text: /* ssl/record/ssl3_record.c */
  /* 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.]
   */
  /* ====================================================================
   * Copyright (c) 1998-2015 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).
   *
   */
  
  #include "../ssl_locl.h"
  #include "internal/constant_time_locl.h"
  #include <openssl/rand.h>
  #include "record_locl.h"
  
  static const unsigned char ssl3_pad_1[48] = {
      0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
      0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
      0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
      0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
      0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
      0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36
  };
  
  static const unsigned char ssl3_pad_2[48] = {
      0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c,
      0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c,
      0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c,
      0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c,
      0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c,
      0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c
  };
  
  /*
   * Clear the contents of an SSL3_RECORD but retain any memory allocated
   */
  void SSL3_RECORD_clear(SSL3_RECORD *r)
  {
      unsigned char *comp = r->comp;
  
      memset(r, 0, sizeof(*r));
      r->comp = comp;
  }
  
  void SSL3_RECORD_release(SSL3_RECORD *r)
  {
      OPENSSL_free(r->comp);
      r->comp = NULL;
  }
  
  int SSL3_RECORD_setup(SSL3_RECORD *r)
  {
      if (r->comp == NULL)
          r->comp = (unsigned char *)
              OPENSSL_malloc(SSL3_RT_MAX_ENCRYPTED_LENGTH);
      if (r->comp == NULL)
          return 0;
      return 1;
  }
  
  void SSL3_RECORD_set_seq_num(SSL3_RECORD *r, const unsigned char *seq_num)
  {
      memcpy(r->seq_num, seq_num, SEQ_NUM_SIZE);
  }
  
  /*
   * MAX_EMPTY_RECORDS defines the number of consecutive, empty records that
   * will be processed per call to ssl3_get_record. Without this limit an
   * attacker could send empty records at a faster rate than we can process and
   * cause ssl3_get_record to loop forever.
   */
  #define MAX_EMPTY_RECORDS 32
  
  #define SSL2_RT_HEADER_LENGTH   2
  /*-
   * Call this to get a new input record.
   * It will return <= 0 if more data is needed, normally due to an error
   * or non-blocking IO.
   * When it finishes, one packet has been decoded and can be found in
   * ssl->s3->rrec.type    - is the type of record
   * ssl->s3->rrec.data,   - data
   * ssl->s3->rrec.length, - number of bytes
   */
  /* used only by ssl3_read_bytes */
  int ssl3_get_record(SSL *s)
  {
      int ssl_major, ssl_minor, al;
      int enc_err, n, i, ret = -1;
      SSL3_RECORD *rr;
      SSL_SESSION *sess;
      unsigned char *p;
      unsigned char md[EVP_MAX_MD_SIZE];
      short version;
      unsigned mac_size;
      size_t extra;
      unsigned empty_record_count = 0;
  
      rr = RECORD_LAYER_get_rrec(&s->rlayer);
      sess = s->session;
  
      if (s->options & SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER)
          extra = SSL3_RT_MAX_EXTRA;
      else
          extra = 0;
      if (extra && !s->s3->init_extra) {
          /*
           * An application error: SLS_OP_MICROSOFT_BIG_SSLV3_BUFFER set after
           * ssl3_setup_buffers() was done
           */
          SSLerr(SSL_F_SSL3_GET_RECORD, ERR_R_INTERNAL_ERROR);
          return -1;
      }
  
   again:
      /* check if we have the header */
      if ((RECORD_LAYER_get_rstate(&s->rlayer) != SSL_ST_READ_BODY) ||
          (RECORD_LAYER_get_packet_length(&s->rlayer) < SSL3_RT_HEADER_LENGTH)) {
          n = ssl3_read_n(s, SSL3_RT_HEADER_LENGTH,
              SSL3_BUFFER_get_len(&s->rlayer.rbuf), 0);
          if (n <= 0)
              return (n);         /* error or non-blocking */
          RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_BODY);
  
          p = RECORD_LAYER_get_packet(&s->rlayer);
  
          /*
           * Check whether this is a regular record or an SSLv2 style record. The
           * latter is only used in an initial ClientHello for old clients. We
           * check s->read_hash and s->enc_read_ctx to ensure this does not apply
           * during renegotiation
           */
          if (s->first_packet && s->server && !s->read_hash && !s->enc_read_ctx
                  && (p[0] & 0x80) && (p[2] == SSL2_MT_CLIENT_HELLO)) {
              /* SSLv2 style record */
              rr->type = SSL3_RT_HANDSHAKE;
              rr->rec_version = SSL2_VERSION;
  
              rr->length = ((p[0] & 0x7f) << 8) | p[1];
  
              if (rr->length > SSL3_BUFFER_get_len(&s->rlayer.rbuf)
                                      - SSL2_RT_HEADER_LENGTH) {
                  al = SSL_AD_RECORD_OVERFLOW;
                  SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_PACKET_LENGTH_TOO_LONG);
                  goto f_err;
              }
  
              if (rr->length < MIN_SSL2_RECORD_LEN) {
                  al = SSL_AD_HANDSHAKE_FAILURE;
                  SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_LENGTH_TOO_SHORT);
                  goto f_err;
              }
          } else {
              /* SSLv3+ style record */
              if (s->msg_callback)
                  s->msg_callback(0, 0, SSL3_RT_HEADER, p, 5, s,
                                  s->msg_callback_arg);
  
              /* Pull apart the header into the SSL3_RECORD */
              rr->type = *(p++);
              ssl_major = *(p++);
              ssl_minor = *(p++);
              version = (ssl_major << 8) | ssl_minor;
              rr->rec_version = version;
              n2s(p, rr->length);
  
              /* Lets check version */
              if (!s->first_packet && version != s->version) {
                  SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
                  if ((s->version & 0xFF00) == (version & 0xFF00)
                      && !s->enc_write_ctx && !s->write_hash) {
                      if (rr->type == SSL3_RT_ALERT) {
                          /*
                           * The record is using an incorrect version number, but
                           * what we've got appears to be an alert. We haven't
                           * read the body yet to check whether its a fatal or
                           * not - but chances are it is. We probably shouldn't
                           * send a fatal alert back. We'll just end.
                           */
                           goto err;
                      }
                      /*
                       * Send back error using their minor version number :-)
                       */
                      s->version = (unsigned short)version;
                  }
                  al = SSL_AD_PROTOCOL_VERSION;
                  goto f_err;
              }
  
              if ((version >> 8) != SSL3_VERSION_MAJOR) {
                  SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_WRONG_VERSION_NUMBER);
                  goto err;
              }
  
              if (rr->length >
                      SSL3_BUFFER_get_len(&s->rlayer.rbuf)
                      - SSL3_RT_HEADER_LENGTH) {
                  al = SSL_AD_RECORD_OVERFLOW;
                  SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_PACKET_LENGTH_TOO_LONG);
                  goto f_err;
              }
          }
  
