Attachment 14575 Details for Bug 13600 – patch for 4.9 with CVE

[patch] patch for 4.9 with CVE

CVE-2018-14629-v4-9.patch (text/plain), 2.78 KB, created by Andrew Bartlett on 2018-11-06 01:24:52 UTC

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Creator: Andrew Bartlett

Created: 2018-11-06 01:24:52 UTC

Size: 2.78 KB

patch

obsolete

>From d570209bfbeebf07fcf5c225721c239cea3c894d Mon Sep 17 00:00:00 2001
>From: Aaron Haslett <aaronhaslett@catalyst.net.nz>
>Date: Tue, 23 Oct 2018 17:25:51 +1300
>Subject: [PATCH] CVE-2018-14629 dns: CNAME loop prevention using counter
>
>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>
>---
> python/samba/tests/dns.py      | 22 ++++++++++++++++++++++
> source4/dns_server/dns_query.c |  6 ++++++
> 2 files changed, 28 insertions(+)
>
>diff --git a/python/samba/tests/dns.py b/python/samba/tests/dns.py
>index 6771e3bb8c4..3e6306e2be8 100644
>--- a/python/samba/tests/dns.py
>+++ b/python/samba/tests/dns.py
>@@ -844,6 +844,28 @@ 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):
>diff --git a/source4/dns_server/dns_query.c b/source4/dns_server/dns_query.c
>index 923f7233eb9..65faeac3b6a 100644
>--- a/source4/dns_server/dns_query.c
>+++ b/source4/dns_server/dns_query.c
>@@ -40,6 +40,7 @@
> 
> #undef DBGC_CLASS
> #define DBGC_CLASS DBGC_DNS
>+#define MAX_Q_RECURSION_DEPTH 20
> 
> struct forwarder_string {
> 	const char *forwarder;
>@@ -419,6 +420,11 @@ static struct tevent_req *handle_dnsrpcrec_send(
> 	state->answers = answers;
> 	state->nsrecs = nsrecs;
> 
>+	if (talloc_array_length(*answers) >= MAX_Q_RECURSION_DEPTH) {
>+		tevent_req_done(req);
>+		return tevent_req_post(req, ev);
>+	}
>+
> 	resolve_cname = ((rec->wType == DNS_TYPE_CNAME) &&
> 			 ((question->question_type == DNS_QTYPE_A) ||
> 			  (question->question_type == DNS_QTYPE_AAAA)));
>-- 
>2.11.0
>

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