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 <asm/byteorder.h>
  20
  21 #define CHKSUM_BLOCK_SIZE       32
  22 #define CHKSUM_DIGEST_SIZE      4
  23
  24 struct chksum_ctx {
  25         u32 crc;
  26 };
  27
  28 /*
  29  * Steps through buffer one byte at at time, calculates reflected
  30  * crc using table.
  31  */
  32
  33 static void chksum_init(void *ctx)
  34 {
  35         struct chksum_ctx *mctx = ctx;
  36
  37         mctx->crc = ~(u32)0;                    /* common usage */
  38 }
  39
  40 /*
  41  * Setting the seed allows arbitrary accumulators and flexible XOR policy
  42  * If your algorithm starts with ~0, then XOR with ~0 before you set
  43  * the seed.
  44  */
  45 static int chksum_setkey(void *ctx, const u8 *key, unsigned int keylen,
  46                           u32 *flags)
  47 {
  48         struct chksum_ctx *mctx = ctx;
  49
  50         if (keylen != sizeof(mctx->crc)) {
  51                 if (flags)
  52                         *flags = CRYPTO_TFM_RES_BAD_KEY_LEN;
  53                 return -EINVAL;
  54         }
  55         mctx->crc = __cpu_to_le32(*(u32 *)key);
  56         return 0;
  57 }
  58
  59 static void chksum_update(void *ctx, const u8 *data, unsigned int length)
  60 {
  61         struct chksum_ctx *mctx = ctx;
  62         u32 mcrc;
  63
  64         mcrc = crc32c(mctx->crc, data, (size_t)length);
  65
  66         mctx->crc = mcrc;
  67 }
  68
  69 static void chksum_final(void *ctx, u8 *out)
  70 {
  71         struct chksum_ctx *mctx = ctx;
  72         u32 mcrc = (mctx->crc ^ ~(u32)0);
  73
  74         *(u32 *)out = __le32_to_cpu(mcrc);
  75 }
  76
  77 static struct crypto_alg alg = {
  78         .cra_name       =       "crc32c",
  79         .cra_flags      =       CRYPTO_ALG_TYPE_DIGEST,
  80         .cra_blocksize  =       CHKSUM_BLOCK_SIZE,
  81         .cra_ctxsize    =       sizeof(struct chksum_ctx),
  82         .cra_module     =       THIS_MODULE,
  83         .cra_list       =       LIST_HEAD_INIT(alg.cra_list),
  84         .cra_u          =       {
  85                 .digest = {
  86                          .dia_digestsize=       CHKSUM_DIGEST_SIZE,
  87                          .dia_setkey    =       chksum_setkey,
  88                          .dia_init      =       chksum_init,
  89                          .dia_update    =       chksum_update,
  90                          .dia_final     =       chksum_final
  91                  }
  92         }
  93 };
  94
  95 static int __init init(void)
  96 {
  97         return crypto_register_alg(&alg);
  98 }
  99
 100 static void __exit fini(void)
 101 {
 102         crypto_unregister_alg(&alg);
 103 }
 104
 105 module_init(init);
 106 module_exit(fini);
 107
 108 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
 109 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
 110 MODULE_LICENSE("GPL");