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 21 struct arc4_ctx { 22 u32 S[256]; 23 u32 x, y; 24 }; 25 26 static 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 50 static 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 56 static 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 93 static 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 98 static 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 } 115 116 static 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 }; 132 133 static 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 }; 145 146 static 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 } 159 160 static void __exit arc4_exit(void) 161 { 162 crypto_unregister_alg(&arc4_cipher); 163 crypto_unregister_skcipher(&arc4_skcipher); 164 } 165 166 subsys_initcall(arc4_init); 167 module_exit(arc4_exit); 168 169 MODULE_LICENSE("GPL"); 170 MODULE_DESCRIPTION("ARC4 Cipher Algorithm"); 171 MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>"); 172 MODULE_ALIAS_CRYPTO("arc4"); 173