text: /* arcfour.c  -  The arcfour stream cipher
   *	Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
   *
   * This file is part of Libgcrypt.
   *
   * Libgcrypt 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.
   *
   * Libgcrypt 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 this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
   *
   * For a description of the algorithm, see:
   *   Bruce Schneier: Applied Cryptography. John Wiley & Sons, 1996.
   *   ISBN 0-471-11709-9. Pages 397 ff.
   */
  
  
  #include <config.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include "types.h"
  #include "g10lib.h"
  #include "cipher.h"
  
  /* USE_AMD64_ASM indicates whether to use AMD64 assembly code. */
  #undef USE_AMD64_ASM
  #if defined(__x86_64__) && (defined(HAVE_COMPATIBLE_GCC_AMD64_PLATFORM_AS) || \
      defined(HAVE_COMPATIBLE_GCC_WIN64_PLATFORM_AS))
  # define USE_AMD64_ASM 1
  #endif
  
  static const char *selftest(void);
  
  #ifdef USE_AMD64_ASM
  
  typedef struct {
      u32 sbox[256];
      u32 idx_i, idx_j;
  } ARCFOUR_context;
  
  void _gcry_arcfour_amd64(void *key, size_t len, const byte *indata,
  			 byte *outdata);
  
  static void
  encrypt_stream (void *context,
                  byte *outbuf, const byte *inbuf, size_t length)
  {
  #ifdef HAVE_COMPATIBLE_GCC_WIN64_PLATFORM_AS
    const void *fn = _gcry_arcfour_amd64;
    /* Call SystemV ABI function without storing non-volatile XMM registers,
     * as target function does not use vector instruction sets. */
    asm volatile ("callq *%0\n\t"
                  : "+a" (fn),
                    "+D" (context),
                    "+S" (length),
                    "+d" (inbuf),
                    "+c" (outbuf)
                  :
                  : "cc", "memory", "r8", "r9", "r10", "r11");
  #else
    _gcry_arcfour_amd64 (context, length, inbuf, outbuf );
  #endif
  }
  
  #else /*!USE_AMD64_ASM*/
  
  typedef struct {
      byte sbox[256];
      int idx_i, idx_j;
  } ARCFOUR_context;
  
  static void
  do_encrypt_stream( ARCFOUR_context *ctx,
  		   byte *outbuf, const byte *inbuf, size_t length )
  {
  #ifndef __i386__
    register unsigned int i = ctx->idx_i;
    register byte j = ctx->idx_j;
    register byte *sbox = ctx->sbox;
    register byte t, u;
  
    while ( length-- )
      {
        i++;
        t = sbox[(byte)i];
        j += t;
        u = sbox[j];
        sbox[(byte)i] = u;
        u += t;
        sbox[j] = t;
        *outbuf++ = sbox[u] ^ *inbuf++;
      }
  
    ctx->idx_i = (byte)i;
    ctx->idx_j = (byte)j;
  #else /*__i386__*/
    /* Old implementation of arcfour is faster on i386 than the version above.
     * This is because version above increases register pressure which on i386
     * would push some of the variables to memory/stack.  Therefore keep this
     * version for i386 to avoid regressing performance.  */
    register int i = ctx->idx_i;
    register int j = ctx->idx_j;
    register byte *sbox = ctx->sbox;
    register int t;
  
    while ( length-- )
      {
        i++;
        i = i & 255; /* The and-op seems to be faster than the mod-op. */
        j += sbox[i];
        j &= 255;
        t = sbox[i]; sbox[i] = sbox[j]; sbox[j] = t;
        *outbuf++ = *inbuf++ ^ sbox[(sbox[i] + sbox[j]) & 255];
      }
  
    ctx->idx_i = i;
    ctx->idx_j = j;
  #endif
  }
  
  static void
  encrypt_stream (void *context,
                  byte *outbuf, const byte *inbuf, size_t length)
  {
    ARCFOUR_context *ctx = (ARCFOUR_context *) context;
    do_encrypt_stream (ctx, outbuf, inbuf, length );
    _gcry_burn_stack (64);
  }
  
  #endif /*!USE_AMD64_ASM*/
  
  
  static gcry_err_code_t
  do_arcfour_setkey (void *context, const byte *key, unsigned int keylen)
  {
    static int initialized;
    static const char* selftest_failed;
    int i, j;
    byte karr[256];
    ARCFOUR_context *ctx = (ARCFOUR_context *) context;
  
    if (!initialized )
      {
        initialized = 1;
        selftest_failed = selftest();
        if( selftest_failed )
          log_error ("ARCFOUR selftest failed (%s)\n", selftest_failed );
      }
    if( selftest_failed )
      return GPG_ERR_SELFTEST_FAILED;
  
    if( keylen < 40/8 ) /* we want at least 40 bits */
      return GPG_ERR_INV_KEYLEN;
  
    ctx->idx_i = ctx->idx_j = 0;
    for (i=0; i < 256; i++ )
      ctx->sbox[i] = i;
    for (i=j=0; i < 256; i++,j++ )
      {
        if (j >= keylen)
          j = 0;
        karr[i] = key[j];
      }
    for (i=j=0; i < 256; i++ )
      {
        int t;
        j = (j + ctx->sbox[i] + karr[i]) & 255;
        t = ctx->sbox[i];
        ctx->sbox[i] = ctx->sbox[j];
        ctx->sbox[j] = t;
      }
    wipememory( karr, sizeof(karr) );
  
    return GPG_ERR_NO_ERROR;
  }
  
  static gcry_err_code_t
  arcfour_setkey ( void *context, const byte *key, unsigned int keylen )
  {
    ARCFOUR_context *ctx = (ARCFOUR_context *) context;
    gcry_err_code_t rc = do_arcfour_setkey (ctx, key, keylen );
    return rc;
  }
  
  
  static const char*
  selftest(void)
  {
    ARCFOUR_context ctx;
    byte scratch[16];
  
    /* Test vector from Cryptlib labeled there: "from the
       State/Commerce Department". */
    static const byte key_1[] =
      { 0x61, 0x8A, 0x63, 0xD2, 0xFB };
    static const byte plaintext_1[] =
      { 0xDC, 0xEE, 0x4C, 0xF9, 0x2C };
    static const byte ciphertext_1[] =
      { 0xF1, 0x38, 0x29, 0xC9, 0xDE };
  
    arcfour_setkey( &ctx, key_1, sizeof(key_1));
    encrypt_stream( &ctx, scratch, plaintext_1, sizeof(plaintext_1));
    if ( memcmp (scratch, ciphertext_1, sizeof (ciphertext_1)))
      return "Arcfour encryption test 1 failed.";
    arcfour_setkey( &ctx, key_1, sizeof(key_1));
    encrypt_stream(&ctx, scratch, scratch, sizeof(plaintext_1)); /* decrypt */
    if ( memcmp (scratch, plaintext_1, sizeof (plaintext_1)))
      return "Arcfour decryption test 1 failed.";
    return NULL;
  }
  
  
  gcry_cipher_spec_t _gcry_cipher_spec_arcfour =
    {
      GCRY_CIPHER_ARCFOUR, {0, 0},
      "ARCFOUR", NULL, NULL, 1, 128, sizeof (ARCFOUR_context),
      arcfour_setkey, NULL, NULL, encrypt_stream, encrypt_stream,
    };
  