crypto/twofish_generic.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Twofish for CryptoAPI
   4  *
   5  * Originally Twofish for GPG
   6  * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998
   7  * 256-bit key length added March 20, 1999
   8  * Some modifications to reduce the text size by Werner Koch, April, 1998
   9  * Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com>
  10  * Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net>
  11  *
  12  * The original author has disclaimed all copyright interest in this
  13  * code and thus put it in the public domain. The subsequent authors
  14  * have put this under the GNU General Public License.
  15  *
  16  * This code is a "clean room" implementation, written from the paper
  17  * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
  18  * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
  19  * through http://www.counterpane.com/twofish.html
  20  *
  21  * For background information on multiplication in finite fields, used for
  22  * the matrix operations in the key schedule, see the book _Contemporary
  23  * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
  24  * Third Edition.
  25  */
  26
  27 #include <asm/byteorder.h>
  28 #include <crypto/twofish.h>
  29 #include <linux/module.h>
  30 #include <linux/init.h>
  31 #include <linux/types.h>
  32 #include <linux/errno.h>
  33 #include <linux/crypto.h>
  34 #include <linux/bitops.h>
  35
  36 /* Macros to compute the g() function in the encryption and decryption
  37  * rounds.  G1 is the straight g() function; G2 includes the 8-bit
  38  * rotation for the high 32-bit word. */
  39
  40 #define G1(a) \
  41      (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
  42    ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
  43
  44 #define G2(b) \
  45      (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
  46    ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
  47
  48 /* Encryption and decryption Feistel rounds.  Each one calls the two g()
  49  * macros, does the PHT, and performs the XOR and the appropriate bit
  50  * rotations.  The parameters are the round number (used to select subkeys),
  51  * and the four 32-bit chunks of the text. */
  52
  53 #define ENCROUND(n, a, b, c, d) \
  54    x = G1 (a); y = G2 (b); \
  55    x += y; y += x + ctx->k[2 * (n) + 1]; \
  56    (c) ^= x + ctx->k[2 * (n)]; \
  57    (c) = ror32((c), 1); \
  58    (d) = rol32((d), 1) ^ y
  59
  60 #define DECROUND(n, a, b, c, d) \
  61    x = G1 (a); y = G2 (b); \
  62    x += y; y += x; \
  63    (d) ^= y + ctx->k[2 * (n) + 1]; \
  64    (d) = ror32((d), 1); \
  65    (c) = rol32((c), 1); \
  66    (c) ^= (x + ctx->k[2 * (n)])
  67
  68 /* Encryption and decryption cycles; each one is simply two Feistel rounds
  69  * with the 32-bit chunks re-ordered to simulate the "swap" */
  70
  71 #define ENCCYCLE(n) \
  72    ENCROUND (2 * (n), a, b, c, d); \
  73    ENCROUND (2 * (n) + 1, c, d, a, b)
  74
  75 #define DECCYCLE(n) \
  76    DECROUND (2 * (n) + 1, c, d, a, b); \
  77    DECROUND (2 * (n), a, b, c, d)
  78
  79 /* Macros to convert the input and output bytes into 32-bit words,
  80  * and simultaneously perform the whitening step.  INPACK packs word
  81  * number n into the variable named by x, using whitening subkey number m.
  82  * OUTUNPACK unpacks word number n from the variable named by x, using
  83  * whitening subkey number m. */
  84
  85 #define INPACK(n, x, m) \
  86    x = le32_to_cpu(src[n]) ^ ctx->w[m]
  87
  88 #define OUTUNPACK(n, x, m) \
  89    x ^= ctx->w[m]; \
  90    dst[n] = cpu_to_le32(x)
  91
  92
  93
  94 /* Encrypt one block.  in and out may be the same. */
  95 static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
  96 {
  97         struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
  98         const __le32 *src = (const __le32 *)in;
  99         __le32 *dst = (__le32 *)out;
 100
 101         /* The four 32-bit chunks of the text. */
 102         u32 a, b, c, d;
 103
 104         /* Temporaries used by the round function. */
 105         u32 x, y;
 106
 107         /* Input whitening and packing. */
 108         INPACK (0, a, 0);
 109         INPACK (1, b, 1);
 110         INPACK (2, c, 2);
 111         INPACK (3, d, 3);
 112
 113         /* Encryption Feistel cycles. */
 114         ENCCYCLE (0);
 115         ENCCYCLE (1);
 116         ENCCYCLE (2);
 117         ENCCYCLE (3);
 118         ENCCYCLE (4);
 119         ENCCYCLE (5);
 120         ENCCYCLE (6);
 121         ENCCYCLE (7);
 122
 123         /* Output whitening and unpacking. */
 124         OUTUNPACK (0, c, 4);
 125         OUTUNPACK (1, d, 5);
 126         OUTUNPACK (2, a, 6);
 127         OUTUNPACK (3, b, 7);
 128
 129 }
 130
 131 /* Decrypt one block.  in and out may be the same. */
 132 static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
 133 {
 134         struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
 135         const __le32 *src = (const __le32 *)in;
 136         __le32 *dst = (__le32 *)out;
 137
 138         /* The four 32-bit chunks of the text. */
 139         u32 a, b, c, d;
 140
 141         /* Temporaries used by the round function. */
 142         u32 x, y;
 143
 144         /* Input whitening and packing. */
 145         INPACK (0, c, 4);
 146         INPACK (1, d, 5);
 147         INPACK (2, a, 6);
 148         INPACK (3, b, 7);
 149
 150         /* Encryption Feistel cycles. */
 151         DECCYCLE (7);
 152         DECCYCLE (6);
 153         DECCYCLE (5);
 154         DECCYCLE (4);
 155         DECCYCLE (3);
 156         DECCYCLE (2);
 157         DECCYCLE (1);
 158         DECCYCLE (0);
 159
 160         /* Output whitening and unpacking. */
 161         OUTUNPACK (0, a, 0);
 162         OUTUNPACK (1, b, 1);
 163         OUTUNPACK (2, c, 2);
 164         OUTUNPACK (3, d, 3);
 165
 166 }
 167
 168 static struct crypto_alg alg = {
 169         .cra_name           =   "twofish",
 170         .cra_driver_name    =   "twofish-generic",
 171         .cra_priority       =   100,
 172         .cra_flags          =   CRYPTO_ALG_TYPE_CIPHER,
 173         .cra_blocksize      =   TF_BLOCK_SIZE,
 174         .cra_ctxsize        =   sizeof(struct twofish_ctx),
 175         .cra_alignmask      =   3,
 176         .cra_module         =   THIS_MODULE,
 177         .cra_u              =   { .cipher = {
 178         .cia_min_keysize    =   TF_MIN_KEY_SIZE,
 179         .cia_max_keysize    =   TF_MAX_KEY_SIZE,
 180         .cia_setkey         =   twofish_setkey,
 181         .cia_encrypt        =   twofish_encrypt,
 182         .cia_decrypt        =   twofish_decrypt } }
 183 };
 184
 185 static int __init twofish_mod_init(void)
 186 {
 187         return crypto_register_alg(&alg);
 188 }
 189
 190 static void __exit twofish_mod_fini(void)
 191 {
 192         crypto_unregister_alg(&alg);
 193 }
 194
 195 subsys_initcall(twofish_mod_init);
 196 module_exit(twofish_mod_fini);
 197
 198 MODULE_LICENSE("GPL");
 199 MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
 200 MODULE_ALIAS_CRYPTO("twofish");
 201 MODULE_ALIAS_CRYPTO("twofish-generic");