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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 <linux/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(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(*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
140 .base.cra_name = "crc32c",
141 .base.cra_driver_name = "crc32c-lib",
142 .base.cra_priority = 100,
143 .base.cra_flags = CRYPTO_ALG_OPTIONAL_KEY,
144 .base.cra_blocksize = CHKSUM_BLOCK_SIZE,
145 .base.cra_ctxsize = sizeof(struct chksum_ctx),
146 .base.cra_module = THIS_MODULE,
147 .base.cra_init = crc32c_cra_init,
148};
149
150static int __init crc32c_mod_init(void)
151{
152 return crypto_register_shash(&alg);
153}
154
155static void __exit crc32c_mod_fini(void)
156{
157 crypto_unregister_shash(&alg);
158}
159
160module_init(crc32c_mod_init);
161module_exit(crc32c_mod_fini);
162
163MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
164MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
165MODULE_LICENSE("GPL");
166MODULE_ALIAS_CRYPTO("crc32c");