res_pjsip_nat.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2013, Digium, Inc.
 *
 * Joshua Colp <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*** MODULEINFO
 <depend>pjproject</depend>
 <depend>res_pjsip</depend>
 <depend>res_pjsip_session</depend>
 <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <pjsip.h>
#include <pjsip_ua.h>

#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_session.h"
#include "asterisk/module.h"
#include "asterisk/acl.h"

/*! URI parameter for original host/port */
#define AST_SIP_X_AST_ORIG_HOST "x-ast-orig-host"
#define AST_SIP_X_AST_ORIG_HOST_LEN 15

#define is_sip_uri(uri) \
 (PJSIP_URI_SCHEME_IS_SIP(uri) || PJSIP_URI_SCHEME_IS_SIPS(uri))

static void save_orig_contact_host(pjsip_rx_data *rdata, pjsip_sip_uri *uri)
{
 pjsip_param *x_orig_host;
 pj_str_t p_value;
#define COLON_LEN 1
#define MAX_PORT_LEN 5

 if (rdata->msg_info.msg->type != PJSIP_REQUEST_MSG ||
 rdata->msg_info.msg->line.req.method.id != PJSIP_REGISTER_METHOD) {
 return;
 }

 ast_debug(1, "Saving contact '%.*s:%d'\n",
 (int)uri->host.slen, uri->host.ptr, uri->port);

 x_orig_host = PJ_POOL_ALLOC_T(rdata->tp_info.pool, pjsip_param);
 x_orig_host->name = pj_strdup3(rdata->tp_info.pool, AST_SIP_X_AST_ORIG_HOST);
 p_value.slen = pj_strlen(&uri->host) + COLON_LEN + MAX_PORT_LEN;
 p_value.ptr = (char*)pj_pool_alloc(rdata->tp_info.pool, p_value.slen + 1);
 p_value.slen = snprintf(p_value.ptr, p_value.slen + 1, "%.*s:%d", (int)uri->host.slen, uri->host.ptr, uri->port);
 pj_strassign(&x_orig_host->value, &p_value);
 pj_list_insert_before(&uri->other_param, x_orig_host);

 return;
}

static void rewrite_uri(pjsip_rx_data *rdata, pjsip_sip_uri *uri, pj_pool_t *pool)
{

 if (pj_strcmp2(&uri->host, rdata->pkt_info.src_name) != 0) {
 save_orig_contact_host(rdata, uri);
 }

 pj_strdup2(pool, &uri->host, rdata->pkt_info.src_name);
 uri->port = rdata->pkt_info.src_port;
 if (!strcasecmp("WSS", rdata->tp_info.transport->type_name)) {
 /* WSS is special, we don't want to overwrite the URI at all as it needs to be ws */
 } else if (strcasecmp("udp", rdata->tp_info.transport->type_name)) {
 uri->transport_param = pj_str(rdata->tp_info.transport->type_name);
 } else {
 uri->transport_param.slen = 0;
 }
}

/*
 * Update the Record-Route headers in the request or response and in the dialog
 * object if exists.
 *
 * When NAT is in use, the address of the next hop in the SIP may be incorrect.
 * To address this asterisk uses two strategies in parallel:
 * 1. intercept the messages at the transaction level and rewrite the
 * messages before arriving at the dialog layer
 * 2. after the application processing, update the dialog object with the
 * correct information
 *
 * The first strategy has a limitation that the SIP message may not have all
 * the information required to determine if the next hop is in the route set
 * or in the contact. Causing risk that asterisk will update the Contact on
 * receipt of an in-dialog message despite there being a route set saved in
 * the dialog.
 *
 * The second strategy has a limitation that not all UAC layers have interfaces
 * available to invoke this module after dialog creation. (pjsip_sesion does
 * but pjsip_pubsub does not), thus this strategy can't update the dialog in
 * all cases needed.
 *
 * The ideal solution would be to implement an "incomming_request" event
 * in pubsub module that can then pass the dialog object to this module
 * on SUBSCRIBE, this module then should add itself as a listener to the dialog
 * for the subsequent requests and responses & then be able to properly update
 * the dialog object for all required events.
 */

static int rewrite_route_set(pjsip_rx_data *rdata, pjsip_dialog *dlg)
{
 pjsip_rr_hdr *rr = NULL;
 pjsip_sip_uri *uri;
 int res = -1;
 int ignore_rr = 0;
 int pubsub = 0;

