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 <asm/unaligned.h>
  13 #include <crypto/algapi.h>
  14 #include <crypto/chacha20.h>
  15 #include <crypto/internal/skcipher.h>
  16 #include <linux/module.h>
  17
  18 static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
  19                              unsigned int bytes)
  20 {
  21         u32 stream[CHACHA20_BLOCK_WORDS];
  22
  23         if (dst != src)
  24                 memcpy(dst, src, bytes);
  25
  26         while (bytes >= CHACHA20_BLOCK_SIZE) {
  27                 chacha20_block(state, stream);
  28                 crypto_xor(dst, (const u8 *)stream, CHACHA20_BLOCK_SIZE);
  29                 bytes -= CHACHA20_BLOCK_SIZE;
  30                 dst += CHACHA20_BLOCK_SIZE;
  31         }
  32         if (bytes) {
  33                 chacha20_block(state, stream);
  34                 crypto_xor(dst, (const u8 *)stream, bytes);
  35         }
  36 }
  37
  38 void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
  39 {
  40         state[0]  = 0x61707865; /* "expa" */
  41         state[1]  = 0x3320646e; /* "nd 3" */
  42         state[2]  = 0x79622d32; /* "2-by" */
  43         state[3]  = 0x6b206574; /* "te k" */
  44         state[4]  = ctx->key[0];
  45         state[5]  = ctx->key[1];
  46         state[6]  = ctx->key[2];
  47         state[7]  = ctx->key[3];
  48         state[8]  = ctx->key[4];
  49         state[9]  = ctx->key[5];
  50         state[10] = ctx->key[6];
  51         state[11] = ctx->key[7];
  52         state[12] = get_unaligned_le32(iv +  0);
  53         state[13] = get_unaligned_le32(iv +  4);
  54         state[14] = get_unaligned_le32(iv +  8);
  55         state[15] = get_unaligned_le32(iv + 12);
  56 }
  57 EXPORT_SYMBOL_GPL(crypto_chacha20_init);
  58
  59 int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
  60                            unsigned int keysize)
  61 {
  62         struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
  63         int i;
  64
  65         if (keysize != CHACHA20_KEY_SIZE)
  66                 return -EINVAL;
  67
  68         for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
  69                 ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
  70
  71         return 0;
  72 }
  73 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
  74
  75 int crypto_chacha20_crypt(struct skcipher_request *req)
  76 {
  77         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  78         struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
  79         struct skcipher_walk walk;
  80         u32 state[16];
  81         int err;
  82
  83         err = skcipher_walk_virt(&walk, req, true);
  84
  85         crypto_chacha20_init(state, ctx, walk.iv);
  86
  87         while (walk.nbytes > 0) {
  88                 unsigned int nbytes = walk.nbytes;
  89
  90                 if (nbytes < walk.total)
  91                         nbytes = round_down(nbytes, walk.stride);
  92
  93                 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
  94                                  nbytes);
  95                 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
  96         }
  97
  98         return err;
  99 }
 100 EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
 101
 102 static struct skcipher_alg alg = {
 103         .base.cra_name          = "chacha20",
 104         .base.cra_driver_name   = "chacha20-generic",
 105         .base.cra_priority      = 100,
 106         .base.cra_blocksize     = 1,
 107         .base.cra_ctxsize       = sizeof(struct chacha20_ctx),
 108         .base.cra_module        = THIS_MODULE,
 109
 110         .min_keysize            = CHACHA20_KEY_SIZE,
 111         .max_keysize            = CHACHA20_KEY_SIZE,
 112         .ivsize                 = CHACHA20_IV_SIZE,
 113         .chunksize              = CHACHA20_BLOCK_SIZE,
 114         .setkey                 = crypto_chacha20_setkey,
 115         .encrypt                = crypto_chacha20_crypt,
 116         .decrypt                = crypto_chacha20_crypt,
 117 };
 118
 119 static int __init chacha20_generic_mod_init(void)
 120 {
 121         return crypto_register_skcipher(&alg);
 122 }
 123
 124 static void __exit chacha20_generic_mod_fini(void)
 125 {
 126         crypto_unregister_skcipher(&alg);
 127 }
 128
 129 module_init(chacha20_generic_mod_init);
 130 module_exit(chacha20_generic_mod_fini);
 131
 132 MODULE_LICENSE("GPL");
 133 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 134 MODULE_DESCRIPTION("chacha20 cipher algorithm");
 135 MODULE_ALIAS_CRYPTO("chacha20");
 136 MODULE_ALIAS_CRYPTO("chacha20-generic");