          /* now s->rlayer.rstate == SSL_ST_READ_BODY */
      }
  
      /*
       * s->rlayer.rstate == SSL_ST_READ_BODY, get and decode the data.
       * Calculate how much more data we need to read for the rest of the record
       */
      if (rr->rec_version == SSL2_VERSION) {
          i = rr->length + SSL2_RT_HEADER_LENGTH - SSL3_RT_HEADER_LENGTH;
      } else {
          i = rr->length;
      }
      if (i > 0) {
          /* now s->packet_length == SSL3_RT_HEADER_LENGTH */
  
          n = ssl3_read_n(s, i, i, 1);
          if (n <= 0)
              return (n);         /* error or non-blocking io */
      }
  
      /* set state for later operations */
      RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_HEADER);
  
      /*
       * At this point, s->packet_length == SSL3_RT_HEADER_LENGTH + rr->length,
       * or s->packet_length == SSL2_RT_HEADER_LENGTH + rr->length
       * and we have that many bytes in s->packet
       */
      if(rr->rec_version == SSL2_VERSION) {
          rr->input = &(RECORD_LAYER_get_packet(&s->rlayer)[SSL2_RT_HEADER_LENGTH]);
      } else {
          rr->input = &(RECORD_LAYER_get_packet(&s->rlayer)[SSL3_RT_HEADER_LENGTH]);
      }
  
      /*
       * ok, we can now read from 's->packet' data into 'rr' rr->input points
       * at rr->length bytes, which need to be copied into rr->data by either
       * the decryption or by the decompression When the data is 'copied' into
       * the rr->data buffer, rr->input will be pointed at the new buffer
       */
  
      /*
       * We now have - encrypted [ MAC [ compressed [ plain ] ] ] rr->length
       * bytes of encrypted compressed stuff.
       */
  
      /* check is not needed I believe */
      if (rr->length > SSL3_RT_MAX_ENCRYPTED_LENGTH + extra) {
          al = SSL_AD_RECORD_OVERFLOW;
          SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_ENCRYPTED_LENGTH_TOO_LONG);
          goto f_err;
      }
  
      /* decrypt in place in 'rr->input' */
      rr->data = rr->input;
      rr->orig_len = rr->length;
      /*
       * If in encrypt-then-mac mode calculate mac from encrypted record. All
       * the details below are public so no timing details can leak.
       */
      if (SSL_USE_ETM(s) && s->read_hash) {
          unsigned char *mac;
          mac_size = EVP_MD_CTX_size(s->read_hash);
          OPENSSL_assert(mac_size <= EVP_MAX_MD_SIZE);
          if (rr->length < mac_size) {
              al = SSL_AD_DECODE_ERROR;
              SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_LENGTH_TOO_SHORT);
              goto f_err;
          }
          rr->length -= mac_size;
          mac = rr->data + rr->length;
          i = s->method->ssl3_enc->mac(s, md, 0 /* not send */ );
          if (i < 0 || CRYPTO_memcmp(md, mac, (size_t)mac_size) != 0) {
              al = SSL_AD_BAD_RECORD_MAC;
              SSLerr(SSL_F_SSL3_GET_RECORD,
                     SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC);
              goto f_err;
          }
      }
  
      enc_err = s->method->ssl3_enc->enc(s, 0);
      /*-
       * enc_err is:
       *    0: (in non-constant time) if the record is publically invalid.
       *    1: if the padding is valid
       *    -1: if the padding is invalid
       */
      if (enc_err == 0) {
          al = SSL_AD_DECRYPTION_FAILED;
          SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_BLOCK_CIPHER_PAD_IS_WRONG);
          goto f_err;
      }
  #ifdef TLS_DEBUG
      printf("dec %d\n", rr->length);
      {
          unsigned int z;
          for (z = 0; z < rr->length; z++)
              printf("%02X%c", rr->data[z], ((z + 1) % 16) ? ' ' : '\n');
      }
      printf("\n");
  #endif
  
      /* r->length is now the compressed data plus mac */
      if ((sess != NULL) &&
          (s->enc_read_ctx != NULL) &&
          (EVP_MD_CTX_md(s->read_hash) != NULL) && !SSL_USE_ETM(s)) {
          /* s->read_hash != NULL => mac_size != -1 */
          unsigned char *mac = NULL;
          unsigned char mac_tmp[EVP_MAX_MD_SIZE];
          mac_size = EVP_MD_CTX_size(s->read_hash);
          OPENSSL_assert(mac_size <= EVP_MAX_MD_SIZE);
  
          /*
           * orig_len is the length of the record before any padding was
           * removed. This is public information, as is the MAC in use,
           * therefore we can safely process the record in a different amount
           * of time if it's too short to possibly contain a MAC.
           */
          if (rr->orig_len < mac_size ||
              /* CBC records must have a padding length byte too. */
              (EVP_CIPHER_CTX_mode(s->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
               rr->orig_len < mac_size + 1)) {
              al = SSL_AD_DECODE_ERROR;
              SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_LENGTH_TOO_SHORT);
              goto f_err;
          }
  
          if (EVP_CIPHER_CTX_mode(s->enc_read_ctx) == EVP_CIPH_CBC_MODE) {
              /*
               * We update the length so that the TLS header bytes can be
               * constructed correctly but we need to extract the MAC in
               * constant time from within the record, without leaking the
               * contents of the padding bytes.
               */
              mac = mac_tmp;
              ssl3_cbc_copy_mac(mac_tmp, rr, mac_size);
              rr->length -= mac_size;
          } else {
              /*
               * In this case there's no padding, so |rec->orig_len| equals
               * |rec->length| and we checked that there's enough bytes for
               * |mac_size| above.
               */
              rr->length -= mac_size;
              mac = &rr->data[rr->length];
          }
  
          i = s->method->ssl3_enc->mac(s, md, 0 /* not send */ );
          if (i < 0 || mac == NULL
              || CRYPTO_memcmp(md, mac, (size_t)mac_size) != 0)
              enc_err = -1;
          if (rr->length > SSL3_RT_MAX_COMPRESSED_LENGTH + extra + mac_size)
              enc_err = -1;
      }
  
      if (enc_err < 0) {
          /*
           * A separate 'decryption_failed' alert was introduced with TLS 1.0,
           * SSL 3.0 only has 'bad_record_mac'.  But unless a decryption
           * failure is directly visible from the ciphertext anyway, we should
           * not reveal which kind of error occurred -- this might become
           * visible to an attacker (e.g. via a logfile)
           */
          al = SSL_AD_BAD_RECORD_MAC;
          SSLerr(SSL_F_SSL3_GET_RECORD,
                 SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC);
          goto f_err;
      }
  
