1 /*
2  * Twofish for CryptoAPI
3  *
4  * Originally Twofish for GPG
5  * By Matthew Skala <mskala@ansuz.sooke.bc.ca>, July 26, 1998
6  * 256-bit key length added March 20, 1999
7  * Some modifications to reduce the text size by Werner Koch, April, 1998
8  * Ported to the kerneli patch by Marc Mutz <Marc@Mutz.com>
9  * Ported to CryptoAPI by Colin Slater <hoho@tacomeat.net>
10  *
11  * The original author has disclaimed all copyright interest in this
12  * code and thus put it in the public domain. The subsequent authors
13  * have put this under the GNU General Public License.
14  *
15  * This program is free software; you can redistribute it and/or modify
16  * it under the terms of the GNU General Public License as published by
17  * the Free Software Foundation; either version 2 of the License, or
18  * (at your option) any later version.
19  *
20  * This program is distributed in the hope that it will be useful,
21  * but WITHOUT ANY WARRANTY; without even the implied warranty of
22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
23  * GNU General Public License for more details.
24  *
25  * You should have received a copy of the GNU General Public License
26  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
27  *
28  *
29  * This code is a "clean room" implementation, written from the paper
30  * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,
31  * Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson, available
32  * through http://www.counterpane.com/twofish.html
33  *
34  * For background information on multiplication in finite fields, used for
35  * the matrix operations in the key schedule, see the book _Contemporary
36  * Abstract Algebra_ by Joseph A. Gallian, especially chapter 22 in the
37  * Third Edition.
38  */
39 
40 #include <asm/byteorder.h>
41 #include <crypto/twofish.h>
42 #include <linux/module.h>
43 #include <linux/init.h>
44 #include <linux/types.h>
45 #include <linux/errno.h>
46 #include <linux/crypto.h>
47 #include <linux/bitops.h>
48 
49 /* Macros to compute the g() function in the encryption and decryption
50  * rounds.  G1 is the straight g() function; G2 includes the 8-bit
51  * rotation for the high 32-bit word. */
52 
53 #define G1(a) \
54      (ctx->s[0][(a) & 0xFF]) ^ (ctx->s[1][((a) >> 8) & 0xFF]) \
55    ^ (ctx->s[2][((a) >> 16) & 0xFF]) ^ (ctx->s[3][(a) >> 24])
56 
57 #define G2(b) \
58      (ctx->s[1][(b) & 0xFF]) ^ (ctx->s[2][((b) >> 8) & 0xFF]) \
59    ^ (ctx->s[3][((b) >> 16) & 0xFF]) ^ (ctx->s[0][(b) >> 24])
60 
61 /* Encryption and decryption Feistel rounds.  Each one calls the two g()
62  * macros, does the PHT, and performs the XOR and the appropriate bit
63  * rotations.  The parameters are the round number (used to select subkeys),
64  * and the four 32-bit chunks of the text. */
65 
66 #define ENCROUND(n, a, b, c, d) \
67    x = G1 (a); y = G2 (b); \
68    x += y; y += x + ctx->k[2 * (n) + 1]; \
69    (c) ^= x + ctx->k[2 * (n)]; \
70    (c) = ror32((c), 1); \
71    (d) = rol32((d), 1) ^ y
72 
73 #define DECROUND(n, a, b, c, d) \
74    x = G1 (a); y = G2 (b); \
75    x += y; y += x; \
76    (d) ^= y + ctx->k[2 * (n) + 1]; \
77    (d) = ror32((d), 1); \
78    (c) = rol32((c), 1); \
79    (c) ^= (x + ctx->k[2 * (n)])
80 
81 /* Encryption and decryption cycles; each one is simply two Feistel rounds
82  * with the 32-bit chunks re-ordered to simulate the "swap" */
83 
84 #define ENCCYCLE(n) \
85    ENCROUND (2 * (n), a, b, c, d); \
86    ENCROUND (2 * (n) + 1, c, d, a, b)
87 
88 #define DECCYCLE(n) \
89    DECROUND (2 * (n) + 1, c, d, a, b); \
90    DECROUND (2 * (n), a, b, c, d)
91 
92 /* Macros to convert the input and output bytes into 32-bit words,
93  * and simultaneously perform the whitening step.  INPACK packs word
94  * number n into the variable named by x, using whitening subkey number m.
