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res_rtp_asterisk: Enable Forward Secrecy (PFS) for DTLS.

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Since July 2014, TLS based protocols (SIP over TLS, Secure WebSockets, HTTPS)
support PFS thanks to ASTERISK-23905. In July 2015, the same feature was added
for DTLS. The source code from main/tcptls.c should have been re-used to ease
security audits. Therefore, this change rolls back the change from July 2015 and
re-uses the code from July 2014. This has the additional benefits to work under
CentOS 7 and enabling not just ECDHE but DHE based cipher suites as well.

ASTERISK-25659 #close
Reported by: StefanEng86, urbaniak, pay123
Tested by: sarumjanuch, traud
patches:
res_rtp_asterisk.patch submitted by sarumjanuch
dtls_centos_step_1.patch submitted by traud
dtls_centos_step_2.patch submitted by traud

Change-Id: I537cadf4421f092a613146b230f2c0ee1be28d5c
This commit is contained in:
Alexander Traud
2016-06-22 14:13:39 +02:00
parent 8cea01ab1b
commit 332beb27d8
5 changed files with 57 additions and 84 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
res/res_rtp_asterisk.c
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@@ -1340,7 +1340,7 @@ static int ast_rtp_dtls_set_configuration(struct ast_rtp_instance *instance, con
{
struct ast_rtp *rtp = ast_rtp_instance_get_data(instance);
int res;
#ifndef HAVE_OPENSSL_ECDH_AUTO
#ifdef HAVE_OPENSSL_EC
EC_KEY *ecdh;
#endif
@@ -1368,15 +1368,42 @@ static int ast_rtp_dtls_set_configuration(struct ast_rtp_instance *instance, con
SSL_CTX_set_read_ahead(rtp->ssl_ctx, 1);
#ifdef HAVE_OPENSSL_ECDH_AUTO
SSL_CTX_set_ecdh_auto(rtp->ssl_ctx, 1);
#else
#ifdef HAVE_OPENSSL_EC
if (!ast_strlen_zero(dtls_cfg->pvtfile)) {
BIO *bio = BIO_new_file(dtls_cfg->pvtfile, "r");
if (bio != NULL) {
DH *dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
if (dh != NULL) {
if (SSL_CTX_set_tmp_dh(rtp->ssl_ctx, dh)) {
long options = SSL_OP_CIPHER_SERVER_PREFERENCE |
SSL_OP_SINGLE_DH_USE | SSL_OP_SINGLE_ECDH_USE;
options = SSL_CTX_set_options(rtp->ssl_ctx, options);
ast_verb(2, "DTLS DH initialized, PFS enabled\n");
}
DH_free(dh);
}
BIO_free(bio);
}
}
/* enables AES-128 ciphers, to get AES-256 use NID_secp384r1 */
ecdh = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
if (ecdh) {
SSL_CTX_set_tmp_ecdh(rtp->ssl_ctx, ecdh);
if (ecdh != NULL) {
if (SSL_CTX_set_tmp_ecdh(rtp->ssl_ctx, ecdh)) {
#ifndef SSL_CTRL_SET_ECDH_AUTO
#define SSL_CTRL_SET_ECDH_AUTO 94
#endif
/* SSL_CTX_set_ecdh_auto(rtp->ssl_ctx, on); requires OpenSSL 1.0.2 which wraps: */
if (SSL_CTX_ctrl(rtp->ssl_ctx, SSL_CTRL_SET_ECDH_AUTO, 1, NULL)) {
ast_verb(2, "DTLS ECDH initialized (automatic), faster PFS enabled\n");
} else {
ast_verb(2, "DTLS ECDH initialized (secp256r1), faster PFS enabled\n");
}
}
EC_KEY_free(ecdh);
}
#endif
#endif /* #ifdef HAVE_OPENSSL_EC */
rtp->dtls_verify = dtls_cfg->verify;