      /* r->length is now just compressed */
      if (s->expand != NULL) {
          if (rr->length > SSL3_RT_MAX_COMPRESSED_LENGTH + extra) {
              al = SSL_AD_RECORD_OVERFLOW;
              SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_COMPRESSED_LENGTH_TOO_LONG);
              goto f_err;
          }
          if (!ssl3_do_uncompress(s)) {
              al = SSL_AD_DECOMPRESSION_FAILURE;
              SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_BAD_DECOMPRESSION);
              goto f_err;
          }
      }
  
      if (rr->length > SSL3_RT_MAX_PLAIN_LENGTH + extra) {
          al = SSL_AD_RECORD_OVERFLOW;
          SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_DATA_LENGTH_TOO_LONG);
          goto f_err;
      }
  
      rr->off = 0;
      /*-
       * So at this point the following is true
       * ssl->s3->rrec.type   is the type of record
       * ssl->s3->rrec.length == number of bytes in record
       * ssl->s3->rrec.off    == offset to first valid byte
       * ssl->s3->rrec.data   == where to take bytes from, increment
       *                         after use :-).
       */
  
      /* we have pulled in a full packet so zero things */
      RECORD_LAYER_reset_packet_length(&s->rlayer);
  
      /* just read a 0 length packet */
      if (rr->length == 0) {
          empty_record_count++;
          if (empty_record_count > MAX_EMPTY_RECORDS) {
              al = SSL_AD_UNEXPECTED_MESSAGE;
              SSLerr(SSL_F_SSL3_GET_RECORD, SSL_R_RECORD_TOO_SMALL);
              goto f_err;
          }
          goto again;
      }
  
      return (1);
  
   f_err:
      ssl3_send_alert(s, SSL3_AL_FATAL, al);
   err:
      return (ret);
  }
  
  int ssl3_do_uncompress(SSL *ssl)
  {
  #ifndef OPENSSL_NO_COMP
      int i;
      SSL3_RECORD *rr;
  
      rr = RECORD_LAYER_get_rrec(&ssl->rlayer);
      i = COMP_expand_block(ssl->expand, rr->comp,
                            SSL3_RT_MAX_PLAIN_LENGTH, rr->data,
                            (int)rr->length);
      if (i < 0)
          return (0);
      else
          rr->length = i;
      rr->data = rr->comp;
  #endif
      return (1);
  }
  
  int ssl3_do_compress(SSL *ssl)
  {
  #ifndef OPENSSL_NO_COMP
      int i;
      SSL3_RECORD *wr;
  
      wr = RECORD_LAYER_get_wrec(&ssl->rlayer);
      i = COMP_compress_block(ssl->compress, wr->data,
                              SSL3_RT_MAX_COMPRESSED_LENGTH,
                              wr->input, (int)wr->length);
      if (i < 0)
          return (0);
      else
          wr->length = i;
  
      wr->input = wr->data;
  #endif
      return (1);
  }
  
  /*-
   * ssl3_enc encrypts/decrypts the record in |s->wrec| / |s->rrec|, respectively.
   *
   * Returns:
   *   0: (in non-constant time) if the record is publically invalid (i.e. too
   *       short etc).
   *   1: if the record's padding is valid / the encryption was successful.
   *   -1: if the record's padding is invalid or, if sending, an internal error
   *       occurred.
   */
  int ssl3_enc(SSL *s, int send)
  {
      SSL3_RECORD *rec;
      EVP_CIPHER_CTX *ds;
      unsigned long l;
      int bs, i, mac_size = 0;
      const EVP_CIPHER *enc;
  
      if (send) {
          ds = s->enc_write_ctx;
          rec = RECORD_LAYER_get_wrec(&s->rlayer);
          if (s->enc_write_ctx == NULL)
              enc = NULL;
          else
              enc = EVP_CIPHER_CTX_cipher(s->enc_write_ctx);
      } else {
          ds = s->enc_read_ctx;
          rec = RECORD_LAYER_get_rrec(&s->rlayer);
          if (s->enc_read_ctx == NULL)
              enc = NULL;
          else
              enc = EVP_CIPHER_CTX_cipher(s->enc_read_ctx);
      }
  
      if ((s->session == NULL) || (ds == NULL) || (enc == NULL)) {
          memmove(rec->data, rec->input, rec->length);
          rec->input = rec->data;
      } else {
          l = rec->length;
          bs = EVP_CIPHER_block_size(ds->cipher);
  
          /* COMPRESS */
  
          if ((bs != 1) && send) {
              i = bs - ((int)l % bs);
  
              /* we need to add 'i-1' padding bytes */
              l += i;
              /*
               * the last of these zero bytes will be overwritten with the
               * padding length.
               */
              memset(&rec->input[rec->length], 0, i);
              rec->length += i;
              rec->input[l - 1] = (i - 1);
          }
  
          if (!send) {
              if (l == 0 || l % bs != 0)
                  return 0;
              /* otherwise, rec->length >= bs */
          }
  
          if (EVP_Cipher(ds, rec->data, rec->input, l) < 1)
              return -1;
  
          if (EVP_MD_CTX_md(s->read_hash) != NULL)
              mac_size = EVP_MD_CTX_size(s->read_hash);
          if ((bs != 1) && !send)
              return ssl3_cbc_remove_padding(s, rec, bs, mac_size);
      }
      return (1);
  }
  
  /*-
   * tls1_enc encrypts/decrypts the record in |s->wrec| / |s->rrec|, respectively.
   *
   * Returns:
   *   0: (in non-constant time) if the record is publically invalid (i.e. too
   *       short etc).
   *   1: if the record's padding is valid / the encryption was successful.
   *   -1: if the record's padding/AEAD-authenticator is invalid or, if sending,
   *       an internal error occurred.
   */
  int tls1_enc(SSL *s, int send)
  {
      SSL3_RECORD *rec;
      EVP_CIPHER_CTX *ds;
      unsigned long l;
      int bs, i, j, k, pad = 0, ret, mac_size = 0;
      const EVP_CIPHER *enc;
  
