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