using GnuTLS; public class DtlsSrtp { public signal void send_data(uint8[] data); private X509.Certificate[] own_cert; private X509.PrivateKey private_key; private Cond buffer_cond = new Cond(); private Mutex buffer_mutex = new Mutex(); private Gee.LinkedList buffer_queue = new Gee.LinkedList(); private uint pull_timeout = uint.MAX; private string peer_fingerprint; private Crypto.Srtp.Session srtp_session = new Crypto.Srtp.Session(); public static DtlsSrtp setup() throws GLib.Error { var obj = new DtlsSrtp(); obj.generate_credentials(); return obj; } internal string get_own_fingerprint(DigestAlgorithm digest_algo) { return format_certificate(own_cert[0], digest_algo); } public void set_peer_fingerprint(string fingerprint) { this.peer_fingerprint = fingerprint; } public uint8[] process_incoming_data(uint component_id, uint8[] data) { if (srtp_session.has_decrypt) { try { if (component_id == 1) { if (data.length >= 2 && data[1] >= 192 && data[1] < 224) { return srtp_session.decrypt_rtcp(data); } return srtp_session.decrypt_rtp(data); } if (component_id == 2) return srtp_session.decrypt_rtcp(data); } catch (Error e) { warning("%s (%d)", e.message, e.code); return null; } } else if (component_id == 1) { on_data_rec(data); } return null; } public uint8[] process_outgoing_data(uint component_id, uint8[] data) { if (srtp_session.has_encrypt) { try { if (component_id == 1) { if (data.length >= 2 && data[1] >= 192 && data[1] < 224) { return srtp_session.encrypt_rtcp(data); } return srtp_session.encrypt_rtp(data); } if (component_id == 2) return srtp_session.encrypt_rtcp(data); } catch (Error e) { warning("%s (%d)", e.message, e.code); return null; } } return null; } public void on_data_rec(owned uint8[] data) { buffer_mutex.lock(); buffer_queue.add(new Bytes.take(data)); buffer_cond.signal(); buffer_mutex.unlock(); } private void generate_credentials() throws GLib.Error { int err = 0; private_key = X509.PrivateKey.create(); err = private_key.generate(PKAlgorithm.RSA, 2048); throw_if_error(err); var start_time = new DateTime.now_local().add_days(1); var end_time = start_time.add_days(2); X509.Certificate cert = X509.Certificate.create(); cert.set_key(private_key); cert.set_version(1); cert.set_activation_time ((time_t) start_time.to_unix ()); cert.set_expiration_time ((time_t) end_time.to_unix ()); uint32 serial = 1; cert.set_serial(&serial, sizeof(uint32)); cert.sign(cert, private_key); own_cert = new X509.Certificate[] { (owned)cert }; } public async void setup_dtls_connection(bool server) { InitFlags server_or_client = server ? InitFlags.SERVER : InitFlags.CLIENT; debug("Setting up DTLS connection. We're %s", server_or_client.to_string()); CertificateCredentials cert_cred = CertificateCredentials.create(); int err = cert_cred.set_x509_key(own_cert, private_key); throw_if_error(err); Session? session = Session.create(server_or_client | InitFlags.DATAGRAM); session.enable_heartbeat(1); session.set_srtp_profile_direct("SRTP_AES128_CM_HMAC_SHA1_80"); session.set_credentials(GnuTLS.CredentialsType.CERTIFICATE, cert_cred); session.server_set_request(CertificateRequest.REQUEST); session.set_priority_from_string("NORMAL:!VERS-TLS-ALL:+VERS-DTLS-ALL:+CTYPE-CLI-X509"); session.set_transport_pointer(this); session.set_pull_function(pull_function); session.set_pull_timeout_function(pull_timeout_function); session.set_push_function(push_function); session.set_verify_function(verify_function); Thread thread = new Thread (null, () => { DateTime maximum_time = new DateTime.now_utc().add_seconds(20); do { err = session.handshake(); DateTime current_time = new DateTime.now_utc(); if (maximum_time.compare(current_time) < 0) { warning("DTLS handshake timeouted"); return -1; } } while (err < 0 && !