// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * seqiv: Sequence Number IV Generator
 *
 * This generator generates an IV based on a sequence number by xoring it
 * with a salt.  This algorithm is mainly useful for CTR and similar modes.
 *
 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
 */

#include <crypto/internal/geniv.h>
#include <crypto/scatterwalk.h>
#include <crypto/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>

static void seqiv_aead_encrypt_complete2(struct aead_request *req, int err)
{
	struct aead_request *subreq = aead_request_ctx(req);
	struct crypto_aead *geniv;

	if (err == -EINPROGRESS || err == -EBUSY)
		return;

	if (err)
		goto out;

	geniv = crypto_aead_reqtfm(req);
	memcpy(req->iv, subreq->iv, crypto_aead_ivsize(geniv));

out:
	kfree_sensitive(subreq->iv);
}

static void seqiv_aead_encrypt_complete(struct crypto_async_request *base,
					int err)
{
	struct aead_request *req = base->data;

	seqiv_aead_encrypt_complete2(req, err);
	aead_request_complete(req, err);
}

static int seqiv_aead_encrypt(struct aead_request *req)
{
	struct crypto_aead *geniv = crypto_aead_reqtfm(req);
	struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
	struct aead_request *subreq = aead_request_ctx(req);
	crypto_completion_t compl;
	void *data;
	u8 *info;
	unsigned int ivsize = 8;
	int err;

	if (req->cryptlen < ivsize)
		return -EINVAL;

	aead_request_set_tfm(subreq, ctx->child);

	compl = req->base.complete;
	data = req->base.data;
	info = req->iv;

	if (req->src != req->dst) {
		SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);

		skcipher_request_set_sync_tfm(nreq, ctx->sknull);
		skcipher_request_set_callback(nreq, req->base.flags,
					      NULL, NULL);
		skcipher_request_set_crypt(nreq, req->src, req->dst,
					   req->assoclen + req->cryptlen,
					   NULL);

		err = crypto_skcipher_encrypt(nreq);
		if (err)
			return err;
	}

	if (unlikely(!IS_ALIGNED((unsigned long)info,
				 crypto_aead_alignmask(geniv) + 1))) {
		info = kmemdup(req->iv, ivsize, req->base.flags &
			       CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL :
			       GFP_ATOMIC);
		if (!info)
			return -ENOMEM;

		compl = seqiv_aead_encrypt_complete;
		data = req;
	}

	aead_request_set_callback(subreq, req->base.flags, compl, data);
	aead_request_set_crypt(subreq, req->dst, req->dst,
			       req->cryptlen - ivsize, info);
	aead_request_set_ad(subreq, req->assoclen + ivsize);

	crypto_xor(info, ctx->salt, ivsize);
	scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);

	err = crypto_aead_encrypt(subreq);
	if (unlikely(info != req->iv))
		seqiv_aead_encrypt_complete2(req, err);
	return err;
}

static int seqiv_aead_decrypt(struct aead_request *req)
{
	struct crypto_aead *geniv = crypto_aead_reqtfm(req);
	struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
	struct aead_request *subreq = aead_request_ctx(req);
	crypto_completion_t compl;
	void *data;
	unsigned int ivsize = 8;

	if (req->cryptlen < ivsize + crypto_aead_authsize(geniv))
		return -EINVAL;

	aead_request_set_tfm(subreq, ctx->child);

	compl = req->base.complete;
	data = req->base.data;

	aead_request_set_callback(subreq, req->base.flags, compl, data);
	aead_request_set_crypt(subreq, req->src, req->dst,
			       req->cryptlen - ivsize, req->iv);
	aead_request_set_ad(subreq, req->assoclen + ivsize);

	scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);

	return crypto_aead_decrypt(subreq);
}

static int seqiv_aead_create(struct crypto_template *tmpl, struct rtattr **tb)
{
	struct aead_instance *inst;
	int err;

	inst = aead_geniv_alloc(tmpl, tb);

	if (IS_ERR(inst))
		return PTR_ERR(inst);

	err = -EINVAL;
	if (inst->alg.ivsize != sizeof(u64))
		goto free_inst;

	inst->alg.encrypt = seqiv_aead_encrypt;
	inst->alg.decrypt = seqiv_aead_decrypt;

	inst->alg.init = aead_init_geniv;
	inst->alg.exit = aead_exit_geniv;

	inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
	inst->alg.base.cra_ctxsize += inst->alg.ivsize;

	err = aead_register_instance(tmpl, inst);
	if (err) {
free_inst:
		inst->free(inst);
	}
	return err;
}

static struct crypto_template seqiv_tmpl = {
	.name = "seqiv",
	.create = seqiv_aead_create,
	.module = THIS_MODULE,
};

static int __init seqiv_module_init(void)
{
	return crypto_register_template(&seqiv_tmpl);
}

static void __exit seqiv_module_exit(void)
{
	crypto_unregister_template(&seqiv_tmpl);
}

subsys_initcall(seqiv_module_init);
module_exit(seqiv_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Sequence Number IV Generator");
MODULE_ALIAS_CRYPTO("seqiv");