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
49struct chksum_ctx {
50 u32 key;
51};
52
53struct 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
62static 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 */
77static 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
90static 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
99static 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
107static 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
113static 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
121static 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
129static 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
137static 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
158static int __init crc32c_mod_init(void)
159{
160 return crypto_register_shash(&alg);
161}
162
163static void __exit crc32c_mod_fini(void)
164{
165 crypto_unregister_shash(&alg);
166}
167
168module_init(crc32c_mod_init);
169module_exit(crc32c_mod_fini);
170
171MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
172MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
173MODULE_LICENSE("GPL");
174MODULE_ALIAS_CRYPTO("crc32c");
175MODULE_ALIAS_CRYPTO("crc32c-generic");
176