// 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, &alg); if (IS_ERR(inst)) return PTR_ERR(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); crypto_mod_put(alg); 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");