LXR linux/crypto/chacha20

   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
  18static 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
  38void 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}
  57EXPORT_SYMBOL_GPL(crypto_chacha20_init);
  58
  59int 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}
  73EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
  74
  75int 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}
 100EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
 101
 102static 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
 119static int __init chacha20_generic_mod_init(void)
 120{
 121        return crypto_register_skcipher(&alg);
 122}
 123
 124static void __exit chacha20_generic_mod_fini(void)
 125{
 126        crypto_unregister_skcipher(&alg);
 127}
 128
 129module_init(chacha20_generic_mod_init);
 130module_exit(chacha20_generic_mod_fini);
 131
 132MODULE_LICENSE("GPL");
 133MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 134MODULE_DESCRIPTION("chacha20 cipher algorithm");
 135MODULE_ALIAS_CRYPTO("chacha20");
 136MODULE_ALIAS_CRYPTO("chacha20-generic");
 137