Root/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 <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("crc32c");
174MODULE_SOFTDEP("pre: crc32c");
175

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