[CRYPTO] eseqiv: Add Encrypted Sequence Number IV Generator

crypto_blkcipher-objs += blkcipher.o

obj-$(CONFIG_CRYPTO_BLKCIPHER) += crypto_blkcipher.o

obj-$(CONFIG_CRYPTO_BLKCIPHER) += chainiv.o

obj-$(CONFIG_CRYPTO_BLKCIPHER) += eseqiv.o

crypto_hash-objs := hash.o

obj-$(CONFIG_CRYPTO_HASH) += crypto_hash.o

/*

 * eseqiv: Encrypted Sequence Number IV Generator

 *

 * This generator generates an IV based on a sequence number by xoring it

 * with a salt and then encrypting it with the same key as used to encrypt

 * the plain text.  This algorithm requires that the block size be equal

 * to the IV size.  It is mainly useful for CBC.

 *

 * 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 <crypto/scatterwalk.h>

#include <linux/err.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/mm.h>

#include <linux/module.h>

#include <linux/random.h>

#include <linux/scatterlist.h>

#include <linux/spinlock.h>

#include <linux/string.h>

struct eseqiv_request_ctx {

	struct scatterlist src[2];

	struct scatterlist dst[2];

	char tail[];

};

struct eseqiv_ctx {

	spinlock_t lock;

	unsigned int reqoff;

	char salt[];

};

static void eseqiv_complete2(struct skcipher_givcrypt_request *req)

{

	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);

	struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);

	memcpy(req->giv, PTR_ALIGN((u8 *)reqctx->tail,

			 crypto_ablkcipher_alignmask(geniv) + 1),

	       crypto_ablkcipher_ivsize(geniv));

}

static void eseqiv_complete(struct crypto_async_request *base, int err)

{

	struct skcipher_givcrypt_request *req = base->data;

	if (err)

		goto out;

	eseqiv_complete2(req);

out:

	skcipher_givcrypt_complete(req, err);

}

static void eseqiv_chain(struct scatterlist *head, struct scatterlist *sg,

			 int chain)

{

	if (chain) {

		head->length += sg->length;

		sg = scatterwalk_sg_next(sg);

	}

	if (sg)

		scatterwalk_sg_chain(head, 2, sg);

	else

		sg_mark_end(head);

}

static int eseqiv_givencrypt(struct skcipher_givcrypt_request *req)

{

	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);

	struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);

	struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req);

	struct ablkcipher_request *subreq;

	crypto_completion_t complete;

	void *data;

	struct scatterlist *osrc, *odst;

	struct scatterlist *dst;

	struct page *srcp;

	struct page *dstp;

	u8 *giv;

	u8 *vsrc;

	u8 *vdst;

	__be64 seq;

	unsigned int ivsize;

	unsigned int len;

	int err;

	subreq = (void *)(reqctx->tail + ctx->reqoff);

	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));

	giv = req->giv;

	complete = req->creq.base.complete;

	data = req->creq.base.data;

	osrc = req->creq.src;

	odst = req->creq.dst;

	srcp = sg_page(osrc);

	dstp = sg_page(odst);

	vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + osrc->offset;

	vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + odst->offset;

	ivsize = crypto_ablkcipher_ivsize(geniv);

	if (vsrc != giv + ivsize && vdst != giv + ivsize) {

		giv = PTR_ALIGN((u8 *)reqctx->tail,

				crypto_ablkcipher_alignmask(geniv) + 1);

		complete = eseqiv_complete;

		data = req;

	}

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

					data);

	sg_init_table(reqctx->src, 2);

	sg_set_buf(reqctx->src, giv, ivsize);

	eseqiv_chain(reqctx->src, osrc, vsrc == giv + ivsize);

	dst = reqctx->src;

	if (osrc != odst) {

		sg_init_table(reqctx->dst, 2);

		sg_set_buf(reqctx->dst, giv, ivsize);

		eseqiv_chain(reqctx->dst, odst, vdst == giv + ivsize);

		dst = reqctx->dst;

	}

	ablkcipher_request_set_crypt(subreq, reqctx->src, dst,

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

	memcpy(req->creq.info, ctx->salt, ivsize);

	len = ivsize;

	if (ivsize > sizeof(u64)) {

		memset(req->giv, 0, ivsize - sizeof(u64));

		len = sizeof(u64);

	}

	seq = cpu_to_be64(req->seq);

	memcpy(req->giv + ivsize - len, &seq, len);

	err = crypto_ablkcipher_encrypt(subreq);

	if (err)

		goto out;

	eseqiv_complete2(req);

out:

	return err;

}

static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req)

{

	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);

	struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);

	spin_lock_bh(&ctx->lock);

	if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first)

		goto unlock;

	crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt;

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

unlock:

	spin_unlock_bh(&ctx->lock);

	return eseqiv_givencrypt(req);

}

static int eseqiv_init(struct crypto_tfm *tfm)

{

	struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);

	struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);

	unsigned long alignmask;

	unsigned int reqsize;

	spin_lock_init(&ctx->lock);

	alignmask = crypto_tfm_ctx_alignment() - 1;

	reqsize = sizeof(struct eseqiv_request_ctx);

	if (alignmask & reqsize) {

		alignmask &= reqsize;

		alignmask--;

	}

	alignmask = ~alignmask;

	alignmask &= crypto_ablkcipher_alignmask(geniv);

	reqsize += alignmask;

	reqsize += crypto_ablkcipher_ivsize(geniv);

	reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment());

	ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx);

	tfm->crt_ablkcipher.reqsize = reqsize +

				      sizeof(struct ablkcipher_request);

	return skcipher_geniv_init(tfm);

}

static struct crypto_template eseqiv_tmpl;

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

{

	struct crypto_instance *inst;

	int err;

	inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0);

	if (IS_ERR(inst))

		goto out;

	err = -EINVAL;

	if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize)

		goto free_inst;

	inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first;

	inst->alg.cra_init = eseqiv_init;

	inst->alg.cra_exit = skcipher_geniv_exit;

	inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx);

	inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;

out:

	return inst;

free_inst:

	skcipher_geniv_free(inst);

	inst = ERR_PTR(err);

	goto out;

}

static struct crypto_template eseqiv_tmpl = {

	.name = "eseqiv",

	.alloc = eseqiv_alloc,

	.free = skcipher_geniv_free,

	.module = THIS_MODULE,

};

static int __init eseqiv_module_init(void)

{

	return crypto_register_template(&eseqiv_tmpl);

}

static void __exit eseqiv_module_exit(void)

{

	crypto_unregister_template(&eseqiv_tmpl);

}

module_init(eseqiv_module_init);

module_exit(eseqiv_module_exit);

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator");