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/*

 * 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>

 *

 * 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/algapi.h>

#include <linux/err.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/scatterlist.h>

#include <linux/slab.h>

struct crypto_pcbc_ctx {

        struct crypto_cipher *child;

        void (*xor)(u8 *dst, const u8 *src, unsigned int bs);

};

static int crypto_pcbc_setkey(struct crypto_tfm *parent, const u8 *key,

                              unsigned int keylen)

{

        struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(parent);

        struct crypto_cipher *child = ctx->child;

        int err;

        crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);

        crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &

                                CRYPTO_TFM_REQ_MASK);

        err = crypto_cipher_setkey(child, key, keylen);

        crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &

                             CRYPTO_TFM_RES_MASK);

        return err;

}

static int crypto_pcbc_encrypt_segment(struct blkcipher_desc *desc,

                                       struct blkcipher_walk *walk,

                                       struct crypto_cipher *tfm,

                                       void (*xor)(u8 *, const u8 *,

                                                   unsigned int))

{

        void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =

                crypto_cipher_alg(tfm)->cia_encrypt;

        int bsize = crypto_cipher_blocksize(tfm);

        unsigned int nbytes = walk->nbytes;

        u8 *src = walk->src.virt.addr;

        u8 *dst = walk->dst.virt.addr;

        u8 *iv = walk->iv;

        do {

                xor(iv, src, bsize);

                fn(crypto_cipher_tfm(tfm), dst, iv);

                memcpy(iv, dst, bsize);

                xor(iv, src, bsize);

                src += bsize;

                dst += bsize;

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

        return nbytes;

}

static int crypto_pcbc_encrypt_inplace(struct blkcipher_desc *desc,

                                       struct blkcipher_walk *walk,

                                       struct crypto_cipher *tfm,

                                       void (*xor)(u8 *, const u8 *,

                                                   unsigned int))

{

        void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =

                crypto_cipher_alg(tfm)->cia_encrypt;

        int bsize = crypto_cipher_blocksize(tfm);

        unsigned int nbytes = walk->nbytes;

        u8 *src = walk->src.virt.addr;

        u8 *iv = walk->iv;

        u8 tmpbuf[bsize];

        do {

                memcpy(tmpbuf, src, bsize);

                xor(iv, tmpbuf, bsize);

                fn(crypto_cipher_tfm(tfm), src, iv);

                memcpy(iv, src, bsize);

                xor(iv, tmpbuf, bsize);

                src += bsize;

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

        memcpy(walk->iv, iv, bsize);

        return nbytes;

}

static int crypto_pcbc_encrypt(struct blkcipher_desc *desc,

                               struct scatterlist *dst, struct scatterlist *src,

                               unsigned int nbytes)

{

        struct blkcipher_walk walk;

        struct crypto_blkcipher *tfm = desc->tfm;

        struct crypto_pcbc_ctx *ctx = crypto_blkcipher_ctx(tfm);

        struct crypto_cipher *child = ctx->child;

        void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor;

        int err;

        blkcipher_walk_init(&walk, dst, src, nbytes);

        err = blkcipher_walk_virt(desc, &walk);

        while ((nbytes = walk.nbytes)) {

                if (walk.src.virt.addr == walk.dst.virt.addr)

                        nbytes = crypto_pcbc_encrypt_inplace(desc, &walk, child,

                                                             xor);

                else

                        nbytes = crypto_pcbc_encrypt_segment(desc, &walk, child,

                                                             xor);

                err = blkcipher_walk_done(desc, &walk, nbytes);

        }

        return err;

}

static int crypto_pcbc_decrypt_segment(struct blkcipher_desc *desc,

                                       struct blkcipher_walk *walk,

                                       struct crypto_cipher *tfm,

                                       void (*xor)(u8 *, const u8 *,

                                                   unsigned int))

{

        void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =

                crypto_cipher_alg(tfm)->cia_decrypt;

        int bsize = crypto_cipher_blocksize(tfm);

        unsigned int nbytes = walk->nbytes;

        u8 *src = walk->src.virt.addr;

        u8 *dst = walk->dst.virt.addr;

        u8 *iv = walk->iv;

        do {

                fn(crypto_cipher_tfm(tfm), dst, src);

                xor(dst, iv, bsize);

                memcpy(iv, src, bsize);

                xor(iv, dst, bsize);

                src += bsize;

                dst += bsize;

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

        memcpy(walk->iv, iv, bsize);

        return nbytes;

}

static int crypto_pcbc_decrypt_inplace(struct blkcipher_desc *desc,

                                       struct blkcipher_walk *walk,

                                       struct crypto_cipher *tfm,

                                       void (*xor)(u8 *, const u8 *,

                                                   unsigned int))

{

        void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =

                crypto_cipher_alg(tfm)->cia_decrypt;

        int bsize = crypto_cipher_blocksize(tfm);

        unsigned int nbytes = walk->nbytes;

        u8 *src = walk->src.virt.addr;

        u8 *iv = walk->iv;

        u8 tmpbuf[bsize];

        do {

                memcpy(tmpbuf, src, bsize);

                fn(crypto_cipher_tfm(tfm), src, src);

                xor(src, iv, bsize);

                memcpy(iv, tmpbuf, bsize);

                xor(iv, src, bsize);

                src += bsize;

