asterisk/res/res_pjsip_authenticator_dig...

575 lines
16 KiB
C

/*
* Asterisk -- An open source telephony toolkit.
*
* Copyright (C) 2013, Digium, Inc.
*
* Mark Michelson <mmichelson@digium.com>
*
* 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.
*/
#include "asterisk.h"
#include <pjsip.h>
#include "asterisk/res_pjsip.h"
#include "asterisk/logger.h"
#include "asterisk/module.h"
#include "asterisk/strings.h"
#include "asterisk/test.h"
/*** MODULEINFO
<depend>pjproject</depend>
<depend>res_pjsip</depend>
<support_level>core</support_level>
***/
/* From the auth/realm realtime column size */
#define MAX_REALM_LENGTH 40
static char default_realm[MAX_REALM_LENGTH + 1];
AO2_GLOBAL_OBJ_STATIC(entity_id);
/*!
* \brief Determine if authentication is required
*
* Authentication is required if the endpoint has at least one auth
* section specified
*/
static int digest_requires_authentication(struct ast_sip_endpoint *endpoint, pjsip_rx_data *rdata)
{
RAII_VAR(struct ast_sip_endpoint *, artificial, ast_sip_get_artificial_endpoint(), ao2_cleanup);
return endpoint == artificial || AST_VECTOR_SIZE(&endpoint->inbound_auths) > 0;
}
static void auth_store_cleanup(void *data)
{
struct ast_sip_auth **auth = data;
ao2_cleanup(*auth);
ast_free(data);
}
/*!
* \brief Thread-local storage for \ref ast_sip_auth
*
* The PJSIP authentication API is a bit annoying. When you set
* up an authentication server, you specify a lookup callback to
* call into when verifying incoming credentials. The problem
* with this callback is that it only gives you the realm and
* authentication username. In 2.0.5, there is a new version of
* the callback you can use that gives the pjsip_rx_data in
* addition.
*
* Unfortunately, the data we actually \b need is the
* \ref ast_sip_auth we are currently observing. So we have two
* choices:
* 1) Use the current PJSIP API and use thread-local storage
* to temporarily store our SIP authentication information. Then
* in the callback, we can retrieve the authentication info and
* use as needed. Given our threading model, this is safe.
* 2) Use the 2.0.5 API and temporarily store the authentication
* information in the rdata's endpoint_info. Then in the callback,
* we can retrieve the authentication info from the rdata.
*
* I've chosen option 1 since it does not require backporting
* any APIs from future versions of PJSIP, plus I feel the
* thread-local option is a bit cleaner.
*/
AST_THREADSTORAGE_CUSTOM(auth_store, NULL, auth_store_cleanup);
/*!
* \brief Store shallow copy authentication information in thread-local storage
*/
static int store_auth(const struct ast_sip_auth *auth)
{
const struct ast_sip_auth **pointing;
pointing = ast_threadstorage_get(&auth_store, sizeof(pointing));
if (!pointing) {
return -1;
}
*pointing = auth;
return 0;
}
/*!
* \brief Remove shallow copy authentication information from thread-local storage
*/
static int remove_auth(void)
{
struct ast_sip_auth **pointing;
pointing = ast_threadstorage_get(&auth_store, sizeof(pointing));
if (!pointing) {
return -1;
}
*pointing = NULL;
return 0;
}
/*!
* \brief Retrieve shallow copy authentication information from thread-local storage
*/
static const struct ast_sip_auth *get_auth(void)
{
struct ast_sip_auth **auth;
auth = ast_threadstorage_get(&auth_store, sizeof(auth));
if (auth) {
return *auth;
}
return NULL;
}
/*!
* \brief Lookup callback for authentication verification
*
* This function is called when we call pjsip_auth_srv_verify(). It
* expects us to verify that the realm and account name from the
* Authorization header is correct. We are then supposed to supply
* a password or MD5 sum of credentials.
