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<Bytes> buffer_queue = new Gee.LinkedList<Bytes>();
private uint pull_timeout = uint.MAX;
private string peer_fingerprint;
private Crypto.Srtp.Session encrypt_session;
private Crypto.Srtp.Session decrypt_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 (decrypt_session != null) {
if (component_id == 1) return decrypt_session.decrypt_rtp(data);
if (component_id == 2) return decrypt_session.decrypt_rtcp(data);
} else if (component_id == 1) {
on_data_rec(data);
}
return null;
}
public uint8[] process_outgoing_data(uint component_id, uint8[] data) {
if (encrypt_session != null) {
if (component_id == 1) return encrypt_session.encrypt_rtp(data);
if (component_id == 2) return encrypt_session.encrypt_rtcp(data);
}
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<int> thread = new Thread<int> (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");
}
Crypto.Srtp.Session encrypt_session = new Crypto.Srtp.Session(Crypto.Srtp.Encryption.AES_CM, Crypto.Srtp.Authentication.HMAC_SHA1, 10, Crypto.Srtp.Prf.AES_CM, 0);
Crypto.Srtp.Session decrypt_session = new Crypto.Srtp.Session(Crypto.Srtp.Encryption.AES_CM, Crypto.Srtp.Authentication.HMAC_SHA1, 10, Crypto.Srtp.Prf.AES_CM, 0);
if (server) {
encrypt_session.setkey(server_key.extract(), server_salt.extract());
decrypt_session.setkey(client_key.extract(), client_salt.extract());
} else {
encrypt_session.setkey(client_key.extract(), client_salt.extract());
decrypt_session.setkey(server_key.extract(), server_salt.extract());
}
this.encrypt_session = (owned)encrypt_session;
this.decrypt_session = (owned)decrypt_session;
}
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;
}
private uint8[] uint8_pt_to_a(uint8* data, uint size) {
uint8[size] ret = new uint8[size];
for (int i = 0; i < size; i++) {
ret[i] = data[i];
}
return ret;
}
}
