dtls.c

/*! \file    dtls.c
 * \author   Lorenzo Miniero <lorenzo@meetecho.com>
 * \copyright GNU General Public License v3
 * \brief    DTLS/SRTP processing
 * \details  Implementation (based on OpenSSL and libsrtp) of the DTLS/SRTP
 * transport. The code takes care of the DTLS handshake between peers and
 * the server, and sets the proper SRTP and SRTCP context up accordingly.
 * A DTLS alert from a peer is notified to the plugin handling him/her
 * by means of the hangup_media callback.
 *
 * \ingroup protocols
 * \ref protocols
 */

#include "janus.h"
#include "debug.h"
#include "dtls.h"
#include "rtcp.h"
#include "events.h"

#include <openssl/err.h>
#include <openssl/bn.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/asn1.h>


const gchar *janus_get_dtls_srtp_state(janus_dtls_state state) {
	switch(state) {
		case JANUS_DTLS_STATE_CREATED:
			return "created";
		case JANUS_DTLS_STATE_TRYING:
			return "trying";
		case JANUS_DTLS_STATE_CONNECTED:
			return "connected";
		case JANUS_DTLS_STATE_FAILED:
			return "failed";
		default:
			return NULL;
	}
	return NULL;
}

const gchar *janus_get_dtls_srtp_role(janus_dtls_role role) {
	switch(role) {
		case JANUS_DTLS_ROLE_ACTPASS:
			return "actpass";
		case JANUS_DTLS_ROLE_SERVER:
			return "passive";
		case JANUS_DTLS_ROLE_CLIENT:
			return "active";
		default:
			return NULL;
	}
	return NULL;
}

const gchar *janus_get_dtls_srtp_profile(int profile) {
	switch(profile) {
		case SRTP_AES128_CM_SHA1_80:
			return "SRTP_AES128_CM_SHA1_80";
		case SRTP_AES128_CM_SHA1_32:
			return "SRTP_AES128_CM_SHA1_32";
#ifdef HAVE_SRTP_AESGCM
		case SRTP_AEAD_AES_256_GCM:
			return "SRTP_AEAD_AES_256_GCM";
		case SRTP_AEAD_AES_128_GCM:
			return "SRTP_AEAD_AES_128_GCM";
#endif
		default:
			return NULL;
	}
	return NULL;
}

/* Helper to notify DTLS state changes to the event handlers */
static void janus_dtls_notify_state_change(janus_dtls_srtp *dtls) {
	if(!janus_events_is_enabled())
		return;
	if(dtls == NULL)
		return;
	janus_ice_component *component = (janus_ice_component *)dtls->component;
	if(component == NULL)
		return;
	janus_ice_stream *stream = component->stream;
	if(stream == NULL)
		return;
	janus_ice_handle *handle = stream->handle;
	if(handle == NULL)
		return;
	janus_session *session = (janus_session *)handle->session;
	if(session == NULL)
		return;
	json_t *info = json_object();
	json_object_set_new(info, "dtls", json_string(janus_get_dtls_srtp_state(dtls->dtls_state)));
	json_object_set_new(info, "stream_id", json_integer(stream->stream_id));
	json_object_set_new(info, "component_id", json_integer(component->component_id));
	json_object_set_new(info, "retransmissions", json_integer(dtls->retransmissions));
	janus_events_notify_handlers(JANUS_EVENT_TYPE_WEBRTC, session->session_id, handle->handle_id, handle->opaque_id, info);
}

gboolean janus_is_dtls(char *buf) {
	return ((*buf >= 20) && (*buf <= 64));
}

/* DTLS stuff */
#define DTLS_CIPHERS	"HIGH:!aNULL:!MD5:!RC4"
/* Duration for the self-generated certs: 1 year */
#define DTLS_AUTOCERT_DURATION	60*60*24*365

/* DTLS timeout base to enforce: notice that this can currently only be
 * modified if you're using BoringSSL, as OpenSSL uses 1s (1000ms) and
 * that value cannot be modified (it will in OpenSSL v1.1.1) */
static guint dtls_timeout_base = 1000;

static SSL_CTX *ssl_ctx = NULL;
static X509 *ssl_cert = NULL;
static EVP_PKEY *ssl_key = NULL;

static gchar local_fingerprint[160];
gchar *janus_dtls_get_local_fingerprint(void) {
	return (gchar *)local_fingerprint;
}


#if JANUS_USE_OPENSSL_PRE_1_1_API
/*
 * DTLS locking stuff to make OpenSSL thread safe (not needed for 1.1.0)
 *
 * Note: this is an attempt to fix the infamous issue #316:
 * 		https://github.com/meetecho/janus-gateway/issues/316
 * that is the "tlsv1 alert decrypt error" randomly happening when
 * doing handshakes that force Janus to be restarted (issue affecting
 * OpenSSL but NOT BoringSSL, apparently). The cause might be related
 * to race conditions, and in fact OpenSSL docs state that:
 *
 * 		"OpenSSL can safely be used in multi-threaded applications
 * 		provided that at least two callback functions are set,
 * 		locking_function and threadid_func."
 *
 * See here for the whole docs:
 * 		https://www.openssl.org/docs/manmaster/crypto/threads.html
 *
 * The fix proposed here is heavily derived from a discussion related to
 * RTPEngine:
 * 		http://lists.sip-router.org/pipermail/sr-dev/2015-January/026860.html
 * where it was mentioned the issue was fixed in this commit:
 * 		https://github.com/sipwise/rtpengine/commit/935487b66363c9932684d8085f47450d65a8c37e
 * which does indeed implement the callbacks the OpenSSL docs suggest.
 *
 */
static pthread_mutex_t *janus_dtls_locks;

static void janus_dtls_cb_openssl_threadid(CRYPTO_THREADID *tid) {
	/* FIXME Assuming pthread, which is fine as GLib wraps pthread and
	 * so that's what we use anyway? */
	pthread_t me = pthread_self();

