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/types.h>
  20#include <asm/byteorder.h>
  21
  22#define CHKSUM_BLOCK_SIZE       32
  23#define CHKSUM_DIGEST_SIZE      4
  24
  25struct chksum_ctx {
  26        u32 crc;
  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 = ~(u32)0;                    /* common usage */
  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, u32 *flags)
  48{
  49        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  50
  51        if (keylen != sizeof(mctx->crc)) {
  52                if (flags)
  53                        *flags = CRYPTO_TFM_RES_BAD_KEY_LEN;
  54                return -EINVAL;
  55        }
  56        mctx->crc = __cpu_to_le32(*(u32 *)key);
  57        return 0;
  58}
  59
  60static void chksum_update(struct crypto_tfm *tfm, const u8 *data,
  61                          unsigned int length)
  62{
  63        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  64        u32 mcrc;
  65
  66        mcrc = crc32c(mctx->crc, data, (size_t)length);
  67
  68        mctx->crc = mcrc;
  69}
  70
  71static void chksum_final(struct crypto_tfm *tfm, u8 *out)
  72{
  73        struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  74        u32 mcrc = (mctx->crc ^ ~(u32)0);
  75        
  76        *(u32 *)out = __le32_to_cpu(mcrc);
  77}
  78
  79static struct crypto_alg alg = {
  80        .cra_name       =       "crc32c",
  81        .cra_flags      =       CRYPTO_ALG_TYPE_DIGEST,
  82        .cra_blocksize  =       CHKSUM_BLOCK_SIZE,
  83        .cra_ctxsize    =       sizeof(struct chksum_ctx),
  84        .cra_module     =       THIS_MODULE,
  85        .cra_list       =       LIST_HEAD_INIT(alg.cra_list),
  86        .cra_u          =       {
  87                .digest = {
  88                         .dia_digestsize=       CHKSUM_DIGEST_SIZE,
  89                         .dia_setkey    =       chksum_setkey,
  90                         .dia_init      =       chksum_init,
  91                         .dia_update    =       chksum_update,
  92                         .dia_final     =       chksum_final
  93                 }
  94        }
  95};
  96
  97static int __init init(void)
  98{
  99        return crypto_register_alg(&alg);
 100}
 101
 102static void __exit fini(void)
 103{
 104        crypto_unregister_alg(&alg);
 105}
 106
 107module_init(init);
 108module_exit(fini);
 109
 110MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
 111MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
 112MODULE_LICENSE("GPL");
 113