+#define LISTEN_SUCCESS 2
+#define LISTEN_SEND_VERIFY_REQUEST 1
+
+#ifndef OPENSSL_NO_SOCK
+int DTLSv1_listen(SSL *s, BIO_ADDR *client)
+{
+ int next, n, ret = 0, clearpkt = 0;
+ unsigned char cookie[DTLS1_COOKIE_LENGTH];
+ unsigned char seq[SEQ_NUM_SIZE];
+ const unsigned char *data;
+ unsigned char *buf;
+ size_t fragoff, fraglen, msglen;
+ unsigned int rectype, versmajor, msgseq, msgtype, clientvers, cookielen;
+ BIO *rbio, *wbio;
+ BUF_MEM *bufm;
+ BIO_ADDR *tmpclient = NULL;
+ PACKET pkt, msgpkt, msgpayload, session, cookiepkt;
+
+ /* Ensure there is no state left over from a previous invocation */
+ if (!SSL_clear(s))
+ return -1;
+
+ ERR_clear_error();
+
+ rbio = SSL_get_rbio(s);
+ wbio = SSL_get_wbio(s);
+
+ if (!rbio || !wbio) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_BIO_NOT_SET);
+ return -1;
+ }
+
+ /*
+ * We only peek at incoming ClientHello's until we're sure we are going to
+ * to respond with a HelloVerifyRequest. If its a ClientHello with a valid
+ * cookie then we leave it in the BIO for accept to handle.
+ */
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
+
+ /*
+ * Note: This check deliberately excludes DTLS1_BAD_VER because that version
+ * requires the MAC to be calculated *including* the first ClientHello
+ * (without the cookie). Since DTLSv1_listen is stateless that cannot be
+ * supported. DTLS1_BAD_VER must use cookies in a stateful manner (e.g. via
+ * SSL_accept)
+ */
+ if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00)) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNSUPPORTED_SSL_VERSION);
+ return -1;
+ }
+
+ if (s->init_buf == NULL) {
+ if ((bufm = BUF_MEM_new()) == NULL) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
+ return -1;
+ }
+
+ if (!BUF_MEM_grow(bufm, SSL3_RT_MAX_PLAIN_LENGTH)) {
+ BUF_MEM_free(bufm);
+ SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
+ return -1;
+ }
+ s->init_buf = bufm;
+ }
+ buf = (unsigned char *)s->init_buf->data;
+
+ do {
+ /* Get a packet */
+
+ clear_sys_error();
+ /*
+ * Technically a ClientHello could be SSL3_RT_MAX_PLAIN_LENGTH
+ * + DTLS1_RT_HEADER_LENGTH bytes long. Normally init_buf does not store
+ * the record header as well, but we do here. We've set up init_buf to
+ * be the standard size for simplicity. In practice we shouldn't ever
+ * receive a ClientHello as long as this. If we do it will get dropped
+ * in the record length check below.
+ */
+ n = BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
+
+ if (n <= 0) {
+ if (BIO_should_retry(rbio)) {
+ /* Non-blocking IO */
+ goto end;
+ }
+ return -1;
+ }
+
+ /* If we hit any problems we need to clear this packet from the BIO */
+ clearpkt = 1;
+
+ if (!PACKET_buf_init(&pkt, buf, n)) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_INTERNAL_ERROR);
+ return -1;
+ }
+
+ /*
+ * Parse the received record. If there are any problems with it we just
+ * dump it - with no alert. RFC6347 says this "Unlike TLS, DTLS is
+ * resilient in the face of invalid records (e.g., invalid formatting,
+ * length, MAC, etc.). In general, invalid records SHOULD be silently
+ * discarded, thus preserving the association; however, an error MAY be
+ * logged for diagnostic purposes."
+ */
+
+ /* this packet contained a partial record, dump it */
+ if (n < DTLS1_RT_HEADER_LENGTH) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_RECORD_TOO_SMALL);
+ goto end;
+ }
+
+ if (s->msg_callback)
+ s->msg_callback(0, 0, SSL3_RT_HEADER, buf,
+ DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
+
+ /* Get the record header */
+ if (!PACKET_get_1(&pkt, &rectype)
+ || !PACKET_get_1(&pkt, &versmajor)) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ if (rectype != SSL3_RT_HANDSHAKE) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
+ goto end;
+ }
+
+ /*
+ * Check record version number. We only check that the major version is
+ * the same.