 if (rdata->msg_info.msg->type == PJSIP_RESPONSE_MSG) {
 pjsip_hdr *iter;
 for (iter = rdata->msg_info.msg->hdr.prev; iter != &rdata->msg_info.msg->hdr; iter = iter->prev) {
 if (iter->type == PJSIP_H_RECORD_ROUTE) {
 rr = (pjsip_rr_hdr *)iter;
 break;
 }
 }
 } else if (pjsip_method_cmp(&rdata->msg_info.msg->line.req.method, &pjsip_register_method)) {
 rr = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_RECORD_ROUTE, NULL);
 } else {
 /**
 * Record-Route header has no meaning in REGISTER requests
 * and should be ignored
 */
 ignore_rr = 1;
 }

 if (!pjsip_method_cmp(&rdata->msg_info.cseq->method, &pjsip_subscribe_method) ||
 !pjsip_method_cmp(&rdata->msg_info.cseq->method, &pjsip_notify_method)) {
 /**
 * There is currently no good way to get the dlg object for a pubsub dialog
 * so we will just look at the rr & contact of the current message and
 * hope for the best
 */
 pubsub = 1;
 }

 if (rr) {
 uri = pjsip_uri_get_uri(&rr->name_addr);
 rewrite_uri(rdata, uri, rdata->tp_info.pool);
 res = 0;
 }

 if (dlg && !pj_list_empty(&dlg->route_set) && !dlg->route_set_frozen) {
 pjsip_routing_hdr *route = dlg->route_set.next;
 uri = pjsip_uri_get_uri(&route->name_addr);
 rewrite_uri(rdata, uri, dlg->pool);
 res = 0;
 }

 if (!dlg && !rr && !ignore_rr && !pubsub && rdata->msg_info.to->tag.slen){
 /**
 * Even if this message doesn't have any route headers
 * the dialog may, so wait until a later invocation that
 * has a dialog reference to make sure there isn't a
 * previously saved routset in the dialog before deciding
 * the contact needs to be modified
 */
 res = 0;
 }

 return res;
}

static int rewrite_contact(pjsip_rx_data *rdata, pjsip_dialog *dlg)
{
 pjsip_contact_hdr *contact;

 contact = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_CONTACT, NULL);
 if (contact && !contact->star && (PJSIP_URI_SCHEME_IS_SIP(contact->uri) || PJSIP_URI_SCHEME_IS_SIPS(contact->uri))) {
 pjsip_sip_uri *uri = pjsip_uri_get_uri(contact->uri);

 rewrite_uri(rdata, uri, rdata->tp_info.pool);

 if (dlg && pj_list_empty(&dlg->route_set) && (!dlg->remote.contact
 || pjsip_uri_cmp(PJSIP_URI_IN_REQ_URI, dlg->remote.contact->uri, contact->uri))) {
 dlg->remote.contact = (pjsip_contact_hdr*)pjsip_hdr_clone(dlg->pool, contact);
 dlg->target = dlg->remote.contact->uri;
 }
 return 0;
 }

 return -1;
}

static pj_bool_t handle_rx_message(struct ast_sip_endpoint *endpoint, pjsip_rx_data *rdata)
{
 pjsip_dialog *dlg = pjsip_rdata_get_dlg(rdata);

 if (!endpoint) {
 return PJ_FALSE;
 }

 if (endpoint->nat.rewrite_contact) {
 /* rewrite_contact is intended to ensure we send requests/responses to
 * a routeable address when NAT is involved. The URI that dictates where
 * we send requests/responses can be determined either by Record-Route
 * headers or by the Contact header if no Record-Route headers are present.
 * We therefore will attempt to rewrite a Record-Route header first, and if
 * none are present, we fall back to rewriting the Contact header instead.
 */
 if (rewrite_route_set(rdata, dlg)) {
 rewrite_contact(rdata, dlg);
 }
 }

 if (endpoint->nat.force_rport) {
 rdata->msg_info.via->rport_param = rdata->pkt_info.src_port;
 }

 return PJ_FALSE;
}

static pj_bool_t nat_on_rx_message(pjsip_rx_data *rdata)
{
 pj_bool_t res;
 struct ast_sip_endpoint *endpoint;

 endpoint = ast_pjsip_rdata_get_endpoint(rdata);
 res = handle_rx_message(endpoint, rdata);
 ao2_cleanup(endpoint);
 return res;
}

