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41 results

ctr.c

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  • Forked from Nettle / nettle
    2462 commits behind the upstream repository.
    Niels Möller's avatar
    Niels Möller authored
    blocks at a time. Handle the case of a single block specially.
    
    Rev: nettle/ctr.c:1.3
    9042f85e
    History
    ctr.c 3.04 KiB
    /* ctr.c
     *
     * Cipher counter mode.
     */
    
    /* nettle, low-level cryptographics library
     *
     * Copyright (C) 2005 Niels Mller
     *  
     * The nettle library is free software; you can redistribute it and/or modify
     * it under the terms of the GNU Lesser General Public License as published by
     * the Free Software Foundation; either version 2.1 of the License, or (at your
     * option) any later version.
     * 
     * The nettle library is distributed in the hope that it will be useful, but
     * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
     * License for more details.
     * 
     * You should have received a copy of the GNU Lesser General Public License
     * along with the nettle library; see the file COPYING.LIB.  If not, write to
     * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
     * MA 02111-1307, USA.
     */
    
    #if HAVE_CONFIG_H
    # include "config.h"
    #endif
    
    #include <assert.h>
    #include <stdlib.h>
    #include <string.h>
    
    #include "ctr.h"
    
    #include "macros.h"
    #include "memxor.h"
    #include "nettle-internal.h"
    
    #define NBLOCKS 4
    
    void
    ctr_crypt(void *ctx, nettle_crypt_func f,
    	  unsigned block_size, uint8_t *ctr,
    	  unsigned length, uint8_t *dst,
    	  const uint8_t *src)
    {
      if (src != dst)
        {
          if (length == block_size)
    	{
    	  f(ctx, block_size, dst, ctr);
    	  INCREMENT(block_size, ctr);
    	  memxor(dst, src, block_size);
    	}
          else
    	{
    	  unsigned left;
    	  uint8_t *p;	  
    
    	  for (p = dst, left = length;
    	       left >= block_size;
    	       left -= block_size, p += block_size)
    	    {
    	      memcpy (p, ctr, block_size);
    	      INCREMENT(block_size, ctr);
    	    }
    
    	  f(ctx, length - left, dst, dst);
    	  memxor(dst, src, length - left);
    
    	  if (left)
    	    {
    	      TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
    	      TMP_ALLOC(buffer, block_size);
    
    	      f(ctx, block_size, buffer, ctr);
    	      INCREMENT(block_size, ctr);
    	      memxor3(dst + length - left, src + length - left, buffer, left);
    	    }
    	}
        }
      else
        {
          if (length <= block_size)
    	{
    	  TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
    	  TMP_ALLOC(buffer, block_size);
    
    	  f(ctx, block_size, buffer, ctr);
    	  INCREMENT(block_size, ctr);
    	  memxor3(dst, src, buffer, length);
    	}
          else
    	{
    	  TMP_DECL(buffer, uint8_t, NBLOCKS * NETTLE_MAX_CIPHER_BLOCK_SIZE);
    	  unsigned chunk = NBLOCKS * block_size;
    
    	  TMP_ALLOC(buffer, chunk);
    
    	  for (; length >= chunk;
    	       length -= chunk, src += chunk, dst += chunk)
    	    {
    	      unsigned n;
    	      uint8_t *p;	  
    	      for (n = 0, p = buffer; n < NBLOCKS; n++, p += block_size)
    		{
    		  memcpy (p, ctr, block_size);
    		  INCREMENT(block_size, ctr);
    		}
    	      f(ctx, chunk, buffer, buffer);
    	      memxor(dst, buffer, chunk);
    	    }
    
    	  if (length > 0)
    	    {
    	      /* Final, possibly partial, blocks */
    	      for (chunk = 0; chunk < length; chunk += block_size)
    		{
    		  memcpy (buffer + chunk, ctr, block_size);
    		  INCREMENT(block_size, ctr);
    		}
    	      f(ctx, chunk, buffer, buffer);
    	      memxor3(dst, src, buffer, length);
    	    }
    	}
        }
    }