+ */
+ if (versmajor != DTLS1_VERSION_MAJOR) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_BAD_PROTOCOL_VERSION_NUMBER);
+ goto end;
+ }
+
+ if (!PACKET_forward(&pkt, 1)
+ /* Save the sequence number: 64 bits, with top 2 bytes = epoch */
+ || !PACKET_copy_bytes(&pkt, seq, SEQ_NUM_SIZE)
+ || !PACKET_get_length_prefixed_2(&pkt, &msgpkt)) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+ /*
+ * We allow data remaining at the end of the packet because there could
+ * be a second record (but we ignore it)
+ */
+
+ /* This is an initial ClientHello so the epoch has to be 0 */
+ if (seq[0] != 0 || seq[1] != 0) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
+ goto end;
+ }
+
+ /* Get a pointer to the raw message for the later callback */
+ data = PACKET_data(&msgpkt);
+
+ /* Finished processing the record header, now process the message */
+ if (!PACKET_get_1(&msgpkt, &msgtype)
+ || !PACKET_get_net_3_len(&msgpkt, &msglen)
+ || !PACKET_get_net_2(&msgpkt, &msgseq)
+ || !PACKET_get_net_3_len(&msgpkt, &fragoff)
+ || !PACKET_get_net_3_len(&msgpkt, &fraglen)
+ || !PACKET_get_sub_packet(&msgpkt, &msgpayload, fraglen)
+ || PACKET_remaining(&msgpkt) != 0) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ if (msgtype != SSL3_MT_CLIENT_HELLO) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
+ goto end;
+ }
+
+ /* Message sequence number can only be 0 or 1 */
+ if (msgseq > 2) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_INVALID_SEQUENCE_NUMBER);
+ goto end;
+ }
+
+ /*
+ * We don't support fragment reassembly for ClientHellos whilst
+ * listening because that would require server side state (which is
+ * against the whole point of the ClientHello/HelloVerifyRequest
+ * mechanism). Instead we only look at the first ClientHello fragment
+ * and require that the cookie must be contained within it.
+ */
+ if (fragoff != 0 || fraglen > msglen) {
+ /* Non initial ClientHello fragment (or bad fragment) */
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_FRAGMENTED_CLIENT_HELLO);
+ goto end;
+ }
+
+ if (s->msg_callback)
+ s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, data,
+ fraglen + DTLS1_HM_HEADER_LENGTH, s,
+ s->msg_callback_arg);
+
+ if (!PACKET_get_net_2(&msgpayload, &clientvers)) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ /*
+ * Verify client version is supported
+ */
+ if (DTLS_VERSION_LT(clientvers, (unsigned int)s->method->version) &&
+ s->method->version != DTLS_ANY_VERSION) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_WRONG_VERSION_NUMBER);
+ goto end;
+ }
+
+ if (!PACKET_forward(&msgpayload, SSL3_RANDOM_SIZE)
+ || !PACKET_get_length_prefixed_1(&msgpayload, &session)
+ || !PACKET_get_length_prefixed_1(&msgpayload, &cookiepkt)) {
+ /*
+ * Could be malformed or the cookie does not fit within the initial
+ * ClientHello fragment. Either way we can't handle it.
+ */
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
+ goto end;
+ }
+
+ /*
+ * Check if we have a cookie or not. If not we need to send a
+ * HelloVerifyRequest.
+ */
+ if (PACKET_remaining(&cookiepkt) == 0) {
+ next = LISTEN_SEND_VERIFY_REQUEST;
+ } else {
+ /*
+ * We have a cookie, so lets check it.
+ */
+ if (s->ctx->app_verify_cookie_cb == NULL) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_NO_VERIFY_COOKIE_CALLBACK);
+ /* This is fatal */
+ return -1;
+ }
+ if (s->ctx->app_verify_cookie_cb(s, PACKET_data(&cookiepkt),
+ (unsigned int)PACKET_remaining(&cookiepkt)) == 0) {
+ /*
+ * We treat invalid cookies in the same was as no cookie as
+ * per RFC6347
+ */
+ next = LISTEN_SEND_VERIFY_REQUEST;
+ } else {
+ /* Cookie verification succeeded */
+ next = LISTEN_SUCCESS;
+ }
+ }
+
+ if (next == LISTEN_SEND_VERIFY_REQUEST) {
+ WPACKET wpkt;
+ unsigned int version;
+ size_t wreclen;
+
+ /*
+ * There was no cookie in the ClientHello so we need to send a
+ * HelloVerifyRequest. If this fails we do not worry about trying
+ * to resend, we just drop it.
+ */
+
+ /*
+ * Dump the read packet, we don't need it any more. Ignore return
+ * value
+ */
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
+ BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
+
+ /* Generate the cookie */
+ if (s->ctx->app_gen_cookie_cb == NULL ||
+ s->ctx->app_gen_cookie_cb(s, cookie, &cookielen) == 0 ||
+ cookielen > 255) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_COOKIE_GEN_CALLBACK_FAILURE);
+ /* This is fatal */
+ return -1;
+ }
+
+ /*
+ * Special case: for hello verify request, client version 1.0 and we
+ * haven't decided which version to use yet send back using version
+ * 1.0 header: otherwise some clients will ignore it.