/*! \brief Structure which contains information about a transport */
struct request_transport_details {
 /*! \brief Type of transport */
 enum ast_transport type;
 /*! \brief Potential pointer to the transport itself, if UDP */
 pjsip_transport *transport;
 /*! \brief Potential pointer to the transport factory itself, if TCP/TLS */
 pjsip_tpfactory *factory;
 /*! \brief Local address for transport */
 pj_str_t local_address;
 /*! \brief Local port for transport */
 int local_port;
};

/*! \brief Callback function for finding the transport the request is going out on */
static int find_transport_state_in_use(void *obj, void *arg, int flags)
{
 struct ast_sip_transport_state *transport_state = obj;
 struct request_transport_details *details = arg;

 /* If an explicit transport or factory matches then this is what is in use, if we are unavailable
 * to compare based on that we make sure that the type is the same and the source IP address/port are the same
 */
 if (transport_state && ((details->transport && details->transport == transport_state->transport) ||
 (details->factory && details->factory == transport_state->factory) ||
 ((details->type == transport_state->type) && (transport_state->factory) &&
 !pj_strcmp(&transport_state->factory->addr_name.host, &details->local_address) &&
 transport_state->factory->addr_name.port == details->local_port))) {
 return CMP_MATCH;
 }

 return 0;
}

/*! \brief Helper function which returns the SIP URI of a Contact header */
static pjsip_sip_uri *nat_get_contact_sip_uri(pjsip_tx_data *tdata)
{
 pjsip_contact_hdr *contact = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_CONTACT, NULL);

 if (!contact || (!PJSIP_URI_SCHEME_IS_SIP(contact->uri) && !PJSIP_URI_SCHEME_IS_SIPS(contact->uri))) {
 return NULL;
 }

 return pjsip_uri_get_uri(contact->uri);
}

/*! \brief Structure which contains hook details */
struct nat_hook_details {
 /*! \brief Outgoing message itself */
 pjsip_tx_data *tdata;
 /*! \brief Chosen transport */
 struct ast_sip_transport *transport;
};

/*! \brief Callback function for invoking hooks */
static int nat_invoke_hook(void *obj, void *arg, int flags)
{
 struct ast_sip_nat_hook *hook = obj;
 struct nat_hook_details *details = arg;

 if (hook->outgoing_external_message) {
 hook->outgoing_external_message(details->tdata, details->transport);
 }

 return 0;
}

static void restore_orig_contact_host(pjsip_tx_data *tdata)
{
 pjsip_contact_hdr *contact;
 pj_str_t x_name = { AST_SIP_X_AST_ORIG_HOST, AST_SIP_X_AST_ORIG_HOST_LEN };
 pjsip_param *x_orig_host;
 pjsip_sip_uri *uri;
 pjsip_hdr *hdr;

 if (tdata->msg->type == PJSIP_REQUEST_MSG) {
 if (is_sip_uri(tdata->msg->line.req.uri)) {
 uri = pjsip_uri_get_uri(tdata->msg->line.req.uri);
 while ((x_orig_host = pjsip_param_find(&uri->other_param, &x_name))) {
 pj_list_erase(x_orig_host);
 }
 }
 for (hdr = tdata->msg->hdr.next; hdr != &tdata->msg->hdr; hdr = hdr->next) {
 if (hdr->type == PJSIP_H_TO) {
 if (is_sip_uri(((pjsip_fromto_hdr *) hdr)->uri)) {
 uri = pjsip_uri_get_uri(((pjsip_fromto_hdr *) hdr)->uri);
 while ((x_orig_host = pjsip_param_find(&uri->other_param, &x_name))) {
 pj_list_erase(x_orig_host);
 }
 }
 }
 }
 }

 if (tdata->msg->type != PJSIP_RESPONSE_MSG) {
 return;
 }

 contact = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_CONTACT, NULL);
 while (contact) {
 pjsip_sip_uri *contact_uri = pjsip_uri_get_uri(contact->uri);
 x_orig_host = pjsip_param_find(&contact_uri->other_param, &x_name);

 if (x_orig_host) {
 char host_port[x_orig_host->value.slen + 1];
 char *sep;

