Tue Aug 20 16:35:15 2013

Asterisk developer's documentation


sdp_crypto.c File Reference

SDP Security descriptions. More...

#include "asterisk.h"
#include "asterisk/options.h"
#include "asterisk/utils.h"
#include "include/sdp_crypto.h"

Go to the source code of this file.

Data Structures

struct  sdp_crypto

Defines

#define SRTP_MASTER_LEN   30
#define SRTP_MASTER_LEN64   (((SRTP_MASTER_LEN) * 8 + 5) / 6 + 1)
#define SRTP_MASTERKEY_LEN   16
#define SRTP_MASTERSALT_LEN   ((SRTP_MASTER_LEN) - (SRTP_MASTERKEY_LEN))

Functions

static int sdp_crypto_activate (struct sdp_crypto *p, int suite_val, unsigned char *remote_key, struct ast_rtp_instance *rtp)
static struct sdp_cryptosdp_crypto_alloc (void)
const char * sdp_crypto_attrib (struct sdp_crypto *p)
void sdp_crypto_destroy (struct sdp_crypto *crypto)
int sdp_crypto_offer (struct sdp_crypto *p)
int sdp_crypto_process (struct sdp_crypto *p, const char *attr, struct ast_rtp_instance *rtp)
struct sdp_cryptosdp_crypto_setup (void)
static int set_crypto_policy (struct ast_srtp_policy *policy, int suite_val, const unsigned char *master_key, unsigned long ssrc, int inbound)

Variables

struct ast_srtp_resres_srtp
struct ast_srtp_policy_resres_srtp_policy

Detailed Description

SDP Security descriptions.

Specified in RFC 4568

Author:
Mikael Magnusson <mikma@users.sourceforge.net>

Definition in file sdp_crypto.c.


Define Documentation

#define SRTP_MASTER_LEN   30

Definition at line 40 of file sdp_crypto.c.

Referenced by sdp_crypto_process(), and sdp_crypto_setup().

#define SRTP_MASTER_LEN64   (((SRTP_MASTER_LEN) * 8 + 5) / 6 + 1)

Definition at line 43 of file sdp_crypto.c.

#define SRTP_MASTERKEY_LEN   16

Definition at line 41 of file sdp_crypto.c.

Referenced by set_crypto_policy().

#define SRTP_MASTERSALT_LEN   ((SRTP_MASTER_LEN) - (SRTP_MASTERKEY_LEN))

Definition at line 42 of file sdp_crypto.c.

Referenced by set_crypto_policy().


Function Documentation

static int sdp_crypto_activate ( struct sdp_crypto p,
int  suite_val,
unsigned char *  remote_key,
struct ast_rtp_instance rtp 
) [static]

Definition at line 136 of file sdp_crypto.c.

References ast_srtp_policy_res::alloc, ast_debug, ast_log(), ast_rtp_engine_srtp_is_registered(), ast_rtp_instance_add_srtp_policy(), ast_rtp_instance_get_stats(), AST_RTP_INSTANCE_STAT_LOCAL_SSRC, ast_srtp_policy_res::destroy, sdp_crypto::local_key, ast_rtp_instance_stats::local_ssrc, LOG_WARNING, and set_crypto_policy().

Referenced by sdp_crypto_process().

