/*
   * Twofish for CryptoAPI
   *
   * Originally Twofish for GPG
   * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998
   * 256-bit key length added March 20, 1999
   * Some modifications to reduce the text size by Werner Koch, April, 1998
   * Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com>
   * Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net>
   *
   * The original author has disclaimed all copyright interest in this
   * code and thus put it in the public domain. The subsequent authors 
   * have put this under the GNU General Public License.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program 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 General Public License for more details.
   * 
   * You should have received a copy of the GNU 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
   *
   * This code is a "clean room" implementation, written from the paper
   * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
   * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
   * through http://www.counterpane.com/twofish.html
   *
   * For background information on multiplication in finite fields, used for
   * the matrix operations in the key schedule, see the book _Contemporary
   * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
   * Third Edition.
   */
  
  #include <asm/byteorder.h>
  #include <crypto/twofish.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/types.h>
  #include <linux/errno.h>
  #include <linux/crypto.h>
  #include <linux/bitops.h>
  
  /* Macros to compute the g() function in the encryption and decryption
   * rounds.  G1 is the straight g() function; G2 includes the 8-bit
   * rotation for the high 32-bit word. */
  
  #define G1(a) \
       (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
     ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
  
  #define G2(b) \
       (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
     ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
  
  /* Encryption and decryption Feistel rounds.  Each one calls the two g()
   * macros, does the PHT, and performs the XOR and the appropriate bit
   * rotations.  The parameters are the round number (used to select subkeys),
   * and the four 32-bit chunks of the text. */
  
  #define ENCROUND(n, a, b, c, d) \
     x = G1 (a); y = G2 (b); \
     x += y; y += x + ctx->k[2 * (n) + 1]; \
     (c) ^= x + ctx->k[2 * (n)]; \
     (c) = ror32((c), 1); \
     (d) = rol32((d), 1) ^ y
  
  #define DECROUND(n, a, b, c, d) \
     x = G1 (a); y = G2 (b); \
     x += y; y += x; \
     (d) ^= y + ctx->k[2 * (n) + 1]; \
     (d) = ror32((d), 1); \
     (c) = rol32((c), 1); \
     (c) ^= (x + ctx->k[2 * (n)])
  
  /* Encryption and decryption cycles; each one is simply two Feistel rounds
   * with the 32-bit chunks re-ordered to simulate the "swap" */
  
  #define ENCCYCLE(n) \
     ENCROUND (2 * (n), a, b, c, d); \
     ENCROUND (2 * (n) + 1, c, d, a, b)
  
  #define DECCYCLE(n) \
     DECROUND (2 * (n) + 1, c, d, a, b); \
     DECROUND (2 * (n), a, b, c, d)
  
  /* Macros to convert the input and output bytes into 32-bit words,
   * and simultaneously perform the whitening step.  INPACK packs word
   * number n into the variable named by x, using whitening subkey number m.
   * OUTUNPACK unpacks word number n from the variable named by x, using
   * whitening subkey number m. */
  
  #define INPACK(n, x, m) \
     x = le32_to_cpu(src[n]) ^ ctx->w[m]
  
  #define OUTUNPACK(n, x, m) \
     x ^= ctx->w[m]; \
     dst[n] = cpu_to_le32(x)
  
  
  
  /* Encrypt one block.  in and out may be the same. */
  static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
  {
  	struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
  	const __le32 *src = (const __le32 *)in;
  	__le32 *dst = (__le32 *)out;
  
  	/* The four 32-bit chunks of the text. */
  	u32 a, b, c, d;
  	
  	/* Temporaries used by the round function. */
  	u32 x, y;
  
  	/* Input whitening and packing. */
  	INPACK (0, a, 0);
  	INPACK (1, b, 1);
  	INPACK (2, c, 2);
  	INPACK (3, d, 3);
  	
  	/* Encryption Feistel cycles. */
  	ENCCYCLE (0);
  	ENCCYCLE (1);
  	ENCCYCLE (2);
  	ENCCYCLE (3);
  	ENCCYCLE (4);
  	ENCCYCLE (5);
  	ENCCYCLE (6);
  	ENCCYCLE (7);
  	
  	/* Output whitening and unpacking. */
  	OUTUNPACK (0, c, 4);
  	OUTUNPACK (1, d, 5);
  	OUTUNPACK (2, a, 6);
  	OUTUNPACK (3, b, 7);
  	
  }
  
  /* Decrypt one block.  in and out may be the same. */
  static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
  {
  	struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
  	const __le32 *src = (const __le32 *)in;
  	__le32 *dst = (__le32 *)out;
    
  	/* The four 32-bit chunks of the text. */
  	u32 a, b, c, d;
  	
  	/* Temporaries used by the round function. */
  	u32 x, y;
  	
  	/* Input whitening and packing. */
  	INPACK (0, c, 4);
  	INPACK (1, d, 5);
  	INPACK (2, a, 6);
  	INPACK (3, b, 7);
  	
  	/* Encryption Feistel cycles. */
  	DECCYCLE (7);
  	DECCYCLE (6);
  	DECCYCLE (5);
  	DECCYCLE (4);
  	DECCYCLE (3);
  	DECCYCLE (2);
  	DECCYCLE (1);
  	DECCYCLE (0);
  
  	/* Output whitening and unpacking. */
  	OUTUNPACK (0, a, 0);
  	OUTUNPACK (1, b, 1);
  	OUTUNPACK (2, c, 2);
  	OUTUNPACK (3, d, 3);
  
  }
  
  static struct crypto_alg alg = {
  	.cra_name           =   "twofish",
  	.cra_driver_name    =   "twofish-generic",
  	.cra_priority       =   100,
  	.cra_flags          =   CRYPTO_ALG_TYPE_CIPHER,
  	.cra_blocksize      =   TF_BLOCK_SIZE,
  	.cra_ctxsize        =   sizeof(struct twofish_ctx),
  	.cra_alignmask      =	3,
  	.cra_module         =   THIS_MODULE,
  	.cra_u              =   { .cipher = {
  	.cia_min_keysize    =   TF_MIN_KEY_SIZE,
  	.cia_max_keysize    =   TF_MAX_KEY_SIZE,
  	.cia_setkey         =   twofish_setkey,
  	.cia_encrypt        =   twofish_encrypt,
  	.cia_decrypt        =   twofish_decrypt } }
  };
  
  static int __init twofish_mod_init(void)
  {
  	return crypto_register_alg(&alg);
  }
  
  static void __exit twofish_mod_fini(void)
  {
  	crypto_unregister_alg(&alg);
  }
  
  module_init(twofish_mod_init);
  module_exit(twofish_mod_fini);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
  MODULE_ALIAS("twofish");