crypto/chacha_generic.c

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