--- /dev/null
+From 4eeb16d1a316aa3d6f5710a2f6beffb0fecb6121 Mon Sep 17 00:00:00 2001
+From: Richard Mudgett <rmudgett@digium.com>
+Date: Mon, 30 Apr 2018 17:38:58 -0500
+Subject: [PATCH] AST-2018-008: Fix enumeration of endpoints from ACL rejected addresses.
+
+When endpoint specific ACL rules block a SIP request they respond with a
+403 forbidden. However, if an endpoint is not identified then a 401
+unauthorized response is sent. This vulnerability just discloses which
+requests hit a defined endpoint. The ACL rules cannot be bypassed to gain
+access to the disclosed endpoints.
+
+* Made endpoint specific ACL rules now respond with a 401 unauthorized
+which is the same as if an endpoint were not identified. The fix is
+accomplished by replacing the found endpoint with the artificial endpoint
+which always fails authentication.
+
+ASTERISK-27818
+
+Change-Id: Icb275a54ff8e2df6c671a6d9bda37b5d732b3b32
+---
+
+diff --git a/res/res_pjsip/pjsip_distributor.c b/res/res_pjsip/pjsip_distributor.c
+index e056b60..19266df 100644
+--- a/res/res_pjsip/pjsip_distributor.c
++++ b/res/res_pjsip/pjsip_distributor.c
+@@ -666,6 +666,26 @@
+ ao2_unlock(unid);
+ }
+
++static int apply_endpoint_acl(pjsip_rx_data *rdata, struct ast_sip_endpoint *endpoint);
++static int apply_endpoint_contact_acl(pjsip_rx_data *rdata, struct ast_sip_endpoint *endpoint);
++
++static void apply_acls(pjsip_rx_data *rdata)
++{
++ struct ast_sip_endpoint *endpoint;
++
++ /* Is the endpoint allowed with the source or contact address? */
++ endpoint = rdata->endpt_info.mod_data[endpoint_mod.id];
++ if (endpoint != artificial_endpoint
++ && (apply_endpoint_acl(rdata, endpoint)
++ || apply_endpoint_contact_acl(rdata, endpoint))) {
++ ast_debug(1, "Endpoint '%s' not allowed by ACL\n",
++ ast_sorcery_object_get_id(endpoint));
++
++ /* Replace the rdata endpoint with the artificial endpoint. */
++ ao2_replace(rdata->endpt_info.mod_data[endpoint_mod.id], artificial_endpoint);
++ }
++}
++
+ static pj_bool_t endpoint_lookup(pjsip_rx_data *rdata)
+ {
+ struct ast_sip_endpoint *endpoint;
+@@ -684,6 +704,7 @@
+ ao2_unlink(unidentified_requests, unid);
+ ao2_ref(unid, -1);
+ }
++ apply_acls(rdata);
+ return PJ_FALSE;
+ }
+
+@@ -743,6 +764,8 @@
+ ast_sip_report_invalid_endpoint(name, rdata);
+ }
+ }
++
++ apply_acls(rdata);
+ return PJ_FALSE;
+ }
+
+@@ -826,16 +849,11 @@
+
+ ast_assert(endpoint != NULL);
+
+- if (endpoint!=artificial_endpoint) {
+- if (apply_endpoint_acl(rdata, endpoint) || apply_endpoint_contact_acl(rdata, endpoint)) {
+- if (!is_ack) {
+- pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 403, NULL, NULL, NULL);
+- }
+- return PJ_TRUE;
+- }
++ if (is_ack) {
++ return PJ_FALSE;
+ }
+
+- if (!is_ack && ast_sip_requires_authentication(endpoint, rdata)) {
++ if (ast_sip_requires_authentication(endpoint, rdata)) {
+ pjsip_tx_data *tdata;
+ struct unidentified_request *unid;
+
+@@ -871,6 +889,10 @@
+ return PJ_TRUE;
+ }
+ pjsip_tx_data_dec_ref(tdata);
++ } else if (endpoint == artificial_endpoint) {
++ /* Uh. Oh. The artificial endpoint couldn't challenge so block the request. */
++ pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 500, NULL, NULL, NULL);
++ return PJ_TRUE;
+ }
+
+ return PJ_FALSE;
+