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enc_read.c

/* crypto/des/enc_read.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.]
 */

#include <stdio.h>
#include <errno.h>
#include "cryptlib.h"
#include "des_locl.h"

/* This has some uglies in it but it works - even over sockets. */
/*extern int errno;*/
OPENSSL_IMPLEMENT_GLOBAL(int,DES_rw_mode)=DES_PCBC_MODE;


/*
 * WARNINGS:
 *
 *  -  The data format used by DES_enc_write() and DES_enc_read()
 *     has a cryptographic weakness: When asked to write more
 *     than MAXWRITE bytes, DES_enc_write will split the data
 *     into several chunks that are all encrypted
 *     using the same IV.  So don't use these functions unless you
 *     are sure you know what you do (in which case you might
 *     not want to use them anyway).
 *
 *  -  This code cannot handle non-blocking sockets.
 *
 *  -  This function uses an internal state and thus cannot be
 *     used on multiple files.
 */


int DES_enc_read(int fd, void *buf, int len, DES_key_schedule *sched,
             DES_cblock *iv)
      {
      /* data to be unencrypted */
      int net_num=0;
      static unsigned char *net=NULL;
      /* extra unencrypted data 
       * for when a block of 100 comes in but is des_read one byte at
       * a time. */
      static unsigned char *unnet=NULL;
      static int unnet_start=0;
      static int unnet_left=0;
      static unsigned char *tmpbuf=NULL;
      int i;
      long num=0,rnum;
      unsigned char *p;

      if (tmpbuf == NULL)
            {
            tmpbuf=OPENSSL_malloc(BSIZE);
            if (tmpbuf == NULL) return(-1);
            }
      if (net == NULL)
            {
            net=OPENSSL_malloc(BSIZE);
            if (net == NULL) return(-1);
            }
      if (unnet == NULL)
            {
            unnet=OPENSSL_malloc(BSIZE);
            if (unnet == NULL) return(-1);
            }
      /* left over data from last decrypt */
      if (unnet_left != 0)
            {
            if (unnet_left < len)
                  {
                  /* we still still need more data but will return
                   * with the number of bytes we have - should always
                   * check the return value */
                  memcpy(buf,&(unnet[unnet_start]),
                         unnet_left);
                  /* eay 26/08/92 I had the next 2 lines
                   * reversed :-( */
                  i=unnet_left;
                  unnet_start=unnet_left=0;
                  }
            else
                  {
                  memcpy(buf,&(unnet[unnet_start]),len);
                  unnet_start+=len;
                  unnet_left-=len;
                  i=len;
                  }
            return(i);
            }

      /* We need to get more data. */
      if (len > MAXWRITE) len=MAXWRITE;

      /* first - get the length */
      while (net_num < HDRSIZE) 
            {
            i=read(fd,(void *)&(net[net_num]),HDRSIZE-net_num);
#ifdef EINTR
            if ((i == -1) && (errno == EINTR)) continue;
#endif
            if (i <= 0) return(0);
            net_num+=i;
            }

      /* we now have at net_num bytes in net */
      p=net;
      /* num=0;  */
      n2l(p,num);
      /* num should be rounded up to the next group of eight
       * we make sure that we have read a multiple of 8 bytes from the net.
       */
      if ((num > MAXWRITE) || (num < 0)) /* error */
            return(-1);
      rnum=(num < 8)?8:((num+7)/8*8);

      net_num=0;
      while (net_num < rnum)
            {
            i=read(fd,(void *)&(net[net_num]),rnum-net_num);
#ifdef EINTR
            if ((i == -1) && (errno == EINTR)) continue;
#endif
            if (i <= 0) return(0);
            net_num+=i;
            }

      /* Check if there will be data left over. */
      if (len < num)
            {
            if (DES_rw_mode & DES_PCBC_MODE)
                  DES_pcbc_encrypt(net,unnet,num,sched,iv,DES_DECRYPT);
            else
                  DES_cbc_encrypt(net,unnet,num,sched,iv,DES_DECRYPT);
            memcpy(buf,unnet,len);
            unnet_start=len;
            unnet_left=num-len;

            /* The following line is done because we return num
             * as the number of bytes read. */
            num=len;
            }
      else
            {
            /* >output is a multiple of 8 byes, if len < rnum
             * >we must be careful.  The user must be aware that this
             * >routine will write more bytes than he asked for.
             * >The length of the buffer must be correct.
             * FIXED - Should be ok now 18-9-90 - eay */
            if (len < rnum)
                  {

                  if (DES_rw_mode & DES_PCBC_MODE)
                        DES_pcbc_encrypt(net,tmpbuf,num,sched,iv,
                                     DES_DECRYPT);
                  else
                        DES_cbc_encrypt(net,tmpbuf,num,sched,iv,
                                    DES_DECRYPT);

                  /* eay 26/08/92 fix a bug that returned more
                   * bytes than you asked for (returned len bytes :-( */
                  memcpy(buf,tmpbuf,num);
                  }
            else
                  {
                  if (DES_rw_mode & DES_PCBC_MODE)
                        DES_pcbc_encrypt(net,buf,num,sched,iv,
                                     DES_DECRYPT);
                  else
                        DES_cbc_encrypt(net,buf,num,sched,iv,
                                    DES_DECRYPT);
                  }
            }
      return num;
      }


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