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 MODULE_ALIAS_CRYPTO("arc4"); 170