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/kernel.h>
  20
  21 #define CHKSUM_BLOCK_SIZE       32
  22 #define CHKSUM_DIGEST_SIZE      4
  23
  24 struct 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
  34 static 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  */
  46 static 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
  59 static 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
  67 static 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
  74 static 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
  82 static 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
 101 static int __init init(void)
 102 {
 103         return crypto_register_alg(&alg);
 104 }
 105
 106 static void __exit fini(void)
 107 {
 108         crypto_unregister_alg(&alg);
 109 }
 110
 111 module_init(init);
 112 module_exit(fini);
 113
 114 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
 115 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
 116 MODULE_LICENSE("GPL");