tls: set SNI for outbound connections via xavp

- new parameter: xavp_cfg to set the name of the xavp that holds
  attributes for tls connections
- server_name attribute can be used to specify SNI for outbound
  connections:

modparam("tls", "xavp_cfg", "tls")
...
  $xavp(tls=>server_name) = "kamailio.org";
  $du = "sip:kamailio.org:5061;transport=tls";
  route(RELAY);

- note: kamailio tries to identify the client context from tls.cfg by ip, port
  and server_name, but many OSes allocate a local random port when
  initiating TCP/TLS connection, so it is hard to add such contexts, in
  this case the client:default being used

modules/tls/tls_domain.c

@@ -1302,6 +1302,12 @@ tls_domain_t* tls_lookup_cfg(tls_domains_cfg_t* cfg, int type,
 	}
 
 	while (p) {
+		if(sname) {
+			LM_DBG("comparing addr: [%s:%d]  [%s:%d] -- sni: [%.*s] [%.*s]\n",
+				ip_addr2a(&p->ip), p->port, ip_addr2a(ip), port,
+				p->server_name.len, ZSW(p->server_name.s),
+				sname->len, ZSW(sname->s));
+		}
 		if ((p->port == port) && ip_addr_cmp(&p->ip, ip)) {
 			if(sname && sname->len>0) {
 				if(p->server_name.len==sname->len

modules/tls/tls_mod.c

@@ -82,6 +82,7 @@ static int is_peer_verified(struct sip_msg* msg, char* foo, char* foo2);
 MODULE_VERSION
 
 
+str sr_tls_xavp_cfg = {0, 0};
 /*
  * Default settings when modparams are used 
  */
@@ -203,6 +204,7 @@ static param_export_t params[] = {
 	{"low_mem_threshold1",  PARAM_INT,    &default_tls_cfg.low_mem_threshold1},
 	{"low_mem_threshold2",  PARAM_INT,    &default_tls_cfg.low_mem_threshold2},
 	{"renegotiation",       PARAM_INT,    &sr_tls_renegotiation},
+	{"xavp_cfg",            PARAM_STR,    &sr_tls_xavp_cfg},
 	{0, 0, 0}
 };
 

modules/tls/tls_server.c

@@ -42,6 +42,7 @@
 #include "../../route.h"
 #include "../../forward.h"
 #include "../../onsend.h"
+#include "../../xavp.h"
 
 #include "tls_init.h"
 #include "tls_domain.h"
@@ -127,6 +128,30 @@ int tls_run_event_routes(struct tcp_connection *c);
 #endif /* TLS_RD_DEBUG */
 
 
+extern str sr_tls_xavp_cfg;
+
+/**
+ * get the server name (sni) for outbound connections from xavp
+ */
+static str *tls_get_connect_server_name(void)
+{
+#ifndef OPENSSL_NO_TLSEXT
+	sr_xavp_t *vavp = NULL;
+	str sname = {"server_name", 11};
+
+	if(sr_tls_xavp_cfg.s!=NULL)
+		vavp = xavp_get_child_with_sval(&sr_tls_xavp_cfg, &sname);
+	if(vavp==NULL || vavp->val.v.s.len<=0) {
+		LM_DBG("xavp with outbound server name not found\n");
+		return NULL;
+	}
+	LM_DBG("found xavp with outbound server name: %s\n", vavp->val.v.s.s);
+	return &vavp->val.v.s;
+#else
+	return NULL;
+#endif
+}
+
 /** finish the ssl init.
  * Creates the SSL context + internal tls_extra_data and sets
  * extra_data to it.
@@ -141,6 +166,7 @@ static int tls_complete_init(struct tcp_connection* c)
 	struct tls_extra_data* data = 0;
 	tls_domains_cfg_t* cfg;
 	enum tls_conn_states state;
+	str *sname = NULL;
 
 	if (LOW_MEM_NEW_CONNECTION_TEST()){
 		ERR("tls: ssl bug #1491 workaround: not enough memory for safe"
@@ -169,8 +195,9 @@ static int tls_complete_init(struct tcp_connection* c)
 								&c->rcv.dst_ip, c->rcv.dst_port, 0);
 	} else {
 		state=S_TLS_CONNECTING;
+		sname = tls_get_connect_server_name();
 		dom = tls_lookup_cfg(cfg, TLS_DOMAIN_CLI,
-								&c->rcv.dst_ip, c->rcv.dst_port, 0);
+								&c->rcv.dst_ip, c->rcv.dst_port, sname);
 	}
 	if (unlikely(c->state<0)) {
 		BUG("Invalid connection (state %d)\n", c->state);
@@ -199,6 +226,20 @@ static int tls_complete_init(struct tcp_connection* c)
 			BIO_free(data->rwbio);
 		goto error;
 	}
+
+#ifndef OPENSSL_NO_TLSEXT
+	if (sname!=NULL) {
+		if(!SSL_set_tlsext_host_name(data->ssl, sname->s)) {
+			if (data->ssl)
+				SSL_free(data->ssl);
+			if (data->rwbio)
+				BIO_free(data->rwbio);
+			goto error;
+		}
+		LM_DBG("outbound TLS server name set to: %s\n", sname->s);
+	}
+#endif
+
 #ifdef TLS_KSSL_WORKARROUND
 	 /* if needed apply workaround for openssl bug #1467 */
 	if (data->ssl->kssl_ctx && openssl_kssl_malloc_bug){
@@ -211,7 +252,6 @@ static int tls_complete_init(struct tcp_connection* c)
 
 	/* link the extra data struct inside ssl connection*/
 	SSL_set_app_data(data->ssl, data);
-
 	return 0;
 
  error: