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1 | /* |
2 | * Cryptographic API |
3 | * |
4 | * ARC4 Cipher Algorithm |
5 | * |
6 | * Jon Oberheide <jon@oberheide.org> |
7 | * |
8 | * This program is free software; you can redistribute it and/or modify |
9 | * it under the terms of the GNU General Public License as published by |
10 | * the Free Software Foundation; either version 2 of the License, or |
11 | * (at your option) any later version. |
12 | * |
13 | */ |
14 | |
15 | #include <linux/module.h> |
16 | #include <linux/init.h> |
17 | #include <linux/crypto.h> |
18 | #include <crypto/algapi.h> |
19 | |
20 | #define ARC4_MIN_KEY_SIZE 1 |
21 | #define ARC4_MAX_KEY_SIZE 256 |
22 | #define ARC4_BLOCK_SIZE 1 |
23 | |
24 | struct arc4_ctx { |
25 | u32 S[256]; |
26 | u32 x, y; |
27 | }; |
28 | |
29 | static int arc4_set_key(struct crypto_tfm *tfm, const u8 *in_key, |
30 | unsigned int key_len) |
31 | { |
32 | struct arc4_ctx *ctx = crypto_tfm_ctx(tfm); |
33 | int i, j = 0, k = 0; |
34 | |
35 | ctx->x = 1; |
36 | ctx->y = 0; |
37 | |
38 | for (i = 0; i < 256; i++) |
39 | ctx->S[i] = i; |
40 | |
41 | for (i = 0; i < 256; i++) { |
42 | u32 a = ctx->S[i]; |
43 | j = (j + in_key[k] + a) & 0xff; |
44 | ctx->S[i] = ctx->S[j]; |
45 | ctx->S[j] = a; |
46 | if (++k >= key_len) |
47 | k = 0; |
48 | } |
49 | |
50 | return 0; |
51 | } |
52 | |
53 | static void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, |
54 | unsigned int len) |
55 | { |
56 | u32 *const S = ctx->S; |
57 | u32 x, y, a, b; |
58 | u32 ty, ta, tb; |
59 | |
60 | if (len == 0) |
61 | return; |
62 | |
63 | x = ctx->x; |
64 | y = ctx->y; |
65 | |
66 | a = S[x]; |
67 | y = (y + a) & 0xff; |
68 | b = S[y]; |
69 | |
70 | do { |
71 | S[y] = a; |
72 | a = (a + b) & 0xff; |
73 | S[x] = b; |
74 | x = (x + 1) & 0xff; |
75 | ta = S[x]; |
76 | ty = (y + ta) & 0xff; |
77 | tb = S[ty]; |
78 | *out++ = *in++ ^ S[a]; |
79 | if (--len == 0) |
80 | break; |
81 | y = ty; |
82 | a = ta; |
83 | b = tb; |
84 | } while (true); |
85 | |
86 | ctx->x = x; |
87 | ctx->y = y; |
88 | } |
89 | |
90 | static void arc4_crypt_one(struct crypto_tfm *tfm, u8 *out, const u8 *in) |
91 | { |
92 | arc4_crypt(crypto_tfm_ctx(tfm), out, in, 1); |
93 | } |
94 | |
95 | static int ecb_arc4_crypt(struct blkcipher_desc *desc, struct scatterlist *dst, |
96 | struct scatterlist *src, unsigned int nbytes) |
97 | { |
98 | struct arc4_ctx *ctx = crypto_blkcipher_ctx(desc->tfm); |
99 | struct blkcipher_walk walk; |
100 | int err; |
101 | |
102 | blkcipher_walk_init(&walk, dst, src, nbytes); |
103 | |
104 | err = blkcipher_walk_virt(desc, &walk); |
105 | |
106 | while (walk.nbytes > 0) { |
107 | u8 *wsrc = walk.src.virt.addr; |
108 | u8 *wdst = walk.dst.virt.addr; |
109 | |
110 | arc4_crypt(ctx, wdst, wsrc, walk.nbytes); |
111 | |
112 | err = blkcipher_walk_done(desc, &walk, 0); |
113 | } |
114 | |
115 | return err; |
116 | } |
117 | |
118 | static struct crypto_alg arc4_algs[2] = { { |
119 | .cra_name = "arc4", |
120 | .cra_flags = CRYPTO_ALG_TYPE_CIPHER, |
121 | .cra_blocksize = ARC4_BLOCK_SIZE, |
122 | .cra_ctxsize = sizeof(struct arc4_ctx), |
123 | .cra_module = THIS_MODULE, |
124 | .cra_u = { |
125 | .cipher = { |
126 | .cia_min_keysize = ARC4_MIN_KEY_SIZE, |
127 | .cia_max_keysize = ARC4_MAX_KEY_SIZE, |
128 | .cia_setkey = arc4_set_key, |
129 | .cia_encrypt = arc4_crypt_one, |
130 | .cia_decrypt = arc4_crypt_one, |
131 | }, |
132 | }, |
133 | }, { |
134 | .cra_name = "ecb(arc4)", |
135 | .cra_priority = 100, |
136 | .cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER, |
137 | .cra_blocksize = ARC4_BLOCK_SIZE, |
138 | .cra_ctxsize = sizeof(struct arc4_ctx), |
139 | .cra_alignmask = 0, |
140 | .cra_type = &crypto_blkcipher_type, |
141 | .cra_module = THIS_MODULE, |
142 | .cra_u = { |
143 | .blkcipher = { |
144 | .min_keysize = ARC4_MIN_KEY_SIZE, |
145 | .max_keysize = ARC4_MAX_KEY_SIZE, |
146 | .setkey = arc4_set_key, |
147 | .encrypt = ecb_arc4_crypt, |
148 | .decrypt = ecb_arc4_crypt, |
149 | }, |
150 | }, |
151 | } }; |
152 | |
153 | static int __init arc4_init(void) |
154 | { |
155 | return crypto_register_algs(arc4_algs, ARRAY_SIZE(arc4_algs)); |
156 | } |
157 | |
158 | static void __exit arc4_exit(void) |
159 | { |
160 | crypto_unregister_algs(arc4_algs, ARRAY_SIZE(arc4_algs)); |
161 | } |
162 | |
163 | module_init(arc4_init); |
164 | module_exit(arc4_exit); |
165 | |
166 | MODULE_LICENSE("GPL"); |
167 | MODULE_DESCRIPTION("ARC4 Cipher Algorithm"); |
168 | MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>"); |
169 |
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