From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 15 Feb 2017 19:05:27 +0000 (+0100)
Subject: resolved: try to authenticate SOA on negative replies
X-Git-Tag: v233~76^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F5347%2Fhead;p=thirdparty%2Fsystemd.git

resolved: try to authenticate SOA on negative replies

For caching negative replies we need the SOA TTL information. Hence,
let's authenticate all auxiliary SOA RRs through DS requests on all
negative requests.
---

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 532169ff249..ecd70686836 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -2009,8 +2009,18 @@ int dns_transaction_request_dnssec_keys(DnsTransaction *t) {
                         r = dns_resource_key_match_rr(t->key, rr, NULL);
                         if (r < 0)
                                 return r;
-                        if (r == 0)
-                                continue;
+                        if (r == 0) {
+                                /* Hmm, so this SOA RR doesn't match our original question. In this case, maybe this is
+                                 * a negative reply, and we need the a SOA RR's TTL in order to cache a negative entry?
+                                 * If so, we need to validate it, too. */
+
+                                r = dns_answer_match_key(t->answer, t->key, NULL);
+                                if (r < 0)
+                                        return r;
+                                if (r > 0) /* positive reply, we won't need the SOA and hence don't need to validate
+                                            * it. */
+                                        continue;
+                        }
 
                         r = dnssec_has_rrsig(t->answer, rr->key);
                         if (r < 0)