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 <crypto/algapi.h>
16#include <crypto/arc4.h>
17#include <crypto/internal/skcipher.h>
18#include <linux/init.h>
19#include <linux/module.h>
20
21struct arc4_ctx {
22 u32 S[256];
23 u32 x, y;
24};
25
26static int arc4_set_key(struct crypto_tfm *tfm, const u8 *in_key,
27 unsigned int key_len)
28{
29 struct arc4_ctx *ctx = crypto_tfm_ctx(tfm);
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 u32 a = ctx->S[i];
40 j = (j + in_key[k] + a) & 0xff;
41 ctx->S[i] = ctx->S[j];
42 ctx->S[j] = a;
43 if (++k >= key_len)
44 k = 0;
45 }
46
47 return 0;
48}
49
50static int arc4_set_key_skcipher(struct crypto_skcipher *tfm, const u8 *in_key,
51 unsigned int key_len)
52{
53 return arc4_set_key(&tfm->base, in_key, key_len);
54}
55
56static void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in,
57 unsigned int len)
58{
59 u32 *const S = ctx->S;
60 u32 x, y, a, b;
61 u32 ty, ta, tb;
62
63 if (len == 0)
64 return;
65
66 x = ctx->x;
67 y = ctx->y;
68
69 a = S[x];
70 y = (y + a) & 0xff;
71 b = S[y];
72
73 do {
74 S[y] = a;
75 a = (a + b) & 0xff;
76 S[x] = b;
77 x = (x + 1) & 0xff;
78 ta = S[x];
79 ty = (y + ta) & 0xff;
80 tb = S[ty];
81 *out++ = *in++ ^ S[a];
82 if (--len == 0)
83 break;
84 y = ty;
85 a = ta;
86 b = tb;
87 } while (true);
88
89 ctx->x = x;
90 ctx->y = y;
91}
92
93static void arc4_crypt_one(struct crypto_tfm *tfm, u8 *out, const u8 *in)
94{
95 arc4_crypt(crypto_tfm_ctx(tfm), out, in, 1);
96}
97
98static int ecb_arc4_crypt(struct skcipher_request *req)
99{
100 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
101 struct arc4_ctx *ctx = crypto_skcipher_ctx(tfm);
102 struct skcipher_walk walk;
103 int err;
104
105 err = skcipher_walk_virt(&walk, req, false);
106
107 while (walk.nbytes > 0) {
108 arc4_crypt(ctx, walk.dst.virt.addr, walk.src.virt.addr,
109 walk.nbytes);
110 err = skcipher_walk_done(&walk, 0);
111 }
112
113 return err;
114}
115
116static struct crypto_alg arc4_cipher = {
117 .cra_name = "arc4",
118 .cra_flags = CRYPTO_ALG_TYPE_CIPHER,
119 .cra_blocksize = ARC4_BLOCK_SIZE,
120 .cra_ctxsize = sizeof(struct arc4_ctx),
121 .cra_module = THIS_MODULE,
122 .cra_u = {
123 .cipher = {
124 .cia_min_keysize = ARC4_MIN_KEY_SIZE,
125 .cia_max_keysize = ARC4_MAX_KEY_SIZE,
126 .cia_setkey = arc4_set_key,
127 .cia_encrypt = arc4_crypt_one,
128 .cia_decrypt = arc4_crypt_one,
129 },
130 },
131};
132
133static struct skcipher_alg arc4_skcipher = {
134 .base.cra_name = "ecb(arc4)",
135 .base.cra_priority = 100,
136 .base.cra_blocksize = ARC4_BLOCK_SIZE,
137 .base.cra_ctxsize = sizeof(struct arc4_ctx),
138 .base.cra_module = THIS_MODULE,
139 .min_keysize = ARC4_MIN_KEY_SIZE,
140 .max_keysize = ARC4_MAX_KEY_SIZE,
141 .setkey = arc4_set_key_skcipher,
142 .encrypt = ecb_arc4_crypt,
143 .decrypt = ecb_arc4_crypt,
144};
145
146static int __init arc4_init(void)
147{
148 int err;
149
150 err = crypto_register_alg(&arc4_cipher);
151 if (err)
152 return err;
153
154 err = crypto_register_skcipher(&arc4_skcipher);
155 if (err)
156 crypto_unregister_alg(&arc4_cipher);
157 return err;
158}
159
160static void __exit arc4_exit(void)
161{
162 crypto_unregister_alg(&arc4_cipher);
163 crypto_unregister_skcipher(&arc4_skcipher);
164}
165
166module_init(arc4_init);
167module_exit(arc4_exit);
168
169MODULE_LICENSE("GPL");
170MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
171MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>");
172MODULE_ALIAS_CRYPTO("arc4");
173