+ */
+ version = (s->method->version == DTLS_ANY_VERSION) ? DTLS1_VERSION
+ : s->version;
+
+ /* Construct the record and message headers */
+ if (!WPACKET_init(&wpkt, s->init_buf)
+ || !WPACKET_put_bytes_u8(&wpkt, SSL3_RT_HANDSHAKE)
+ || !WPACKET_put_bytes_u16(&wpkt, version)
+ /*
+ * Record sequence number is always the same as in the
+ * received ClientHello
+ */
+ || !WPACKET_memcpy(&wpkt, seq, SEQ_NUM_SIZE)
+ /* End of record, start sub packet for message */
+ || !WPACKET_start_sub_packet_u16(&wpkt)
+ /* Message type */
+ || !WPACKET_put_bytes_u8(&wpkt,
+ DTLS1_MT_HELLO_VERIFY_REQUEST)
+ /*
+ * Message length - doesn't follow normal TLS convention:
+ * the length isn't the last thing in the message header.
+ * We'll need to fill this in later when we know the
+ * length. Set it to zero for now
+ */
+ || !WPACKET_put_bytes_u24(&wpkt, 0)
+ /*
+ * Message sequence number is always 0 for a
+ * HelloVerifyRequest
+ */
+ || !WPACKET_put_bytes_u16(&wpkt, 0)
+ /*
+ * We never fragment a HelloVerifyRequest, so fragment
+ * offset is 0
+ */
+ || !WPACKET_put_bytes_u24(&wpkt, 0)
+ /*
+ * Fragment length is the same as message length, but
+ * this *is* the last thing in the message header so we
+ * can just start a sub-packet. No need to come back
+ * later for this one.
+ */
+ || !WPACKET_start_sub_packet_u24(&wpkt)
+ /* Create the actual HelloVerifyRequest body */
+ || !dtls_raw_hello_verify_request(&wpkt, cookie, cookielen)
+ /* Close message body */
+ || !WPACKET_close(&wpkt)
+ /* Close record body */
+ || !WPACKET_close(&wpkt)
+ || !WPACKET_get_total_written(&wpkt, &wreclen)
+ || !WPACKET_finish(&wpkt)) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_INTERNAL_ERROR);
+ WPACKET_cleanup(&wpkt);
+ /* This is fatal */
+ return -1;
+ }
+
+ /*
+ * Fix up the message len in the message header. Its the same as the
+ * fragment len which has been filled in by WPACKET, so just copy
+ * that. Destination for the message len is after the record header
+ * plus one byte for the message content type. The source is the
+ * last 3 bytes of the message header
+ */
+ memcpy(&buf[DTLS1_RT_HEADER_LENGTH + 1],
+ &buf[DTLS1_RT_HEADER_LENGTH + DTLS1_HM_HEADER_LENGTH - 3],
+ 3);
+
+ if (s->msg_callback)
+ s->msg_callback(1, 0, SSL3_RT_HEADER, buf,
+ DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
+
+ if ((tmpclient = BIO_ADDR_new()) == NULL) {
+ SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
+ goto end;
+ }
+
+ /*
+ * This is unnecessary if rbio and wbio are one and the same - but
+ * maybe they're not. We ignore errors here - some BIOs do not
+ * support this.
+ */
+ if (BIO_dgram_get_peer(rbio, tmpclient) > 0) {
+ (void)BIO_dgram_set_peer(wbio, tmpclient);
+ }
+ BIO_ADDR_free(tmpclient);
+ tmpclient = NULL;
+
+ /* TODO(size_t): convert this call */
+ if (BIO_write(wbio, buf, wreclen) < (int)wreclen) {
+ if (BIO_should_retry(wbio)) {
+ /*
+ * Non-blocking IO...but we're stateless, so we're just
+ * going to drop this packet.
+ */
+ goto end;
+ }
+ return -1;
+ }
+
+ if (BIO_flush(wbio) <= 0) {
+ if (BIO_should_retry(wbio)) {
+ /*
+ * Non-blocking IO...but we're stateless, so we're just
+ * going to drop this packet.
+ */
+ goto end;
+ }
+ return -1;
+ }
+ }
+ } while (next != LISTEN_SUCCESS);
+
+ /*
+ * Set expected sequence numbers to continue the handshake.
+ */
+ s->d1->handshake_read_seq = 1;
+ s->d1->handshake_write_seq = 1;
+ s->d1->next_handshake_write_seq = 1;
+ DTLS_RECORD_LAYER_set_write_sequence(&s->rlayer, seq);
+
+ /*
+ * We are doing cookie exchange, so make sure we set that option in the
+ * SSL object
+ */
+ SSL_set_options(s, SSL_OP_COOKIE_EXCHANGE);
+
+ /*
+ * Tell the state machine that we've done the initial hello verify
+ * exchange
+ */
+ ossl_statem_set_hello_verify_done(s);
+
+ /*
+ * Some BIOs may not support this. If we fail we clear the client address
+ */
+ if (BIO_dgram_get_peer(rbio, client) <= 0)
+ BIO_ADDR_clear(client);
+
+ ret = 1;
+ clearpkt = 0;
+ end:
+ BIO_ADDR_free(tmpclient);
+ BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
+ if (clearpkt) {
+ /* Dump this packet. Ignore return value */
+ BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
+ }
+ return ret;
+}
+#endif