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/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. */
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