00137 {
00138    struct ast_srtp_policy *local_policy = NULL;
00139    struct ast_srtp_policy *remote_policy = NULL;
00140    struct ast_rtp_instance_stats stats = {0,};
00141    int res = -1;
00142 
00143    if (!ast_rtp_engine_srtp_is_registered()) {
00144       return -1;
00145    }
00146 
00147    if (!p) {
00148       return -1;
00149    }
00150 
00151    if (!(local_policy = res_srtp_policy->alloc())) {
00152       return -1;
00153    }
00154 
00155    if (!(remote_policy = res_srtp_policy->alloc())) {
00156       goto err;
00157    }
00158 
00159    if (ast_rtp_instance_get_stats(rtp, &stats, AST_RTP_INSTANCE_STAT_LOCAL_SSRC)) {
00160       goto err;
00161    }
00162 
00163    if (set_crypto_policy(local_policy, suite_val, p->local_key, stats.local_ssrc, 0) < 0) {
00164       goto err;
00165    }
00166 
00167    if (set_crypto_policy(remote_policy, suite_val, remote_key, 0, 1) < 0) {
00168       goto err;
00169    }
00170 
00171    /* Add the SRTP policies */
00172    if (ast_rtp_instance_add_srtp_policy(rtp, remote_policy, local_policy)) {
00173       ast_log(LOG_WARNING, "Could not set SRTP policies\n");
00174       goto err;
00175    }
00176 
00177    ast_debug(1 , "SRTP policy activated\n");
00178    res = 0;
00179 
00180 err:
00181    if (local_policy) {
00182       res_srtp_policy->destroy(local_policy);
00183    }
00184 
00185    if (remote_policy) {
00186       res_srtp_policy->destroy(remote_policy);
00187    }
00188 
00189    return res;
00190 }

static struct sdp_crypto* sdp_crypto_alloc ( void   )  [static, read]

Definition at line 59 of file sdp_crypto.c.

References ast_calloc.

Referenced by sdp_crypto_setup().

00060 {
00061    return ast_calloc(1, sizeof(struct sdp_crypto));
00062 }

const char* sdp_crypto_attrib ( struct sdp_crypto p  ) 

Definition at line 318 of file sdp_crypto.c.

References sdp_crypto::a_crypto.

Referenced by get_crypto_attrib().

00319 {
00320    return p->a_crypto;
00321 }

void sdp_crypto_destroy ( struct sdp_crypto crypto  ) 

Definition at line 64 of file sdp_crypto.c.

References sdp_crypto::a_crypto, ast_free, and sdp_crypto::tag.

Referenced by sdp_crypto_setup(), and sip_srtp_destroy().

00065 {
00066    ast_free(crypto->a_crypto);
00067    crypto->a_crypto = NULL;
00068    ast_free(crypto->tag);
00069    crypto->tag = NULL;
00070    ast_free(crypto);
00071 }

int sdp_crypto_offer ( struct sdp_crypto p  ) 

Definition at line 295 of file sdp_crypto.c.

References sdp_crypto::a_crypto, ast_asprintf, ast_free, ast_log(), ast_strlen_zero(), sdp_crypto::local_key64, LOG_DEBUG, LOG_ERROR, sdp_crypto::suite, and sdp_crypto::tag.

Referenced by get_crypto_attrib(), and sdp_crypto_process().

00296 {
00297    if (ast_strlen_zero(p->suite)) {
00298       /* Default crypto offer */
00299       strcpy(p->suite, "AES_CM_128_HMAC_SHA1_80");
00300    }
00301 
00302    /* Rebuild the crypto line */
00303    if (p->a_crypto) {
00304       ast_free(p->a_crypto);
00305    }
00306 
00307    if (ast_asprintf(&p->a_crypto, "a=crypto:%s %s inline:%s\r\n",
00308           p->tag ? p->tag : "1", p->suite, p->local_key64) == -1) {
00309          ast_log(LOG_ERROR, "Could not allocate memory for crypto line\n");
00310       return -1;
00311    }
00312 
00313    ast_log(LOG_DEBUG, "Crypto line: %s", p->a_crypto);
00314 
00315    return 0;
00316 }

int sdp_crypto_process ( struct sdp_crypto p,
const char *  attr,
struct ast_rtp_instance rtp 
)

Definition at line 192 of file sdp_crypto.c.