((ErrorCode)err).is_fatal()); Idle.add(setup_dtls_connection.callback); return err; }); yield; err = thread.join(); uint8[] km = new uint8[150]; Datum? client_key, client_salt, server_key, server_salt; session.get_srtp_keys(km, km.length, out client_key, out client_salt, out server_key, out server_salt); if (client_key == null || client_salt == null || server_key == null || server_salt == null) { warning("SRTP client/server key/salt null"); } if (server) { srtp_session.set_encryption_key(Crypto.Srtp.AES_CM_128_HMAC_SHA1_80, server_key.extract(), server_salt.extract()); srtp_session.set_decryption_key(Crypto.Srtp.AES_CM_128_HMAC_SHA1_80, client_key.extract(), client_salt.extract()); } else { srtp_session.set_encryption_key(Crypto.Srtp.AES_CM_128_HMAC_SHA1_80, client_key.extract(), client_salt.extract()); srtp_session.set_decryption_key(Crypto.Srtp.AES_CM_128_HMAC_SHA1_80, server_key.extract(), server_salt.extract()); } } private static ssize_t pull_function(void* transport_ptr, uint8[] buffer) { DtlsSrtp self = transport_ptr as DtlsSrtp; self.buffer_mutex.lock(); while (self.buffer_queue.size == 0) { self.buffer_cond.wait(self.buffer_mutex); } owned Bytes data = self.buffer_queue.remove_at(0); self.buffer_mutex.unlock(); uint8[] data_uint8 = Bytes.unref_to_data(data); Memory.copy(buffer, data_uint8, data_uint8.length); // The callback should return 0 on connection termination, a positive number indicating the number of bytes received, and -1 on error. return (ssize_t)data.length; } private static int pull_timeout_function(void* transport_ptr, uint ms) { DtlsSrtp self = transport_ptr as DtlsSrtp; DateTime current_time = new DateTime.now_utc(); current_time.add_seconds(ms/1000); int64 end_time = current_time.to_unix(); self.buffer_mutex.lock(); while (self.buffer_queue.size == 0) { self.buffer_cond.wait_until(self.buffer_mutex, end_time); DateTime new_current_time = new DateTime.now_utc(); if (new_current_time.compare(current_time) > 0) { break; } } self.buffer_mutex.unlock(); // The callback should return 0 on timeout, a positive number if data can be received, and -1 on error. return 1; } private static ssize_t push_function(void* transport_ptr, uint8[] buffer) { DtlsSrtp self = transport_ptr as DtlsSrtp; self.send_data(buffer); // The callback should return a positive number indicating the bytes sent, and -1 on error. return (ssize_t)buffer.length; } private static int verify_function(Session session) { DtlsSrtp self = session.get_transport_pointer() as DtlsSrtp; try { bool valid = self.verify_peer_cert(session); if (!valid) { warning("DTLS certificate invalid. Aborting handshake."); return 1; } } catch (Error e) { warning("Error during DTLS certificate validation: %s. Aborting handshake.", e.message); return 1; } // The callback function should return 0 for the handshake to continue or non-zero to terminate. return 0; } private bool verify_peer_cert(Session session) throws GLib.Error { unowned Datum[] cert_datums = session.get_peer_certificates(); if (cert_datums.length == 0) { warning("No peer certs"); return false; } if (cert_datums.length > 1) warning("More than one peer cert"); X509.Certificate peer_cert = X509.Certificate.create(); peer_cert.import(ref cert_datums[0], CertificateFormat.DER); string peer_fp_str = format_certificate(peer_cert, DigestAlgorithm.SHA256); if (peer_fp_str.down() != this.peer_fingerprint.down()) { warning("First cert in peer cert list doesn't equal advertised one %s vs %s", peer_fp_str, this.peer_fingerprint); return false; } return true; } private string format_certificate(X509.Certificate certificate, DigestAlgorithm digest_algo) { uint8[] buf = new uint8[512]; size_t buf_out_size = 512; certificate.get_fingerprint(digest_algo, buf, ref buf_out_size); var sb = new StringBuilder(); for (int i = 0; i < buf_out_size; i++) { sb.append("%02x".printf(buf[i])); if (i < buf_out_size - 1) { sb.append(":"); } } return sb.str; } }