*
* \param pool A memory pool we can use for allocations
* \param realm The realm from the Authorization header
* \param acc_name the user from the Authorization header
* \param[out] info The credentials we need to fill in
* \retval PJ_SUCCESS Successful authentication
* \retval other Unsuccessful
*/
static pj_status_t digest_lookup(pj_pool_t *pool, const pj_str_t *realm,
const pj_str_t *acc_name, pjsip_cred_info *info)
{
const struct ast_sip_auth *auth;
auth = get_auth();
if (!auth) {
return PJSIP_SC_FORBIDDEN;
}
if (auth->type == AST_SIP_AUTH_TYPE_ARTIFICIAL) {
return PJSIP_SC_FORBIDDEN;
}
if (pj_strcmp2(realm, auth->realm)) {
return PJSIP_SC_FORBIDDEN;
}
if (pj_strcmp2(acc_name, auth->auth_user)) {
return PJSIP_SC_FORBIDDEN;
}
pj_strdup2(pool, &info->realm, auth->realm);
pj_strdup2(pool, &info->username, auth->auth_user);
switch (auth->type) {
case AST_SIP_AUTH_TYPE_USER_PASS:
pj_strdup2(pool, &info->data, auth->auth_pass);
info->data_type = PJSIP_CRED_DATA_PLAIN_PASSWD;
break;
case AST_SIP_AUTH_TYPE_MD5:
pj_strdup2(pool, &info->data, auth->md5_creds);
info->data_type = PJSIP_CRED_DATA_DIGEST;
break;
default:
return PJSIP_SC_FORBIDDEN;
}
return PJ_SUCCESS;
}
/*!
* \brief Calculate a nonce
*
* We use this in order to create authentication challenges. We also use this in order
* to verify that an incoming request with credentials could be in response to one
* of our challenges.
*
* The nonce is calculated from a timestamp, the source IP address, the source port, a
* unique ID for us, and the realm. This helps to ensure that the incoming request
* is from the same source that the nonce was calculated for. Including the realm
* ensures that multiple challenges to the same request have different nonces.
*
* \param nonce
* \param timestamp A UNIX timestamp expressed as a string
* \param rdata The incoming request
* \param realm The realm for which authentication should occur
*/
static int build_nonce(struct ast_str **nonce, const char *timestamp, const pjsip_rx_data *rdata, const char *realm)
{
struct ast_str *str = ast_str_alloca(256);
RAII_VAR(char *, eid, ao2_global_obj_ref(entity_id), ao2_cleanup);
char hash[33];
/*
* Note you may be tempted to think why not include the port. The reason
* is that when using TCP the port can potentially differ from before.
*/
ast_str_append(&str, 0, "%s", timestamp);
ast_str_append(&str, 0, ":%s", rdata->pkt_info.src_name);
ast_str_append(&str, 0, ":%s", eid);
ast_str_append(&str, 0, ":%s", realm);
ast_md5_hash(hash, ast_str_buffer(str));
ast_str_append(nonce, 0, "%s/%s", timestamp, hash);
return 0;
}
/*!
* \brief Ensure that a nonce on an incoming request is sane.
*
* The nonce in an incoming Authorization header needs to pass some scrutiny in order
* for us to consider accepting it. What we do is re-build a nonce based on request
* data and a realm and see if it matches the nonce they sent us.
* \param candidate The nonce on an incoming request
* \param rdata The incoming request
* \param auth The auth credentials we are trying to match against.
* \retval 0 Nonce does not pass validity checks
* \retval 1 Nonce passes validity check
*/
static int check_nonce(const char *candidate, const pjsip_rx_data *rdata, const struct ast_sip_auth *auth)
{
char *copy = ast_strdupa(candidate);
char *timestamp = strsep(&copy, "/");
int timestamp_int;
time_t now = time(NULL);
struct ast_str *calculated = ast_str_alloca(64);
if (!copy) {
/* Clearly a bad nonce! */
return 0;
}
if (sscanf(timestamp, "%30d", &timestamp_int) != 1) {
return 0;
}
if ((int) now - timestamp_int > auth->nonce_lifetime) {
return 0;
}
build_nonce(&calculated, timestamp, rdata, auth->realm);
ast_debug(3, "Calculated nonce %s. Actual nonce is %s\n", ast_str_buffer(calculated), candidate);
if (strcmp(ast_str_buffer(calculated), candidate)) {
return 0;
}
return 1;
}
static int find_challenge(const pjsip_rx_data *rdata, const struct ast_sip_auth *auth)
{
struct pjsip_authorization_hdr *auth_hdr = (pjsip_authorization_hdr *) &rdata->msg_info.msg->hdr;
int challenge_found = 0;
char nonce[64];
while ((auth_hdr = (pjsip_authorization_hdr *) pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_AUTHORIZATION, auth_hdr->next))) {
ast_copy_pj_str(nonce, &auth_hdr->credential.digest.nonce, sizeof(nonce));
if (check_nonce(nonce, rdata, auth) && !pj_strcmp2(&auth_hdr->credential.digest.realm, auth->realm)) {
challenge_found = 1;
break;
}
}
return challenge_found;
}
/*!
