resolved: partially implement RFC5011 Trust Anchor support

With this patch resolved will properly handle revoked keys, but not
augment the locally configured trust anchor database with newly learned
keys.

Specifically, resolved now refuses validating RRsets with
revoked keys, and it will remove revoked keys from the configured trust
anchors (only until reboot).

This patch does not add logic for adding new keys to the set of trust
anchors. This is a deliberate decision as this only can work with
persistent disk storage, and would result in a different update logic
for stateful and stateless systems.  Since we have to support stateless
systems anyway, and don't want to encourage two independent upgrade
paths we focus on upgrading the trust anchor database via the usual OS
upgrade logic.

Whenever a trust anchor entry is found revoked and removed from the
trust anchor a recognizable log message is written, encouraging the user
to update the trust anchor or update his operating system.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/resolve/resolved-dns-answer.h b/src/resolve/resolved-dns-answer.h
index 28ded3b252..715e487d94 100644
--- a/src/resolve/resolved-dns-answer.h
+++ b/src/resolve/resolved-dns-answer.h
@@ -77,6 +77,8 @@ int dns_answer_reserve(DnsAnswer **a, unsigned n_free);
 int dns_answer_reserve_or_clone(DnsAnswer **a, unsigned n_free);
 
 int dns_answer_remove_by_key(DnsAnswer **a, const DnsResourceKey *key);
+int dns_answer_remove_by_rr(DnsAnswer **a, DnsResourceRecord *rr);
+
 int dns_answer_copy_by_key(DnsAnswer **a, DnsAnswer *source, const DnsResourceKey *key, DnsAnswerFlags or_flags);
 int dns_answer_move_by_key(DnsAnswer **to, DnsAnswer **from, const DnsResourceKey *key, DnsAnswerFlags or_flags);