linux/crypto/crc32c.c
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   1/* 
   2 * Cryptographic API.
   3 *
   4 * CRC32C chksum
   5 *
   6 * This module file is a wrapper to invoke the lib/crc32c routines.
   7 *
   8 * This program is free software; you can redistribute it and/or modify it
   9 * under the terms of the GNU General Public License as published by the Free
  10 * Software Foundation; either version 2 of the License, or (at your option) 
  11 * any later version.
  12 *
  13 */
  14#include <linux/init.h>
  15#include <linux/module.h>
  16#include <linux/string.h>
  17#include <linux/crypto.h>
  18#include <linux/crc32c.h>
  19#include <linux/kernel.h>
  20
  21#define CHKSUM_BLOCK_SIZE       32
  22#define CHKSUM_DIGEST_SIZE      4
  23
  24struct chksum_ctx {
  25        u32 crc;
  26        u32 key;
  27};
  28
  29/*
  30 * Steps through buffer one byte at at time, calculates reflected 
  31 * crc using table.
  32 */
  33
  34static void chksum_init(struct crypto_tfm *tfm)
  35{
  36        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  37
  38        mctx->crc = mctx->key;
  39}
  40
  41/*
  42 * Setting the seed allows arbitrary accumulators and flexible XOR policy
  43 * If your algorithm starts with ~0, then XOR with ~0 before you set
  44 * the seed.
  45 */
  46static int chksum_setkey(struct crypto_tfm *tfm, const u8 *key,
  47                         unsigned int keylen)
  48{
  49        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  50
  51        if (keylen != sizeof(mctx->crc)) {
  52                tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
  53                return -EINVAL;
  54        }
  55        mctx->key = le32_to_cpu(*(__le32 *)key);
  56        return 0;
  57}
  58
  59static void chksum_update(struct crypto_tfm *tfm, const u8 *data,
  60                          unsigned int length)
  61{
  62        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  63
  64        mctx->crc = crc32c(mctx->crc, data, length);
  65}
  66
  67static void chksum_final(struct crypto_tfm *tfm, u8 *out)
  68{
  69        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  70        
  71        *(__le32 *)out = ~cpu_to_le32(mctx->crc);
  72}
  73
  74static int crc32c_cra_init(struct crypto_tfm *tfm)
  75{
  76        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  77
  78        mctx->key = ~0;
  79        return 0;
  80}
  81
  82static struct crypto_alg alg = {
  83        .cra_name       =       "crc32c",
  84        .cra_flags      =       CRYPTO_ALG_TYPE_DIGEST,
  85        .cra_blocksize  =       CHKSUM_BLOCK_SIZE,
  86        .cra_ctxsize    =       sizeof(struct chksum_ctx),
  87        .cra_module     =       THIS_MODULE,
  88        .cra_list       =       LIST_HEAD_INIT(alg.cra_list),
  89        .cra_init       =       crc32c_cra_init,
  90        .cra_u          =       {
  91                .digest = {
  92                         .dia_digestsize=       CHKSUM_DIGEST_SIZE,
  93                         .dia_setkey    =       chksum_setkey,
  94                         .dia_init      =       chksum_init,
  95                         .dia_update    =       chksum_update,
  96                         .dia_final     =       chksum_final
  97                 }
  98        }
  99};
 100
 101static int __init init(void)
 102{
 103        return crypto_register_alg(&alg);
 104}
 105
 106static void __exit fini(void)
 107{
 108        crypto_unregister_alg(&alg);
 109}
 110
 111module_init(init);
 112module_exit(fini);
 113
 114MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
 115MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
 116MODULE_LICENSE("GPL");
 117
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