crypto/crc32c_generic.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 <asm/unaligned.h>
  39 #include <crypto/internal/hash.h>
  40 #include <linux/init.h>
  41 #include <linux/module.h>
  42 #include <linux/string.h>
  43 #include <linux/kernel.h>
  44 #include <linux/crc32.h>
  45
  46 #define CHKSUM_BLOCK_SIZE       1
  47 #define CHKSUM_DIGEST_SIZE      4
  48
  49 struct chksum_ctx {
  50         u32 key;
  51 };
  52
  53 struct chksum_desc_ctx {
  54         u32 crc;
  55 };
  56
  57 /*
  58  * Steps through buffer one byte at at time, calculates reflected
  59  * crc using table.
  60  */
  61
  62 static int chksum_init(struct shash_desc *desc)
  63 {
  64         struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
  65         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  66
  67         ctx->crc = mctx->key;
  68
  69         return 0;
  70 }
  71
  72 /*
  73  * Setting the seed allows arbitrary accumulators and flexible XOR policy
  74  * If your algorithm starts with ~0, then XOR with ~0 before you set
  75  * the seed.
  76  */
  77 static int chksum_setkey(struct crypto_shash *tfm, const u8 *key,
  78                          unsigned int keylen)
  79 {
  80         struct chksum_ctx *mctx = crypto_shash_ctx(tfm);
  81
  82         if (keylen != sizeof(mctx->key)) {
  83                 crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
  84                 return -EINVAL;
  85         }
  86         mctx->key = get_unaligned_le32(key);
  87         return 0;
  88 }
  89
  90 static int chksum_update(struct shash_desc *desc, const u8 *data,
  91                          unsigned int length)
  92 {
  93         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  94
  95         ctx->crc = __crc32c_le(ctx->crc, data, length);
  96         return 0;
  97 }
  98
  99 static int chksum_final(struct shash_desc *desc, u8 *out)
 100 {
 101         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 102
 103         put_unaligned_le32(~ctx->crc, out);
 104         return 0;
 105 }
 106
 107 static int __chksum_finup(u32 *crcp, const u8 *data, unsigned int len, u8 *out)
 108 {
 109         put_unaligned_le32(~__crc32c_le(*crcp, data, len), out);
 110         return 0;
 111 }
 112
 113 static int chksum_finup(struct shash_desc *desc, const u8 *data,
 114                         unsigned int len, u8 *out)
 115 {
 116         struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 117
 118         return __chksum_finup(&ctx->crc, data, len, out);
 119 }
 120
 121 static int chksum_digest(struct shash_desc *desc, const u8 *data,
 122                          unsigned int length, u8 *out)
 123 {
 124         struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
 125
 126         return __chksum_finup(&mctx->key, data, length, out);
 127 }
 128
 129 static int crc32c_cra_init(struct crypto_tfm *tfm)
 130 {
 131         struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
 132
 133         mctx->key = ~0;
 134         return 0;
 135 }
 136
 137 static struct shash_alg alg = {
 138         .digestsize             =       CHKSUM_DIGEST_SIZE,
 139         .setkey                 =       chksum_setkey,
 140         .init           =       chksum_init,
 141         .update         =       chksum_update,
 142         .final          =       chksum_final,
 143         .finup          =       chksum_finup,
 144         .digest         =       chksum_digest,
 145         .descsize               =       sizeof(struct chksum_desc_ctx),
 146         .base                   =       {
 147                 .cra_name               =       "crc32c",
 148                 .cra_driver_name        =       "crc32c-generic",
 149                 .cra_priority           =       100,
 150                 .cra_flags              =       CRYPTO_ALG_OPTIONAL_KEY,
 151                 .cra_blocksize          =       CHKSUM_BLOCK_SIZE,
 152                 .cra_ctxsize            =       sizeof(struct chksum_ctx),
 153                 .cra_module             =       THIS_MODULE,
 154                 .cra_init               =       crc32c_cra_init,
 155         }
 156 };
 157
 158 static int __init crc32c_mod_init(void)
 159 {
 160         return crypto_register_shash(&alg);
 161 }
 162
 163 static void __exit crc32c_mod_fini(void)
 164 {
 165         crypto_unregister_shash(&alg);
 166 }
 167
 168 module_init(crc32c_mod_init);
 169 module_exit(crc32c_mod_fini);
 170
 171 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
 172 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
 173 MODULE_LICENSE("GPL");
 174 MODULE_ALIAS_CRYPTO("crc32c");
 175 MODULE_ALIAS_CRYPTO("crc32c-generic");