crypto/chacha20_generic.c

   1 /*
   2  * ChaCha20 256-bit cipher algorithm, RFC7539
   3  *
   4  * Copyright (C) 2015 Martin Willi
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  */
  11
  12 #include <crypto/algapi.h>
  13 #include <crypto/chacha20.h>
  14 #include <crypto/internal/skcipher.h>
  15 #include <linux/module.h>
  16
  17 static inline u32 le32_to_cpuvp(const void *p)
  18 {
  19         return le32_to_cpup(p);
  20 }
  21
  22 static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
  23                              unsigned int bytes)
  24 {
  25         /* aligned to potentially speed up crypto_xor() */
  26         u8 stream[CHACHA20_BLOCK_SIZE] __aligned(sizeof(long));
  27
  28         if (dst != src)
  29                 memcpy(dst, src, bytes);
  30
  31         while (bytes >= CHACHA20_BLOCK_SIZE) {
  32                 chacha20_block(state, stream);
  33                 crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
  34                 bytes -= CHACHA20_BLOCK_SIZE;
  35                 dst += CHACHA20_BLOCK_SIZE;
  36         }
  37         if (bytes) {
  38                 chacha20_block(state, stream);
  39                 crypto_xor(dst, stream, bytes);
  40         }
  41 }
  42
  43 void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
  44 {
  45         static const char constant[16] = "expand 32-byte k";
  46
  47         state[0]  = le32_to_cpuvp(constant +  0);
  48         state[1]  = le32_to_cpuvp(constant +  4);
  49         state[2]  = le32_to_cpuvp(constant +  8);
  50         state[3]  = le32_to_cpuvp(constant + 12);
  51         state[4]  = ctx->key[0];
  52         state[5]  = ctx->key[1];
  53         state[6]  = ctx->key[2];
  54         state[7]  = ctx->key[3];
  55         state[8]  = ctx->key[4];
  56         state[9]  = ctx->key[5];
  57         state[10] = ctx->key[6];
  58         state[11] = ctx->key[7];
  59         state[12] = le32_to_cpuvp(iv +  0);
  60         state[13] = le32_to_cpuvp(iv +  4);
  61         state[14] = le32_to_cpuvp(iv +  8);
  62         state[15] = le32_to_cpuvp(iv + 12);
  63 }
  64 EXPORT_SYMBOL_GPL(crypto_chacha20_init);
  65
  66 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
  67                            unsigned int keysize)
  68 {
  69         struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
  70         int i;
  71
  72         if (keysize != CHACHA20_KEY_SIZE)
  73                 return -EINVAL;
  74
  75         for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
  76                 ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
  77
  78         return 0;
  79 }
  80 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
  81
  82 int crypto_chacha20_crypt(struct skcipher_request *req)
  83 {
  84         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  85         struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
  86         struct skcipher_walk walk;
  87         u32 state[16];
  88         int err;
  89
  90         err = skcipher_walk_virt(&walk, req, true);
  91
  92         crypto_chacha20_init(state, ctx, walk.iv);
  93
  94         while (walk.nbytes > 0) {
  95                 unsigned int nbytes = walk.nbytes;
  96
  97                 if (nbytes < walk.total)
  98                         nbytes = round_down(nbytes, walk.stride);
  99
 100                 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
 101                                  nbytes);
 102                 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 103         }
 104
 105         return err;
 106 }
 107 EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
 108
 109 static struct skcipher_alg alg = {
 110         .base.cra_name          = "chacha20",
 111         .base.cra_driver_name   = "chacha20-generic",
 112         .base.cra_priority      = 100,
 113         .base.cra_blocksize     = 1,
 114         .base.cra_ctxsize       = sizeof(struct chacha20_ctx),
 115         .base.cra_alignmask     = sizeof(u32) - 1,
 116         .base.cra_module        = THIS_MODULE,
 117
 118         .min_keysize            = CHACHA20_KEY_SIZE,
 119         .max_keysize            = CHACHA20_KEY_SIZE,
 120         .ivsize                 = CHACHA20_IV_SIZE,
 121         .chunksize              = CHACHA20_BLOCK_SIZE,
 122         .setkey                 = crypto_chacha20_setkey,
 123         .encrypt                = crypto_chacha20_crypt,
 124         .decrypt                = crypto_chacha20_crypt,
 125 };
 126
 127 static int __init chacha20_generic_mod_init(void)
 128 {
 129         return crypto_register_skcipher(&alg);
 130 }
 131
 132 static void __exit chacha20_generic_mod_fini(void)
 133 {
 134         crypto_unregister_skcipher(&alg);
 135 }
 136
 137 module_init(chacha20_generic_mod_init);
 138 module_exit(chacha20_generic_mod_fini);
 139
 140 MODULE_LICENSE("GPL");
 141 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 142 MODULE_DESCRIPTION("chacha20 cipher algorithm");
 143 MODULE_ALIAS_CRYPTO("chacha20");
 144 MODULE_ALIAS_CRYPTO("chacha20-generic");