      if (send) {
          if (EVP_MD_CTX_md(s->write_hash)) {
              int n = EVP_MD_CTX_size(s->write_hash);
              OPENSSL_assert(n >= 0);
          }
          ds = s->enc_write_ctx;
          rec = RECORD_LAYER_get_wrec(&s->rlayer);
          if (s->enc_write_ctx == NULL)
              enc = NULL;
          else {
              int ivlen;
              enc = EVP_CIPHER_CTX_cipher(s->enc_write_ctx);
              /* For TLSv1.1 and later explicit IV */
              if (SSL_USE_EXPLICIT_IV(s)
                  && EVP_CIPHER_mode(enc) == EVP_CIPH_CBC_MODE)
                  ivlen = EVP_CIPHER_iv_length(enc);
              else
                  ivlen = 0;
              if (ivlen > 1) {
                  if (rec->data != rec->input)
                      /*
                       * we can't write into the input stream: Can this ever
                       * happen?? (steve)
                       */
                      fprintf(stderr,
                              "%s:%d: rec->data != rec->input\n",
                              __FILE__, __LINE__);
                  else if (RAND_bytes(rec->input, ivlen) <= 0)
                      return -1;
              }
          }
      } else {
          if (EVP_MD_CTX_md(s->read_hash)) {
              int n = EVP_MD_CTX_size(s->read_hash);
              OPENSSL_assert(n >= 0);
          }
          ds = s->enc_read_ctx;
          rec = RECORD_LAYER_get_rrec(&s->rlayer);
          if (s->enc_read_ctx == NULL)
              enc = NULL;
          else
              enc = EVP_CIPHER_CTX_cipher(s->enc_read_ctx);
      }
  
      if ((s->session == NULL) || (ds == NULL) || (enc == NULL)) {
          memmove(rec->data, rec->input, rec->length);
          rec->input = rec->data;
          ret = 1;
      } else {
          l = rec->length;
          bs = EVP_CIPHER_block_size(ds->cipher);
  
          if (EVP_CIPHER_flags(ds->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) {
              unsigned char buf[EVP_AEAD_TLS1_AAD_LEN], *seq;
  
              seq = send ? RECORD_LAYER_get_write_sequence(&s->rlayer)
                  : RECORD_LAYER_get_read_sequence(&s->rlayer);
  
              if (SSL_IS_DTLS(s)) {
                  unsigned char dtlsseq[9], *p = dtlsseq;
  
                  s2n(send ? DTLS_RECORD_LAYER_get_w_epoch(&s->rlayer) :
                      DTLS_RECORD_LAYER_get_r_epoch(&s->rlayer), p);
                  memcpy(p, &seq[2], 6);
                  memcpy(buf, dtlsseq, 8);
              } else {
                  memcpy(buf, seq, 8);
                  for (i = 7; i >= 0; i--) { /* increment */
                      ++seq[i];
                      if (seq[i] != 0)
                          break;
                  }
              }
  
              buf[8] = rec->type;
              buf[9] = (unsigned char)(s->version >> 8);
              buf[10] = (unsigned char)(s->version);
              buf[11] = rec->length >> 8;
              buf[12] = rec->length & 0xff;
              pad = EVP_CIPHER_CTX_ctrl(ds, EVP_CTRL_AEAD_TLS1_AAD,
                                        EVP_AEAD_TLS1_AAD_LEN, buf);
              if (pad <= 0)
                  return -1;
              if (send) {
                  l += pad;
                  rec->length += pad;
              }
          } else if ((bs != 1) && send) {
              i = bs - ((int)l % bs);
  
              /* Add weird padding of upto 256 bytes */
  
              /* we need to add 'i' padding bytes of value j */
              j = i - 1;
              for (k = (int)l; k < (int)(l + i); k++)
                  rec->input[k] = j;
              l += i;
              rec->length += i;
          }
  
          if (!send) {
              if (l == 0 || l % bs != 0)
                  return 0;
          }
  
          i = EVP_Cipher(ds, rec->data, rec->input, l);
          if ((EVP_CIPHER_flags(ds->cipher) & EVP_CIPH_FLAG_CUSTOM_CIPHER)
              ? (i < 0)
              : (i == 0))
              return -1;          /* AEAD can fail to verify MAC */
          if (send == 0) {
              if (EVP_CIPHER_mode(enc) == EVP_CIPH_GCM_MODE) {
                  rec->data += EVP_GCM_TLS_EXPLICIT_IV_LEN;
                  rec->input += EVP_GCM_TLS_EXPLICIT_IV_LEN;
                  rec->length -= EVP_GCM_TLS_EXPLICIT_IV_LEN;
              } else if (EVP_CIPHER_mode(enc) == EVP_CIPH_CCM_MODE) {
                  rec->data += EVP_CCM_TLS_EXPLICIT_IV_LEN;
                  rec->input += EVP_CCM_TLS_EXPLICIT_IV_LEN;
                  rec->length -= EVP_CCM_TLS_EXPLICIT_IV_LEN;
              }
          }
  
          ret = 1;
          if (!SSL_USE_ETM(s) && EVP_MD_CTX_md(s->read_hash) != NULL)
              mac_size = EVP_MD_CTX_size(s->read_hash);
          if ((bs != 1) && !send)
              ret = tls1_cbc_remove_padding(s, rec, bs, mac_size);
          if (pad && !send)
              rec->length -= pad;
      }
      return ret;
  }
  
  int n_ssl3_mac(SSL *ssl, unsigned char *md, int send)
  {
      SSL3_RECORD *rec;
      unsigned char *mac_sec, *seq;
      EVP_MD_CTX md_ctx;
      const EVP_MD_CTX *hash;
      unsigned char *p, rec_char;
      size_t md_size;
      int npad;
      int t;
  
      if (send) {
          rec = RECORD_LAYER_get_wrec(&ssl->rlayer);
          mac_sec = &(ssl->s3->write_mac_secret[0]);
          seq = RECORD_LAYER_get_write_sequence(&ssl->rlayer);
          hash = ssl->write_hash;
      } else {
          rec = RECORD_LAYER_get_rrec(&ssl->rlayer);
          mac_sec = &(ssl->s3->read_mac_secret[0]);
          seq = RECORD_LAYER_get_read_sequence(&ssl->rlayer);
          hash = ssl->read_hash;
      }
  
      t = EVP_MD_CTX_size(hash);
      if (t < 0)
          return -1;
      md_size = t;
      npad = (48 / md_size) * md_size;
  
      if (!send &&
          EVP_CIPHER_CTX_mode(ssl->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
          ssl3_cbc_record_digest_supported(hash)) {
          /*
           * This is a CBC-encrypted record. We must avoid leaking any
           * timing-side channel information about how many blocks of data we
           * are hashing because that gives an attacker a timing-oracle.
           */
  
