crypto/crc32c.c

   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
  25 struct 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
  34 static void chksum_init(void *ctx)
  35 {
  36         struct chksum_ctx *mctx = ctx;
  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  */
  46 static int chksum_setkey(void *ctx, const u8 *key, unsigned int keylen,
  47                           u32 *flags)
  48 {
  49         struct chksum_ctx *mctx = ctx;
  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
  60 static void chksum_update(void *ctx, const u8 *data, unsigned int length)
  61 {
  62         struct chksum_ctx *mctx = ctx;
  63         u32 mcrc;
  64
  65         mcrc = crc32c(mctx->crc, data, (size_t)length);
  66
  67         mctx->crc = mcrc;
  68 }
  69
  70 static void chksum_final(void *ctx, u8 *out)
  71 {
  72         struct chksum_ctx *mctx = ctx;
  73         u32 mcrc = (mctx->crc ^ ~(u32)0);
  74
  75         *(u32 *)out = __le32_to_cpu(mcrc);
  76 }
  77
  78 static struct crypto_alg alg = {
  79         .cra_name       =       "crc32c",
  80         .cra_flags      =       CRYPTO_ALG_TYPE_DIGEST,
  81         .cra_blocksize  =       CHKSUM_BLOCK_SIZE,
  82         .cra_ctxsize    =       sizeof(struct chksum_ctx),
  83         .cra_module     =       THIS_MODULE,
  84         .cra_list       =       LIST_HEAD_INIT(alg.cra_list),
  85         .cra_u          =       {
  86                 .digest = {
  87                          .dia_digestsize=       CHKSUM_DIGEST_SIZE,
  88                          .dia_setkey    =       chksum_setkey,
  89                          .dia_init      =       chksum_init,
  90                          .dia_update    =       chksum_update,
  91                          .dia_final     =       chksum_final
  92                  }
  93         }
  94 };
  95
  96 static int __init init(void)
  97 {
  98         return crypto_register_alg(&alg);
  99 }
 100
 101 static void __exit fini(void)
 102 {
 103         crypto_unregister_alg(&alg);
 104 }
 105
 106 module_init(init);
 107 module_exit(fini);
 108
 109 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
 110 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
 111 MODULE_LICENSE("GPL");