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 <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 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 = 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. */ 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 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. */ 130 static 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 } 163 164 static 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 }; 179 180 static int __init twofish_mod_init(void) 181 { 182 return crypto_register_alg(&alg); 183 } 184 185 static void __exit twofish_mod_fini(void) 186 { 187 crypto_unregister_alg(&alg); 188 } 189 190 subsys_initcall(twofish_mod_init); 191 module_exit(twofish_mod_fini); 192 193 MODULE_LICENSE("GPL"); 194 MODULE_DESCRIPTION ("Twofish Cipher Algorithm"); 195 MODULE_ALIAS_CRYPTO("twofish"); 196 MODULE_ALIAS_CRYPTO("twofish-generic"); 197