          /*-
           * npad is, at most, 48 bytes and that's with MD5:
           *   16 + 48 + 8 (sequence bytes) + 1 + 2 = 75.
           *
           * With SHA-1 (the largest hash speced for SSLv3) the hash size
           * goes up 4, but npad goes down by 8, resulting in a smaller
           * total size.
           */
          unsigned char header[75];
          unsigned j = 0;
          memcpy(header + j, mac_sec, md_size);
          j += md_size;
          memcpy(header + j, ssl3_pad_1, npad);
          j += npad;
          memcpy(header + j, seq, 8);
          j += 8;
          header[j++] = rec->type;
          header[j++] = rec->length >> 8;
          header[j++] = rec->length & 0xff;
  
          /* Final param == is SSLv3 */
          ssl3_cbc_digest_record(hash,
                                 md, &md_size,
                                 header, rec->input,
                                 rec->length + md_size, rec->orig_len,
                                 mac_sec, md_size, 1);
      } else {
          unsigned int md_size_u;
          /* Chop the digest off the end :-) */
          EVP_MD_CTX_init(&md_ctx);
  
          EVP_MD_CTX_copy_ex(&md_ctx, hash);
          EVP_DigestUpdate(&md_ctx, mac_sec, md_size);
          EVP_DigestUpdate(&md_ctx, ssl3_pad_1, npad);
          EVP_DigestUpdate(&md_ctx, seq, 8);
          rec_char = rec->type;
          EVP_DigestUpdate(&md_ctx, &rec_char, 1);
          p = md;
          s2n(rec->length, p);
          EVP_DigestUpdate(&md_ctx, md, 2);
          EVP_DigestUpdate(&md_ctx, rec->input, rec->length);
          EVP_DigestFinal_ex(&md_ctx, md, NULL);
  
          EVP_MD_CTX_copy_ex(&md_ctx, hash);
          EVP_DigestUpdate(&md_ctx, mac_sec, md_size);
          EVP_DigestUpdate(&md_ctx, ssl3_pad_2, npad);
          EVP_DigestUpdate(&md_ctx, md, md_size);
          EVP_DigestFinal_ex(&md_ctx, md, &md_size_u);
          md_size = md_size_u;
  
          EVP_MD_CTX_cleanup(&md_ctx);
      }
  
      ssl3_record_sequence_update(seq);
      return (md_size);
  }
  
  int tls1_mac(SSL *ssl, unsigned char *md, int send)
  {
      SSL3_RECORD *rec;
      unsigned char *seq;
      EVP_MD_CTX *hash;
      size_t md_size;
      int i;
      EVP_MD_CTX hmac, *mac_ctx;
      unsigned char header[13];
      int stream_mac = (send ? (ssl->mac_flags & SSL_MAC_FLAG_WRITE_MAC_STREAM)
                        : (ssl->mac_flags & SSL_MAC_FLAG_READ_MAC_STREAM));
      int t;
  
      if (send) {
          rec = RECORD_LAYER_get_wrec(&ssl->rlayer);
          seq = RECORD_LAYER_get_write_sequence(&ssl->rlayer);
          hash = ssl->write_hash;
      } else {
          rec = RECORD_LAYER_get_rrec(&ssl->rlayer);
          seq = RECORD_LAYER_get_read_sequence(&ssl->rlayer);
          hash = ssl->read_hash;
      }
  
      t = EVP_MD_CTX_size(hash);
      OPENSSL_assert(t >= 0);
      md_size = t;
  
      /* I should fix this up TLS TLS TLS TLS TLS XXXXXXXX */
      if (stream_mac) {
          mac_ctx = hash;
      } else {
          if (!EVP_MD_CTX_copy(&hmac, hash))
              return -1;
          mac_ctx = &hmac;
      }
  
      if (SSL_IS_DTLS(ssl)) {
          unsigned char dtlsseq[8], *p = dtlsseq;
  
          s2n(send ? DTLS_RECORD_LAYER_get_w_epoch(&ssl->rlayer) :
              DTLS_RECORD_LAYER_get_r_epoch(&ssl->rlayer), p);
          memcpy(p, &seq[2], 6);
  
          memcpy(header, dtlsseq, 8);
      } else
          memcpy(header, seq, 8);
  
      header[8] = rec->type;
      header[9] = (unsigned char)(ssl->version >> 8);
      header[10] = (unsigned char)(ssl->version);
      header[11] = (rec->length) >> 8;
      header[12] = (rec->length) & 0xff;
  
      if (!send && !SSL_USE_ETM(ssl) &&
          EVP_CIPHER_CTX_mode(ssl->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
          ssl3_cbc_record_digest_supported(mac_ctx)) {
          /*
           * This is a CBC-encrypted record. We must avoid leaking any
           * timing-side channel information about how many blocks of data we
           * are hashing because that gives an attacker a timing-oracle.
           */
          /* Final param == not SSLv3 */
          ssl3_cbc_digest_record(mac_ctx,
                                 md, &md_size,
                                 header, rec->input,
                                 rec->length + md_size, rec->orig_len,
                                 ssl->s3->read_mac_secret,
                                 ssl->s3->read_mac_secret_size, 0);
      } else {
          EVP_DigestSignUpdate(mac_ctx, header, sizeof(header));
          EVP_DigestSignUpdate(mac_ctx, rec->input, rec->length);
          t = EVP_DigestSignFinal(mac_ctx, md, &md_size);
          if (t <= 0)
              return -1;
          if (!send && !SSL_USE_ETM(ssl) && FIPS_mode())
              tls_fips_digest_extra(ssl->enc_read_ctx,
                                    mac_ctx, rec->input,
                                    rec->length, rec->orig_len);
      }
  
      if (!stream_mac)
          EVP_MD_CTX_cleanup(&hmac);
  #ifdef TLS_DEBUG
      fprintf(stderr, "seq=");
      {
          int z;
          for (z = 0; z < 8; z++)
              fprintf(stderr, "%02X ", seq[z]);
          fprintf(stderr, "\n");
      }
      fprintf(stderr, "rec=");
      {
          unsigned int z;
          for (z = 0; z < rec->length; z++)
              fprintf(stderr, "%02X ", rec->data[z]);
          fprintf(stderr, "\n");
      }
  #endif
  
      if (!SSL_IS_DTLS(ssl)) {
          for (i = 7; i >= 0; i--) {
              ++seq[i];
              if (seq[i] != 0)
                  break;
          }
      }
  #ifdef TLS_DEBUG
      {
          unsigned int z;
          for (z = 0; z < md_size; z++)
              fprintf(stderr, "%02X ", md[z]);
          fprintf(stderr, "\n");
      }
  #endif
      return (md_size);
  }
  
