text: /* DTLS implementation written by Nagendra Modadugu
   * (nagendra@cs.stanford.edu) for the OpenSSL project 2005. */
  /* ====================================================================
   * Copyright (c) 1998-2005 The OpenSSL Project.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. All advertising materials mentioning features or use of this
   *    software must display the following acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
   *
   * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For written permission, please contact
   *    openssl-core@openssl.org.
   *
   * 5. Products derived from this software may not be called "OpenSSL"
   *    nor may "OpenSSL" appear in their names without prior written
   *    permission of the OpenSSL Project.
   *
   * 6. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
   *
   * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
   * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   * ====================================================================
   *
   * This product includes cryptographic software written by Eric Young
   * (eay@cryptsoft.com).  This product includes software written by Tim
   * Hudson (tjh@cryptsoft.com).
   *
   */
  /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   * All rights reserved.
   *
   * This package is an SSL implementation written
   * by Eric Young (eay@cryptsoft.com).
   * The implementation was written so as to conform with Netscapes SSL.
   *
   * This library is free for commercial and non-commercial use as long as
   * the following conditions are aheared to.  The following conditions
   * apply to all code found in this distribution, be it the RC4, RSA,
   * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
   * included with this distribution is covered by the same copyright terms
   * except that the holder is Tim Hudson (tjh@cryptsoft.com).
   *
   * Copyright remains Eric Young's, and as such any Copyright notices in
   * the code are not to be removed.
   * If this package is used in a product, Eric Young should be given attribution
   * as the author of the parts of the library used.
   * This can be in the form of a textual message at program startup or
   * in documentation (online or textual) provided with the package.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *    "This product includes cryptographic software written by
   *     Eric Young (eay@cryptsoft.com)"
   *    The word 'cryptographic' can be left out if the rouines from the library
   *    being used are not cryptographic related :-).
   * 4. If you include any Windows specific code (or a derivative thereof) from
   *    the apps directory (application code) you must include an acknowledgement:
   *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
   *
   * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * The licence and distribution terms for any publically available version or
   * derivative of this code cannot be changed.  i.e. this code cannot simply be
   * copied and put under another distribution licence
   * [including the GNU Public Licence.] */
  
  #include <openssl/ssl.h>
  
  #include <assert.h>
  #include <string.h>
  
  #include <openssl/bio.h>
  #include <openssl/buf.h>
  #include <openssl/bytestring.h>
  #include <openssl/mem.h>
  #include <openssl/evp.h>
  #include <openssl/err.h>
  #include <openssl/rand.h>
  
  #include "../crypto/internal.h"
  #include "internal.h"
  
  
  namespace bssl {
  
  ssl_open_record_t dtls1_open_app_data(SSL *ssl, Span<uint8_t> *out,
                                        size_t *out_consumed, uint8_t *out_alert,
                                        Span<uint8_t> in) {
    assert(!SSL_in_init(ssl));
  
    uint8_t type;
    Span<uint8_t> record;
    auto ret = dtls_open_record(ssl, &type, &record, out_consumed, out_alert, in);
    if (ret != ssl_open_record_success) {
      return ret;
    }
  
    if (type == SSL3_RT_HANDSHAKE) {
      // Parse the first fragment header to determine if this is a pre-CCS or
      // post-CCS handshake record. DTLS resets handshake message numbers on each
      // handshake, so renegotiations and retransmissions are ambiguous.
      CBS cbs, body;
      struct hm_header_st msg_hdr;
      CBS_init(&cbs, record.data(), record.size());
      if (!dtls1_parse_fragment(&cbs, &msg_hdr, &body)) {
        OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_HANDSHAKE_RECORD);
        *out_alert = SSL_AD_DECODE_ERROR;
        return ssl_open_record_error;
      }
  
      if (msg_hdr.type == SSL3_MT_FINISHED &&
          msg_hdr.seq == ssl->d1->handshake_read_seq - 1) {
        if (msg_hdr.frag_off == 0) {
          // Retransmit our last flight of messages. If the peer sends the second
          // Finished, they may not have received ours. Only do this for the
          // first fragment, in case the Finished was fragmented.
          if (!dtls1_check_timeout_num(ssl)) {
            *out_alert = 0;  // TODO(davidben): Send an alert?
            return ssl_open_record_error;
          }
  
          dtls1_retransmit_outgoing_messages(ssl);
        }
        return ssl_open_record_discard;
      }
  