	if(sizeof(me) == sizeof(void *)) {
		CRYPTO_THREADID_set_pointer(tid, (void *) me);
	} else {
		CRYPTO_THREADID_set_numeric(tid, (unsigned long) me);
	}
}

static void janus_dtls_cb_openssl_lock(int mode, int type, const char *file, int line) {
	if((mode & CRYPTO_LOCK)) {
		pthread_mutex_lock(&janus_dtls_locks[type]);
	} else {
		pthread_mutex_unlock(&janus_dtls_locks[type]);
	}
}
#endif


static int janus_dtls_generate_keys(X509 **certificate, EVP_PKEY **private_key) {
	static const int num_bits = 2048;
	BIGNUM *bne = NULL;
	RSA *rsa_key = NULL;
	X509_NAME *cert_name = NULL;

	JANUS_LOG(LOG_VERB, "Generating DTLS key / cert\n");

	/* Create a big number object. */
	bne = BN_new();
	if(!bne) {
		JANUS_LOG(LOG_FATAL, "BN_new() failed\n");
		goto error;
	}

	if(!BN_set_word(bne, RSA_F4)) {  /* RSA_F4 == 65537 */
		JANUS_LOG(LOG_FATAL, "BN_set_word() failed\n");
		goto error;
	}

	/* Generate a RSA key. */
	rsa_key = RSA_new();
	if(!rsa_key) {
		JANUS_LOG(LOG_FATAL, "RSA_new() failed\n");
		goto error;
	}

	/* This takes some time. */
	if(!RSA_generate_key_ex(rsa_key, num_bits, bne, NULL)) {
		JANUS_LOG(LOG_FATAL, "RSA_generate_key_ex() failed\n");
		goto error;
	}

	/* Create a private key object (needed to hold the RSA key). */
	*private_key = EVP_PKEY_new();
	if(!*private_key) {
		JANUS_LOG(LOG_FATAL, "EVP_PKEY_new() failed\n");
		goto error;
	}

	if(!EVP_PKEY_assign_RSA(*private_key, rsa_key)) {
		JANUS_LOG(LOG_FATAL, "EVP_PKEY_assign_RSA() failed\n");
		goto error;
	}
	/* The RSA key now belongs to the private key, so don't clean it up separately. */
	rsa_key = NULL;

	/* Create the X509 certificate. */
	*certificate = X509_new();
	if(!*certificate) {
		JANUS_LOG(LOG_FATAL, "X509_new() failed\n");
		goto error;
	}

	/* Set version 3 (note that 0 means version 1). */
	X509_set_version(*certificate, 2);

	/* Set serial number. */
	ASN1_INTEGER_set(X509_get_serialNumber(*certificate), (long)g_random_int());

	/* Set valid period. */
	X509_gmtime_adj(X509_get_notBefore(*certificate), -1 * DTLS_AUTOCERT_DURATION);  /* -1 year */
	X509_gmtime_adj(X509_get_notAfter(*certificate), DTLS_AUTOCERT_DURATION);  /* 1 year */

	/* Set the public key for the certificate using the key. */
	if(!X509_set_pubkey(*certificate, *private_key)) {
		JANUS_LOG(LOG_FATAL, "X509_set_pubkey() failed\n");
		goto error;
	}

	/* Set certificate fields. */
	cert_name = X509_get_subject_name(*certificate);
	if(!cert_name) {
		JANUS_LOG(LOG_FATAL, "X509_get_subject_name() failed\n");
		goto error;
	}
	X509_NAME_add_entry_by_txt(cert_name, "O", MBSTRING_ASC, (const unsigned char*)"Janus", -1, -1, 0);
	X509_NAME_add_entry_by_txt(cert_name, "CN", MBSTRING_ASC, (const unsigned char*)"Janus", -1, -1, 0);

	/* It is self-signed so set the issuer name to be the same as the subject. */
	if(!X509_set_issuer_name(*certificate, cert_name)) {
		JANUS_LOG(LOG_FATAL, "X509_set_issuer_name() failed\n");
		goto error;
	}

	/* Sign the certificate with the private key. */
	if(!X509_sign(*certificate, *private_key, EVP_sha1())) {
		JANUS_LOG(LOG_FATAL, "X509_sign() failed\n");
		goto error;
	}

	/* Free stuff and resurn. */
	BN_free(bne);
	return 0;

error:
	if(bne)
		BN_free(bne);
	if(rsa_key && !*private_key)
		RSA_free(rsa_key);
	if(*private_key)
		EVP_PKEY_free(*private_key);  /* This also frees the RSA key. */
	if(*certificate)
		X509_free(*certificate);
	return -1;
}


static int janus_dtls_load_keys(const char *server_pem, const char *server_key, const char *password,
		X509 **certificate, EVP_PKEY **private_key) {
	FILE *f = NULL;

	f = fopen(server_pem, "r");
	if(!f) {
		JANUS_LOG(LOG_FATAL, "Error opening certificate file\n");
		goto error;
	}
	*certificate = PEM_read_X509(f, NULL, NULL, NULL);
	if(!*certificate) {
		JANUS_LOG(LOG_FATAL, "PEM_read_X509 failed\n");
		goto error;
	}
	fclose(f);

	f = fopen(server_key, "r");
	if(!f) {
		JANUS_LOG(LOG_FATAL, "Error opening key file\n");
		goto error;
	}
	*private_key = PEM_read_PrivateKey(f, NULL, NULL, (void *)password);
	if(!*private_key) {
		JANUS_LOG(LOG_FATAL, "PEM_read_PrivateKey failed\n");
		goto error;
	}
	fclose(f);

	return 0;

error:
	if(*certificate) {
		X509_free(*certificate);
		*certificate = NULL;
	}
	if(*private_key) {
		EVP_PKEY_free(*private_key);
		*private_key = NULL;
	}
	return -1;
}