* \brief Common code for initializing a pjsip_auth_srv
*/
static void setup_auth_srv(pj_pool_t *pool, pjsip_auth_srv *auth_server, const char *realm)
{
pj_str_t realm_str;
pj_cstr(&realm_str, realm);
pjsip_auth_srv_init(pool, auth_server, &realm_str, digest_lookup, 0);
}
/*!
* \brief Result of digest verification
*/
enum digest_verify_result {
/*! Authentication credentials incorrect */
AUTH_FAIL = 0,
/*! Authentication credentials correct */
AUTH_SUCCESS,
/*! Authentication credentials correct but nonce mismatch */
AUTH_STALE,
/*! Authentication credentials were not provided */
AUTH_NOAUTH,
};
static char *verify_result_str[] = {
"FAIL",
"SUCCESS",
"STALE",
"NOAUTH"
};
/*!
* \brief astobj2 callback for verifying incoming credentials
*
* \param auth The ast_sip_auth to check against
* \param rdata The incoming request
* \param pool A pool to use for the auth server
* \return CMP_MATCH on successful authentication
* \return 0 on failed authentication
*/
static int verify(const struct ast_sip_auth *auth, pjsip_rx_data *rdata, pj_pool_t *pool)
{
pj_status_t authed;
int response_code;
pjsip_auth_srv auth_server;
int stale = 0;
int res = AUTH_FAIL;
if (!find_challenge(rdata, auth)) {
/* Couldn't find a challenge with a sane nonce.
* Nonce mismatch may just be due to staleness.
*/
stale = 1;
}
setup_auth_srv(pool, &auth_server, auth->realm);
store_auth(auth);
authed = pjsip_auth_srv_verify(&auth_server, rdata, &response_code);
remove_auth();
if (authed == PJ_SUCCESS) {
if (stale) {
res = AUTH_STALE;
} else {
res = AUTH_SUCCESS;
}
}
if (authed == PJSIP_EAUTHNOAUTH) {
res = AUTH_NOAUTH;
}
ast_debug(3, "Realm: %s Username: %s Result: %s\n",
auth->realm, auth->auth_user, verify_result_str[res]);
ast_test_suite_event_notify("INCOMING_AUTH_VERIFY_RESULT",
"Realm: %s\r\n"
"Username: %s\r\n"
"Status: %s",
auth->realm, auth->auth_user, verify_result_str[res]);
return res;
}
/*!
* \brief astobj2 callback for adding digest challenges to responses
*
* \param realm An auth's realm to build a challenge from
* \param tdata The response to add the challenge to
* \param rdata The request the challenge is in response to
* \param is_stale Indicates whether nonce on incoming request was stale
*/
static void challenge(const char *realm, pjsip_tx_data *tdata, const pjsip_rx_data *rdata, int is_stale)
{
pj_str_t qop;
pj_str_t pj_nonce;
pjsip_auth_srv auth_server;
struct ast_str *nonce = ast_str_alloca(256);
char time_buf[32];
time_t timestamp = time(NULL);
snprintf(time_buf, sizeof(time_buf), "%d", (int) timestamp);
build_nonce(&nonce, time_buf, rdata, realm);
setup_auth_srv(tdata->pool, &auth_server, realm);
pj_cstr(&pj_nonce, ast_str_buffer(nonce));
pj_cstr(&qop, "auth");
pjsip_auth_srv_challenge(&auth_server, &qop, &pj_nonce, NULL, is_stale ? PJ_TRUE : PJ_FALSE, tdata);
}
/*!
* \brief Check authentication using Digest scheme
*
* This function will check an incoming message against configured authentication
* options. If \b any of the incoming Authorization headers result in successful
* authentication, then authentication is considered successful.
*
* \see ast_sip_check_authentication
*/
static enum ast_sip_check_auth_result digest_check_auth(struct ast_sip_endpoint *endpoint,
pjsip_rx_data *rdata, pjsip_tx_data *tdata)
{
struct ast_sip_auth **auths;
struct ast_sip_auth **auths_shallow;
enum digest_verify_result *verify_res;
struct ast_sip_endpoint *artificial_endpoint;
enum ast_sip_check_auth_result res;
int idx;
int is_artificial;
int failures = 0;
size_t auth_size;
auth_size = AST_VECTOR_SIZE(&endpoint->inbound_auths);
ast_assert(0 < auth_size);
auths = ast_alloca(auth_size * sizeof(*auths));
verify_res = ast_alloca(auth_size * sizeof(*verify_res));
artificial_endpoint = ast_sip_get_artificial_endpoint();
if (!artificial_endpoint) {
/* Should not happen except possibly if we are shutting down. */
return AST_SIP_AUTHENTICATION_ERROR;
}
is_artificial = endpoint == artificial_endpoint;
ao2_ref(artificial_endpoint, -1);
if (is_artificial) {
ast_assert(auth_size == 1);
auths[0] = ast_sip_get_artificial_auth();
if (!auths[0]) {
/* Should not happen except possibly if we are shutting down. */
return AST_SIP_AUTHENTICATION_ERROR;
}
} else {
memset(auths, 0, auth_size * sizeof(*auths));
if (ast_sip_retrieve_auths(&endpoint->inbound_auths, auths)) {
res = AST_SIP_AUTHENTICATION_ERROR;
goto cleanup;
}
}
/* Setup shallow copy of auths */
if (ast_strlen_zero(default_realm)) {
auths_shallow = auths;
} else {
/*
* Set default realm on a shallow copy of the authentication
* objects that don't have a realm set.
