1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Cryptographic API.
  4 *
  5 * CRC32C chksum
  6 *
  7 *@Article{castagnoli-crc,
  8 * author =       { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
  9 * title =        {{Optimization of Cyclic Redundancy-Check Codes with 24
 10 *                 and 32 Parity Bits}},
 11 * journal =      IEEE Transactions on Communication,
 12 * year =         {1993},
 13 * volume =       {41},
 14 * number =       {6},
 15 * pages =        {},
 16 * month =        {June},
 17 *}
 18 * Used by the iSCSI driver, possibly others, and derived from
 19 * the iscsi-crc.c module of the linux-iscsi driver at
 20 * http://linux-iscsi.sourceforge.net.
 21 *
 22 * Following the example of lib/crc32, this function is intended to be
 23 * flexible and useful for all users.  Modules that currently have their
 24 * own crc32c, but hopefully may be able to use this one are:
 25 *  net/sctp (please add all your doco to here if you change to
 26 *            use this one!)
 27 *  <endoflist>
 28 *
 29 * Copyright (c) 2004 Cisco Systems, Inc.
 30 * Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
 31 */
 32
 33#include <asm/unaligned.h>
 34#include <crypto/internal/hash.h>
 35#include <linux/init.h>
 36#include <linux/module.h>
 37#include <linux/string.h>
 38#include <linux/kernel.h>
 39#include <linux/crc32.h>
 40
 41#define CHKSUM_BLOCK_SIZE	1
 42#define CHKSUM_DIGEST_SIZE	4
 43
 44struct chksum_ctx {
 45	u32 key;
 46};
 47
 48struct chksum_desc_ctx {
 49	u32 crc;
 50};
 51
 52/*
 53 * Steps through buffer one byte at a time, calculates reflected
 54 * crc using table.
 55 */
 56
 57static int chksum_init(struct shash_desc *desc)
 58{
 59	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
 60	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 61
 62	ctx->crc = mctx->key;
 63
 64	return 0;
 65}
 66
 67/*
 68 * Setting the seed allows arbitrary accumulators and flexible XOR policy
 69 * If your algorithm starts with ~0, then XOR with ~0 before you set
 70 * the seed.
 71 */
 72static int chksum_setkey(struct crypto_shash *tfm, const u8 *key,
 73			 unsigned int keylen)
 74{
 75	struct chksum_ctx *mctx = crypto_shash_ctx(tfm);
 76
 77	if (keylen != sizeof(mctx->key))
 78		return -EINVAL;
 79	mctx->key = get_unaligned_le32(key);
 80	return 0;
 81}
 82
 83static int chksum_update(struct shash_desc *desc, const u8 *data,
 84			 unsigned int length)
 85{
 86	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 87
 88	ctx->crc = __crc32c_le(ctx->crc, data, length);
 89	return 0;
 90}
 91
 92static int chksum_final(struct shash_desc *desc, u8 *out)
 93{
 94	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 95
 96	put_unaligned_le32(~ctx->crc, out);
 97	return 0;
 98}
 99
100static int __chksum_finup(u32 *crcp, const u8 *data, unsigned int len, u8 *out)
101{
102	put_unaligned_le32(~__crc32c_le(*crcp, data, len), out);
103	return 0;
104}
105
106static int chksum_finup(struct shash_desc *desc, const u8 *data,
107			unsigned int len, u8 *out)
108{
109	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
110
111	return __chksum_finup(&ctx->crc, data, len, out);
112}
113
114static int chksum_digest(struct shash_desc *desc, const u8 *data,
115			 unsigned int length, u8 *out)
116{
117	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
118
119	return __chksum_finup(&mctx->key, data, length, out);
120}
121
122static int crc32c_cra_init(struct crypto_tfm *tfm)
123{
124	struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
125
126	mctx->key = ~0;
127	return 0;
128}
129
130static struct shash_alg alg = {
131	.digestsize		=	CHKSUM_DIGEST_SIZE,
132	.setkey			=	chksum_setkey,
133	.init		=	chksum_init,
134	.update		=	chksum_update,
135	.final		=	chksum_final,
136	.finup		=	chksum_finup,
137	.digest		=	chksum_digest,
138	.descsize		=	sizeof(struct chksum_desc_ctx),
139	.base			=	{
140		.cra_name		=	"crc32c",
141		.cra_driver_name	=	"crc32c-generic",
142		.cra_priority		=	100,
143		.cra_flags		=	CRYPTO_ALG_OPTIONAL_KEY,
144		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
145		.cra_ctxsize		=	sizeof(struct chksum_ctx),
146		.cra_module		=	THIS_MODULE,
147		.cra_init		=	crc32c_cra_init,
148	}
149};
150
151static int __init crc32c_mod_init(void)
152{
153	return crypto_register_shash(&alg);
154}
155
156static void __exit crc32c_mod_fini(void)
157{
158	crypto_unregister_shash(&alg);
159}
160
161subsys_initcall(crc32c_mod_init);
162module_exit(crc32c_mod_fini);
163
164MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
165MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
166MODULE_LICENSE("GPL");
167MODULE_ALIAS_CRYPTO("crc32c");
168MODULE_ALIAS_CRYPTO("crc32c-generic");