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// SPDX-License-Identifier: GPL-2.0
/*
* OFB: Output FeedBack mode
*
* Copyright (C) 2018 ARM Limited or its affiliates.
* All rights reserved.
*
* Based loosely on public domain code gleaned from libtomcrypt
* (https://github.com/libtom/libtomcrypt).
*/
#include <crypto/algapi.h>
#include <crypto/internal/skcipher.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_ofb_ctx {
struct crypto_cipher *child;
int cnt;
};
static int crypto_ofb_setkey(struct crypto_skcipher *parent, const u8 *key,
unsigned int keylen)
{
struct crypto_ofb_ctx *ctx = crypto_skcipher_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_skcipher_get_flags(parent) &
CRYPTO_TFM_REQ_MASK);
err = crypto_cipher_setkey(child, key, keylen);
crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
CRYPTO_TFM_RES_MASK);
return err;
}
static int crypto_ofb_encrypt_segment(struct crypto_ofb_ctx *ctx,
struct skcipher_walk *walk,
struct crypto_cipher *tfm)
{
int bsize = crypto_cipher_blocksize(tfm);
int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
u8 *iv = walk->iv;
do {
if (ctx->cnt == bsize) {
if (nbytes < bsize)
break;
crypto_cipher_encrypt_one(tfm, iv, iv);
ctx->cnt = 0;
}
*dst = *src ^ iv[ctx->cnt];
src++;
dst++;
ctx->cnt++;
} while (--nbytes);
return nbytes;
}
static int crypto_ofb_encrypt(struct skcipher_request *req)
{
struct skcipher_walk walk;
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
unsigned int bsize;
struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
struct crypto_cipher *child = ctx->child;
int ret = 0;
bsize = crypto_cipher_blocksize(child);
ctx->cnt = bsize;
ret = skcipher_walk_virt(&walk, req, false);
while (walk.nbytes) {
ret = crypto_ofb_encrypt_segment(ctx, &walk, child);
ret = skcipher_walk_done(&walk, ret);
}
return ret;
}
/* OFB encrypt and decrypt are identical */
static int crypto_ofb_decrypt(struct skcipher_request *req)
{
return crypto_ofb_encrypt(req);
}
static int crypto_ofb_init_tfm(struct crypto_skcipher *tfm)
{
struct skcipher_instance *inst = skcipher_alg_instance(tfm);
struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
struct crypto_cipher *cipher;
cipher = crypto_spawn_cipher(spawn);
if (IS_ERR(cipher))
return PTR_ERR(cipher);
ctx->child = cipher;
return 0;
}
static void crypto_ofb_exit_tfm(struct crypto_skcipher *tfm)
{
struct crypto_ofb_ctx *ctx = crypto_skcipher_ctx(tfm);
crypto_free_cipher(ctx->child);
}
static void crypto_ofb_free(struct skcipher_instance *inst)
{
crypto_drop_skcipher(skcipher_instance_ctx(inst));
kfree(inst);
}
static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb)
{
struct skcipher_instance *inst;
struct crypto_attr_type *algt;
struct crypto_spawn *spawn;
struct crypto_alg *alg;
u32 mask;
int err;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER);
if (err)
return err;
inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
if (!inst)
return -ENOMEM;
algt = crypto_get_attr_type(tb);
err = PTR_ERR(algt);
if (IS_ERR(algt))
goto err_free_inst;
mask = CRYPTO_ALG_TYPE_MASK |
crypto_requires_off(algt->type, algt->mask,
CRYPTO_ALG_NEED_FALLBACK);
alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);
err = PTR_ERR(alg);
if (IS_ERR(alg))
goto err_free_inst;
spawn = skcipher_instance_ctx(inst);
err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
CRYPTO_ALG_TYPE_MASK);
crypto_mod_put(alg);
if (err)
goto err_free_inst;
err = crypto_inst_setname(skcipher_crypto_instance(inst), "ofb", alg);
if (err)
goto err_drop_spawn;
inst->alg.base.cra_priority = alg->cra_priority;
inst->alg.base.cra_blocksize = alg->cra_blocksize;
inst->alg.base.cra_alignmask = alg->cra_alignmask;
/* We access the data as u32s when xoring. */
inst->alg.base.cra_alignmask |= __alignof__(u32) - 1;
inst->alg.ivsize = alg->cra_blocksize;
inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;
inst->alg.base.cra_ctxsize = sizeof(struct crypto_ofb_ctx);
inst->alg.init = crypto_ofb_init_tfm;
inst->alg.exit = crypto_ofb_exit_tfm;
inst->alg.setkey = crypto_ofb_setkey;
inst->alg.encrypt = crypto_ofb_encrypt;
inst->alg.decrypt = crypto_ofb_decrypt;
inst->free = crypto_ofb_free;
err = skcipher_register_instance(tmpl, inst);
if (err)
goto err_drop_spawn;
out:
return err;
err_drop_spawn:
crypto_drop_spawn(spawn);
err_free_inst:
kfree(inst);
goto out;
}
static struct crypto_template crypto_ofb_tmpl = {
.name = "ofb",
.create = crypto_ofb_create,
.module = THIS_MODULE,
};
static int __init crypto_ofb_module_init(void)
{
return crypto_register_template(&crypto_ofb_tmpl);
}
static void __exit crypto_ofb_module_exit(void)
{
crypto_unregister_template(&crypto_ofb_tmpl);
}
module_init(crypto_ofb_module_init);
module_exit(crypto_ofb_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("OFB block cipher algorithm");
MODULE_ALIAS_CRYPTO("ofb");
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