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. */ |
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: &alg); |
183 | } |
184 | |
185 | static void __exit twofish_mod_fini(void) |
186 | { |
187 | crypto_unregister_alg(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 | |