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 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/crypto.h>
17
18 #define ARC4_MIN_KEY_SIZE 1
19 #define ARC4_MAX_KEY_SIZE 256
20 #define ARC4_BLOCK_SIZE 1
21
22 struct arc4_ctx {
23 u8 S[256];
24 u8 x, y;
25 };
26
arc4_set_key(void * ctx_arg,const u8 * in_key,unsigned int key_len,u32 * flags)27 static int arc4_set_key(void *ctx_arg, const u8 *in_key, unsigned int key_len, u32 *flags)
28 {
29 struct arc4_ctx *ctx = ctx_arg;
30 int i, j = 0, k = 0;
31
32 ctx->x = 1;
33 ctx->y = 0;
34
35 for(i = 0; i < 256; i++)
36 ctx->S[i] = i;
37
38 for(i = 0; i < 256; i++)
39 {
40 u8 a = ctx->S[i];
41 j = (j + in_key[k] + a) & 0xff;
42 ctx->S[i] = ctx->S[j];
43 ctx->S[j] = a;
44 if(++k >= key_len)
45 k = 0;
46 }
47
48 return 0;
49 }
50
arc4_crypt(void * ctx_arg,u8 * out,const u8 * in)51 static void arc4_crypt(void *ctx_arg, u8 *out, const u8 *in)
52 {
53 struct arc4_ctx *ctx = ctx_arg;
54
55 u8 *const S = ctx->S;
56 u8 x = ctx->x;
57 u8 y = ctx->y;
58 u8 a, b;
59
60 a = S[x];
61 y = (y + a) & 0xff;
62 b = S[y];
63 S[x] = b;
64 S[y] = a;
65 x = (x + 1) & 0xff;
66 *out++ = *in ^ S[(a + b) & 0xff];
67
68 ctx->x = x;
69 ctx->y = y;
70 }
71
72 static struct crypto_alg arc4_alg = {
73 .cra_name = "arc4",
74 .cra_flags = CRYPTO_ALG_TYPE_CIPHER,
75 .cra_blocksize = ARC4_BLOCK_SIZE,
76 .cra_ctxsize = sizeof(struct arc4_ctx),
77 .cra_module = THIS_MODULE,
78 .cra_list = LIST_HEAD_INIT(arc4_alg.cra_list),
79 .cra_u = { .cipher = {
80 .cia_min_keysize = ARC4_MIN_KEY_SIZE,
81 .cia_max_keysize = ARC4_MAX_KEY_SIZE,
82 .cia_setkey = arc4_set_key,
83 .cia_encrypt = arc4_crypt,
84 .cia_decrypt = arc4_crypt } }
85 };
86
arc4_init(void)87 static int __init arc4_init(void)
88 {
89 return crypto_register_alg(&arc4_alg);
90 }
91
92
arc4_exit(void)93 static void __exit arc4_exit(void)
94 {
95 crypto_unregister_alg(&arc4_alg);
96 }
97
98 module_init(arc4_init);
99 module_exit(arc4_exit);
100
101 MODULE_LICENSE("GPL");
102 MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
103 MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>");
104