/* DTLS-SRTP initialization */
gint janus_dtls_srtp_init(const char *server_pem, const char *server_key, const char *password, guint timeout) {
	const char *crypto_lib = NULL;
#if JANUS_USE_OPENSSL_PRE_1_1_API
#if defined(LIBRESSL_VERSION_NUMBER)
	crypto_lib = "LibreSSL";
#else
	crypto_lib = "OpenSSL pre-1.1.0";
#endif
	/* First of all make OpenSSL thread safe (see note above on issue #316) */
	janus_dtls_locks = g_malloc0(sizeof(*janus_dtls_locks) * CRYPTO_num_locks());
	int l=0;
	for(l = 0; l < CRYPTO_num_locks(); l++) {
		pthread_mutex_init(&janus_dtls_locks[l], NULL);
	}
	CRYPTO_THREADID_set_callback(janus_dtls_cb_openssl_threadid);
	CRYPTO_set_locking_callback(janus_dtls_cb_openssl_lock);
#else
	crypto_lib = "OpenSSL >= 1.1.0";
#endif
#ifdef HAVE_BORINGSSL
	crypto_lib = "BoringSSL";
#endif
	JANUS_LOG(LOG_INFO, "Crypto: %s\n", crypto_lib);
#ifndef HAVE_SRTP_AESGCM
	JANUS_LOG(LOG_WARN, "The libsrtp installation does not support AES-GCM profiles\n");
#endif

	/* Go on and create the DTLS context */
#if JANUS_USE_OPENSSL_PRE_1_1_API
	ssl_ctx = SSL_CTX_new(DTLSv1_method());
#else
	ssl_ctx = SSL_CTX_new(DTLS_method());
#endif
	if(!ssl_ctx) {
		JANUS_LOG(LOG_FATAL, "Ops, error creating DTLS context?\n");
		return -1;
	}
	SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, janus_dtls_verify_callback);
	SSL_CTX_set_tlsext_use_srtp(ssl_ctx,
#ifdef HAVE_SRTP_AESGCM
		"SRTP_AEAD_AES_256_GCM:SRTP_AEAD_AES_128_GCM:SRTP_AES128_CM_SHA1_80:SRTP_AES128_CM_SHA1_32");
#else
		"SRTP_AES128_CM_SHA1_80:SRTP_AES128_CM_SHA1_32");
#endif

	if(!server_pem && !server_key) {
		JANUS_LOG(LOG_WARN, "No cert/key specified, autogenerating some...\n");
		if(janus_dtls_generate_keys(&ssl_cert, &ssl_key) != 0) {
			JANUS_LOG(LOG_FATAL, "Error generating DTLS key/certificate\n");
			return -2;
		}
	} else if(!server_pem || !server_key) {
		JANUS_LOG(LOG_FATAL, "DTLS certificate and key must be specified\n");
		return -2;
	} else if(janus_dtls_load_keys(server_pem, server_key, password, &ssl_cert, &ssl_key) != 0) {
		return -3;
	}

	if(!SSL_CTX_use_certificate(ssl_ctx, ssl_cert)) {
		JANUS_LOG(LOG_FATAL, "Certificate error (%s)\n", ERR_reason_error_string(ERR_get_error()));
		return -4;
	}
	if(!SSL_CTX_use_PrivateKey(ssl_ctx, ssl_key)) {
		JANUS_LOG(LOG_FATAL, "Certificate key error (%s)\n", ERR_reason_error_string(ERR_get_error()));
		return -5;
	}
	if(!SSL_CTX_check_private_key(ssl_ctx)) {
		JANUS_LOG(LOG_FATAL, "Certificate check error (%s)\n", ERR_reason_error_string(ERR_get_error()));
		return -6;
	}
	SSL_CTX_set_read_ahead(ssl_ctx,1);

	unsigned int size;
	unsigned char fingerprint[EVP_MAX_MD_SIZE];
	if(X509_digest(ssl_cert, EVP_sha256(), (unsigned char *)fingerprint, &size) == 0) {
		JANUS_LOG(LOG_FATAL, "Error converting X509 structure (%s)\n", ERR_reason_error_string(ERR_get_error()));
		return -7;
	}
	char *lfp = (char *)&local_fingerprint;
	unsigned int i = 0;
	for(i = 0; i < size; i++) {
		g_snprintf(lfp, 4, "%.2X:", fingerprint[i]);
		lfp += 3;
	}
	*(lfp-1) = 0;
	JANUS_LOG(LOG_INFO, "Fingerprint of our certificate: %s\n", local_fingerprint);
	SSL_CTX_set_cipher_list(ssl_ctx, DTLS_CIPHERS);

	if(janus_dtls_bio_agent_init() < 0) {
		JANUS_LOG(LOG_FATAL, "Error initializing BIO agent\n");
		return -8;
	}

	dtls_timeout_base = timeout;
#ifndef HAVE_BORINGSSL
	if(dtls_timeout_base != 1000) {
		JANUS_LOG(LOG_WARN, "DTLS timeout set to %u ms, but not using BoringSSL: ignoring\n", timeout);
	}
#endif

	/* Initialize libsrtp */
	if(srtp_init() != srtp_err_status_ok) {
		JANUS_LOG(LOG_FATAL, "Ops, error setting up libsrtp?\n");
		return 5;
	}
	return 0;
}

static void janus_dtls_srtp_free(const janus_refcount *dtls_ref) {
	janus_dtls_srtp *dtls = janus_refcount_containerof(dtls_ref, janus_dtls_srtp, ref);
	/* This stack can be destroyed, free all the resources */
	dtls->component = NULL;
	if(dtls->ssl != NULL) {
		SSL_free(dtls->ssl);
		dtls->ssl = NULL;
	}
	/* BIOs are destroyed by SSL_free */
	dtls->read_bio = NULL;
	dtls->write_bio = NULL;
	if(dtls->srtp_valid) {
		if(dtls->srtp_in) {
			srtp_dealloc(dtls->srtp_in);
			dtls->srtp_in = NULL;
		}
		if(dtls->srtp_out) {
			srtp_dealloc(dtls->srtp_out);
			dtls->srtp_out = NULL;
		}
		/* FIXME What about dtls->remote_policy and dtls->local_policy? */
	}
	g_free(dtls);
	dtls = NULL;
}

void janus_dtls_srtp_cleanup(void) {
	if(ssl_cert != NULL) {
		X509_free(ssl_cert);
		ssl_cert = NULL;
	}
	if(ssl_key != NULL) {
		EVP_PKEY_free(ssl_key);
		ssl_key = NULL;
	}
	if(ssl_ctx != NULL) {
		SSL_CTX_free(ssl_ctx);
		ssl_ctx = NULL;
	}
#if JANUS_USE_OPENSSL_PRE_1_1_API
	g_free(janus_dtls_locks);
#endif
}


janus_dtls_srtp *janus_dtls_srtp_create(void *ice_component, janus_dtls_role role) {
	janus_ice_component *component = (janus_ice_component *)ice_component;
	if(component == NULL) {
		JANUS_LOG(LOG_ERR, "No component, no DTLS...\n");
		return NULL;
	}
	janus_ice_stream *stream = component->stream;
	if(!stream) {
		JANUS_LOG(LOG_ERR, "No stream, no DTLS...\n");
		return NULL;
	}
	janus_ice_handle *handle = stream->handle;
	if(!handle || !handle->agent) {
		JANUS_LOG(LOG_ERR, "No handle/agent, no DTLS...\n");
		return NULL;
	}
	janus_dtls_srtp *dtls = g_malloc0(sizeof(janus_dtls_srtp));
	g_atomic_int_set(&dtls->destroyed, 0);
	janus_refcount_init(&dtls->ref, janus_dtls_srtp_free);
	/* Create SSL context, at last */
	dtls->srtp_valid = 0;
	dtls->ssl = SSL_new(ssl_ctx);
	if(!dtls->ssl) {
		JANUS_LOG(LOG_ERR, "[%"SCNu64"]     Error creating DTLS session! (%s)\n",
			handle->handle_id, ERR_reason_error_string(ERR_get_error()));
		janus_refcount_decrease(&dtls->ref);
		return NULL;
	}
	SSL_set_ex_data(dtls->ssl, 0, dtls);
	SSL_set_info_callback(dtls->ssl, janus_dtls_callback);
	dtls->read_bio = BIO_new(BIO_s_mem());
	if(!dtls->read_bio) {
		JANUS_LOG(LOG_ERR, "[%"SCNu64"]   Error creating read BIO! (%s)\n",
			handle->handle_id, ERR_reason_error_string(ERR_get_error()));
		janus_refcount_decrease(&dtls->ref);
		return NULL;
	}
	BIO_set_mem_eof_return(dtls->read_bio, -1);
	dtls->write_bio = BIO_janus_dtls_agent_new(dtls);
	if(!dtls->write_bio) {
		JANUS_LOG(LOG_ERR, "[%"SCNu64"]   Error creating write BIO! (%s)\n",
			handle->handle_id, ERR_reason_error_string(ERR_get_error()));
		janus_refcount_decrease(&dtls->ref);
		return NULL;
	}
	SSL_set_bio(dtls->ssl, dtls->read_bio, dtls->write_bio);
	/* The role may change later, depending on the negotiation */
	dtls->dtls_role = role;
	/* https://code.google.com/p/chromium/issues/detail?id=406458
	 * Specify an ECDH group for ECDHE ciphers, otherwise they cannot be
	 * negotiated when acting as the server. Use NIST's P-256 which is
	 * commonly supported.
	 */
	EC_KEY *ecdh = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
	if(ecdh == NULL) {
		JANUS_LOG(LOG_ERR, "[%"SCNu64"]   Error creating ECDH group! (%s)\n",
			handle->handle_id, ERR_reason_error_string(ERR_get_error()));
		janus_refcount_decrease(&dtls->ref);
		return NULL;
	}
	const long flags = SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 | SSL_OP_NO_COMPRESSION | SSL_OP_SINGLE_ECDH_USE;
	SSL_set_options(dtls->ssl, flags);
	SSL_set_tmp_ecdh(dtls->ssl, ecdh);
	EC_KEY_free(ecdh);
#ifdef HAVE_DTLS_SETTIMEOUT
	JANUS_LOG(LOG_VERB, "[%"SCNu64"]   Setting DTLS initial timeout: %u\n", handle->handle_id, dtls_timeout_base);
	DTLSv1_set_initial_timeout_duration(dtls->ssl, dtls_timeout_base);
#endif
	dtls->ready = 0;
	dtls->retransmissions = 0;
#ifdef HAVE_SCTP
	dtls->sctp = NULL;
#endif
	/* Done */
	dtls->dtls_connected = 0;
	dtls->component = component;
	return dtls;
}

void janus_dtls_srtp_handshake(janus_dtls_srtp *dtls) {
	if(dtls == NULL || dtls->ssl == NULL)
		return;
	if(dtls->dtls_state == JANUS_DTLS_STATE_CREATED) {
		/* Starting the handshake now: enforce the role */
		dtls->dtls_started = janus_get_monotonic_time();
		if(dtls->dtls_role == JANUS_DTLS_ROLE_CLIENT) {
			SSL_set_connect_state(dtls->ssl);
		} else {
			SSL_set_accept_state(dtls->ssl);
		}
		dtls->dtls_state = JANUS_DTLS_STATE_TRYING;
	}
	SSL_do_handshake(dtls->ssl);