 ast_debug(1, "Restoring contact %.*s:%d to %.*s\n", (int)contact_uri->host.slen,
 contact_uri->host.ptr, contact_uri->port,
 (int)x_orig_host->value.slen, x_orig_host->value.ptr);

 strncpy(host_port, x_orig_host->value.ptr, x_orig_host->value.slen);
 host_port[x_orig_host->value.slen] = '\0';
 sep = strchr(host_port, ':');
 if (sep) {
 *sep = '\0';
 sep++;
 pj_strdup2(tdata->pool, &contact_uri->host, host_port);
 contact_uri->port = strtol(sep, NULL, 10);
 }
 pj_list_erase(x_orig_host);
 }
 contact = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_CONTACT, contact->next);
 }
}

static pj_status_t process_nat(pjsip_tx_data *tdata)
{
 RAII_VAR(struct ao2_container *, transport_states, NULL, ao2_cleanup);
 RAII_VAR(struct ast_sip_transport *, transport, NULL, ao2_cleanup);
 RAII_VAR(struct ast_sip_transport_state *, transport_state, NULL, ao2_cleanup);
 struct request_transport_details details = { 0, };
 pjsip_via_hdr *via = NULL;
 struct ast_sockaddr addr = { { 0, } };
 pjsip_sip_uri *uri = NULL;
 RAII_VAR(struct ao2_container *, hooks, NULL, ao2_cleanup);

 /* If a transport selector is in use we know the transport or factory, so explicitly find it */
 if (tdata->tp_sel.type == PJSIP_TPSELECTOR_TRANSPORT) {
 details.transport = tdata->tp_sel.u.transport;
 } else if (tdata->tp_sel.type == PJSIP_TPSELECTOR_LISTENER) {
 details.factory = tdata->tp_sel.u.listener;
 } else if (tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP || tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP6) {
 /* Connectionless uses the same transport for all requests */
 details.type = AST_TRANSPORT_UDP;
 details.transport = tdata->tp_info.transport;
 } else {
 if (tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_TCP) {
 details.type = AST_TRANSPORT_TCP;
 } else if (tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_TLS) {
 details.type = AST_TRANSPORT_TLS;
 } else {
 /* Unknown transport type, we can't map and thus can't apply NAT changes */
 return PJ_SUCCESS;
 }

 if ((uri = nat_get_contact_sip_uri(tdata))) {
 details.local_address = uri->host;
 details.local_port = uri->port;
 } else if ((tdata->msg->type == PJSIP_REQUEST_MSG) &&
 (via = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_VIA, NULL))) {
 details.local_address = via->sent_by.host;
 details.local_port = via->sent_by.port;
 } else {
 return PJ_SUCCESS;
 }

 if (!details.local_port) {
 details.local_port = (details.type == AST_TRANSPORT_TLS) ? 5061 : 5060;
 }
 }

 if (!(transport_states = ast_sip_get_transport_states())) {
 return PJ_SUCCESS;
 }

 if (!(transport_state = ao2_callback(transport_states, 0, find_transport_state_in_use, &details))) {
 return PJ_SUCCESS;
 }

 if (!(transport = ast_sorcery_retrieve_by_id(ast_sip_get_sorcery(), "transport", transport_state->id))) {
 return PJ_SUCCESS;
 }

 if (transport_state->localnet) {
 ast_sockaddr_parse(&addr, tdata->tp_info.dst_name, PARSE_PORT_FORBID);
 ast_sockaddr_set_port(&addr, tdata->tp_info.dst_port);

 /* See if where we are sending this request is local or not, and if not that we can get a Contact URI to modify */
 if (ast_sip_transport_is_local(transport_state, &addr)) {
 ast_debug(5, "Request is being sent to local address, skipping NAT manipulation\n");
 return PJ_SUCCESS;
 }
 }

 if (!ast_sockaddr_isnull(&transport_state->external_signaling_address)) {
 pjsip_cseq_hdr *cseq = PJSIP_MSG_CSEQ_HDR(tdata->msg);

