1 /* 2 * Cryptographic API. 3 * 4 * CRC32C chksum 5 * 6 * This module file is a wrapper to invoke the lib/crc32c routines. 7 * 8 * This program is free software; you can redistribute it and/or modify it 9 * under the terms of the GNU General Public License as published by the Free 10 * Software Foundation; either version 2 of the License, or (at your option) 11 * any later version. 12 * 13 */ 14 #include <linux/init.h> 15 #include <linux/module.h> 16 #include <linux/string.h> 17 #include <linux/crypto.h> 18 #include <linux/crc32c.h> 19 #include <linux/kernel.h> 20 21 #define CHKSUM_BLOCK_SIZE 32 22 #define CHKSUM_DIGEST_SIZE 4 23 24 struct chksum_ctx { 25 u32 crc; 26 u32 key; 27 }; 28 29 /* 30 * Steps through buffer one byte at at time, calculates reflected 31 * crc using table. 32 */ 33 34 static void chksum_init(struct crypto_tfm *tfm) 35 { 36 struct chksum_ctx *mctx = crypto_tfm_ctx(tfm); 37 38 mctx->crc = mctx->key; 39 } 40 41 /* 42 * Setting the seed allows arbitrary accumulators and flexible XOR policy 43 * If your algorithm starts with ~0, then XOR with ~0 before you set 44 * the seed. 45 */ 46 static int chksum_setkey(struct crypto_tfm *tfm, const u8 *key, 47 unsigned int keylen) 48 { 49 struct chksum_ctx *mctx = crypto_tfm_ctx(tfm); 50 51 if (keylen != sizeof(mctx->crc)) { 52 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN; 53 return -EINVAL; 54 } 55 mctx->key = le32_to_cpu(*(__le32 *)key); 56 return 0; 57 } 58 59 static void chksum_update(struct crypto_tfm *tfm, const u8 *data, 60 unsigned int length) 61 { 62 struct chksum_ctx *mctx = crypto_tfm_ctx(tfm); 63 64 mctx->crc = crc32c(mctx->crc, data, length); 65 } 66 67 static void chksum_final(struct crypto_tfm *tfm, u8 *out) 68 { 69 struct chksum_ctx *mctx = crypto_tfm_ctx(tfm); 70 71 *(__le32 *)out = ~cpu_to_le32(mctx->crc); 72 } 73 74 static int crc32c_cra_init(struct crypto_tfm *tfm) 75 { 76 struct chksum_ctx *mctx = crypto_tfm_ctx(tfm); 77 78 mctx->key = ~0; 79 return 0; 80 } 81 82 static struct crypto_alg alg = { 83 .cra_name = "crc32c", 84 .cra_flags = CRYPTO_ALG_TYPE_DIGEST, 85 .cra_blocksize = CHKSUM_BLOCK_SIZE, 86 .cra_ctxsize = sizeof(struct chksum_ctx), 87 .cra_module = THIS_MODULE, 88 .cra_list = LIST_HEAD_INIT(alg.cra_list), 89 .cra_init = crc32c_cra_init, 90 .cra_u = { 91 .digest = { 92 .dia_digestsize= CHKSUM_DIGEST_SIZE, 93 .dia_setkey = chksum_setkey, 94 .dia_init = chksum_init, 95 .dia_update = chksum_update, 96 .dia_final = chksum_final 97 } 98 } 99 }; 100 101 static int __init init(void) 102 { 103 return crypto_register_alg(&alg); 104 } 105 106 static void __exit fini(void) 107 { 108 crypto_unregister_alg(&alg); 109 } 110 111 module_init(init); 112 module_exit(fini); 113 114 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>"); 115 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c"); 116 MODULE_LICENSE("GPL"); 117