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CVE-2018-14629 dns: CNAME loop prevention using counter

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Count number of answers generated by internal DNS query routine and stop at
20 to match Microsoft's loop prevention mechanism.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13600

Signed-off-by: Aaron Haslett <aaronhaslett@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
This commit is contained in:
Aaron Haslett
2018-10-23 17:25:51 +13:00
committed by Karolin Seeger
parent c3f6085991
commit 97b426baba
3 changed files with 34 additions and 0 deletions
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22
python/samba/tests/dns.py
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@ -846,6 +846,28 @@ class TestComplexQueries(DNSTest):
self.assertEquals(response.answers[1].name, name2)
self.assertEquals(response.answers[1].rdata, name0)
def test_cname_loop(self):
cname1 = "cnamelooptestrec." + self.get_dns_domain()
cname2 = "cnamelooptestrec2." + self.get_dns_domain()
cname3 = "cnamelooptestrec3." + self.get_dns_domain()
self.make_dns_update(cname1, cname2, dnsp.DNS_TYPE_CNAME)
self.make_dns_update(cname2, cname3, dnsp.DNS_TYPE_CNAME)
self.make_dns_update(cname3, cname1, dnsp.DNS_TYPE_CNAME)
p = self.make_name_packet(dns.DNS_OPCODE_QUERY)
questions = []
q = self.make_name_question(cname1,
dns.DNS_QTYPE_A,
dns.DNS_QCLASS_IN)
questions.append(q)
self.finish_name_packet(p, questions)
(response, response_packet) =\
self.dns_transaction_udp(p, host=self.server_ip)
max_recursion_depth = 20
self.assertEquals(len(response.answers), max_recursion_depth)
class TestInvalidQueries(DNSTest):
def setUp(self):