// SPDX-License-Identifier: GPL-2.0
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/*
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* OFB: Output FeedBack mode
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*
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* Copyright (C) 2018 ARM Limited or its affiliates.
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* All rights reserved.
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*/
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#include <crypto/algapi.h>
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#include <crypto/internal/cipher.h>
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#include <crypto/internal/skcipher.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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static int crypto_ofb_crypt(struct skcipher_request *req)
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{
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
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struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
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const unsigned int bsize = crypto_cipher_blocksize(cipher);
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struct skcipher_walk walk;
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int err;
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err = skcipher_walk_virt(&walk, req, false);
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while (walk.nbytes >= bsize) {
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const u8 *src = walk.src.virt.addr;
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u8 *dst = walk.dst.virt.addr;
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u8 * const iv = walk.iv;
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unsigned int nbytes = walk.nbytes;
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do {
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crypto_cipher_encrypt_one(cipher, iv, iv);
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crypto_xor_cpy(dst, src, iv, bsize);
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dst += bsize;
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src += bsize;
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} while ((nbytes -= bsize) >= bsize);
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err = skcipher_walk_done(&walk, nbytes);
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}
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if (walk.nbytes) {
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crypto_cipher_encrypt_one(cipher, walk.iv, walk.iv);
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crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr, walk.iv,
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walk.nbytes);
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err = skcipher_walk_done(&walk, 0);
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}
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return err;
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}
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static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb)
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{
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struct skcipher_instance *inst;
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struct crypto_alg *alg;
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int err;
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inst = skcipher_alloc_instance_simple(tmpl, tb);
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if (IS_ERR(inst))
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return PTR_ERR(inst);
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alg = skcipher_ialg_simple(inst);
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/* OFB mode is a stream cipher. */
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inst->alg.base.cra_blocksize = 1;
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/*
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* To simplify the implementation, configure the skcipher walk to only
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* give a partial block at the very end, never earlier.
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*/
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inst->alg.chunksize = alg->cra_blocksize;
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inst->alg.encrypt = crypto_ofb_crypt;
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inst->alg.decrypt = crypto_ofb_crypt;
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err = skcipher_register_instance(tmpl, inst);
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if (err)
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inst->free(inst);
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return err;
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}
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static struct crypto_template crypto_ofb_tmpl = {
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.name = "ofb",
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.create = crypto_ofb_create,
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.module = THIS_MODULE,
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};
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static int __init crypto_ofb_module_init(void)
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{
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return crypto_register_template(&crypto_ofb_tmpl);
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}
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static void __exit crypto_ofb_module_exit(void)
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{
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crypto_unregister_template(&crypto_ofb_tmpl);
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}
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subsys_initcall(crypto_ofb_module_init);
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module_exit(crypto_ofb_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("OFB block cipher mode of operation");
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MODULE_ALIAS_CRYPTO("ofb");
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MODULE_IMPORT_NS(CRYPTO_INTERNAL);
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