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
44 struct chksum_ctx {
45 u32 key;
46 };
47
48 struct 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
57 static 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 */
72 static 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
83 static 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
92 static 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
100 static 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
106 static 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
114 static 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
122 static 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
130 static 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
151 static int __init crc32c_mod_init(void)
152 {
153 return crypto_register_shash(&alg);
154 }
155
156 static void __exit crc32c_mod_fini(void)
157 {
158 crypto_unregister_shash(&alg);
159 }
160
161 subsys_initcall(crc32c_mod_init);
162 module_exit(crc32c_mod_fini);
163
164 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
165 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
166 MODULE_LICENSE("GPL");
167 MODULE_ALIAS_CRYPTO("crc32c");
168 MODULE_ALIAS_CRYPTO("crc32c-generic");
169
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