/*
 * GHASH: digest algorithm for GCM (Galois/Counter Mode).
 *
 * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
 * Copyright (c) 2009 Intel Corp.
 *   Author: Huang Ying <ying.huang@intel.com>
 *
 * 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_list		= LIST_HEAD_INIT(ghash_alg.base.cra_list),
		.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");