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
 48struct chksum_ctx {
 49	u32 key;
 50};
 51
 52struct 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
 61static 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 */
 76static 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
 89static 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
 98static 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
106static 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
112static 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
120static 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
128static 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
136static 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
157static int __init crc32c_mod_init(void)
158{
159	return crypto_register_shash(&alg);
160}
161
162static void __exit crc32c_mod_fini(void)
163{
164	crypto_unregister_shash(&alg);
165}
166
167module_init(crc32c_mod_init);
168module_exit(crc32c_mod_fini);
169
170MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
171MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
172MODULE_LICENSE("GPL");
173MODULE_ALIAS_CRYPTO("crc32c");
174MODULE_ALIAS_CRYPTO("crc32c-generic");