+ 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),
+ 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) {
+ /*
+ * 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;
+ }
+
+ p = &buf[DTLS1_RT_HEADER_LENGTH];
+ msglen = dtls_raw_hello_verify_request(p + DTLS1_HM_HEADER_LENGTH,
+ cookie, cookielen);
+
+ *p++ = DTLS1_MT_HELLO_VERIFY_REQUEST;
+
+ /* Message length */
+ l2n3(msglen, p);
+
+ /* Message sequence number is always 0 for a HelloVerifyRequest */
+ s2n(0, p);
+
+ /*
+ * We never fragment a HelloVerifyRequest, so fragment offset is 0
+ * and fragment length is message length
+ */
+ l2n3(0, p);
+ l2n3(msglen, p);
+
+ /* Set reclen equal to length of whole handshake message */
+ reclen = msglen + DTLS1_HM_HEADER_LENGTH;
+
+ /* Add the record header */
+ p = buf;
+
+ *(p++) = SSL3_RT_HANDSHAKE;
+ /*
+ * 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.
+ */
+ if (s->method->version == DTLS_ANY_VERSION) {
+ *(p++) = DTLS1_VERSION >> 8;
+ *(p++) = DTLS1_VERSION & 0xff;
+ } else {
+ *(p++) = s->version >> 8;
+ *(p++) = s->version & 0xff;
+ }
+
+ /*
+ * Record sequence number is always the same as in the received
+ * ClientHello
+ */
+ memcpy(p, seq, SEQ_NUM_SIZE);
+ p += SEQ_NUM_SIZE;
+
+ /* Length */
+ s2n(reclen, p);
+
+ /*
+ * Set reclen equal to length of whole record including record
+ * header
+ */
+ reclen += DTLS1_RT_HEADER_LENGTH;
+
+ 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;
+
+ if (BIO_write(wbio, buf, reclen) < (int)reclen) {
+ 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
+ */