crypto/crc32c.c

   1 /*
   2  * Cryptographic API.
   3  *
   4  * CRC32C chksum
   5  *
   6  *@Article{castagnoli-crc,
   7  * author =       { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
   8  * title =        {{Optimization of Cyclic Redundancy-Check Codes with 24
   9  *                 and 32 Parity Bits}},
  10  * journal =      IEEE Transactions on Communication,
  11  * year =         {1993},
  12  * volume =       {41},
  13  * number =       {6},
  14  * pages =        {},
  15  * month =        {June},
  16  *}
  17  * Used by the iSCSI driver, possibly others, and derived from the
  18  * the iscsi-crc.c module of the linux-iscsi driver at
  19  * http://linux-iscsi.sourceforge.net.
  20  *
  21  * Following the example of lib/crc32, this function is intended to be
  22  * flexible and useful for all users.  Modules that currently have their
  23  * own crc32c, but hopefully may be able to use this one are:
  24  *  net/sctp (please add all your doco to here if you change to
  25  *            use this one!)
  26  *  <endoflist>
  27  *
  28  * Copyright (c) 2004 Cisco Systems, Inc.
  29  * Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
  30  *
  31  * This program is free software; you can redistribute it and/or modify it
  32  * under the terms of the GNU General Public License as published by the Free
  33  * Software Foundation; either version 2 of the License, or (at your option)
  34  * any later version.
  35  *
  36  */
  37
  38 #include <crypto/internal/hash.h>
  39 #include <linux/init.h>
  40 #include <linux/module.h>
  41 #include <linux/string.h>
  42 #include <linux/kernel.h>
  43 #include <linux/crc32.h>
  44
  45 #define CHKSUM_BLOCK_SIZE       1
  46 #define CHKSUM_DIGEST_SIZE      4
  47
  48 struct chksum_ctx {
  49         u32 key;
  50 };
  51
  52 struct chksum_desc_ctx {
  53         u32 crc;
  54 };
  55
  56 /*
  57  * Steps through buffer one byte at at time, calculates reflected
  58  * crc using table.
  59  */
  60
  61 static int chksum_init(struct shash_desc *desc)
  62 {
  63         struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
  64         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  65
  66         ctx->crc = mctx->key;
  67
  68         return 0;
  69 }
  70
  71 /*
  72  * Setting the seed allows arbitrary accumulators and flexible XOR policy
  73  * If your algorithm starts with ~0, then XOR with ~0 before you set
  74  * the seed.
  75  */
  76 static int chksum_setkey(struct crypto_shash *tfm, const u8 *key,
  77                          unsigned int keylen)
  78 {
  79         struct chksum_ctx *mctx = crypto_shash_ctx(tfm);
  80
  81         if (keylen != sizeof(mctx->key)) {
  82                 crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
  83                 return -EINVAL;
  84         }
  85         mctx->key = le32_to_cpu(*(__le32 *)key);
  86         return 0;
  87 }
  88
  89 static int chksum_update(struct shash_desc *desc, const u8 *data,
  90                          unsigned int length)
  91 {
  92         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  93
  94         ctx->crc = __crc32c_le(ctx->crc, data, length);
  95         return 0;
  96 }
  97
  98 static int chksum_final(struct shash_desc *desc, u8 *out)
  99 {
 100         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 101
 102         *(__le32 *)out = ~cpu_to_le32p(&ctx->crc);
 103         return 0;
 104 }
 105
 106 static int __chksum_finup(u32 *crcp, const u8 *data, unsigned int len, u8 *out)
 107 {
 108         *(__le32 *)out = ~cpu_to_le32(__crc32c_le(*crcp, data, len));
 109         return 0;
 110 }
 111
 112 static int chksum_finup(struct shash_desc *desc, const u8 *data,
 113                         unsigned int len, u8 *out)
 114 {
 115         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 116
 117         return __chksum_finup(&ctx->crc, data, len, out);
 118 }
 119
 120 static int chksum_digest(struct shash_desc *desc, const u8 *data,
 121                          unsigned int length, u8 *out)
 122 {
 123         struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
 124
 125         return __chksum_finup(&mctx->key, data, length, out);
 126 }
 127
 128 static int crc32c_cra_init(struct crypto_tfm *tfm)
 129 {
 130         struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
 131
 132         mctx->key = ~0;
 133         return 0;
 134 }
 135
 136 static struct shash_alg alg = {
 137         .digestsize             =       CHKSUM_DIGEST_SIZE,
 138         .setkey                 =       chksum_setkey,
 139         .init           =       chksum_init,
 140         .update         =       chksum_update,
 141         .final          =       chksum_final,
 142         .finup          =       chksum_finup,
 143         .digest         =       chksum_digest,
 144         .descsize               =       sizeof(struct chksum_desc_ctx),
 145         .base                   =       {
 146                 .cra_name               =       "crc32c",
 147                 .cra_driver_name        =       "crc32c-generic",
 148                 .cra_priority           =       100,
 149                 .cra_blocksize          =       CHKSUM_BLOCK_SIZE,
 150                 .cra_alignmask          =       3,
 151                 .cra_ctxsize            =       sizeof(struct chksum_ctx),
 152                 .cra_module             =       THIS_MODULE,
 153                 .cra_init               =       crc32c_cra_init,
 154         }
 155 };
 156
 157 static int __init crc32c_mod_init(void)
 158 {
 159         return crypto_register_shash(&alg);
 160 }
 161
 162 static void __exit crc32c_mod_fini(void)
 163 {
 164         crypto_unregister_shash(&alg);
 165 }
 166
 167 module_init(crc32c_mod_init);
 168 module_exit(crc32c_mod_fini);
 169
 170 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
 171 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
 172 MODULE_LICENSE("GPL");