95  * OUTUNPACK unpacks word number n from the variable named by x, using
96  * whitening subkey number m. */
97 
98 #define INPACK(n, x, m) \
99    x = le32_to_cpu(src[n]) ^ ctx->w[m]
100 
101 #define OUTUNPACK(n, x, m) \
102    x ^= ctx->w[m]; \
103    dst[n] = cpu_to_le32(x)
104 
105 
106 
107 /* Encrypt one block.  in and out may be the same. */
twofish_encrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)108 static void twofish_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
109 {
110 	struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
111 	const __le32 *src = (const __le32 *)in;
112 	__le32 *dst = (__le32 *)out;
113 
114 	/* The four 32-bit chunks of the text. */
115 	u32 a, b, c, d;
116 
117 	/* Temporaries used by the round function. */
118 	u32 x, y;
119 
120 	/* Input whitening and packing. */
121 	INPACK (0, a, 0);
122 	INPACK (1, b, 1);
123 	INPACK (2, c, 2);
124 	INPACK (3, d, 3);
125 
126 	/* Encryption Feistel cycles. */
127 	ENCCYCLE (0);
128 	ENCCYCLE (1);
129 	ENCCYCLE (2);
130 	ENCCYCLE (3);
131 	ENCCYCLE (4);
132 	ENCCYCLE (5);
133 	ENCCYCLE (6);
134 	ENCCYCLE (7);
135 
136 	/* Output whitening and unpacking. */
137 	OUTUNPACK (0, c, 4);
138 	OUTUNPACK (1, d, 5);
139 	OUTUNPACK (2, a, 6);
140 	OUTUNPACK (3, b, 7);
141 
142 }
143 
144 /* Decrypt one block.  in and out may be the same. */
twofish_decrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)145 static void twofish_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
146 {
147 	struct twofish_ctx *ctx = crypto_tfm_ctx(tfm);
148 	const __le32 *src = (const __le32 *)in;
149 	__le32 *dst = (__le32 *)out;
150 
151 	/* The four 32-bit chunks of the text. */
152 	u32 a, b, c, d;
153 
154 	/* Temporaries used by the round function. */
155 	u32 x, y;
156 
157 	/* Input whitening and packing. */
158 	INPACK (0, c, 4);
159 	INPACK (1, d, 5);
160 	INPACK (2, a, 6);
161 	INPACK (3, b, 7);
162 
163 	/* Encryption Feistel cycles. */
164 	DECCYCLE (7);
165 	DECCYCLE (6);
166 	DECCYCLE (5);
167 	DECCYCLE (4);
168 	DECCYCLE (3);
169 	DECCYCLE (2);
170 	DECCYCLE (1);
171 	DECCYCLE (0);
172 
173 	/* Output whitening and unpacking. */
174 	OUTUNPACK (0, a, 0);
175 	OUTUNPACK (1, b, 1);
176 	OUTUNPACK (2, c, 2);
177 	OUTUNPACK (3, d, 3);
178 
179 }
180 
181 static struct crypto_alg alg = {
182 	.cra_name           =   "twofish",
183 	.cra_driver_name    =   "twofish-generic",
184 	.cra_priority       =   100,
185 	.cra_flags          =   CRYPTO_ALG_TYPE_CIPHER,
186 	.cra_blocksize      =   TF_BLOCK_SIZE,
187 	.cra_ctxsize        =   sizeof(struct twofish_ctx),
188 	.cra_alignmask      =	3,
189 	.cra_module         =   THIS_MODULE,
190 	.cra_u              =   { .cipher = {
191 	.cia_min_keysize    =   TF_MIN_KEY_SIZE,
192 	.cia_max_keysize    =   TF_MAX_KEY_SIZE,
193 	.cia_setkey         =   twofish_setkey,
194 	.cia_encrypt        =   twofish_encrypt,
195 	.cia_decrypt        =   twofish_decrypt } }
196 };
197 
twofish_mod_init(void)198 static int __init twofish_mod_init(void)
199 {
200 	return crypto_register_alg(&alg);
201 }
202 
twofish_mod_fini(void)203 static void __exit twofish_mod_fini(void)
204 {
205 	crypto_unregister_alg(&alg);
206 }
207 
208 module_init(twofish_mod_init);
209 module_exit(twofish_mod_fini);
210 
211 MODULE_LICENSE("GPL");
212 MODULE_DESCRIPTION ("Twofish Cipher Algorithm");
213 MODULE_ALIAS_CRYPTO("twofish");
214 MODULE_ALIAS_CRYPTO("twofish-generic");
215