References AST_AES_CM_128_HMAC_SHA1_32, AST_AES_CM_128_HMAC_SHA1_80, ast_base64decode(), ast_copy_string(), ast_debug, ast_log(), ast_rtp_engine_srtp_is_registered(), ast_strdup, ast_strdupa, LOG_DEBUG, LOG_ERROR, LOG_NOTICE, LOG_WARNING, sdp_crypto::remote_key, sdp_crypto_activate(), sdp_crypto_offer(), SRTP_MASTER_LEN, str, sdp_crypto::suite, and sdp_crypto::tag.

Referenced by process_crypto().

00193 {
00194    char *str = NULL;
00195    char *tag = NULL;
00196    char *suite = NULL;
00197    char *key_params = NULL;
00198    char *key_param = NULL;
00199    char *session_params = NULL;
00200    char *key_salt = NULL;
00201    char *lifetime = NULL;
00202    int found = 0;
00203    int key_len = 0;
00204    int suite_val = 0;
00205    unsigned char remote_key[SRTP_MASTER_LEN];
00206 
00207    if (!ast_rtp_engine_srtp_is_registered()) {
00208       return -1;
00209    }
00210 
00211    str = ast_strdupa(attr);
00212 
00213    strsep(&str, ":");
00214    tag = strsep(&str, " ");
00215    suite = strsep(&str, " ");
00216    key_params = strsep(&str, " ");
00217    session_params = strsep(&str, " ");
00218 
00219    if (!tag || !suite) {
00220       ast_log(LOG_WARNING, "Unrecognized a=%s", attr);
00221       return -1;
00222    }
00223 
00224    if (session_params) {
00225       ast_log(LOG_WARNING, "Unsupported crypto parameters: %s", session_params);
00226       return -1;
00227    }
00228 
00229    if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_80")) {
00230       suite_val = AST_AES_CM_128_HMAC_SHA1_80;
00231    } else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
00232       suite_val = AST_AES_CM_128_HMAC_SHA1_32;
00233    } else {
00234       ast_log(LOG_WARNING, "Unsupported crypto suite: %s\n", suite);
00235       return -1;
00236    }
00237 
00238    while ((key_param = strsep(&key_params, ";"))) {
00239       char *method = NULL;
00240       char *info = NULL;
00241 
00242       method = strsep(&key_param, ":");
00243       info = strsep(&key_param, ";");
00244 
00245       if (!strcmp(method, "inline")) {
00246          key_salt = strsep(&info, "|");
00247          lifetime = strsep(&info, "|");
00248 
00249          if (lifetime) {
00250             ast_log(LOG_NOTICE, "Crypto life time unsupported: %s\n", attr);
00251             continue;
00252          }
00253 
00254          found = 1;
00255          break;
00256       }
00257    }
00258 
00259    if (!found) {
00260       ast_log(LOG_NOTICE, "SRTP crypto offer not acceptable\n");
00261       return -1;
00262    }
00263 
00264    if ((key_len = ast_base64decode(remote_key, key_salt, sizeof(remote_key))) != SRTP_MASTER_LEN) {
00265       ast_log(LOG_WARNING, "SRTP descriptions key %d != %d\n", key_len, SRTP_MASTER_LEN);
00266       return -1;
00267    }
00268 
00269    if (!memcmp(p->remote_key, remote_key, sizeof(p->remote_key))) {
00270       ast_debug(1, "SRTP remote key unchanged; maintaining current policy\n");
00271       return 0;
00272    }
00273 
00274    /* Set the accepted policy and remote key */
00275    ast_copy_string(p->suite, suite, sizeof(p->suite));
00276    memcpy(p->remote_key, remote_key, sizeof(p->remote_key));
00277 
00278    if (sdp_crypto_activate(p, suite_val, remote_key, rtp) < 0) {
00279       return -1;
00280    }
00281 
00282    if (!p->tag) {
00283       ast_log(LOG_DEBUG, "Accepting crypto tag %s\n", tag);
00284       p->tag = ast_strdup(tag);
00285       if (!p->tag) {
00286          ast_log(LOG_ERROR, "Could not allocate memory for tag\n");
00287          return -1;
00288       }
00289    }
00290 
00291    /* Finally, rebuild the crypto line */
00292    return sdp_crypto_offer(p);
00293 }

struct sdp_crypto* sdp_crypto_setup ( void   )  [read]

Definition at line 73 of file sdp_crypto.c.

