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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Twofish for CryptoAPI4 *5 * Originally Twofish for GPG6 * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 19987 * 256-bit key length added March 20, 19998 * Some modifications to reduce the text size by Werner Koch, April, 19989 * 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 this13 * 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 paper17 * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,18 * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available19 * through http://www.counterpane.com/twofish.html20 *21 * For background information on multiplication in finite fields, used for22 * the matrix operations in the key schedule, see the book _Contemporary23 * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the24 * Third Edition.25 */26 27#include <linux/unaligned.h>28#include <crypto/algapi.h>29#include <crypto/twofish.h>30#include <linux/module.h>31#include <linux/init.h>32#include <linux/types.h>33#include <linux/errno.h>34#include <linux/bitops.h>35 36/* Macros to compute the g() function in the encryption and decryption37 * rounds. G1 is the straight g() function; G2 includes the 8-bit38 * 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 bit50 * 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) ^ y59 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 rounds69 * 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 word81 * 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, using83 * whitening subkey number m. */84 85#define INPACK(n, x, m) \86 x = get_unaligned_le32(in + (n) * 4) ^ ctx->w[m]87 88#define OUTUNPACK(n, x, m) \89 x ^= ctx->w[m]; \90 put_unaligned_le32(x, out + (n) * 4)91 92 93 94/* Encrypt one block. in and out may be the same. */95static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)96{97 struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);98 99 /* The four 32-bit chunks of the text. */100 u32 a, b, c, d;101 102 /* Temporaries used by the round function. */103 u32 x, y;104 105 /* Input whitening and packing. */106 INPACK (0, a, 0);107 INPACK (1, b, 1);108 INPACK (2, c, 2);109 INPACK (3, d, 3);110 111 /* Encryption Feistel cycles. */112 ENCCYCLE (0);113 ENCCYCLE (1);114 ENCCYCLE (2);115 ENCCYCLE (3);116 ENCCYCLE (4);117 ENCCYCLE (5);118 ENCCYCLE (6);119 ENCCYCLE (7);120 121 /* Output whitening and unpacking. */122 OUTUNPACK (0, c, 4);123 OUTUNPACK (1, d, 5);124 OUTUNPACK (2, a, 6);125 OUTUNPACK (3, b, 7);126 127}128 129/* Decrypt one block. in and out may be the same. */130static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)131{132 struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);133 134 /* The four 32-bit chunks of the text. */135 u32 a, b, c, d;136 137 /* Temporaries used by the round function. */138 u32 x, y;139 140 /* Input whitening and packing. */141 INPACK (0, c, 4);142 INPACK (1, d, 5);143 INPACK (2, a, 6);144 INPACK (3, b, 7);145 146 /* Encryption Feistel cycles. */147 DECCYCLE (7);148 DECCYCLE (6);149 DECCYCLE (5);150 DECCYCLE (4);151 DECCYCLE (3);152 DECCYCLE (2);153 DECCYCLE (1);154 DECCYCLE (0);155 156 /* Output whitening and unpacking. */157 OUTUNPACK (0, a, 0);158 OUTUNPACK (1, b, 1);159 OUTUNPACK (2, c, 2);160 OUTUNPACK (3, d, 3);161 162}163 164static struct crypto_alg alg = {165 .cra_name = "twofish",166 .cra_driver_name = "twofish-generic",167 .cra_priority = 100,168 .cra_flags = CRYPTO_ALG_TYPE_CIPHER,169 .cra_blocksize = TF_BLOCK_SIZE,170 .cra_ctxsize = sizeof(struct twofish_ctx),171 .cra_module = THIS_MODULE,172 .cra_u = { .cipher = {173 .cia_min_keysize = TF_MIN_KEY_SIZE,174 .cia_max_keysize = TF_MAX_KEY_SIZE,175 .cia_setkey = twofish_setkey,176 .cia_encrypt = twofish_encrypt,177 .cia_decrypt = twofish_decrypt } }178};179 180static int __init twofish_mod_init(void)181{182 return crypto_register_alg(&alg);183}184 185static void __exit twofish_mod_fini(void)186{187 crypto_unregister_alg(&alg);188}189 190subsys_initcall(twofish_mod_init);191module_exit(twofish_mod_fini);192 193MODULE_LICENSE("GPL");194MODULE_DESCRIPTION ("Twofish Cipher Algorithm");195MODULE_ALIAS_CRYPTO("twofish");196MODULE_ALIAS_CRYPTO("twofish-generic");197