	/* Notify event handlers */
	janus_dtls_notify_state_change(dtls);
}

int janus_dtls_srtp_create_sctp(janus_dtls_srtp *dtls) {
#ifdef HAVE_SCTP
	if(dtls == NULL)
		return -1;
	janus_ice_component *component = (janus_ice_component *)dtls->component;
	if(component == NULL)
		return -2;
	janus_ice_stream *stream = component->stream;
	if(!stream)
		return -3;
	janus_ice_handle *handle = stream->handle;
	if(!handle || !handle->agent)
		return -4;
	if(janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_ALERT))
		return -5;
	dtls->sctp = janus_sctp_association_create(dtls, handle, 5000);
	if(dtls->sctp == NULL) {
		JANUS_LOG(LOG_ERR, "[%"SCNu64"] Error creating SCTP association...\n", handle->handle_id);
		return -6;
	}
	return 0;
#else
	/* Support for datachannels hasn't been built in */
	return -1;
#endif
}

void janus_dtls_srtp_incoming_msg(janus_dtls_srtp *dtls, char *buf, uint16_t len) {
	if(dtls == NULL) {
		JANUS_LOG(LOG_ERR, "No DTLS-SRTP stack, no incoming message...\n");
		return;
	}
	janus_ice_component *component = (janus_ice_component *)dtls->component;
	if(component == NULL) {
		JANUS_LOG(LOG_ERR, "No component, no DTLS...\n");
		return;
	}
	janus_ice_stream *stream = component->stream;
	if(!stream) {
		JANUS_LOG(LOG_ERR, "No stream, no DTLS...\n");
		return;
	}
	janus_ice_handle *handle = stream->handle;
	if(!handle || !handle->agent) {
		JANUS_LOG(LOG_ERR, "No handle/agent, no DTLS...\n");
		return;
	}
	if(janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_ALERT)) {
		JANUS_LOG(LOG_WARN, "[%"SCNu64"] Alert already triggered, clearing up...\n", handle->handle_id);
		return;
	}
	if(!dtls->ssl || !dtls->read_bio) {
		JANUS_LOG(LOG_ERR, "[%"SCNu64"] No DTLS stuff for component %d in stream %d??\n", handle->handle_id, component->component_id, stream->stream_id);
		return;
	}
	if(dtls->dtls_started == 0) {
		/* Handshake not started yet: maybe we're still waiting for the answer and the DTLS role? */
		return;
	}
	int written = BIO_write(dtls->read_bio, buf, len);
	if(written != len) {
		JANUS_LOG(LOG_WARN, "[%"SCNu64"]     Only written %d/%d of those bytes on the read BIO...\n", handle->handle_id, written, len);
	} else {
		JANUS_LOG(LOG_HUGE, "[%"SCNu64"]     Written %d bytes on the read BIO...\n", handle->handle_id, written);
	}
	/* Try to read data */
	char data[1500];	/* FIXME */
	memset(&data, 0, 1500);
	int read = SSL_read(dtls->ssl, &data, 1500);
	JANUS_LOG(LOG_HUGE, "[%"SCNu64"]     ... and read %d of them from SSL...\n", handle->handle_id, read);
	if(read < 0) {
		unsigned long err = SSL_get_error(dtls->ssl, read);
		if(err == SSL_ERROR_SSL) {
			/* Ops, something went wrong with the DTLS handshake */
			char error[200];
			ERR_error_string_n(ERR_get_error(), error, 200);
			JANUS_LOG(LOG_ERR, "[%"SCNu64"] Handshake error: %s\n", handle->handle_id, error);
			return;
		}
	}
	if(janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_STOP) || janus_is_stopping()) {
		/* DTLS alert triggered, we should end it here */
		JANUS_LOG(LOG_VERB, "[%"SCNu64"] Forced to stop it here...\n", handle->handle_id);
		return;
	}
	if(!SSL_is_init_finished(dtls->ssl)) {
		/* Nothing else to do for now */
		JANUS_LOG(LOG_HUGE, "[%"SCNu64"] Initialization not finished yet...\n", handle->handle_id);
		return;
	}
	if(dtls->ready) {
		/* There's data to be read? */
		JANUS_LOG(LOG_HUGE, "[%"SCNu64"] Any data available?\n", handle->handle_id);
#ifdef HAVE_SCTP
		if(dtls->sctp != NULL && read > 0) {
			JANUS_LOG(LOG_HUGE, "[%"SCNu64"] Sending data (%d bytes) to the SCTP stack...\n", handle->handle_id, read);
			janus_sctp_data_from_dtls(dtls->sctp, data, read);
		}
#else
		if(read > 0) {
			JANUS_LOG(LOG_WARN, "[%"SCNu64"] Data available but Data Channels support disabled...\n", handle->handle_id);
		}
#endif
	} else {
		JANUS_LOG(LOG_VERB, "[%"SCNu64"] DTLS established, yay!\n", handle->handle_id);
		/* Check the remote fingerprint */
		X509 *rcert = SSL_get_peer_certificate(dtls->ssl);
		if(!rcert) {
			JANUS_LOG(LOG_ERR, "[%"SCNu64"] No remote certificate?? (%s)\n",
				handle->handle_id, ERR_reason_error_string(ERR_get_error()));
		} else {
			unsigned int rsize;
			unsigned char rfingerprint[EVP_MAX_MD_SIZE];
			char remote_fingerprint[160];
			char *rfp = (char *)&remote_fingerprint;
			if(stream->remote_hashing && !strcasecmp(stream->remote_hashing, "sha-1")) {
				JANUS_LOG(LOG_VERB, "[%"SCNu64"] Computing sha-1 fingerprint of remote certificate...\n", handle->handle_id);
				X509_digest(rcert, EVP_sha1(), (unsigned char *)rfingerprint, &rsize);
			} else {
