From 392ec4d241eb19c812cd49ff73bd32b2b09d8533 Mon Sep 17 00:00:00 2001 From: Kai Blin Date: Tue, 13 May 2014 08:13:29 +0200 Subject: [PATCH] bug #10609: CVE-2014-0239 Don't reply to replies Due to insufficient input checking, the DNS server will reply to a packet that has the "reply" bit set. Over UDP, this allows to send a packet with a spoofed sender address and have two servers DOS each other with circular replies. This patch fixes bug #10609 and adds a test to make sure we don't regress. CVE-2014-2039 has been assigned to this issue. Bug: https://bugzilla.samba.org/show_bug.cgi?id=10609 Signed-off-by: Kai Blin Reviewed-by: Stefan Metzmacher Autobuild-User(master): Kai Blin Autobuild-Date(master): Tue May 20 04:15:44 CEST 2014 on sn-devel-104 --- python/samba/tests/dns.py | 29 +++++++++++++++++++++++++++++ source4/dns_server/dns_server.c | 6 ++++++ 2 files changed, 35 insertions(+) diff --git a/python/samba/tests/dns.py b/python/samba/tests/dns.py index 9c0b27471a7..400321fe161 100644 --- a/python/samba/tests/dns.py +++ b/python/samba/tests/dns.py @@ -833,6 +833,35 @@ class TestInvalidQueries(DNSTest): self.assertEquals(response.answers[0].rdata, os.getenv('SERVER_IP')) + def test_one_a_reply(self): + "send a reply instead of a query" + + p = self.make_name_packet(dns.DNS_OPCODE_QUERY) + questions = [] + + name = "%s.%s" % ('fakefakefake', self.get_dns_domain()) + q = self.make_name_question(name, dns.DNS_QTYPE_A, dns.DNS_QCLASS_IN) + print "asking for ", q.name + questions.append(q) + + self.finish_name_packet(p, questions) + p.operation |= dns.DNS_FLAG_REPLY + s = None + try: + send_packet = ndr.ndr_pack(p) + s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) + host=os.getenv('SERVER_IP') + s.connect((host, 53)) + tcp_packet = struct.pack('!H', len(send_packet)) + tcp_packet += send_packet + s.send(tcp_packet, 0) + recv_packet = s.recv(0xffff + 2, 0) + self.assertEquals(0, len(recv_packet)) + finally: + if s is not None: + s.close() + + if __name__ == "__main__": import unittest unittest.main() diff --git a/source4/dns_server/dns_server.c b/source4/dns_server/dns_server.c index 976774d020f..60ce27c6ff9 100644 --- a/source4/dns_server/dns_server.c +++ b/source4/dns_server/dns_server.c @@ -156,6 +156,12 @@ static struct tevent_req *dns_process_send(TALLOC_CTX *mem_ctx, return tevent_req_post(req, ev); } + if (state->in_packet.operation & DNS_FLAG_REPLY) { + DEBUG(1, ("Won't reply to replies.\n")); + tevent_req_werror(req, WERR_INVALID_PARAM); + return tevent_req_post(req, ev); + } + state->state.flags = state->in_packet.operation; state->state.flags |= DNS_FLAG_REPLY; -- 2.11.4.GIT