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, 47 insertions, 8 deletions

diff --git a/src/resolve/resolved-dns-answer.h b/src/resolve/resolved-dns-answer.h
index 56b462ed7e..569f283d03 100644
--- a/src/resolve/resolved-dns-answer.h
+++ b/src/resolve/resolved-dns-answer.h
@@ -32,11 +32,17 @@ typedef struct DnsAnswerItem DnsAnswerItem;
  * can qualify A and AAAA RRs referring to a local link with the
  * right ifindex.
  *
- * Note that we usually encode the empty answer as a simple NULL. */
+ * Note that we usually encode the the empty DnsAnswer object as a simple NULL. */
+
+typedef enum DnsAnswerFlags {
+        DNS_ANSWER_AUTHENTICATED = 1,
+        DNS_ANSWER_CACHEABLE     = 2,
+} DnsAnswerFlags;
 
 struct DnsAnswerItem {
         DnsResourceRecord *rr;
         int ifindex;
+        DnsAnswerFlags flags;
 };
 
 struct DnsAnswer {
@@ -49,15 +55,17 @@ DnsAnswer *dns_answer_new(unsigned n);
 DnsAnswer *dns_answer_ref(DnsAnswer *a);
 DnsAnswer *dns_answer_unref(DnsAnswer *a);
 
-int dns_answer_add(DnsAnswer *a, DnsResourceRecord *rr, int ifindex);
-int dns_answer_add_extend(DnsAnswer **a, DnsResourceRecord *rr, int ifindex);
+int dns_answer_add(DnsAnswer *a, DnsResourceRecord *rr, int ifindex, DnsAnswerFlags flags);
+int dns_answer_add_extend(DnsAnswer **a, DnsResourceRecord *rr, int ifindex, DnsAnswerFlags flags);
 int dns_answer_add_soa(DnsAnswer *a, const char *name, uint32_t ttl);
 
-int dns_answer_match_key(DnsAnswer *a, const DnsResourceKey *key);
-int dns_answer_contains_rr(DnsAnswer *a, DnsResourceRecord *rr);
+int dns_answer_match_key(DnsAnswer *a, const DnsResourceKey *key, DnsAnswerFlags *combined_flags);
+int dns_answer_contains_rr(DnsAnswer *a, DnsResourceRecord *rr, DnsAnswerFlags *combined_flags);
+int dns_answer_contains_key(DnsAnswer *a, const DnsResourceKey *key, DnsAnswerFlags *combined_flags);
+int dns_answer_contains_nsec_or_nsec3(DnsAnswer *a);
 
 int dns_answer_find_soa(DnsAnswer *a, const DnsResourceKey *key, DnsResourceRecord **ret);
-int dns_answer_find_cname_or_dname(DnsAnswer *a, const DnsResourceKey *key, DnsResourceRecord **ret);
+int dns_answer_find_cname_or_dname(DnsAnswer *a, const DnsResourceKey *key, DnsResourceRecord **ret, DnsAnswerFlags *flags);
 
 int dns_answer_merge(DnsAnswer *a, DnsAnswer *b, DnsAnswer **ret);
 int dns_answer_extend(DnsAnswer **a, DnsAnswer *b);
@@ -68,7 +76,8 @@ 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_copy_by_key(DnsAnswer **a, DnsAnswer *source, const DnsResourceKey *key);
+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);
 
 static inline unsigned dns_answer_size(DnsAnswer *a) {
         return a ? a->n_rrs : 0;
@@ -93,6 +102,36 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(DnsAnswer*, dns_answer_unref);
                                 0;                                      \
                         });                                             \
              (a) && (UNIQ_T(i, q) < (a)->n_rrs);                        \
-             UNIQ_T(i, q)++, (kk) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].rr : NULL), (ifi) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].ifindex : 0))
+             UNIQ_T(i, q)++,                                            \
+                     (kk) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].rr : NULL), \
+                     (ifi) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].ifindex : 0))
 
 #define DNS_ANSWER_FOREACH_IFINDEX(kk, ifindex, a) _DNS_ANSWER_FOREACH_IFINDEX(UNIQ, kk, ifindex, a)
+
+#define _DNS_ANSWER_FOREACH_FLAGS(q, kk, fl, a)                         \
+        for (unsigned UNIQ_T(i, q) = ({                                 \
+                                (kk) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].rr : NULL; \
+                                (fl) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].flags : 0; \
+                                0;                                      \
+                        });                                             \
+             (a) && (UNIQ_T(i, q) < (a)->n_rrs);                        \
+             UNIQ_T(i, q)++,                                            \
+                     (kk) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].rr : NULL), \
+                     (fl) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].flags : 0))
+
+#define DNS_ANSWER_FOREACH_FLAGS(kk, flags, a) _DNS_ANSWER_FOREACH_FLAGS(UNIQ, kk, flags, a)
+
+#define _DNS_ANSWER_FOREACH_FULL(q, kk, ifi, fl, a)                     \
+        for (unsigned UNIQ_T(i, q) = ({                                 \
+                                (kk) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].rr : NULL; \
+                                (ifi) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].ifindex : 0; \
+                                (fl) = ((a) && (a)->n_rrs > 0) ? (a)->items[0].flags : 0; \
+                                0;                                      \
+                        });                                             \
+             (a) && (UNIQ_T(i, q) < (a)->n_rrs);                        \
+             UNIQ_T(i, q)++,                                            \
+                     (kk) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].rr : NULL), \
+                     (ifi) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].ifindex : 0), \
+                     (fl) = ((UNIQ_T(i, q) < (a)->n_rrs) ? (a)->items[UNIQ_T(i, q)].flags : 0))
+
+#define DNS_ANSWER_FOREACH_FULL(kk, ifindex, flags, a) _DNS_ANSWER_FOREACH_FULL(UNIQ, kk, ifindex, flags, a)