  /*-
   * ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
   * record in |rec| by updating |rec->length| in constant time.
   *
   * block_size: the block size of the cipher used to encrypt the record.
   * returns:
   *   0: (in non-constant time) if the record is publicly invalid.
   *   1: if the padding was valid
   *  -1: otherwise.
   */
  int ssl3_cbc_remove_padding(const SSL *s,
                              SSL3_RECORD *rec,
                              unsigned block_size, unsigned mac_size)
  {
      unsigned padding_length, good;
      const unsigned overhead = 1 /* padding length byte */  + mac_size;
  
      /*
       * These lengths are all public so we can test them in non-constant time.
       */
      if (overhead > rec->length)
          return 0;
  
      padding_length = rec->data[rec->length - 1];
      good = constant_time_ge(rec->length, padding_length + overhead);
      /* SSLv3 requires that the padding is minimal. */
      good &= constant_time_ge(block_size, padding_length + 1);
      rec->length -= good & (padding_length + 1);
      return constant_time_select_int(good, 1, -1);
  }
  
  /*-
   * tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
   * record in |rec| in constant time and returns 1 if the padding is valid and
   * -1 otherwise. It also removes any explicit IV from the start of the record
   * without leaking any timing about whether there was enough space after the
   * padding was removed.
   *
   * block_size: the block size of the cipher used to encrypt the record.
   * returns:
   *   0: (in non-constant time) if the record is publicly invalid.
   *   1: if the padding was valid
   *  -1: otherwise.
   */
  int tls1_cbc_remove_padding(const SSL *s,
                              SSL3_RECORD *rec,
                              unsigned block_size, unsigned mac_size)
  {
      unsigned padding_length, good, to_check, i;
      const unsigned overhead = 1 /* padding length byte */  + mac_size;
      /* Check if version requires explicit IV */
      if (SSL_USE_EXPLICIT_IV(s)) {
          /*
           * These lengths are all public so we can test them in non-constant
           * time.
           */
          if (overhead + block_size > rec->length)
              return 0;
          /* We can now safely skip explicit IV */
          rec->data += block_size;
          rec->input += block_size;
          rec->length -= block_size;
          rec->orig_len -= block_size;
      } else if (overhead > rec->length)
          return 0;
  
      padding_length = rec->data[rec->length - 1];
  
      if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) {
          /* padding is already verified */
          rec->length -= padding_length + 1;
          return 1;
      }
  
      good = constant_time_ge(rec->length, overhead + padding_length);
      /*
       * The padding consists of a length byte at the end of the record and
       * then that many bytes of padding, all with the same value as the length
       * byte. Thus, with the length byte included, there are i+1 bytes of
       * padding. We can't check just |padding_length+1| bytes because that
       * leaks decrypted information. Therefore we always have to check the
       * maximum amount of padding possible. (Again, the length of the record
       * is public information so we can use it.)
       */
      to_check = 255;             /* maximum amount of padding. */
      if (to_check > rec->length - 1)
          to_check = rec->length - 1;
  
      for (i = 0; i < to_check; i++) {
          unsigned char mask = constant_time_ge_8(padding_length, i);
          unsigned char b = rec->data[rec->length - 1 - i];
          /*
           * The final |padding_length+1| bytes should all have the value
           * |padding_length|. Therefore the XOR should be zero.
           */
          good &= ~(mask & (padding_length ^ b));
      }
  
      /*
       * If any of the final |padding_length+1| bytes had the wrong value, one
       * or more of the lower eight bits of |good| will be cleared.
       */
      good = constant_time_eq(0xff, good & 0xff);
      rec->length -= good & (padding_length + 1);
  
      return constant_time_select_int(good, 1, -1);
  }
  
  /*-
   * ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
   * constant time (independent of the concrete value of rec->length, which may
   * vary within a 256-byte window).
   *
   * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
   * this function.
   *
   * On entry:
   *   rec->orig_len >= md_size
   *   md_size <= EVP_MAX_MD_SIZE
   *
   * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
   * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
   * a single or pair of cache-lines, then the variable memory accesses don't
   * actually affect the timing. CPUs with smaller cache-lines [if any] are
   * not multi-core and are not considered vulnerable to cache-timing attacks.
   */
  #define CBC_MAC_ROTATE_IN_PLACE
  
  void ssl3_cbc_copy_mac(unsigned char *out,
                         const SSL3_RECORD *rec, unsigned md_size)
  {
  #if defined(CBC_MAC_ROTATE_IN_PLACE)
      unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE];
      unsigned char *rotated_mac;
  #else
      unsigned char rotated_mac[EVP_MAX_MD_SIZE];
  #endif
  
      /*
       * mac_end is the index of |rec->data| just after the end of the MAC.
       */
      unsigned mac_end = rec->length;
      unsigned mac_start = mac_end - md_size;
      /*
       * scan_start contains the number of bytes that we can ignore because the
       * MAC's position can only vary by 255 bytes.
       */
      unsigned scan_start = 0;
      unsigned i, j;
      unsigned div_spoiler;
      unsigned rotate_offset;
  
      OPENSSL_assert(rec->orig_len >= md_size);
      OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
  
  #if defined(CBC_MAC_ROTATE_IN_PLACE)
      rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63);
  #endif
  
      /* This information is public so it's safe to branch based on it. */
      if (rec->orig_len > md_size + 255 + 1)
          scan_start = rec->orig_len - (md_size + 255 + 1);
      /*
       * div_spoiler contains a multiple of md_size that is used to cause the
       * modulo operation to be constant time. Without this, the time varies
       * based on the amount of padding when running on Intel chips at least.
       * The aim of right-shifting md_size is so that the compiler doesn't
       * figure out that it can remove div_spoiler as that would require it to
       * prove that md_size is always even, which I hope is beyond it.
       */
      div_spoiler = md_size >> 1;
      div_spoiler <<= (sizeof(div_spoiler) - 1) * 8;
      rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
  
      memset(rotated_mac, 0, md_size);
      for (i = scan_start, j = 0; i < rec->orig_len; i++) {
          unsigned char mac_started = constant_time_ge_8(i, mac_start);
          unsigned char mac_ended = constant_time_ge_8(i, mac_end);
          unsigned char b = rec->data[i];
          rotated_mac[j++] |= b & mac_started & ~mac_ended;
          j &= constant_time_lt(j, md_size);
      }
  
