93 lines
3.5 KiB
Diff
93 lines
3.5 KiB
Diff
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From bf596c14c2462b9a15ea738ef4f32b3abb8b63d1 Mon Sep 17 00:00:00 2001
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From: Aaron Haslett <aaronhaslett@catalyst.net.nz>
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Date: Tue, 23 Oct 2018 17:25:51 +1300
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Subject: [PATCH 01/17] 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
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20 to match Microsoft's loop prevention mechanism.
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BUG: https://bugzilla.samba.org/show_bug.cgi?id=13600
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Signed-off-by: Aaron Haslett <aaronhaslett@catalyst.net.nz>
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Reviewed-by: Andrew Bartlett <abartlet@samba.org>
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Reviewed-by: Garming Sam <garming@catalyst.net.nz>
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---
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python/samba/tests/dns.py | 22 ++++++++++++++++++++++
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selftest/knownfail.d/dns | 6 ++++++
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source4/dns_server/dns_query.c | 6 ++++++
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3 files changed, 34 insertions(+)
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diff --git a/python/samba/tests/dns.py b/python/samba/tests/dns.py
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index 6771e3bb8c4..3e6306e2be8 100644
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--- a/python/samba/tests/dns.py
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+++ b/python/samba/tests/dns.py
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@@ -844,6 +844,28 @@ class TestComplexQueries(DNSTest):
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self.assertEquals(response.answers[1].name, name2)
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self.assertEquals(response.answers[1].rdata, name0)
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+ def test_cname_loop(self):
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+ cname1 = "cnamelooptestrec." + self.get_dns_domain()
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+ cname2 = "cnamelooptestrec2." + self.get_dns_domain()
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+ cname3 = "cnamelooptestrec3." + self.get_dns_domain()
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+ self.make_dns_update(cname1, cname2, dnsp.DNS_TYPE_CNAME)
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+ self.make_dns_update(cname2, cname3, dnsp.DNS_TYPE_CNAME)
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+ self.make_dns_update(cname3, cname1, dnsp.DNS_TYPE_CNAME)
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+
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+ p = self.make_name_packet(dns.DNS_OPCODE_QUERY)
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+ questions = []
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+
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+ q = self.make_name_question(cname1,
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+ dns.DNS_QTYPE_A,
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+ dns.DNS_QCLASS_IN)
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+ questions.append(q)
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+ self.finish_name_packet(p, questions)
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+
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+ (response, response_packet) =\
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+ self.dns_transaction_udp(p, host=self.server_ip)
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+
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+ max_recursion_depth = 20
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+ self.assertEquals(len(response.answers), max_recursion_depth)
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class TestInvalidQueries(DNSTest):
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def setUp(self):
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diff --git a/selftest/knownfail.d/dns b/selftest/knownfail.d/dns
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index a5176654cc2..a248432aafa 100644
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--- a/selftest/knownfail.d/dns
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+++ b/selftest/knownfail.d/dns
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@@ -69,3 +69,9 @@ samba.tests.dns.__main__.TestSimpleQueries.test_qtype_all_query\(rodc:local\)
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# The SOA override should not pass against the RODC, it must not overstamp
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samba.tests.dns.__main__.TestSimpleQueries.test_one_SOA_query\(rodc:local\)
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+
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+#
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+# rodc and vampire_dc require signed dns updates, so the test setup
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+# fails, but the test does run on fl2003dc
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+^samba.tests.dns.__main__.TestComplexQueries.test_cname_loop\(rodc:local\)
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+^samba.tests.dns.__main__.TestComplexQueries.test_cname_loop\(vampire_dc:local\)
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diff --git a/source4/dns_server/dns_query.c b/source4/dns_server/dns_query.c
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index 923f7233eb9..65faeac3b6a 100644
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--- a/source4/dns_server/dns_query.c
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+++ b/source4/dns_server/dns_query.c
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@@ -40,6 +40,7 @@
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#undef DBGC_CLASS
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#define DBGC_CLASS DBGC_DNS
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+#define MAX_Q_RECURSION_DEPTH 20
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struct forwarder_string {
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const char *forwarder;
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@@ -419,6 +420,11 @@ static struct tevent_req *handle_dnsrpcrec_send(
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state->answers = answers;
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state->nsrecs = nsrecs;
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+ if (talloc_array_length(*answers) >= MAX_Q_RECURSION_DEPTH) {
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+ tevent_req_done(req);
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+ return tevent_req_post(req, ev);
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+ }
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+
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resolve_cname = ((rec->wType == DNS_TYPE_CNAME) &&
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((question->question_type == DNS_QTYPE_A) ||
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(question->question_type == DNS_QTYPE_AAAA)));
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--
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2.17.1
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