1 /* 2 * ChaCha and XChaCha stream ciphers, including ChaCha20 (RFC7539) 3 * 4 * Copyright (C) 2015 Martin Willi 5 * Copyright (C) 2018 Google LLC 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 */ 12 13 #include <asm/unaligned.h> 14 #include <crypto/algapi.h> 15 #include <crypto/chacha.h> 16 #include <crypto/internal/skcipher.h> 17 #include <linux/module.h> 18 19 static void chacha_docrypt(u32 *state, u8 *dst, const u8 *src, 20 unsigned int bytes, int nrounds) 21 { 22 /* aligned to potentially speed up crypto_xor() */ 23 u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long)); 24 25 if (dst != src) 26 memcpy(dst, src, bytes); 27 28 while (bytes >= CHACHA_BLOCK_SIZE) { 29 chacha_block(state, stream, nrounds); 30 crypto_xor(dst, stream, CHACHA_BLOCK_SIZE); 31 bytes -= CHACHA_BLOCK_SIZE; 32 dst += CHACHA_BLOCK_SIZE; 33 } 34 if (bytes) { 35 chacha_block(state, stream, nrounds); 36 crypto_xor(dst, stream, bytes); 37 } 38 } 39 40 static int chacha_stream_xor(struct skcipher_request *req, 41 struct chacha_ctx *ctx, u8 *iv) 42 { 43 struct skcipher_walk walk; 44 u32 state[16]; 45 int err; 46 47 err = skcipher_walk_virt(&walk, req, false); 48 49 crypto_chacha_init(state, ctx, iv); 50 51 while (walk.nbytes > 0) { 52 unsigned int nbytes = walk.nbytes; 53 54 if (nbytes < walk.total) 55 nbytes = round_down(nbytes, walk.stride); 56 57 chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr, 58 nbytes, ctx->nrounds); 59 err = skcipher_walk_done(&walk, walk.nbytes - nbytes); 60 } 61 62 return err; 63 } 64 65 void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv) 66 { 67 state[0] = 0x61707865; /* "expa" */ 68 state[1] = 0x3320646e; /* "nd 3" */ 69 state[2] = 0x79622d32; /* "2-by" */ 70 state[3] = 0x6b206574; /* "te k" */ 71 state[4] = ctx->key[0]; 72 state[5] = ctx->key[1]; 73 state[6] = ctx->key[2]; 74 state[7] = ctx->key[3]; 75 state[8] = ctx->key[4]; 76 state[9] = ctx->key[5]; 77 state[10] = ctx->key[6]; 78 state[11] = ctx->key[7]; 79 state[12] = get_unaligned_le32(iv + 0); 80 state[13] = get_unaligned_le32(iv + 4); 81 state[14] = get_unaligned_le32(iv + 8); 82 state[15] = get_unaligned_le32(iv + 12); 83 } 84 EXPORT_SYMBOL_GPL(crypto_chacha_init); 85 86 static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key, 87 unsigned int keysize, int nrounds) 88 { 89 struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm); 90 int i; 91 92 if (keysize != CHACHA_KEY_SIZE) 93 return -EINVAL; 94 95 for (i = 0; i < ARRAY_SIZE(ctx->key); i++) 96 ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32)); 97 98 ctx->nrounds = nrounds; 99 return 0; 100 } 101 102 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key, 103 unsigned int keysize) 104 { 105 return chacha_setkey(tfm, key, keysize, 20); 106 } 107 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey); 108 109 int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key, 110 unsigned int keysize) 111 { 112 return chacha_setkey(tfm, key, keysize, 12); 113 } 114 EXPORT_SYMBOL_GPL(crypto_chacha12_setkey); 115 116 int crypto_chacha_crypt(struct skcipher_request *req) 117 { 118 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); 119 struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm); 