src/libelogind/sd-bus/bus-common-errors.h
@@ -75,6 +75,7 @@
 #define BUS_ERROR_CONNECTION_FAILURE "org.freedesktop.resolve1.ConnectionFailure"
 #define BUS_ERROR_NO_SUCH_SERVICE "org.freedesktop.resolve1.NoSuchService"
 #define BUS_ERROR_DNSSEC_FAILED "org.freedesktop.resolve1.DnssecFailed"
+#define BUS_ERROR_NO_TRUST_ANCHOR "org.freedesktop.resolve1.NoTrustAnchor"
 #define _BUS_ERROR_DNS "org.freedesktop.resolve1.DnsError."
 
 #define BUS_ERROR_NO_SUCH_TRANSFER "org.freedesktop.import1.NoSuchTransfer"