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196 lines
5.5 KiB
196 lines
5.5 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Twofish for CryptoAPI |
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* |
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* Originally Twofish for GPG |
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* By Matthew Skala <[email protected]>, July 26, 1998 |
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* 256-bit key length added March 20, 1999 |
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* Some modifications to reduce the text size by Werner Koch, April, 1998 |
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* Ported to the kerneli patch by Marc Mutz <[email protected]> |
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* Ported to CryptoAPI by Colin Slater <[email protected]> |
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* |
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* The original author has disclaimed all copyright interest in this |
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* code and thus put it in the public domain. The subsequent authors |
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* have put this under the GNU General Public License. |
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* |
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* This code is a "clean room" implementation, written from the paper |
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* _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey, |
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* Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available |
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* through http://www.counterpane.com/twofish.html |
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* |
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* For background information on multiplication in finite fields, used for |
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* the matrix operations in the key schedule, see the book _Contemporary |
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* Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the |
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* Third Edition. |
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*/ |
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#include <asm/unaligned.h> |
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#include <crypto/twofish.h> |
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#include <linux/module.h> |
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#include <linux/init.h> |
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#include <linux/types.h> |
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#include <linux/errno.h> |
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#include <linux/crypto.h> |
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#include <linux/bitops.h> |
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/* Macros to compute the g() function in the encryption and decryption |
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* rounds. G1 is the straight g() function; G2 includes the 8-bit |
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* rotation for the high 32-bit word. */ |
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#define G1(a) \ |
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(ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \ |
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^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24]) |
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#define G2(b) \ |
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(ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \ |
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^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24]) |
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/* Encryption and decryption Feistel rounds. Each one calls the two g() |
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* macros, does the PHT, and performs the XOR and the appropriate bit |
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* rotations. The parameters are the round number (used to select subkeys), |
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* and the four 32-bit chunks of the text. */ |
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#define ENCROUND(n, a, b, c, d) \ |
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x = G1 (a); y = G2 (b); \ |
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x += y; y += x + ctx->k[2 * (n) + 1]; \ |
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(c) ^= x + ctx->k[2 * (n)]; \ |
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(c) = ror32((c), 1); \ |
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(d) = rol32((d), 1) ^ y |
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#define DECROUND(n, a, b, c, d) \ |
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x = G1 (a); y = G2 (b); \ |
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x += y; y += x; \ |
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(d) ^= y + ctx->k[2 * (n) + 1]; \ |
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(d) = ror32((d), 1); \ |
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(c) = rol32((c), 1); \ |
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(c) ^= (x + ctx->k[2 * (n)]) |
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/* Encryption and decryption cycles; each one is simply two Feistel rounds |
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* with the 32-bit chunks re-ordered to simulate the "swap" */ |
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#define ENCCYCLE(n) \ |
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ENCROUND (2 * (n), a, b, c, d); \ |
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ENCROUND (2 * (n) + 1, c, d, a, b) |
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#define DECCYCLE(n) \ |
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DECROUND (2 * (n) + 1, c, d, a, b); \ |
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DECROUND (2 * (n), a, b, c, d) |
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/* Macros to convert the input and output bytes into 32-bit words, |
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* and simultaneously perform the whitening step. INPACK packs word |
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* number n into the variable named by x, using whitening subkey number m. |
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* OUTUNPACK unpacks word number n from the variable named by x, using |
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* whitening subkey number m. */ |
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#define INPACK(n, x, m) \ |
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x = get_unaligned_le32(in + (n) * 4) ^ ctx->w[m] |
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#define OUTUNPACK(n, x, m) \ |
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x ^= ctx->w[m]; \ |
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put_unaligned_le32(x, out + (n) * 4) |
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/* Encrypt one block. in and out may be the same. */ |
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static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in) |
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{ |
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struct twofish_ctx *ctx = crypto_tfm_ctx(tfm); |
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/* The four 32-bit chunks of the text. */ |
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u32 a, b, c, d; |
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/* Temporaries used by the round function. */ |
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u32 x, y; |
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/* Input whitening and packing. */ |
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INPACK (0, a, 0); |
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INPACK (1, b, 1); |
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INPACK (2, c, 2); |
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INPACK (3, d, 3); |
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/* Encryption Feistel cycles. */ |
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ENCCYCLE (0); |
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ENCCYCLE (1); |
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ENCCYCLE (2); |
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ENCCYCLE (3); |
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ENCCYCLE (4); |
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ENCCYCLE (5); |
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ENCCYCLE (6); |
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ENCCYCLE (7); |
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/* Output whitening and unpacking. */ |
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OUTUNPACK (0, c, 4); |
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OUTUNPACK (1, d, 5); |
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OUTUNPACK (2, a, 6); |
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OUTUNPACK (3, b, 7); |
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} |
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/* Decrypt one block. in and out may be the same. */ |
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static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in) |
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{ |
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struct twofish_ctx *ctx = crypto_tfm_ctx(tfm); |
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/* The four 32-bit chunks of the text. */ |
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u32 a, b, c, d; |
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/* Temporaries used by the round function. */ |
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u32 x, y; |
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/* Input whitening and packing. */ |
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INPACK (0, c, 4); |
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INPACK (1, d, 5); |
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INPACK (2, a, 6); |
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INPACK (3, b, 7); |
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/* Encryption Feistel cycles. */ |
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DECCYCLE (7); |
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DECCYCLE (6); |
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DECCYCLE (5); |
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DECCYCLE (4); |
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DECCYCLE (3); |
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DECCYCLE (2); |
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DECCYCLE (1); |
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DECCYCLE (0); |
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/* Output whitening and unpacking. */ |
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OUTUNPACK (0, a, 0); |
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OUTUNPACK (1, b, 1); |
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OUTUNPACK (2, c, 2); |
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OUTUNPACK (3, d, 3); |
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} |
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static struct crypto_alg alg = { |
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.cra_name = "twofish", |
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.cra_driver_name = "twofish-generic", |
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.cra_priority = 100, |
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.cra_flags = CRYPTO_ALG_TYPE_CIPHER, |
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.cra_blocksize = TF_BLOCK_SIZE, |
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.cra_ctxsize = sizeof(struct twofish_ctx), |
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.cra_module = THIS_MODULE, |
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.cra_u = { .cipher = { |
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.cia_min_keysize = TF_MIN_KEY_SIZE, |
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.cia_max_keysize = TF_MAX_KEY_SIZE, |
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.cia_setkey = twofish_setkey, |
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.cia_encrypt = twofish_encrypt, |
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.cia_decrypt = twofish_decrypt } } |
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}; |
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static int __init twofish_mod_init(void) |
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{ |
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return crypto_register_alg(&alg); |
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} |
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static void __exit twofish_mod_fini(void) |
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{ |
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crypto_unregister_alg(&alg); |
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} |
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subsys_initcall(twofish_mod_init); |
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module_exit(twofish_mod_fini); |
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MODULE_LICENSE("GPL"); |
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MODULE_DESCRIPTION ("Twofish Cipher Algorithm"); |
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MODULE_ALIAS_CRYPTO("twofish"); |
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MODULE_ALIAS_CRYPTO("twofish-generic");
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