From b9fe94cad99968a58e169592d999306fd059eb14 Mon Sep 17 00:00:00 2001 From: Martin Pitt Date: Fri, 30 Sep 2016 09:30:08 +0200 Subject: resolved: don't query domain-limited DNS servers for other domains (#3621) DNS servers which have route-only domains should only be used for the specified domains. Routing queries about other domains there is a privacy violation, prone to fail (as that DNS server was not meant to be used for other domains), and puts unnecessary load onto that server. Introduce a new helper function dns_server_limited_domains() that checks if the DNS server should only be used for some selected domains, i. e. has some route-only domains without "~.". Use that when determining whether to query it in the scope, and when writing resolv.conf. Extend the test_route_only_dns() case to ensure that the DNS server limited to ~company does not appear in resolv.conf. Add test_route_only_dns_all_domains() to ensure that a server that also has ~. does appear in resolv.conf as global name server. These reproduce #3420. Add a new test_resolved_domain_restricted_dns() test case that verifies that domain-limited DNS servers are only being used for those domains. This reproduces #3421. Clarify what a "routing domain" is in the manpage. Fixes #3420 Fixes #3421 --- src/resolve/resolved-resolv-conf.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'src/resolve/resolved-resolv-conf.c') diff --git a/src/resolve/resolved-resolv-conf.c b/src/resolve/resolved-resolv-conf.c index 31b25ca50f..801014caf5 100644 --- a/src/resolve/resolved-resolv-conf.c +++ b/src/resolve/resolved-resolv-conf.c @@ -154,6 +154,16 @@ static void write_resolv_conf_server(DnsServer *s, FILE *f, unsigned *count) { return; } + /* Check if the DNS server is limited to particular domains; + * resolv.conf does not have a syntax to express that, so it must not + * appear as a global name server to avoid routing unrelated domains to + * it (which is a privacy violation, will most probably fail anyway, + * and adds unnecessary load) */ + if (dns_server_limited_domains(s)) { + log_debug("DNS server %s has route-only domains, not using as global name server", dns_server_string(s)); + return; + } + if (*count == MAXNS) fputs("# Too many DNS servers configured, the following entries may be ignored.\n", f); (*count)++; -- cgit v1.2.3-54-g00ecf