				JANUS_LOG(LOG_VERB, "[%"SCNu64"] Computing sha-256 fingerprint of remote certificate...\n", handle->handle_id);
				X509_digest(rcert, EVP_sha256(), (unsigned char *)rfingerprint, &rsize);
			}
			X509_free(rcert);
			rcert = NULL;
			unsigned int i = 0;
			for(i = 0; i < rsize; i++) {
				g_snprintf(rfp, 4, "%.2X:", rfingerprint[i]);
				rfp += 3;
			}
			*(rfp-1) = 0;
			JANUS_LOG(LOG_VERB, "[%"SCNu64"] Remote fingerprint (%s) of the client is %s\n",
				handle->handle_id, stream->remote_hashing ? stream->remote_hashing : "sha-256", remote_fingerprint);
			if(!strcasecmp(remote_fingerprint, stream->remote_fingerprint ? stream->remote_fingerprint : "(none)")) {
				JANUS_LOG(LOG_VERB, "[%"SCNu64"]  Fingerprint is a match!\n", handle->handle_id);
				dtls->dtls_state = JANUS_DTLS_STATE_CONNECTED;
				dtls->dtls_connected = janus_get_monotonic_time();
				/* Notify event handlers */
				janus_dtls_notify_state_change(dtls);
			} else {
				/* FIXME NOT a match! MITM? */
				JANUS_LOG(LOG_ERR, "[%"SCNu64"]  Fingerprint is NOT a match! got %s, expected %s\n", handle->handle_id, remote_fingerprint, stream->remote_fingerprint);
				dtls->dtls_state = JANUS_DTLS_STATE_FAILED;
				/* Notify event handlers */
				janus_dtls_notify_state_change(dtls);
				goto done;
			}
			if(dtls->dtls_state == JANUS_DTLS_STATE_CONNECTED) {
				/* Which SRTP profile is being negotiated? */
				const SRTP_PROTECTION_PROFILE *srtp_profile = SSL_get_selected_srtp_profile(dtls->ssl);
				if(srtp_profile == NULL) {
					/* Should never happen, but just in case... */
					JANUS_LOG(LOG_ERR, "[%"SCNu64"] No SRTP profile selected...\n", handle->handle_id);
					dtls->dtls_state = JANUS_DTLS_STATE_FAILED;
					/* Notify event handlers */
					janus_dtls_notify_state_change(dtls);
					goto done;
				}
				JANUS_LOG(LOG_VERB, "[%"SCNu64"] %s\n", handle->handle_id, srtp_profile->name);
				int key_length = 0, salt_length = 0, master_length = 0;
				switch(srtp_profile->id) {
					case SRTP_AES128_CM_SHA1_80:
					case SRTP_AES128_CM_SHA1_32:
						key_length = SRTP_MASTER_KEY_LENGTH;
						salt_length = SRTP_MASTER_SALT_LENGTH;
						master_length = SRTP_MASTER_LENGTH;
						break;
#ifdef HAVE_SRTP_AESGCM
					case SRTP_AEAD_AES_256_GCM:
						key_length = SRTP_AESGCM256_MASTER_KEY_LENGTH;
						salt_length = SRTP_AESGCM256_MASTER_SALT_LENGTH;
						master_length = SRTP_AESGCM256_MASTER_LENGTH;
						break;
					case SRTP_AEAD_AES_128_GCM:
						key_length = SRTP_AESGCM128_MASTER_KEY_LENGTH;
						salt_length = SRTP_AESGCM128_MASTER_SALT_LENGTH;
						master_length = SRTP_AESGCM128_MASTER_LENGTH;
						break;
#endif
					default:
						/* Will never happen? */
						JANUS_LOG(LOG_WARN, "[%"SCNu64"] Unsupported SRTP profile %lu\n", handle->handle_id, srtp_profile->id);
						break;
				}
				JANUS_LOG(LOG_VERB, "[%"SCNu64"] Key/Salt/Master: %d/%d/%d\n",
					handle->handle_id, master_length, key_length, salt_length);
				/* Complete with SRTP setup */
				unsigned char material[master_length*2];
				unsigned char *local_key, *local_salt, *remote_key, *remote_salt;
				/* Export keying material for SRTP */
				if(!SSL_export_keying_material(dtls->ssl, material, master_length*2, "EXTRACTOR-dtls_srtp", 19, NULL, 0, 0)) {
					/* Oops... */
					JANUS_LOG(LOG_ERR, "[%"SCNu64"] Oops, couldn't extract SRTP keying material for component %d in stream %d?? (%s)\n",
						handle->handle_id, component->component_id, stream->stream_id, ERR_reason_error_string(ERR_get_error()));
					goto done;
				}
				/* Key derivation (http://tools.ietf.org/html/rfc5764#section-4.2) */
				if(dtls->dtls_role == JANUS_DTLS_ROLE_CLIENT) {
					local_key = material;
					remote_key = local_key + key_length;
					local_salt = remote_key + key_length;
					remote_salt = local_salt + salt_length;
				} else {
					remote_key = material;
					local_key = remote_key + key_length;
					remote_salt = local_key + key_length;
					local_salt = remote_salt + salt_length;
				}
				/* Build master keys and set SRTP policies */
					/* Remote (inbound) */
				switch(srtp_profile->id) {
					case SRTP_AES128_CM_SHA1_80:
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&(dtls->remote_policy.rtp));
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&(dtls->remote_policy.rtcp));
						break;
					case SRTP_AES128_CM_SHA1_32:
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32(&(dtls->remote_policy.rtp));
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&(dtls->remote_policy.rtcp));
						break;
#ifdef HAVE_SRTP_AESGCM
					case SRTP_AEAD_AES_256_GCM:
