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Linux/crypto/crc32c_generic.c

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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 the
 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 at 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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