120 121 return chacha_stream_xor(req, ctx, req->iv); 122 } 123 EXPORT_SYMBOL_GPL(crypto_chacha_crypt); 124 125 int crypto_xchacha_crypt(struct skcipher_request *req) 126 { 127 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); 128 struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm); 129 struct chacha_ctx subctx; 130 u32 state[16]; 131 u8 real_iv[16]; 132 133 /* Compute the subkey given the original key and first 128 nonce bits */ 134 crypto_chacha_init(state, ctx, req->iv); 135 hchacha_block(state, subctx.key, ctx->nrounds); 136 subctx.nrounds = ctx->nrounds; 137 138 /* Build the real IV */ 139 memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */ 140 memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */ 141 142 /* Generate the stream and XOR it with the data */ 143 return chacha_stream_xor(req, &subctx, real_iv); 144 } 145 EXPORT_SYMBOL_GPL(crypto_xchacha_crypt); 146 147 static struct skcipher_alg algs[] = { 148 { 149 .base.cra_name = "chacha20", 150 .base.cra_driver_name = "chacha20-generic", 151 .base.cra_priority = 100, 152 .base.cra_blocksize = 1, 153 .base.cra_ctxsize = sizeof(struct chacha_ctx), 154 .base.cra_module = THIS_MODULE, 155 156 .min_keysize = CHACHA_KEY_SIZE, 157 .max_keysize = CHACHA_KEY_SIZE, 158 .ivsize = CHACHA_IV_SIZE, 159 .chunksize = CHACHA_BLOCK_SIZE, 160 .setkey = crypto_chacha20_setkey, 161 .encrypt = crypto_chacha_crypt, 162 .decrypt = crypto_chacha_crypt, 163 }, { 164 .base.cra_name = "xchacha20", 165 .base.cra_driver_name = "xchacha20-generic", 166 .base.cra_priority = 100, 167 .base.cra_blocksize = 1, 168 .base.cra_ctxsize = sizeof(struct chacha_ctx), 169 .base.cra_module = THIS_MODULE, 170 171 .min_keysize = CHACHA_KEY_SIZE, 172 .max_keysize = CHACHA_KEY_SIZE, 173 .ivsize = XCHACHA_IV_SIZE, 174 .chunksize = CHACHA_BLOCK_SIZE, 175 .setkey = crypto_chacha20_setkey, 176 .encrypt = crypto_xchacha_crypt, 177 .decrypt = crypto_xchacha_crypt, 178 }, { 179 .base.cra_name = "xchacha12", 180 .base.cra_driver_name = "xchacha12-generic", 181 .base.cra_priority = 100, 182 .base.cra_blocksize = 1, 183 .base.cra_ctxsize = sizeof(struct chacha_ctx), 184 .base.cra_module = THIS_MODULE, 185 186 .min_keysize = CHACHA_KEY_SIZE, 187 .max_keysize = CHACHA_KEY_SIZE, 188 .ivsize = XCHACHA_IV_SIZE, 189 .chunksize = CHACHA_BLOCK_SIZE, 190 .setkey = crypto_chacha12_setkey, 191 .encrypt = crypto_xchacha_crypt, 192 .decrypt = crypto_xchacha_crypt, 193 } 194 }; 195 196 static int __init chacha_generic_mod_init(void) 197 { 198 return crypto_register_skciphers(algs, ARRAY_SIZE(algs)); 199 } 200 201 static void __exit chacha_generic_mod_fini(void) 202 { 203 crypto_unregister_skciphers(algs, ARRAY_SIZE(algs)); 204 } 205 206 module_init(chacha_generic_mod_init); 207 module_exit(chacha_generic_mod_fini); 208 209 MODULE_LICENSE("GPL"); 210 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>"); 211 MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)"); 212 MODULE_ALIAS_CRYPTO("chacha20"); 213 MODULE_ALIAS_CRYPTO("chacha20-generic"); 214 MODULE_ALIAS_CRYPTO("xchacha20"); 215 MODULE_ALIAS_CRYPTO("xchacha20-generic"); 216 MODULE_ALIAS_CRYPTO("xchacha12"); 217 MODULE_ALIAS_CRYPTO("xchacha12-generic"); 218