// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * PCBC: Propagating Cipher Block Chaining mode
 *
 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * Derived from cbc.c
 * - Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
 */

#include <crypto/algapi.h>
#include <crypto/internal/cipher.h>
#include <crypto/internal/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

static int crypto_pcbc_encrypt_segment(struct skcipher_request *req,
                                       struct skcipher_walk *walk,
                                       struct crypto_cipher *tfm)
{
        int bsize = crypto_cipher_blocksize(tfm);
        const u8 *src = walk->src.virt.addr;
        unsigned int nbytes = walk->nbytes;
        u8 *dst = walk->dst.virt.addr;
        u8 * const iv = walk->iv;

        do {
                crypto_xor(iv, src, bsize);
                crypto_cipher_encrypt_one(tfm, dst, iv);
                crypto_xor_cpy(iv, dst, src, bsize);

                src += bsize;
                dst += bsize;
        } while ((nbytes -= bsize) >= bsize);

        return nbytes;
}

static int crypto_pcbc_encrypt_inplace(struct skcipher_request *req,
                                       struct skcipher_walk *walk,
                                       struct crypto_cipher *tfm)
{
        int bsize = crypto_cipher_blocksize(tfm);
        unsigned int nbytes = walk->nbytes;
        u8 *dst = walk->dst.virt.addr;
        u8 * const iv = walk->iv;
        u8 tmpbuf[MAX_CIPHER_BLOCKSIZE];

        do {
                memcpy(tmpbuf, dst, bsize);
                crypto_xor(iv, dst, bsize);
                crypto_cipher_encrypt_one(tfm, dst, iv);
                crypto_xor_cpy(iv, tmpbuf, dst, bsize);

                dst += bsize;
        } while ((nbytes -= bsize) >= bsize);

        return nbytes;
}

static int crypto_pcbc_encrypt(struct skcipher_request *req)
{
        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
        struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
        struct skcipher_walk walk;
        unsigned int nbytes;
        int err;

        err = skcipher_walk_virt(&walk, req, false);

        while (walk.nbytes) {
                if (walk.src.virt.addr == walk.dst.virt.addr)
                        nbytes = crypto_pcbc_encrypt_inplace(req, &walk,
                                                             cipher);
                else
                        nbytes = crypto_pcbc_encrypt_segment(req, &walk,
                                                             cipher);
                err = skcipher_walk_done(&walk, nbytes);
        }

        return err;
}

static int crypto_pcbc_decrypt_segment(struct skcipher_request *req,
                                       struct skcipher_walk *walk,
                                       struct crypto_cipher *tfm)
{
        int bsize = crypto_cipher_blocksize(tfm);
        const u8 *src = walk->src.virt.addr;
        unsigned int nbytes = walk->nbytes;
        u8 *dst = walk->dst.virt.addr;
        u8 * const iv = walk->iv;

        do {
                crypto_cipher_decrypt_one(tfm, dst, src);
                crypto_xor(dst, iv, bsize);
                crypto_xor_cpy(iv, dst, src, bsize);

                src += bsize;
                dst += bsize;
        } while ((nbytes -= bsize) >= bsize);

        return nbytes;
}

static int crypto_pcbc_decrypt_inplace(struct skcipher_request *req,
                                       struct skcipher_walk *walk,
                                       struct crypto_cipher *tfm)
{
        int bsize = crypto_cipher_blocksize(tfm);
        unsigned int nbytes = walk->nbytes;
        u8 *dst = walk->dst.virt.addr;
        u8 * const iv = walk->iv;
        u8 tmpbuf[MAX_CIPHER_BLOCKSIZE] __aligned(__alignof__(u32));

        do {
                memcpy(tmpbuf, dst, bsize);
                crypto_cipher_decrypt_one(tfm, dst, dst);
                crypto_xor(dst, iv, bsize);
                crypto_xor_cpy(iv, dst, tmpbuf, bsize);

                dst += bsize;
        } while ((nbytes -= bsize) >= bsize);

        return nbytes;
}

static int crypto_pcbc_decrypt(struct skcipher_request *req)
{
        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
        struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
        struct skcipher_walk walk;
        unsigned int nbytes;
        int err;

        err = skcipher_walk_virt(&walk, req, false);

        while (walk.nbytes) {
                if (walk.src.virt.addr == walk.dst.virt.addr)
                        nbytes = crypto_pcbc_decrypt_inplace(req, &walk,
                                                             cipher);
                else
                        nbytes = crypto_pcbc_decrypt_segment(req, &walk,
                                                             cipher);
                err = skcipher_walk_done(&walk, nbytes);
        }

        return err;
}

static int crypto_pcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
{
        struct skcipher_instance *inst;
        int err;

        inst = skcipher_alloc_instance_simple(tmpl, tb);
        if (IS_ERR(inst))
                return PTR_ERR(inst);

        inst->alg.encrypt = crypto_pcbc_encrypt;
        inst->alg.decrypt = crypto_pcbc_decrypt;

        err = skcipher_register_instance(tmpl, inst);
        if (err)
                inst->free(inst);

        return err;
}

static struct crypto_template crypto_pcbc_tmpl = {
        .name = "pcbc",
        .create = crypto_pcbc_create,
        .module = THIS_MODULE,
};

static int __init crypto_pcbc_module_init(void)
{
        return crypto_register_template(&crypto_pcbc_tmpl);
}

static void __exit crypto_pcbc_module_exit(void)
{
        crypto_unregister_template(&crypto_pcbc_tmpl);
}

module_init(crypto_pcbc_module_init);
module_exit(crypto_pcbc_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("PCBC block cipher mode of operation");
MODULE_ALIAS_CRYPTO("pcbc");
MODULE_IMPORT_NS("CRYPTO_INTERNAL");