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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.
- */
- #include <crypto/algapi.h>
- #include <crypto/internal/cipher.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");
- MODULE_IMPORT_NS(CRYPTO_INTERNAL);
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