						srtp_crypto_policy_set_aes_gcm_256_16_auth(&(dtls->remote_policy.rtp));
						srtp_crypto_policy_set_aes_gcm_256_16_auth(&(dtls->remote_policy.rtcp));
						break;
					case SRTP_AEAD_AES_128_GCM:
						srtp_crypto_policy_set_aes_gcm_128_16_auth(&(dtls->remote_policy.rtp));
						srtp_crypto_policy_set_aes_gcm_128_16_auth(&(dtls->remote_policy.rtcp));
						break;
#endif
					default:
						/* Will never happen? */
						JANUS_LOG(LOG_WARN, "[%"SCNu64"] Unsupported SRTP profile %s\n", handle->handle_id, srtp_profile->name);
						break;
				}
				dtls->remote_policy.ssrc.type = ssrc_any_inbound;
				unsigned char remote_policy_key[master_length];
				dtls->remote_policy.key = (unsigned char *)&remote_policy_key;
				memcpy(dtls->remote_policy.key, remote_key, key_length);
				memcpy(dtls->remote_policy.key + key_length, remote_salt, salt_length);
#if HAS_DTLS_WINDOW_SIZE
				dtls->remote_policy.window_size = 128;
				dtls->remote_policy.allow_repeat_tx = 0;
#endif
				dtls->remote_policy.next = NULL;
					/* Local (outbound) */
				switch(srtp_profile->id) {
					case SRTP_AES128_CM_SHA1_80:
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&(dtls->local_policy.rtp));
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&(dtls->local_policy.rtcp));
						break;
					case SRTP_AES128_CM_SHA1_32:
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_32(&(dtls->local_policy.rtp));
						srtp_crypto_policy_set_aes_cm_128_hmac_sha1_80(&(dtls->local_policy.rtcp));
						break;
#ifdef HAVE_SRTP_AESGCM
					case SRTP_AEAD_AES_256_GCM:
						srtp_crypto_policy_set_aes_gcm_256_16_auth(&(dtls->local_policy.rtp));
						srtp_crypto_policy_set_aes_gcm_256_16_auth(&(dtls->local_policy.rtcp));
						break;
					case SRTP_AEAD_AES_128_GCM:
						srtp_crypto_policy_set_aes_gcm_128_16_auth(&(dtls->local_policy.rtp));
						srtp_crypto_policy_set_aes_gcm_128_16_auth(&(dtls->local_policy.rtcp));
						break;
#endif
					default:
						/* Will never happen? */
						JANUS_LOG(LOG_WARN, "[%"SCNu64"] Unsupported SRTP profile %s\n", handle->handle_id, srtp_profile->name);
						break;
				}
				dtls->local_policy.ssrc.type = ssrc_any_outbound;
				unsigned char local_policy_key[master_length];
				dtls->local_policy.key = (unsigned char *)&local_policy_key;
				memcpy(dtls->local_policy.key, local_key, key_length);
				memcpy(dtls->local_policy.key + key_length, local_salt, salt_length);
#if HAS_DTLS_WINDOW_SIZE
				dtls->local_policy.window_size = 128;
				dtls->local_policy.allow_repeat_tx = 0;
#endif
				dtls->local_policy.next = NULL;
				/* Create SRTP sessions */
				srtp_err_status_t res = srtp_create(&(dtls->srtp_in), &(dtls->remote_policy));
				if(res != srtp_err_status_ok) {
					/* Something went wrong... */
					JANUS_LOG(LOG_ERR, "[%"SCNu64"] Oops, error creating inbound SRTP session for component %d in stream %d??\n", handle->handle_id, component->component_id, stream->stream_id);
					JANUS_LOG(LOG_ERR, "[%"SCNu64"]  -- %d (%s)\n", handle->handle_id, res, janus_srtp_error_str(res));
					goto done;
				}
				JANUS_LOG(LOG_VERB, "[%"SCNu64"] Created inbound SRTP session for component %d in stream %d\n", handle->handle_id, component->component_id, stream->stream_id);
				res = srtp_create(&(dtls->srtp_out), &(dtls->local_policy));
				if(res != srtp_err_status_ok) {
					/* Something went wrong... */
					JANUS_LOG(LOG_ERR, "[%"SCNu64"] Oops, error creating outbound SRTP session for component %d in stream %d??\n", handle->handle_id, component->component_id, stream->stream_id);
					JANUS_LOG(LOG_ERR, "[%"SCNu64"]  -- %d (%s)\n", handle->handle_id, res, janus_srtp_error_str(res));
					goto done;
				}
				dtls->srtp_profile = srtp_profile->id;
				dtls->srtp_valid = 1;
				JANUS_LOG(LOG_VERB, "[%"SCNu64"] Created outbound SRTP session for component %d in stream %d\n", handle->handle_id, component->component_id, stream->stream_id);
#ifdef HAVE_SCTP
				if(janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_DATA_CHANNELS)) {
					/* Create SCTP association as well */
					janus_dtls_srtp_create_sctp(dtls);
				}
#endif
				dtls->ready = 1;
			}
done:
			if(!janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_ALERT) && dtls->srtp_valid) {
				/* Handshake successfully completed */
				janus_ice_dtls_handshake_done(handle, component);
			} else {
				/* Something went wrong in either DTLS or SRTP... tell the plugin about it */
				janus_dtls_callback(dtls->ssl, SSL_CB_ALERT, 0);
				janus_flags_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_CLEANING);
			}
		}
	}
}

