crypto/chacha_generic.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * ChaCha and XChaCha stream ciphers, including ChaCha20 (RFC7539)
   4  *
   5  * Copyright (C) 2015 Martin Willi
   6  * Copyright (C) 2018 Google LLC
   7  */
   8
   9 #include <asm/unaligned.h>
  10 #include <crypto/algapi.h>
  11 #include <crypto/internal/chacha.h>
  12 #include <crypto/internal/skcipher.h>
  13 #include <linux/module.h>
  14
  15 static int chacha_stream_xor(struct skcipher_request *req,
  16                              const struct chacha_ctx *ctx, const u8 *iv)
  17 {
  18         struct skcipher_walk walk;
  19         u32 state[16];
  20         int err;
  21
  22         err = skcipher_walk_virt(&walk, req, false);
  23
  24         chacha_init_generic(state, ctx->key, iv);
  25
  26         while (walk.nbytes > 0) {
  27                 unsigned int nbytes = walk.nbytes;
  28
  29                 if (nbytes < walk.total)
  30                         nbytes = round_down(nbytes, CHACHA_BLOCK_SIZE);
  31
  32                 chacha_crypt_generic(state, walk.dst.virt.addr,
  33                                      walk.src.virt.addr, nbytes, ctx->nrounds);
  34                 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
  35         }
  36
  37         return err;
  38 }
  39
  40 static int crypto_chacha_crypt(struct skcipher_request *req)
  41 {
  42         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  43         struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
  44
  45         return chacha_stream_xor(req, ctx, req->iv);
  46 }
  47
  48 static int crypto_xchacha_crypt(struct skcipher_request *req)
  49 {
  50         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  51         struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
  52         struct chacha_ctx subctx;
  53         u32 state[16];
  54         u8 real_iv[16];
  55
  56         /* Compute the subkey given the original key and first 128 nonce bits */
  57         chacha_init_generic(state, ctx->key, req->iv);
  58         hchacha_block_generic(state, subctx.key, ctx->nrounds);
  59         subctx.nrounds = ctx->nrounds;
  60
  61         /* Build the real IV */
  62         memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */
  63         memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */
  64
  65         /* Generate the stream and XOR it with the data */
  66         return chacha_stream_xor(req, &subctx, real_iv);
  67 }
  68
  69 static struct skcipher_alg algs[] = {
  70         {
  71                 .base.cra_name          = "chacha20",
  72                 .base.cra_driver_name   = "chacha20-generic",
  73                 .base.cra_priority      = 100,
  74                 .base.cra_blocksize     = 1,
  75                 .base.cra_ctxsize       = sizeof(struct chacha_ctx),
  76                 .base.cra_module        = THIS_MODULE,
  77
  78                 .min_keysize            = CHACHA_KEY_SIZE,
  79                 .max_keysize            = CHACHA_KEY_SIZE,
  80                 .ivsize                 = CHACHA_IV_SIZE,
  81                 .chunksize              = CHACHA_BLOCK_SIZE,
  82                 .setkey                 = chacha20_setkey,
  83                 .encrypt                = crypto_chacha_crypt,
  84                 .decrypt                = crypto_chacha_crypt,
  85         }, {
  86                 .base.cra_name          = "xchacha20",
  87                 .base.cra_driver_name   = "xchacha20-generic",
  88                 .base.cra_priority      = 100,
  89                 .base.cra_blocksize     = 1,
  90                 .base.cra_ctxsize       = sizeof(struct chacha_ctx),
  91                 .base.cra_module        = THIS_MODULE,
  92
  93                 .min_keysize            = CHACHA_KEY_SIZE,
  94                 .max_keysize            = CHACHA_KEY_SIZE,
  95                 .ivsize                 = XCHACHA_IV_SIZE,
  96                 .chunksize              = CHACHA_BLOCK_SIZE,
  97                 .setkey                 = chacha20_setkey,
  98                 .encrypt                = crypto_xchacha_crypt,
  99                 .decrypt                = crypto_xchacha_crypt,
 100         }, {
 101                 .base.cra_name          = "xchacha12",
 102                 .base.cra_driver_name   = "xchacha12-generic",
 103                 .base.cra_priority      = 100,
 104                 .base.cra_blocksize     = 1,
 105                 .base.cra_ctxsize       = sizeof(struct chacha_ctx),
 106                 .base.cra_module        = THIS_MODULE,
 107
 108                 .min_keysize            = CHACHA_KEY_SIZE,
 109                 .max_keysize            = CHACHA_KEY_SIZE,
 110                 .ivsize                 = XCHACHA_IV_SIZE,
 111                 .chunksize              = CHACHA_BLOCK_SIZE,
 112                 .setkey                 = chacha12_setkey,
 113                 .encrypt                = crypto_xchacha_crypt,
 114                 .decrypt                = crypto_xchacha_crypt,
 115         }
 116 };
 117
 118 static int __init chacha_generic_mod_init(void)
 119 {
 120         return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
 121 }
 122
 123 static void __exit chacha_generic_mod_fini(void)
 124 {
 125         crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
 126 }
 127
 128 subsys_initcall(chacha_generic_mod_init);
 129 module_exit(chacha_generic_mod_fini);
 130
 131 MODULE_LICENSE("GPL");
 132 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 133 MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");
 134 MODULE_ALIAS_CRYPTO("chacha20");
 135 MODULE_ALIAS_CRYPTO("chacha20-generic");
 136 MODULE_ALIAS_CRYPTO("xchacha20");
 137 MODULE_ALIAS_CRYPTO("xchacha20-generic");
 138 MODULE_ALIAS_CRYPTO("xchacha12");
 139 MODULE_ALIAS_CRYPTO("xchacha12-generic");