*/
auths_shallow = ast_alloca(auth_size * sizeof(*auths_shallow));
for (idx = 0; idx < auth_size; ++idx) {
if (ast_strlen_zero(auths[idx]->realm)) {
/*
* Make a shallow copy and set the default realm on it.
*
* The stack allocation is OK here. Normally this will
* loop one time. If you have multiple auths then you
* shouldn't need more auths than the normal complement
* of fingers and toes. Otherwise, you should check
* your sanity for setting up your system up that way.
*/
auths_shallow[idx] = ast_alloca(sizeof(**auths_shallow));
memcpy(auths_shallow[idx], auths[idx], sizeof(**auths_shallow));
*((char **) (&auths_shallow[idx]->realm)) = default_realm;
ast_debug(3, "Using default realm '%s' on incoming auth '%s'.\n",
default_realm, ast_sorcery_object_get_id(auths_shallow[idx]));
} else {
auths_shallow[idx] = auths[idx];
}
}
}
for (idx = 0; idx < auth_size; ++idx) {
verify_res[idx] = verify(auths_shallow[idx], rdata, tdata->pool);
if (verify_res[idx] == AUTH_SUCCESS) {
res = AST_SIP_AUTHENTICATION_SUCCESS;
goto cleanup;
}
if (verify_res[idx] == AUTH_FAIL) {
failures++;
}
}
for (idx = 0; idx < auth_size; ++idx) {
challenge(auths_shallow[idx]->realm, tdata, rdata, verify_res[idx] == AUTH_STALE);
}
if (failures == auth_size) {
res = AST_SIP_AUTHENTICATION_FAILED;
} else {
res = AST_SIP_AUTHENTICATION_CHALLENGE;
}
cleanup:
ast_sip_cleanup_auths(auths, auth_size);
return res;
}
static struct ast_sip_authenticator digest_authenticator = {
.requires_authentication = digest_requires_authentication,
.check_authentication = digest_check_auth,
};
static int build_entity_id(void)
{
char *eid;
eid = ao2_alloc(AST_UUID_STR_LEN, NULL);
if (!eid) {
return -1;
}
ast_uuid_generate_str(eid, AST_UUID_STR_LEN);
ao2_global_obj_replace_unref(entity_id, eid);
ao2_ref(eid, -1);
return 0;
}
static void global_loaded(const char *object_type)
{
ast_sip_get_default_realm(default_realm, sizeof(default_realm));
}
/*! \brief Observer which is used to update our default_realm when the global setting changes */
static struct ast_sorcery_observer global_observer = {
.loaded = global_loaded,
};
static int reload_module(void)
{
if (build_entity_id()) {
return -1;
}
return 0;
}
static int load_module(void)
{
if (build_entity_id()) {
return AST_MODULE_LOAD_DECLINE;
}
ast_sorcery_observer_add(ast_sip_get_sorcery(), "global", &global_observer);
ast_sorcery_reload_object(ast_sip_get_sorcery(), "global");
if (ast_sip_register_authenticator(&digest_authenticator)) {
ao2_global_obj_release(entity_id);
return AST_MODULE_LOAD_DECLINE;
}
return AST_MODULE_LOAD_SUCCESS;
}
static int unload_module(void)
{
ast_sorcery_observer_remove(ast_sip_get_sorcery(), "global", &global_observer);
ast_sip_unregister_authenticator(&digest_authenticator);
ao2_global_obj_release(entity_id);
return 0;
}
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP authentication resource",
.support_level = AST_MODULE_SUPPORT_CORE,
.load = load_module,
.unload = unload_module,
.reload = reload_module,
.load_pri = AST_MODPRI_CHANNEL_DEPEND - 5,
.requires = "res_pjsip",
);