      /* Now rotate the MAC */
  #if defined(CBC_MAC_ROTATE_IN_PLACE)
      j = 0;
      for (i = 0; i < md_size; i++) {
          /* in case cache-line is 32 bytes, touch second line */
          ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32];
          out[j++] = rotated_mac[rotate_offset++];
          rotate_offset &= constant_time_lt(rotate_offset, md_size);
      }
  #else
      memset(out, 0, md_size);
      rotate_offset = md_size - rotate_offset;
      rotate_offset &= constant_time_lt(rotate_offset, md_size);
      for (i = 0; i < md_size; i++) {
          for (j = 0; j < md_size; j++)
              out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
          rotate_offset++;
          rotate_offset &= constant_time_lt(rotate_offset, md_size);
      }
  #endif
  }
  
  int dtls1_process_record(SSL *s)
  {
      int i, al;
      int enc_err;
      SSL_SESSION *sess;
      SSL3_RECORD *rr;
      unsigned int mac_size;
      unsigned char md[EVP_MAX_MD_SIZE];
  
      rr = RECORD_LAYER_get_rrec(&s->rlayer);
      sess = s->session;
  
      /*
       * At this point, s->packet_length == SSL3_RT_HEADER_LNGTH + rr->length,
       * and we have that many bytes in s->packet
       */
      rr->input = &(RECORD_LAYER_get_packet(&s->rlayer)[DTLS1_RT_HEADER_LENGTH]);
  
      /*
       * ok, we can now read from 's->packet' data into 'rr' rr->input points
       * at rr->length bytes, which need to be copied into rr->data by either
       * the decryption or by the decompression When the data is 'copied' into
       * the rr->data buffer, rr->input will be pointed at the new buffer
       */
  
      /*
       * We now have - encrypted [ MAC [ compressed [ plain ] ] ] rr->length
       * bytes of encrypted compressed stuff.
       */
  
      /* check is not needed I believe */
      if (rr->length > SSL3_RT_MAX_ENCRYPTED_LENGTH) {
          al = SSL_AD_RECORD_OVERFLOW;
          SSLerr(SSL_F_DTLS1_PROCESS_RECORD, SSL_R_ENCRYPTED_LENGTH_TOO_LONG);
          goto f_err;
      }
  
      /* decrypt in place in 'rr->input' */
      rr->data = rr->input;
      rr->orig_len = rr->length;
  
      enc_err = s->method->ssl3_enc->enc(s, 0);
      /*-
       * enc_err is:
       *    0: (in non-constant time) if the record is publically invalid.
       *    1: if the padding is valid
       *   -1: if the padding is invalid
       */
      if (enc_err == 0) {
          /* For DTLS we simply ignore bad packets. */
          rr->length = 0;
          RECORD_LAYER_reset_packet_length(&s->rlayer);
          goto err;
      }
  #ifdef TLS_DEBUG
      printf("dec %d\n", rr->length);
      {
          unsigned int z;
          for (z = 0; z < rr->length; z++)
              printf("%02X%c", rr->data[z], ((z + 1) % 16) ? ' ' : '\n');
      }
      printf("\n");
  #endif
  
      /* r->length is now the compressed data plus mac */
      if ((sess != NULL) &&
          (s->enc_read_ctx != NULL) && (EVP_MD_CTX_md(s->read_hash) != NULL)) {
          /* s->read_hash != NULL => mac_size != -1 */
          unsigned char *mac = NULL;
          unsigned char mac_tmp[EVP_MAX_MD_SIZE];
          mac_size = EVP_MD_CTX_size(s->read_hash);
          OPENSSL_assert(mac_size <= EVP_MAX_MD_SIZE);
  
          /*
           * orig_len is the length of the record before any padding was
           * removed. This is public information, as is the MAC in use,
           * therefore we can safely process the record in a different amount
           * of time if it's too short to possibly contain a MAC.
           */
          if (rr->orig_len < mac_size ||
              /* CBC records must have a padding length byte too. */
              (EVP_CIPHER_CTX_mode(s->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
               rr->orig_len < mac_size + 1)) {
              al = SSL_AD_DECODE_ERROR;
              SSLerr(SSL_F_DTLS1_PROCESS_RECORD, SSL_R_LENGTH_TOO_SHORT);
              goto f_err;
          }
  
          if (EVP_CIPHER_CTX_mode(s->enc_read_ctx) == EVP_CIPH_CBC_MODE) {
              /*
               * We update the length so that the TLS header bytes can be
               * constructed correctly but we need to extract the MAC in
               * constant time from within the record, without leaking the
               * contents of the padding bytes.
               */
              mac = mac_tmp;
              ssl3_cbc_copy_mac(mac_tmp, rr, mac_size);
              rr->length -= mac_size;
          } else {
              /*
               * In this case there's no padding, so |rec->orig_len| equals
               * |rec->length| and we checked that there's enough bytes for
               * |mac_size| above.
               */
              rr->length -= mac_size;
              mac = &rr->data[rr->length];
          }
  
          i = s->method->ssl3_enc->mac(s, md, 0 /* not send */ );
          if (i < 0 || mac == NULL
              || CRYPTO_memcmp(md, mac, (size_t)mac_size) != 0)
              enc_err = -1;
          if (rr->length > SSL3_RT_MAX_COMPRESSED_LENGTH + mac_size)
              enc_err = -1;
      }
  
      if (enc_err < 0) {
          /* decryption failed, silently discard message */
          rr->length = 0;
          RECORD_LAYER_reset_packet_length(&s->rlayer);
          goto err;
      }
  
      /* r->length is now just compressed */
      if (s->expand != NULL) {
          if (rr->length > SSL3_RT_MAX_COMPRESSED_LENGTH) {
              al = SSL_AD_RECORD_OVERFLOW;
              SSLerr(SSL_F_DTLS1_PROCESS_RECORD,
                     SSL_R_COMPRESSED_LENGTH_TOO_LONG);
              goto f_err;
          }
          if (!ssl3_do_uncompress(s)) {
              al = SSL_AD_DECOMPRESSION_FAILURE;
              SSLerr(SSL_F_DTLS1_PROCESS_RECORD, SSL_R_BAD_DECOMPRESSION);
              goto f_err;
          }
      }
  
      if (rr->length > SSL3_RT_MAX_PLAIN_LENGTH) {
          al = SSL_AD_RECORD_OVERFLOW;
          SSLerr(SSL_F_DTLS1_PROCESS_RECORD, SSL_R_DATA_LENGTH_TOO_LONG);
          goto f_err;
      }
  
      rr->off = 0;
      /*-
       * So at this point the following is true
       * ssl->s3->rrec.type   is the type of record
       * ssl->s3->rrec.length == number of bytes in record
       * ssl->s3->rrec.off    == offset to first valid byte
       * ssl->s3->rrec.data   == where to take bytes from, increment
       *                         after use :-).
       */
  
      /* we have pulled in a full packet so zero things */
      RECORD_LAYER_reset_packet_length(&s->rlayer);
      return (1);
  
   f_err:
      ssl3_send_alert(s, SSL3_AL_FATAL, al);
   err:
      return (0);
  }
  
