Quelle michael_mic.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Cryptographic API
*
* Michael MIC (IEEE 802.11i/TKIP) keyed digest
*
* Copyright (c) 2004 Jouni Malinen <j@w1.fi>
*/
#include <crypto/internal/hash.h>
#include <linux/unaligned.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/types.h>

struct michael_mic_ctx {
u32 l, r;
};

struct michael_mic_desc_ctx {
__le32 pending;
size_t pending_len;

u32 l, r;
};

static inline u32 xswap(u32 val)
{
return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
}

#define michael_block(l, r) \
do {    \
r ^= rol32(l, 17); \
l += r;   \
r ^= xswap(l);  \
l += r;   \
r ^= rol32(l, 3); \
l += r;   \
r ^= ror32(l, 2); \
l += r;   \
} while (0)

static int michael_init(struct shash_desc *desc)
{
struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
struct michael_mic_ctx *ctx = crypto_shash_ctx(desc->tfm);
mctx->pending_len = 0;
mctx->l = ctx->l;
mctx->r = ctx->r;

return 0;
}

static int michael_update(struct shash_desc *desc, const u8 *data,
      unsigned int len)
{
struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);

if (mctx->pending_len) {
  int flen = 4 - mctx->pending_len;
  if (flen > len)
   flen = len;
  memcpy((u8 *)&mctx->pending + mctx->pending_len, data, flen);
  mctx->pending_len += flen;
  data += flen;
  len -= flen;

  if (mctx->pending_len < 4)
   return 0;

  mctx->l ^= le32_to_cpu(mctx->pending);
  michael_block(mctx->l, mctx->r);
  mctx->pending_len = 0;
}

while (len >= 4) {
  mctx->l ^= get_unaligned_le32(data);
  michael_block(mctx->l, mctx->r);
  data += 4;
  len -= 4;
}

if (len > 0) {
  mctx->pending_len = len;
  memcpy(&mctx->pending, data, len);
}

return 0;
}

static int michael_final(struct shash_desc *desc, u8 *out)
{
struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
u8 *data = (u8 *)&mctx->pending;

/* Last block and padding (0x5a, 4..7 x 0) */
switch (mctx->pending_len) {
case 0:
  mctx->l ^= 0x5a;
  break;
case 1:
  mctx->l ^= data[0] | 0x5a00;
  break;
case 2:
  mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
  break;
case 3:
  mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
   0x5a000000;
  break;
}
michael_block(mctx->l, mctx->r);
/* l ^= 0; */
michael_block(mctx->l, mctx->r);

put_unaligned_le32(mctx->l, out);
put_unaligned_le32(mctx->r, out + 4);

return 0;
}

static int michael_setkey(struct crypto_shash *tfm, const u8 *key,
     unsigned int keylen)
{
struct michael_mic_ctx *mctx = crypto_shash_ctx(tfm);

if (keylen != 8)
  return -EINVAL;

mctx->l = get_unaligned_le32(key);
mctx->r = get_unaligned_le32(key + 4);
return 0;
}

static struct shash_alg alg = {
.digestsize  = 8,
.setkey   = michael_setkey,
.init   = michael_init,
.update   = michael_update,
.final   = michael_final,
.descsize  = sizeof(struct michael_mic_desc_ctx),
.base   = {
  .cra_name  = "michael_mic",
  .cra_driver_name = "michael_mic-generic",
  .cra_blocksize  = 8,
  .cra_ctxsize  = sizeof(struct michael_mic_ctx),
  .cra_module  = THIS_MODULE,
}
};

static int __init michael_mic_init(void)
{
return crypto_register_shash(&alg);
}

static void __exit michael_mic_exit(void)
{
crypto_unregister_shash(&alg);
}

module_init(michael_mic_init);
module_exit(michael_mic_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Michael MIC");
MODULE_AUTHOR("Jouni Malinen ");
MODULE_ALIAS_CRYPTO("michael_mic");

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