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
48 struct chksum_ctx {
49 u32 key;
50 };
51
52 struct 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
chksum_init(struct shash_desc * desc)61 static 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 */
chksum_setkey(struct crypto_shash * tfm,const u8 * key,unsigned int keylen)76 static 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
chksum_update(struct shash_desc * desc,const u8 * data,unsigned int length)89 static 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
chksum_final(struct shash_desc * desc,u8 * out)98 static 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
__chksum_finup(u32 * crcp,const u8 * data,unsigned int len,u8 * out)106 static 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
chksum_finup(struct shash_desc * desc,const u8 * data,unsigned int len,u8 * out)112 static 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
chksum_digest(struct shash_desc * desc,const u8 * data,unsigned int length,u8 * out)120 static 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
crc32c_cra_init(struct crypto_tfm * tfm)128 static 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
136 static 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
crc32c_mod_init(void)157 static int __init crc32c_mod_init(void)
158 {
159 return crypto_register_shash(&alg);
160 }
161
crc32c_mod_fini(void)162 static void __exit crc32c_mod_fini(void)
163 {
164 crypto_unregister_shash(&alg);
165 }
166
167 module_init(crc32c_mod_init);
168 module_exit(crc32c_mod_fini);
169
170 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
171 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
172 MODULE_LICENSE("GPL");
173 MODULE_ALIAS_CRYPTO("crc32c");
174 MODULE_ALIAS_CRYPTO("crc32c-generic");
175