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

        memcpy(walk->iv, iv, bsize);

        return nbytes;

}

static int crypto_pcbc_decrypt(struct blkcipher_desc *desc,

                               struct scatterlist *dst, struct scatterlist *src,

                               unsigned int nbytes)

{

        struct blkcipher_walk walk;

        struct crypto_blkcipher *tfm = desc->tfm;

        struct crypto_pcbc_ctx *ctx = crypto_blkcipher_ctx(tfm);

        struct crypto_cipher *child = ctx->child;

        void (*xor)(u8 *, const u8 *, unsigned int bs) = ctx->xor;

        int err;

        blkcipher_walk_init(&walk, dst, src, nbytes);

        err = blkcipher_walk_virt(desc, &walk);

        while ((nbytes = walk.nbytes)) {

                if (walk.src.virt.addr == walk.dst.virt.addr)

                        nbytes = crypto_pcbc_decrypt_inplace(desc, &walk, child,

                                                             xor);

                else

                        nbytes = crypto_pcbc_decrypt_segment(desc, &walk, child,

                                                             xor);

                err = blkcipher_walk_done(desc, &walk, nbytes);

        }

        return err;

}

static void xor_byte(u8 *a, const u8 *b, unsigned int bs)

{

        do {

                *a++ ^= *b++;

        } while (--bs);

}

static void xor_quad(u8 *dst, const u8 *src, unsigned int bs)

{

        u32 *a = (u32 *)dst;

        u32 *b = (u32 *)src;

        do {

                *a++ ^= *b++;

        } while ((bs -= 4));

}

static void xor_64(u8 *a, const u8 *b, unsigned int bs)

{

        ((u32 *)a)[0] ^= ((u32 *)b)[0];

        ((u32 *)a)[1] ^= ((u32 *)b)[1];

}

static void xor_128(u8 *a, const u8 *b, unsigned int bs)

{

        ((u32 *)a)[0] ^= ((u32 *)b)[0];

        ((u32 *)a)[1] ^= ((u32 *)b)[1];

        ((u32 *)a)[2] ^= ((u32 *)b)[2];

        ((u32 *)a)[3] ^= ((u32 *)b)[3];

}

static int crypto_pcbc_init_tfm(struct crypto_tfm *tfm)

{

        struct crypto_instance *inst = (void *)tfm->__crt_alg;

        struct crypto_spawn *spawn = crypto_instance_ctx(inst);

        struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(tfm);

        struct crypto_cipher *cipher;

        switch (crypto_tfm_alg_blocksize(tfm)) {

        case 8:

                ctx->xor = xor_64;

                break;

        case 16:

                ctx->xor = xor_128;

                break;

        default:

                if (crypto_tfm_alg_blocksize(tfm) % 4)

                        ctx->xor = xor_byte;

                else

                        ctx->xor = xor_quad;

        }

        cipher = crypto_spawn_cipher(spawn);

        if (IS_ERR(cipher))

                return PTR_ERR(cipher);

        ctx->child = cipher;

        return 0;

}

static void crypto_pcbc_exit_tfm(struct crypto_tfm *tfm)

{

        struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(tfm);

        crypto_free_cipher(ctx->child);

}

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

{

        struct crypto_instance *inst;

        struct crypto_alg *alg;

        int err;

        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);

        if (err)

                return ERR_PTR(err);

        alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,

                                  CRYPTO_ALG_TYPE_MASK);

        if (IS_ERR(alg))

                return ERR_PTR(PTR_ERR(alg));

        inst = crypto_alloc_instance("pcbc", alg);

        if (IS_ERR(inst))

                goto out_put_alg;

        inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;

        inst->alg.cra_priority = alg->cra_priority;

        inst->alg.cra_blocksize = alg->cra_blocksize;

        inst->alg.cra_alignmask = alg->cra_alignmask;

        inst->alg.cra_type = &crypto_blkcipher_type;

        if (!(alg->cra_blocksize % 4))

                inst->alg.cra_alignmask |= 3;

        inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;

        inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;

        inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;

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

        inst->alg.cra_init = crypto_pcbc_init_tfm;

        inst->alg.cra_exit = crypto_pcbc_exit_tfm;

        inst->alg.cra_blkcipher.setkey = crypto_pcbc_setkey;

        inst->alg.cra_blkcipher.encrypt = crypto_pcbc_encrypt;

        inst->alg.cra_blkcipher.decrypt = crypto_pcbc_decrypt;

out_put_alg:

        crypto_mod_put(alg);

        return inst;

}

static void crypto_pcbc_free(struct crypto_instance *inst)

{

        crypto_drop_spawn(crypto_instance_ctx(inst));

        kfree(inst);

}

static struct crypto_template crypto_pcbc_tmpl = {

        .name = "pcbc",

        .alloc = crypto_pcbc_alloc,

        .free = crypto_pcbc_free,

        .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 algorithm");