[CRYPTO] chainiv: Add chain IV generator

crypto_blkcipher-objs := ablkcipher.o

crypto_blkcipher-objs += blkcipher.o

obj-$(CONFIG_CRYPTO_BLKCIPHER) += crypto_blkcipher.o

obj-$(CONFIG_CRYPTO_BLKCIPHER) += chainiv.o

crypto_hash-objs := hash.o

obj-$(CONFIG_CRYPTO_HASH) += crypto_hash.o

/*

 * chainiv: Chain IV Generator

 *

 * Generate IVs simply be using the last block of the previous encryption.

 * This is mainly useful for CBC with a synchronous algorithm.

 *

 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>

 *

 * 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 <crypto/internal/skcipher.h>

#include <linux/err.h>

#include <linux/init.h>

#include <linux/module.h>

#include <linux/random.h>

#include <linux/spinlock.h>

#include <linux/string.h>

struct chainiv_ctx {

	spinlock_t lock;

	char iv[];

};

static int chainiv_givencrypt(struct skcipher_givcrypt_request *req)

{

	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);

	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);

	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);

	unsigned int ivsize;

	int err;

	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));

	ablkcipher_request_set_callback(subreq, req->creq.base.flags &

						~CRYPTO_TFM_REQ_MAY_SLEEP,

					req->creq.base.complete,

					req->creq.base.data);

	ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,

				     req->creq.nbytes, req->creq.info);

	spin_lock_bh(&ctx->lock);

	ivsize = crypto_ablkcipher_ivsize(geniv);

	memcpy(req->giv, ctx->iv, ivsize);

	memcpy(subreq->info, ctx->iv, ivsize);

	err = crypto_ablkcipher_encrypt(subreq);

	if (err)

		goto unlock;

	memcpy(ctx->iv, subreq->info, ivsize);

unlock:

	spin_unlock_bh(&ctx->lock);

	return err;

}

static int chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)

{

	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);

	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);

	spin_lock_bh(&ctx->lock);

	if (crypto_ablkcipher_crt(geniv)->givencrypt !=

	    chainiv_givencrypt_first)

		goto unlock;

	crypto_ablkcipher_crt(geniv)->givencrypt = chainiv_givencrypt;

	get_random_bytes(ctx->iv, crypto_ablkcipher_ivsize(geniv));

unlock:

	spin_unlock_bh(&ctx->lock);

	return chainiv_givencrypt(req);

}

static int chainiv_init(struct crypto_tfm *tfm)

{

	struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);

	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);

	spin_lock_init(&ctx->lock);

	tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);

	return skcipher_geniv_init(tfm);

}

static struct crypto_template chainiv_tmpl;

static struct crypto_instance *chainiv_alloc(struct rtattr **tb)

{

	struct crypto_instance *inst;

	inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0,

				    CRYPTO_ALG_ASYNC);

	if (IS_ERR(inst))

		goto out;

	inst->alg.cra_ablkcipher.givencrypt = chainiv_givencrypt_first;

	inst->alg.cra_init = chainiv_init;

	inst->alg.cra_exit = skcipher_geniv_exit;

	inst->alg.cra_ctxsize = sizeof(struct chainiv_ctx) +

				inst->alg.cra_ablkcipher.ivsize;

out:

	return inst;

}

static struct crypto_template chainiv_tmpl = {

	.name = "chainiv",

	.alloc = chainiv_alloc,

	.free = skcipher_geniv_free,

	.module = THIS_MODULE,

};

static int __init chainiv_module_init(void)

{

	return crypto_register_template(&chainiv_tmpl);

}

static void __exit chainiv_module_exit(void)

{

	crypto_unregister_template(&chainiv_tmpl);

}

module_init(chainiv_module_init);

module_exit(chainiv_module_exit);

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("Chain IV Generator");