 /* Update the Contact header with the external address. We only do this if
 * a CSeq is not present (which should not happen - but we are extra safe),
 * if a request is being sent, or if a response is sent that is not a response
 * to a REGISTER. We specifically don't do this for a response to a REGISTER
 * as the Contact headers would contain the registered Contacts, and not our
 * own Contact.
 */
 if (!cseq || tdata->msg->type == PJSIP_REQUEST_MSG ||
 pjsip_method_cmp(&cseq->method, &pjsip_register_method)) {
 /* We can only rewrite the URI when one is present */
 if (uri || (uri = nat_get_contact_sip_uri(tdata))) {
 pj_strdup2(tdata->pool, &uri->host, ast_sockaddr_stringify_host(&transport_state->external_signaling_address));
 if (transport->external_signaling_port) {
 uri->port = transport->external_signaling_port;
 ast_debug(4, "Re-wrote Contact URI port to %d\n", uri->port);
 }
 }
 }

 /* Update the via header if relevant */
 if ((tdata->msg->type == PJSIP_REQUEST_MSG) && (via || (via = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_VIA, NULL)))) {
 pj_strdup2(tdata->pool, &via->sent_by.host, ast_sockaddr_stringify_host(&transport_state->external_signaling_address));
 if (transport->external_signaling_port) {
 via->sent_by.port = transport->external_signaling_port;
 }
 }
 }

 /* Invoke any additional hooks that may be registered */
 if ((hooks = ast_sorcery_retrieve_by_fields(ast_sip_get_sorcery(), "nat_hook", AST_RETRIEVE_FLAG_MULTIPLE | AST_RETRIEVE_FLAG_ALL, NULL))) {
 struct nat_hook_details hook_details = {
 .tdata = tdata,
 .transport = transport,
 };
 ao2_callback(hooks, 0, nat_invoke_hook, &hook_details);
 }

 return PJ_SUCCESS;
}

static pj_status_t nat_on_tx_message(pjsip_tx_data *tdata) {
 pj_status_t rc;

 rc = process_nat(tdata);
 restore_orig_contact_host(tdata);

 return rc;
}


static pjsip_module nat_module = {
 .name = { "NAT", 3 },
 .id = -1,
 .priority = PJSIP_MOD_PRIORITY_TSX_LAYER - 2,
 .on_rx_request = nat_on_rx_message,
 .on_rx_response = nat_on_rx_message,
 .on_tx_request = nat_on_tx_message,
 .on_tx_response = nat_on_tx_message,
};

/*! \brief Function called when an INVITE goes out */
static int nat_incoming_invite_request(struct ast_sip_session *session, struct pjsip_rx_data *rdata)
{
 if (session->inv_session->state == PJSIP_INV_STATE_INCOMING) {
 pjsip_dlg_add_usage(session->inv_session->dlg, &nat_module, NULL);
 }

 return 0;
}

/*! \brief Function called when an INVITE response comes in */
static void nat_incoming_invite_response(struct ast_sip_session *session, struct pjsip_rx_data *rdata)
{
 handle_rx_message(session->endpoint, rdata);
}

/*! \brief Function called when an INVITE comes in */
static void nat_outgoing_invite_request(struct ast_sip_session *session, struct pjsip_tx_data *tdata)
{
 if (session->inv_session->state == PJSIP_INV_STATE_NULL) {
 pjsip_dlg_add_usage(session->inv_session->dlg, &nat_module, NULL);
 }
}

/*! \brief Supplement for adding NAT functionality to dialog */
static struct ast_sip_session_supplement nat_supplement = {
 .method = "INVITE",
 .priority = AST_SIP_SUPPLEMENT_PRIORITY_FIRST + 1,
 .incoming_request = nat_incoming_invite_request,
 .outgoing_request = nat_outgoing_invite_request,
 .incoming_response = nat_incoming_invite_response,
};


static int unload_module(void)
{
 ast_sip_session_unregister_supplement(&nat_supplement);
 ast_sip_unregister_service(&nat_module);
 return 0;
}

static int load_module(void)
{
 if (ast_sip_register_service(&nat_module)) {
 ast_log(LOG_ERROR, "Could not register NAT module for incoming and outgoing requests\n");
 return AST_MODULE_LOAD_DECLINE;
 }

 ast_sip_session_register_supplement(&nat_supplement);

 return AST_MODULE_LOAD_SUCCESS;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP NAT Support",
 .support_level = AST_MODULE_SUPPORT_CORE,
 .load = load_module,
 .unload = unload_module,
 .load_pri = AST_MODPRI_APP_DEPEND,
 .requires = "res_pjsip,res_pjsip_session",
);