References ast_base64decode(), ast_base64encode(), ast_debug, ast_free, ast_log(), ast_rtp_engine_srtp_is_registered(), ast_srtp_res::get_random, sdp_crypto::local_key, sdp_crypto::local_key64, LOG_ERROR, sdp_crypto::remote_key, sdp_crypto_alloc(), sdp_crypto_destroy(), and SRTP_MASTER_LEN.

Referenced by get_crypto_attrib(), and process_crypto().

00074 {
00075    struct sdp_crypto *p;
00076    int key_len;
00077    unsigned char remote_key[SRTP_MASTER_LEN];
00078 
00079    if (!ast_rtp_engine_srtp_is_registered()) {
00080       return NULL;
00081    }
00082 
00083    if (!(p = sdp_crypto_alloc())) {
00084       return NULL;
00085    }
00086 
00087    if (res_srtp->get_random(p->local_key, sizeof(p->local_key)) < 0) {
00088       sdp_crypto_destroy(p);
00089       return NULL;
00090    }
00091 
00092    ast_base64encode(p->local_key64, p->local_key, SRTP_MASTER_LEN, sizeof(p->local_key64));
00093 
00094    key_len = ast_base64decode(remote_key, p->local_key64, sizeof(remote_key));
00095 
00096    if (key_len != SRTP_MASTER_LEN) {
00097       ast_log(LOG_ERROR, "base64 encode/decode bad len %d != %d\n", key_len, SRTP_MASTER_LEN);
00098       ast_free(p);
00099       return NULL;
00100    }
00101 
00102    if (memcmp(remote_key, p->local_key, SRTP_MASTER_LEN)) {
00103       ast_log(LOG_ERROR, "base64 encode/decode bad key\n");
00104       ast_free(p);
00105       return NULL;
00106    }
00107 
00108    ast_debug(1 , "local_key64 %s len %zu\n", p->local_key64, strlen(p->local_key64));
00109 
00110    return p;
00111 }

static int set_crypto_policy ( struct ast_srtp_policy policy,
int  suite_val,
const unsigned char *  master_key,
unsigned long  ssrc,
int  inbound 
) [static]

Definition at line 113 of file sdp_crypto.c.

References ast_log(), ast_rtp_engine_srtp_is_registered(), LOG_WARNING, ast_srtp_policy_res::set_master_key, ast_srtp_policy_res::set_ssrc, ast_srtp_policy_res::set_suite, SRTP_MASTERKEY_LEN, and SRTP_MASTERSALT_LEN.

Referenced by sdp_crypto_activate().

00114 {
00115    const unsigned char *master_salt = NULL;
00116 
00117    if (!ast_rtp_engine_srtp_is_registered()) {
00118       return -1;
00119    }
00120 
00121    master_salt = master_key + SRTP_MASTERKEY_LEN;
00122    if (res_srtp_policy->set_master_key(policy, master_key, SRTP_MASTERKEY_LEN, master_salt, SRTP_MASTERSALT_LEN) < 0) {
00123       return -1;
00124    }
00125 
00126    if (res_srtp_policy->set_suite(policy, suite_val)) {
00127       ast_log(LOG_WARNING, "Could not set remote SRTP suite\n");
00128       return -1;
00129    }
00130 
00131    res_srtp_policy->set_ssrc(policy, ssrc, inbound);
00132 
00133    return 0;
00134 }


Variable Documentation

Definition at line 48 of file rtp_engine.c.

Definition at line 49 of file rtp_engine.c.


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