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authorLennart Poettering <lennart@poettering.net>2016-02-04 00:14:25 +0100
committerLennart Poettering <lennart@poettering.net>2016-02-04 00:14:25 +0100
commit8e5de09f442874bed2a8889aa28739d2a516b094 (patch)
tree3aac5e1af2a1a878c0115535629a82f006160dd3 /src
parent089b64d5f8418ffe257d07ce80077d8c6c68da15 (diff)
resolved: don't follow CNAMEs originating from DNS on LLMNR
Fixes: #2514
Diffstat (limited to 'src')
-rw-r--r--src/resolve/resolved-dns-query.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/src/resolve/resolved-dns-query.c b/src/resolve/resolved-dns-query.c
index 06d30d7863..b8bdff9dfa 100644
--- a/src/resolve/resolved-dns-query.c
+++ b/src/resolve/resolved-dns-query.c
@@ -967,6 +967,17 @@ static int dns_query_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname)
if (r == 0 && k == 0) /* No actual cname happened? */
return -ELOOP;
+ if (q->answer_protocol == DNS_PROTOCOL_DNS) {
+ /* Don't permit CNAME redirects from unicast DNS to LLMNR or MulticastDNS, so that global resources
+ * cannot invade the local namespace. The opposite way we permit: local names may redirect to global
+ * ones. */
+
+ q->flags &= ~(SD_RESOLVED_LLMNR|SD_RESOLVED_MDNS); /* mask away the local protocols */
+ }
+
+ /* Turn off searching for the new name */
+ q->flags |= SD_RESOLVED_NO_SEARCH;
+
dns_question_unref(q->question_idna);
q->question_idna = nq_idna;
nq_idna = NULL;
@@ -977,10 +988,8 @@ static int dns_query_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname)
dns_query_free_candidates(q);
dns_query_reset_answer(q);
- q->state = DNS_TRANSACTION_NULL;
- /* Turn off searching for the new name */
- q->flags |= SD_RESOLVED_NO_SEARCH;
+ q->state = DNS_TRANSACTION_NULL;
return 0;
}