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. */
twofish_encrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)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. */
twofish_decrypt(struct crypto_tfm * tfm,u8 * out,const u8 * in)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 
twofish_mod_init(void)180 static int __init twofish_mod_init(void)
181 {
182 	return crypto_register_alg(&alg);
183 }
184 
twofish_mod_fini(void)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