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         u8 stream[CHACHA20_BLOCK_SIZE];
  26
  27         if (dst != src)
  28                 memcpy(dst, src, bytes);
  29
  30         while (bytes >= CHACHA20_BLOCK_SIZE) {
  31                 chacha20_block(state, stream);
  32                 crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
  33                 bytes -= CHACHA20_BLOCK_SIZE;
  34                 dst += CHACHA20_BLOCK_SIZE;
  35         }
  36         if (bytes) {
  37                 chacha20_block(state, stream);
  38                 crypto_xor(dst, stream, bytes);
  39         }
  40 }
  41
  42 void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
  43 {
  44         static const char constant[16] = "expand 32-byte k";
  45
  46         state[0]  = le32_to_cpuvp(constant +  0);
  47         state[1]  = le32_to_cpuvp(constant +  4);
  48         state[2]  = le32_to_cpuvp(constant +  8);
  49         state[3]  = le32_to_cpuvp(constant + 12);
  50         state[4]  = ctx->key[0];
  51         state[5]  = ctx->key[1];
  52         state[6]  = ctx->key[2];
  53         state[7]  = ctx->key[3];
  54         state[8]  = ctx->key[4];
  55         state[9]  = ctx->key[5];
  56         state[10] = ctx->key[6];
  57         state[11] = ctx->key[7];
  58         state[12] = le32_to_cpuvp(iv +  0);
  59         state[13] = le32_to_cpuvp(iv +  4);
  60         state[14] = le32_to_cpuvp(iv +  8);
  61         state[15] = le32_to_cpuvp(iv + 12);
  62 }
  63 EXPORT_SYMBOL_GPL(crypto_chacha20_init);
  64
  65 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
  66                            unsigned int keysize)
  67 {
  68         struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
  69         int i;
  70
  71         if (keysize != CHACHA20_KEY_SIZE)
  72                 return -EINVAL;
  73
  74         for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
  75                 ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
  76
  77         return 0;
  78 }
  79 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
  80
  81 int crypto_chacha20_crypt(struct skcipher_request *req)
  82 {
  83         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  84         struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
  85         struct skcipher_walk walk;
  86         u32 state[16];
  87         int err;
  88
  89         err = skcipher_walk_virt(&walk, req, true);
  90
  91         crypto_chacha20_init(state, ctx, walk.iv);
  92
  93         while (walk.nbytes > 0) {
  94                 unsigned int nbytes = walk.nbytes;
  95
  96                 if (nbytes < walk.total)
  97                         nbytes = round_down(nbytes, walk.stride);
  98
  99                 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
 100                                  nbytes);
 101                 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 102         }
 103
 104         return err;
 105 }
 106 EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
 107
 108 static struct skcipher_alg alg = {
 109         .base.cra_name          = "chacha20",
 110         .base.cra_driver_name   = "chacha20-generic",
 111         .base.cra_priority      = 100,
 112         .base.cra_blocksize     = 1,
 113         .base.cra_ctxsize       = sizeof(struct chacha20_ctx),
 114         .base.cra_alignmask     = sizeof(u32) - 1,
 115         .base.cra_module        = THIS_MODULE,
 116
 117         .min_keysize            = CHACHA20_KEY_SIZE,
 118         .max_keysize            = CHACHA20_KEY_SIZE,
 119         .ivsize                 = CHACHA20_IV_SIZE,
 120         .chunksize              = CHACHA20_BLOCK_SIZE,
 121         .setkey                 = crypto_chacha20_setkey,
 122         .encrypt                = crypto_chacha20_crypt,
 123         .decrypt                = crypto_chacha20_crypt,
 124 };
 125
 126 static int __init chacha20_generic_mod_init(void)
 127 {
 128         return crypto_register_skcipher(&alg);
 129 }
 130
 131 static void __exit chacha20_generic_mod_fini(void)
 132 {
 133         crypto_unregister_skcipher(&alg);
 134 }
 135
 136 module_init(chacha20_generic_mod_init);
 137 module_exit(chacha20_generic_mod_fini);
 138
 139 MODULE_LICENSE("GPL");
 140 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 141 MODULE_DESCRIPTION("chacha20 cipher algorithm");
 142 MODULE_ALIAS_CRYPTO("chacha20");
 143 MODULE_ALIAS_CRYPTO("chacha20-generic");