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
arc4_set_key(struct crypto_tfm * tfm,const u8 * in_key,unsigned int key_len)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
arc4_crypt(struct arc4_ctx * ctx,u8 * out,const u8 * in,unsigned int len)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
arc4_crypt_one(struct crypto_tfm * tfm,u8 * out,const u8 * in)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
ecb_arc4_crypt(struct blkcipher_desc * desc,struct scatterlist * dst,struct scatterlist * src,unsigned int nbytes)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
arc4_init(void)153 static int __init arc4_init(void)
154 {
155 return crypto_register_algs(arc4_algs, ARRAY_SIZE(arc4_algs));
156 }
157
arc4_exit(void)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 MODULE_ALIAS_CRYPTO("arc4");
170