      // Otherwise, this is a pre-CCS handshake message from an unsupported
      // renegotiation attempt. Fall through to the error path.
    }
  
    if (type != SSL3_RT_APPLICATION_DATA) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_UNEXPECTED_RECORD);
      *out_alert = SSL_AD_UNEXPECTED_MESSAGE;
      return ssl_open_record_error;
    }
  
    if (record.empty()) {
      return ssl_open_record_discard;
    }
  
    *out = record;
    return ssl_open_record_success;
  }
  
  int dtls1_write_app_data(SSL *ssl, bool *out_needs_handshake, const uint8_t *in,
                           int len) {
    assert(!SSL_in_init(ssl));
    *out_needs_handshake = false;
  
    if (ssl->s3->write_shutdown != ssl_shutdown_none) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_PROTOCOL_IS_SHUTDOWN);
      return -1;
    }
  
    if (len > SSL3_RT_MAX_PLAIN_LENGTH) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_DTLS_MESSAGE_TOO_BIG);
      return -1;
    }
  
    if (len < 0) {
      OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_LENGTH);
      return -1;
    }
  
    if (len == 0) {
      return 0;
    }
  
    int ret = dtls1_write_record(ssl, SSL3_RT_APPLICATION_DATA, in, (size_t)len,
                                 dtls1_use_current_epoch);
    if (ret <= 0) {
      return ret;
    }
    return len;
  }
  
  int dtls1_write_record(SSL *ssl, int type, const uint8_t *in, size_t len,
                         enum dtls1_use_epoch_t use_epoch) {
    SSLBuffer *buf = &ssl->s3->write_buffer;
    assert(len <= SSL3_RT_MAX_PLAIN_LENGTH);
    // There should never be a pending write buffer in DTLS. One can't write half
    // a datagram, so the write buffer is always dropped in
    // |ssl_write_buffer_flush|.
    assert(buf->empty());
  
    if (len > SSL3_RT_MAX_PLAIN_LENGTH) {
      OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
      return -1;
    }
  
    size_t ciphertext_len;
    if (!buf->EnsureCap(ssl_seal_align_prefix_len(ssl),
                        len + SSL_max_seal_overhead(ssl)) ||
        !dtls_seal_record(ssl, buf->remaining().data(), &ciphertext_len,
                          buf->remaining().size(), type, in, len, use_epoch)) {
      buf->Clear();
      return -1;
    }
    buf->DidWrite(ciphertext_len);
  
    int ret = ssl_write_buffer_flush(ssl);
    if (ret <= 0) {
      return ret;
    }
    return 1;
  }
  
  int dtls1_dispatch_alert(SSL *ssl) {
    int ret = dtls1_write_record(ssl, SSL3_RT_ALERT, &ssl->s3->send_alert[0], 2,
                                 dtls1_use_current_epoch);
    if (ret <= 0) {
      return ret;
    }
    ssl->s3->alert_dispatch = 0;
  
    // If the alert is fatal, flush the BIO now.
    if (ssl->s3->send_alert[0] == SSL3_AL_FATAL) {
      BIO_flush(ssl->wbio);
    }
  
    ssl_do_msg_callback(ssl, 1 /* write */, SSL3_RT_ALERT, ssl->s3->send_alert);
  
    int alert = (ssl->s3->send_alert[0] << 8) | ssl->s3->send_alert[1];
    ssl_do_info_callback(ssl, SSL_CB_WRITE_ALERT, alert);
  
    return 1;
  }
  
  }  // namespace bssl
  