ghash-generic.c

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/*
 * GHASH: digest algorithm for GCM (Galois/Counter Mode).
 *
 * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <[email protected]>
 * Copyright (c) 2009 Intel Corp.
 *   Author: Huang Ying <[email protected]>
 *
 * The algorithm implementation is copied from gcm.c.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 */

#include <crypto/algapi.h>
#include <crypto/gf128mul.h>
#include <crypto/internal/hash.h>
#include <linux/crypto.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#define GHASH_BLOCK_SIZE    16
#define GHASH_DIGEST_SIZE   16

struct ghash_ctx {
    struct gf128mul_4k *gf128;
};

struct ghash_desc_ctx {
    u8 buffer[GHASH_BLOCK_SIZE];
    u32 bytes;
};

static int ghash_init(struct shash_desc *desc)
{
    struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);

    memset(dctx, 0, sizeof(*dctx));

    return 0;
}

static int ghash_setkey(struct crypto_shash *tfm,
            const u8 *key, unsigned int keylen)
{
    struct ghash_ctx *ctx = crypto_shash_ctx(tfm);

    if (keylen != GHASH_BLOCK_SIZE) {
        crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
        return -EINVAL;
    }

    if (ctx->gf128)
        gf128mul_free_4k(ctx->gf128);
    ctx->gf128 = gf128mul_init_4k_lle((be128 *)key);
    if (!ctx->gf128)
        return -ENOMEM;

    return 0;
}

static int ghash_update(struct shash_desc *desc,
             const u8 *src, unsigned int srclen)
{
    struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
    struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
    u8 *dst = dctx->buffer;

    if (!ctx->gf128)
        return -ENOKEY;

    if (dctx->bytes) {
        int n = min(srclen, dctx->bytes);
        u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes);

        dctx->bytes -= n;
        srclen -= n;

        while (n--)
            *pos++ ^= *src++;

        if (!dctx->bytes)
            gf128mul_4k_lle((be128 *)dst, ctx->gf128);
    }

    while (srclen >= GHASH_BLOCK_SIZE) {
        crypto_xor(dst, src, GHASH_BLOCK_SIZE);
        gf128mul_4k_lle((be128 *)dst, ctx->gf128);
        src += GHASH_BLOCK_SIZE;
        srclen -= GHASH_BLOCK_SIZE;
    }

    if (srclen) {
        dctx->bytes = GHASH_BLOCK_SIZE - srclen;
        while (srclen--)
            *dst++ ^= *src++;
    }

    return 0;
}

static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx)
{
    u8 *dst = dctx->buffer;

    if (dctx->bytes) {
        u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes);

        while (dctx->bytes--)
            *tmp++ ^= 0;

        gf128mul_4k_lle((be128 *)dst, ctx->gf128);
    }

    dctx->bytes = 0;
}

static int ghash_final(struct shash_desc *desc, u8 *dst)
{
    struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
    struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
    u8 *buf = dctx->buffer;

    if (!ctx->gf128)
        return -ENOKEY;

    ghash_flush(ctx, dctx);
    memcpy(dst, buf, GHASH_BLOCK_SIZE);

    return 0;
}

static void ghash_exit_tfm(struct crypto_tfm *tfm)
{
    struct ghash_ctx *ctx = crypto_tfm_ctx(tfm);
    if (ctx->gf128)
        gf128mul_free_4k(ctx->gf128);
}

static struct shash_alg ghash_alg = {
    .digestsize = GHASH_DIGEST_SIZE,
    .init       = ghash_init,
    .update     = ghash_update,
    .final      = ghash_final,
    .setkey     = ghash_setkey,
    .descsize   = sizeof(struct ghash_desc_ctx),
    .base       = {
        .cra_name       = "ghash",
        .cra_driver_name    = "ghash-generic",
        .cra_priority       = 100,
        .cra_flags      = CRYPTO_ALG_TYPE_SHASH,
        .cra_blocksize      = GHASH_BLOCK_SIZE,
        .cra_ctxsize        = sizeof(struct ghash_ctx),
        .cra_module     = THIS_MODULE,
        .cra_exit       = ghash_exit_tfm,
    },
};

static int __init ghash_mod_init(void)
{
    return crypto_register_shash(&ghash_alg);
}

static void __exit ghash_mod_exit(void)
{
    crypto_unregister_shash(&ghash_alg);
}

module_init(ghash_mod_init);
module_exit(ghash_mod_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("GHASH Message Digest Algorithm");
MODULE_ALIAS("ghash");