Make contactdeny apply to src ip when nat=yes

chan_sip's "contactdeny" feature screens the "to be registered contact".
In case of nat=yes it should not use the address information from the
Contact header (which is not used at all for routing), but the source
IP address of the request.

Thus, if nat=yes and a client sends a request from a denied IP address
(e.g. by spoofing the src-IP address) it can bypass the screening.

This commit makes contactdeny apply to the src ip when nat=yes instead.

(closes issue #17276)
Reported by: klaus3000
Patches: 
      patch-asterisk-trunk-contactdeny.txt uploaded by klaus3000 (license 65)
Tested by: klaus3000


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@270658 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 22 insertions, 21 deletions

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 886425e44..588b63799 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -12535,37 +12535,38 @@ static enum parse_register_result parse_register_contact(struct sip_pvt *pvt, st
 		ao2_t_unlink(peers_by_ip, peer, "ao2_unlink of peer from peers_by_ip table");
 	}
 
-	/* Check that they're allowed to register at this IP */
-	/* XXX This could block for a long time XXX */
-	/*! \todo Check NAPTR/SRV if we have not got a port in the URI */
-	hp = ast_gethostbyname(host, &ahp);
-	if (!hp)  {
-		ast_log(LOG_WARNING, "Invalid host '%s'\n", host);
-		ast_string_field_set(peer, fullcontact, "");
-		ast_string_field_set(pvt, our_contact, "");
-		return PARSE_REGISTER_FAILED;
-	}
-	memcpy(&testsin.sin_addr, hp->h_addr, sizeof(testsin.sin_addr));
-	if (ast_apply_ha(sip_cfg.contact_ha, &testsin) != AST_SENSE_ALLOW ||
-			ast_apply_ha(peer->contactha, &testsin) != AST_SENSE_ALLOW) {
-		ast_log(LOG_WARNING, "Host '%s' disallowed by contact ACL (violating IP %s)\n", host, ast_inet_ntoa(testsin.sin_addr));
-		ast_string_field_set(peer, fullcontact, "");
-		ast_string_field_set(pvt, our_contact, "");
-		return PARSE_REGISTER_DENIED;
-	}
-
-	/*! \todo This could come before the checking of DNS earlier on, to avoid
-		DNS lookups where we don't need it... */
 	if (!ast_test_flag(&peer->flags[0], SIP_NAT_FORCE_RPORT) && !ast_test_flag(&peer->flags[0], SIP_NAT_RPORT_PRESENT)) {
+		/* use the data provided in the Contact header for call routing */
+		ast_debug(1, "Store REGISTER's Contact header for call routing.\n");
+		/* XXX This could block for a long time XXX */
+		/*! \todo Check NAPTR/SRV if we have not got a port in the URI */
+		hp = ast_gethostbyname(host, &ahp);
+		if (!hp)  {
+			ast_log(LOG_WARNING, "Invalid host '%s'\n", host);
+			ast_string_field_set(peer, fullcontact, "");
+			ast_string_field_set(pvt, our_contact, "");
+			return PARSE_REGISTER_FAILED;
+		}
 		peer->addr.sin_family = AF_INET;
 		memcpy(&peer->addr.sin_addr, hp->h_addr, sizeof(peer->addr.sin_addr));
 		peer->addr.sin_port = htons(port);
 	} else {
 		/* Don't trust the contact field.  Just use what they came to us
 		   with */
+		ast_debug(1, "Store REGISTER's src-IP:port for call routing.\n");
 		peer->addr = pvt->recv;
 	}
 
+	/* Check that they're allowed to register at this IP */
+	memcpy(&testsin.sin_addr, &peer->addr.sin_addr, sizeof(testsin.sin_addr));
+	if (ast_apply_ha(sip_cfg.contact_ha, &testsin) != AST_SENSE_ALLOW ||
+			ast_apply_ha(peer->contactha, &testsin) != AST_SENSE_ALLOW) {
+		ast_log(LOG_WARNING, "Host '%s' disallowed by contact ACL (violating IP %s)\n", host, ast_inet_ntoa(testsin.sin_addr));
+		ast_string_field_set(peer, fullcontact, "");
+		ast_string_field_set(pvt, our_contact, "");
+		return PARSE_REGISTER_DENIED;
+	}
+
 	/* if the Contact header information copied into peer->addr matches the
 	 * received address, and the transport types are the same, then copy socket
 	 * data into the peer struct */