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