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