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         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");