resolved: add support NSEC3 proofs, as well as proofs for domains that are OK to be unsigned

This large patch adds a couple of mechanisms to ensure we get NSEC3 and
proof-of-unsigned support into place. Specifically:

- Each item in an DnsAnswer gets two bit flags now:
  DNS_ANSWER_AUTHENTICATED and DNS_ANSWER_CACHEABLE. The former is
  necessary since DNS responses might contain signed as well as unsigned
  RRsets in one, and we need to remember which ones are signed and which
  ones aren't. The latter is necessary, since not we need to keep track
  which RRsets may be cached and which ones may not be, even while
  manipulating DnsAnswer objects.

- The .n_answer_cachable of DnsTransaction is dropped now (it used to
  store how many of the first DnsAnswer entries are cachable), and
  replaced by the DNS_ANSWER_CACHABLE flag instead.

- NSEC3 proofs are implemented now (lacking support for the wildcard
  part, to be added in a later commit).

- Support for the "AD" bit has been dropped. It's unsafe, and now that
  we have end-to-end authentication we don't need it anymore.

- An auxiliary DnsTransaction of a DnsTransactions is now kept around as
  least as long as the latter stays around. We no longer remove the
  auxiliary DnsTransaction as soon as it completed. THis is necessary,
  as we now are interested not only in the RRsets it acquired but also
  in its authentication status.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/resolve/resolved-dns-dnssec.h b/src/resolve/resolved-dns-dnssec.h
index 442e301302..d17d5142f5 100644
--- a/src/resolve/resolved-dns-dnssec.h
+++ b/src/resolve/resolved-dns-dnssec.h
@@ -32,9 +32,6 @@ enum DnssecMode {
         /* No DNSSEC validation is done */
         DNSSEC_NO,
 
-        /* Trust the AD bit sent by the server. UNSAFE! */
-        DNSSEC_TRUST,
-
         /* Validate locally, if the server knows DO, but if not, don't. Don't trust the AD bit */
         DNSSEC_YES,
 
@@ -67,7 +64,7 @@ enum DnssecResult {
 #define DNSSEC_HASH_SIZE_MAX (MAX(20, 32))
 
 int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey);
-int dnssec_key_match_rrsig(DnsResourceKey *key, DnsResourceRecord *rrsig);
+int dnssec_key_match_rrsig(const DnsResourceKey *key, DnsResourceRecord *rrsig);
 
 int dnssec_verify_rrset(DnsAnswer *answer, DnsResourceKey *key, DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, usec_t realtime, DnssecResult *result);
 int dnssec_verify_rrset_search(DnsAnswer *answer, DnsResourceKey *key, DnsAnswer *validated_dnskeys, usec_t realtime, DnssecResult *result);
@@ -75,6 +72,8 @@ int dnssec_verify_rrset_search(DnsAnswer *answer, DnsResourceKey *key, DnsAnswer
 int dnssec_verify_dnskey(DnsResourceRecord *dnskey, DnsResourceRecord *ds);
 int dnssec_verify_dnskey_search(DnsResourceRecord *dnskey, DnsAnswer *validated_ds);
 
+int dnssec_has_rrsig(DnsAnswer *a, const DnsResourceKey *key);
+
 uint16_t dnssec_keytag(DnsResourceRecord *dnskey);
 
 int dnssec_canonicalize(const char *n, char *buffer, size_t buffer_max);
@@ -83,9 +82,11 @@ int dnssec_nsec3_hash(DnsResourceRecord *nsec3, const char *name, void *ret);
 
 typedef enum DnssecNsecResult {
         DNSSEC_NSEC_NO_RR,     /* No suitable NSEC/NSEC3 RR found */
+        DNSSEC_NSEC_UNSUPPORTED_ALGORITHM,
         DNSSEC_NSEC_NXDOMAIN,
         DNSSEC_NSEC_NODATA,
         DNSSEC_NSEC_FOUND,
+        DNSSEC_NSEC_OPTOUT,
 } DnssecNsecResult;
 
 int dnssec_test_nsec(DnsAnswer *answer, DnsResourceKey *key, DnssecNsecResult *result);