4 files changed, 57 insertions, 3 deletions
diff --git a/src/resolve/resolved-dns-cache.c b/src/resolve/resolved-dns-cache.c
index 49d5090d36..413e1080d9 100644
--- a/src/resolve/resolved-dns-cache.c
+++ b/src/resolve/resolved-dns-cache.c
@@ -272,6 +272,30 @@ static DnsCacheItem* dns_cache_get(DnsCache *c, DnsResourceRecord *rr) {
         return NULL;
 }
 
+static usec_t calculate_until(DnsResourceRecord *rr, usec_t timestamp) {
+        usec_t ttl;
+
+        assert(rr);
+
+        ttl = rr->ttl * USEC_PER_SEC;
+
+        if (ttl > CACHE_TTL_MAX_USEC)
+                ttl = CACHE_TTL_MAX_USEC;
+
+        if (rr->expiry != USEC_INFINITY) {
+                usec_t left;
+
+                /* Make use of the DNSSEC RRSIG expiry info, if we have it */
+
+                left = LESS_BY(rr->expiry, now(CLOCK_REALTIME));
+
+                if (ttl > left)
+                        ttl = left;
+        }
+
+        return timestamp + ttl;
+}
+
 static void dns_cache_item_update_positive(
                 DnsCache *c,
                 DnsCacheItem *i,
@@ -302,7 +326,7 @@ static void dns_cache_item_update_positive(
         dns_resource_key_unref(i->key);
         i->key = dns_resource_key_ref(rr->key);
 
-        i->until = timestamp + MIN(rr->ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);
+        i->until = calculate_until(rr, timestamp);
         i->authenticated = authenticated;
         i->shared_owner = shared_owner;
 
@@ -383,7 +407,7 @@ static int dns_cache_put_positive(
         i->type = DNS_CACHE_POSITIVE;
         i->key = dns_resource_key_ref(rr->key);
         i->rr = dns_resource_record_ref(rr);
-        i->until = timestamp + MIN(i->rr->ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);
+        i->until = calculate_until(rr, timestamp);
         i->authenticated = authenticated;
         i->shared_owner = shared_owner;
         i->owner_family = owner_family;
diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c
index 57093ad80c..94543fef3a 100644
--- a/src/resolve/resolved-dns-dnssec.c
+++ b/src/resolve/resolved-dns-dnssec.c
@@ -701,6 +701,30 @@ int dnssec_key_match_rrsig(const DnsResourceKey *key, DnsResourceRecord *rrsig)
         return dns_name_equal(DNS_RESOURCE_KEY_NAME(rrsig->key), DNS_RESOURCE_KEY_NAME(key));
 }
 
+static int dnssec_fix_rrset_ttl(DnsAnswer *a, const DnsResourceKey *key, DnsResourceRecord *rrsig, usec_t realtime) {
+        DnsResourceRecord *rr;
+        int r;
+
+        assert(key);
+        assert(rrsig);
+
+        DNS_ANSWER_FOREACH(rr, a) {
+                r = dns_resource_key_equal(key, rr->key);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                /* Pick the TTL as the minimum of the RR's TTL, the
+                 * RR's original TTL according to the RRSIG and the
+                 * RRSIG's own TTL, see RFC 4035, Section 5.3.3 */
+                rr->ttl = MIN3(rr->ttl, rrsig->rrsig.original_ttl, rrsig->ttl);
+                rr->expiry = rrsig->rrsig.expiration * USEC_PER_SEC;
+        }
+
+        return 0;
+}
+
 int dnssec_verify_rrset_search(
                 DnsAnswer *a,
                 DnsResourceKey *key,
@@ -767,7 +791,11 @@ int dnssec_verify_rrset_search(
 
                         case DNSSEC_VALIDATED:
                                 /* Yay, the RR has been validated,
-                                 * return immediately. */
+                                 * return immediately, but fix up the expiry */
+                                r = dnssec_fix_rrset_ttl(a, key, rrsig, realtime);
+                                if (r < 0)
+                                        return r;
+
                                 *result = DNSSEC_VALIDATED;
                                 return 0;
 
diff --git a/src/resolve/resolved-dns-rr.c b/src/resolve/resolved-dns-rr.c
index 04d442bf03..d479de7125 100644
--- a/src/resolve/resolved-dns-rr.c
+++ b/src/resolve/resolved-dns-rr.c
@@ -339,6 +339,7 @@ DnsResourceRecord* dns_resource_record_new(DnsResourceKey *key) {
 
         rr->n_ref = 1;
         rr->key = dns_resource_key_ref(key);
+        rr->expiry = USEC_INFINITY;
 
         return rr;
 }
diff --git a/src/resolve/resolved-dns-rr.h b/src/resolve/resolved-dns-rr.h
index 95d260f7aa..fccc4dba6a 100644
--- a/src/resolve/resolved-dns-rr.h
+++ b/src/resolve/resolved-dns-rr.h
@@ -100,6 +100,7 @@ struct DnsResourceRecord {
         DnsResourceKey *key;
         char *to_string;
         uint32_t ttl;
+        usec_t expiry; /* RRSIG signature expiry */
         bool unparseable:1;
         bool wire_format_canonical:1;
         void *wire_format;