  
  /*
   * retrieve a buffered record that belongs to the current epoch, ie,
   * processed
   */
  #define dtls1_get_processed_record(s) \
                     dtls1_retrieve_buffered_record((s), \
                     &(DTLS_RECORD_LAYER_get_processed_rcds(&s->rlayer)))
  
  /*-
   * Call this to get a new input record.
   * It will return <= 0 if more data is needed, normally due to an error
   * or non-blocking IO.
   * When it finishes, one packet has been decoded and can be found in
   * ssl->s3->rrec.type    - is the type of record
   * ssl->s3->rrec.data,   - data
   * ssl->s3->rrec.length, - number of bytes
   */
  /* used only by dtls1_read_bytes */
  int dtls1_get_record(SSL *s)
  {
      int ssl_major, ssl_minor;
      int i, n;
      SSL3_RECORD *rr;
      unsigned char *p = NULL;
      unsigned short version;
      DTLS1_BITMAP *bitmap;
      unsigned int is_next_epoch;
  
      rr = RECORD_LAYER_get_rrec(&s->rlayer);
  
      /*
       * The epoch may have changed.  If so, process all the pending records.
       * This is a non-blocking operation.
       */
      if (dtls1_process_buffered_records(s) < 0)
          return -1;
  
      /* if we're renegotiating, then there may be buffered records */
      if (dtls1_get_processed_record(s))
          return 1;
  
      /* get something from the wire */
   again:
      /* check if we have the header */
      if ((RECORD_LAYER_get_rstate(&s->rlayer) != SSL_ST_READ_BODY) ||
          (RECORD_LAYER_get_packet_length(&s->rlayer) < DTLS1_RT_HEADER_LENGTH)) {
          n = ssl3_read_n(s, DTLS1_RT_HEADER_LENGTH,
              SSL3_BUFFER_get_len(&s->rlayer.rbuf), 0);
          /* read timeout is handled by dtls1_read_bytes */
          if (n <= 0)
              return (n);         /* error or non-blocking */
  
          /* this packet contained a partial record, dump it */
          if (RECORD_LAYER_get_packet_length(&s->rlayer) != DTLS1_RT_HEADER_LENGTH) {
              RECORD_LAYER_reset_packet_length(&s->rlayer);
              goto again;
          }
  
          RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_BODY);
  
          p = RECORD_LAYER_get_packet(&s->rlayer);
  
          if (s->msg_callback)
              s->msg_callback(0, 0, SSL3_RT_HEADER, p, DTLS1_RT_HEADER_LENGTH,
                              s, s->msg_callback_arg);
  
          /* Pull apart the header into the DTLS1_RECORD */
          rr->type = *(p++);
          ssl_major = *(p++);
          ssl_minor = *(p++);
          version = (ssl_major << 8) | ssl_minor;
  
          /* sequence number is 64 bits, with top 2 bytes = epoch */
          n2s(p, rr->epoch);
  
          memcpy(&(RECORD_LAYER_get_read_sequence(&s->rlayer)[2]), p, 6);
          p += 6;
  
          n2s(p, rr->length);
  
          /* Lets check version */
          if (!s->first_packet) {
              if (version != s->version) {
                  /* unexpected version, silently discard */
                  rr->length = 0;
                  RECORD_LAYER_reset_packet_length(&s->rlayer);
                  goto again;
              }
          }
  
          if ((version & 0xff00) != (s->version & 0xff00)) {
              /* wrong version, silently discard record */
              rr->length = 0;
              RECORD_LAYER_reset_packet_length(&s->rlayer);
              goto again;
          }
  
          if (rr->length > SSL3_RT_MAX_ENCRYPTED_LENGTH) {
              /* record too long, silently discard it */
              rr->length = 0;
              RECORD_LAYER_reset_packet_length(&s->rlayer);
              goto again;
          }
  
          /* now s->rlayer.rstate == SSL_ST_READ_BODY */
      }
  
      /* s->rlayer.rstate == SSL_ST_READ_BODY, get and decode the data */
  
      if (rr->length >
          RECORD_LAYER_get_packet_length(&s->rlayer) - DTLS1_RT_HEADER_LENGTH) {
          /* now s->packet_length == DTLS1_RT_HEADER_LENGTH */
          i = rr->length;
          n = ssl3_read_n(s, i, i, 1);
          /* this packet contained a partial record, dump it */
          if (n != i) {
              rr->length = 0;
              RECORD_LAYER_reset_packet_length(&s->rlayer);
              goto again;
          }
  
          /*
           * now n == rr->length, and s->packet_length ==
           * DTLS1_RT_HEADER_LENGTH + rr->length
           */
      }
      /* set state for later operations */
      RECORD_LAYER_set_rstate(&s->rlayer, SSL_ST_READ_HEADER);
  
      /* match epochs.  NULL means the packet is dropped on the floor */
      bitmap = dtls1_get_bitmap(s, rr, &is_next_epoch);
      if (bitmap == NULL) {
          rr->length = 0;
          RECORD_LAYER_reset_packet_length(&s->rlayer);   /* dump this record */
          goto again;             /* get another record */
      }
  #ifndef OPENSSL_NO_SCTP
      /* Only do replay check if no SCTP bio */
      if (!BIO_dgram_is_sctp(SSL_get_rbio(s))) {
  #endif
          /* Check whether this is a repeat, or aged record. */
          if (!dtls1_record_replay_check(s, bitmap)) {
              rr->length = 0;
              RECORD_LAYER_reset_packet_length(&s->rlayer); /* dump this record */
              goto again;         /* get another record */
          }
  #ifndef OPENSSL_NO_SCTP
      }
  #endif
  
      /* just read a 0 length packet */
      if (rr->length == 0)
          goto again;
  
      /*
       * If this record is from the next epoch (either HM or ALERT), and a
       * handshake is currently in progress, buffer it since it cannot be
       * processed at this time.
       */
      if (is_next_epoch) {
          if ((SSL_in_init(s) || ossl_statem_get_in_handshake(s))) {
              if (dtls1_buffer_record
                  (s, &(DTLS_RECORD_LAYER_get_unprocessed_rcds(&s->rlayer)),
                  rr->seq_num) < 0)
                  return -1;
              /* Mark receipt of record. */
              dtls1_record_bitmap_update(s, bitmap);
          }
          rr->length = 0;
          RECORD_LAYER_reset_packet_length(&s->rlayer);
          goto again;
      }
  
      if (!dtls1_process_record(s)) {
          rr->length = 0;
          RECORD_LAYER_reset_packet_length(&s->rlayer);   /* dump this record */
          goto again;             /* get another record */
      }
      dtls1_record_bitmap_update(s, bitmap); /* Mark receipt of record. */
  
      return (1);
  
  }
  