root/crypto/crc32c.c

/* 
 * Cryptographic API.
 *
 * CRC32C chksum
 *
 * This module file is a wrapper to invoke the lib/crc32c routines.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option) 
 * any later version.
 *
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/crypto.h>
#include <linux/crc32c.h>
#include <asm/byteorder.h>

#define CHKSUM_BLOCK_SIZE       32
#define CHKSUM_DIGEST_SIZE      4

struct chksum_ctx {
        u32 crc;
};

/*
 * Steps through buffer one byte at at time, calculates reflected 
 * crc using table.
 */

static void chksum_init(void *ctx)
{
        struct chksum_ctx *mctx = ctx;

        mctx->crc = ~(u32)0;                    /* common usage */
}

/*
 * Setting the seed allows arbitrary accumulators and flexible XOR policy
 * If your algorithm starts with ~0, then XOR with ~0 before you set
 * the seed.
 */
static int chksum_setkey(void *ctx, const u8 *key, unsigned int keylen,
                          u32 *flags)
{
        struct chksum_ctx *mctx = ctx;

        if (keylen != sizeof(mctx->crc)) {
                if (flags)
                        *flags = CRYPTO_TFM_RES_BAD_KEY_LEN;
                return -EINVAL;
        }
        mctx->crc = __cpu_to_le32(*(u32 *)key);
        return 0;
}

static void chksum_update(void *ctx, const u8 *data, unsigned int length)
{
        struct chksum_ctx *mctx = ctx;
        u32 mcrc;

        mcrc = crc32c(mctx->crc, data, (size_t)length);

        mctx->crc = mcrc;
}

static void chksum_final(void *ctx, u8 *out)
{
        struct chksum_ctx *mctx = ctx;
        u32 mcrc = (mctx->crc ^ ~(u32)0);
        
        *(u32 *)out = __le32_to_cpu(mcrc);
}

static struct crypto_alg alg = {
        .cra_name       =       "crc32c",
        .cra_flags      =       CRYPTO_ALG_TYPE_DIGEST,
        .cra_blocksize  =       CHKSUM_BLOCK_SIZE,
        .cra_ctxsize    =       sizeof(struct chksum_ctx),
        .cra_module     =       THIS_MODULE,
        .cra_list       =       LIST_HEAD_INIT(alg.cra_list),
        .cra_u          =       {
                .digest = {
                         .dia_digestsize=       CHKSUM_DIGEST_SIZE,
                         .dia_setkey    =       chksum_setkey,
                         .dia_init      =       chksum_init,
                         .dia_update    =       chksum_update,
                         .dia_final     =       chksum_final
                 }
        }
};

static int __init init(void)
{
        return crypto_register_alg(&alg);
}

static void __exit fini(void)
{
        crypto_unregister_alg(&alg);
}

module_init(init);
module_exit(fini);

MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
MODULE_LICENSE("GPL");