void janus_dtls_srtp_send_alert(janus_dtls_srtp *dtls) {
	/* Send alert */
	janus_refcount_increase(&dtls->ref);
	if(dtls != NULL && dtls->ssl != NULL) {
		SSL_shutdown(dtls->ssl);
	}
	janus_refcount_decrease(&dtls->ref);
}

void janus_dtls_srtp_destroy(janus_dtls_srtp *dtls) {
	if(!dtls || !g_atomic_int_compare_and_exchange(&dtls->destroyed, 0, 1))
		return;
	dtls->ready = 0;
	dtls->retransmissions = 0;
#ifdef HAVE_SCTP
	/* Destroy the SCTP association if this is a DataChannel */
	if(dtls->sctp != NULL) {
		janus_sctp_association_destroy(dtls->sctp);
		dtls->sctp = NULL;
	}
#endif
	janus_refcount_decrease(&dtls->ref);
}

/* DTLS alert callback */
void janus_dtls_callback(const SSL *ssl, int where, int ret) {
	/* We only care about alerts */
	if(!(where & SSL_CB_ALERT)) {
		return;
	}
	janus_dtls_srtp *dtls = SSL_get_ex_data(ssl, 0);
	if(!dtls) {
		JANUS_LOG(LOG_ERR, "No DTLS session related to this alert...\n");
		return;
	}
	janus_ice_component *component = dtls->component;
	if(component == NULL) {
		JANUS_LOG(LOG_ERR, "No ICE component related to this alert...\n");
		return;
	}
	janus_ice_stream *stream = component->stream;
	if(!stream) {
		JANUS_LOG(LOG_ERR, "No ICE stream related to this alert...\n");
		return;
	}
	janus_ice_handle *handle = stream->handle;
	if(!handle) {
		JANUS_LOG(LOG_ERR, "No ICE handle related to this alert...\n");
		return;
	}
	JANUS_LOG(LOG_VERB, "[%"SCNu64"] DTLS alert triggered on stream %u (component %u), closing...\n", handle->handle_id, stream->stream_id, component->component_id);
	janus_ice_webrtc_hangup(handle, "DTLS alert");
}

/* DTLS certificate verification callback */
int janus_dtls_verify_callback(int preverify_ok, X509_STORE_CTX *ctx) {
	/* We just use the verify_callback to request a certificate from the client */
	return 1;
}

#ifdef HAVE_SCTP
void janus_dtls_wrap_sctp_data(janus_dtls_srtp *dtls, char *buf, int len) {
	if(dtls == NULL || !dtls->ready || dtls->sctp == NULL || buf == NULL || len < 1)
		return;
	janus_sctp_send_data(dtls->sctp, buf, len);
}

int janus_dtls_send_sctp_data(janus_dtls_srtp *dtls, char *buf, int len) {
	if(dtls == NULL || !dtls->ready || buf == NULL || len < 1)
		return -1;
	int res = SSL_write(dtls->ssl, buf, len);
	if(res <= 0) {
		unsigned long err = SSL_get_error(dtls->ssl, res);
		JANUS_LOG(LOG_ERR, "Error sending data: %s\n", ERR_reason_error_string(err));
	}
	return res;
}

void janus_dtls_notify_data(janus_dtls_srtp *dtls, char *buf, int len) {
	if(dtls == NULL || buf == NULL || len < 1)
		return;
	janus_ice_component *component = (janus_ice_component *)dtls->component;
	if(component == NULL) {
		JANUS_LOG(LOG_ERR, "No component...\n");
		return;
	}
	janus_ice_stream *stream = component->stream;
	if(!stream) {
		JANUS_LOG(LOG_ERR, "No stream...\n");
		return;
	}
	janus_ice_handle *handle = stream->handle;
	if(!handle || !handle->agent || !dtls->write_bio) {
		JANUS_LOG(LOG_ERR, "No handle...\n");
		return;
	}
	janus_ice_incoming_data(handle, buf, len);
}
#endif

gboolean janus_dtls_retry(gpointer stack) {
	janus_dtls_srtp *dtls = (janus_dtls_srtp *)stack;
	if(dtls == NULL)
		return FALSE;
	janus_ice_component *component = (janus_ice_component *)dtls->component;
	if(component == NULL)
		return FALSE;
	janus_ice_stream *stream = component->stream;
	if(!stream)
		goto stoptimer;
	janus_ice_handle *handle = stream->handle;
	if(!handle)
		goto stoptimer;
	if(janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_STOP))
		goto stoptimer;
	if(dtls->dtls_state == JANUS_DTLS_STATE_CONNECTED) {
		JANUS_LOG(LOG_VERB, "[%"SCNu64"] DTLS already set up, disabling retransmission timer!\n", handle->handle_id);
		goto stoptimer;
	}
	if(janus_get_monotonic_time() - dtls->dtls_started >= 20*G_USEC_PER_SEC) {
		/* FIXME Should we really give up after 20 seconds waiting for DTLS? */
		JANUS_LOG(LOG_ERR, "[%"SCNu64"] DTLS taking too much time for component %d in stream %d...\n",
			handle->handle_id, component->component_id, stream->stream_id);
		janus_ice_webrtc_hangup(handle, "DTLS timeout");
		goto stoptimer;
	}
	struct timeval timeout = {0};
	if(DTLSv1_get_timeout(dtls->ssl, &timeout) == 0) {
		/* failed to get timeout. try again on next iter */
		return TRUE;
	}
	guint64 timeout_value = timeout.tv_sec*1000 + timeout.tv_usec/1000;
	JANUS_LOG(LOG_HUGE, "[%"SCNu64"] DTLSv1_get_timeout: %"SCNu64"\n", handle->handle_id, timeout_value);
	if(timeout_value == 0) {
		dtls->retransmissions++;
		JANUS_LOG(LOG_VERB, "[%"SCNu64"] DTLS timeout on component %d of stream %d, retransmitting\n", handle->handle_id, component->component_id, stream->stream_id);
		/* Notify event handlers */
		janus_dtls_notify_state_change(dtls);
		/* Retransmit the packet */
		DTLSv1_handle_timeout(dtls->ssl);
	}
	return TRUE;

stoptimer:
	if(component->dtlsrt_source != NULL) {
		g_source_destroy(component->dtlsrt_source);
		g_source_unref(component->dtlsrt_source);
		component->dtlsrt_source = NULL;
	}
	return FALSE;
}