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![Ard Biesheuvel](/assets/img/avatar_default.png)
The cipher routines in the crypto API are mostly intended for templates implementing skcipher modes generically in software, and shouldn't be used outside of the crypto subsystem. So move the prototypes and all related definitions to a new header file under include/crypto/internal. Also, let's use the new module namespace feature to move the symbol exports into a new namespace CRYPTO_INTERNAL. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
254 lines
6.2 KiB
C
254 lines
6.2 KiB
C
//SPDX-License-Identifier: GPL-2.0
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/*
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* CFB: Cipher FeedBack mode
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*
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* Copyright (c) 2018 James.Bottomley@HansenPartnership.com
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*
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* CFB is a stream cipher mode which is layered on to a block
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* encryption scheme. It works very much like a one time pad where
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* the pad is generated initially from the encrypted IV and then
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* subsequently from the encrypted previous block of ciphertext. The
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* pad is XOR'd into the plain text to get the final ciphertext.
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*
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* The scheme of CFB is best described by wikipedia:
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*
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* https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#CFB
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*
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* Note that since the pad for both encryption and decryption is
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* generated by an encryption operation, CFB never uses the block
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* decryption function.
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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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#include <linux/string.h>
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static unsigned int crypto_cfb_bsize(struct crypto_skcipher *tfm)
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{
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return crypto_cipher_blocksize(skcipher_cipher_simple(tfm));
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}
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static void crypto_cfb_encrypt_one(struct crypto_skcipher *tfm,
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const u8 *src, u8 *dst)
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{
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crypto_cipher_encrypt_one(skcipher_cipher_simple(tfm), dst, src);
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}
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/* final encrypt and decrypt is the same */
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static void crypto_cfb_final(struct skcipher_walk *walk,
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struct crypto_skcipher *tfm)
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{
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const unsigned long alignmask = crypto_skcipher_alignmask(tfm);
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u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
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u8 *stream = PTR_ALIGN(tmp + 0, alignmask + 1);
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u8 *src = walk->src.virt.addr;
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u8 *dst = walk->dst.virt.addr;
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u8 *iv = walk->iv;
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unsigned int nbytes = walk->nbytes;
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crypto_cfb_encrypt_one(tfm, iv, stream);
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crypto_xor_cpy(dst, stream, src, nbytes);
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}
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static int crypto_cfb_encrypt_segment(struct skcipher_walk *walk,
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struct crypto_skcipher *tfm)
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{
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const unsigned int bsize = crypto_cfb_bsize(tfm);
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unsigned int nbytes = walk->nbytes;
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u8 *src = walk->src.virt.addr;
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u8 *dst = walk->dst.virt.addr;
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u8 *iv = walk->iv;
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do {
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crypto_cfb_encrypt_one(tfm, iv, dst);
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crypto_xor(dst, src, bsize);
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iv = dst;
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src += bsize;
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dst += bsize;
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} while ((nbytes -= bsize) >= bsize);
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memcpy(walk->iv, iv, bsize);
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return nbytes;
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}
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static int crypto_cfb_encrypt_inplace(struct skcipher_walk *walk,
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struct crypto_skcipher *tfm)
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{
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const unsigned int bsize = crypto_cfb_bsize(tfm);
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unsigned int nbytes = walk->nbytes;
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u8 *src = walk->src.virt.addr;
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u8 *iv = walk->iv;
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u8 tmp[MAX_CIPHER_BLOCKSIZE];
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do {
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crypto_cfb_encrypt_one(tfm, iv, tmp);
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crypto_xor(src, tmp, bsize);
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iv = src;
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src += bsize;
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} while ((nbytes -= bsize) >= bsize);
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memcpy(walk->iv, iv, bsize);
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return nbytes;
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}
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static int crypto_cfb_encrypt(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 skcipher_walk walk;
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unsigned int bsize = crypto_cfb_bsize(tfm);
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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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if (walk.src.virt.addr == walk.dst.virt.addr)
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err = crypto_cfb_encrypt_inplace(&walk, tfm);
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else
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err = crypto_cfb_encrypt_segment(&walk, tfm);
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err = skcipher_walk_done(&walk, err);
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}
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if (walk.nbytes) {
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crypto_cfb_final(&walk, tfm);
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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_cfb_decrypt_segment(struct skcipher_walk *walk,
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struct crypto_skcipher *tfm)
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{
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const unsigned int bsize = crypto_cfb_bsize(tfm);
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unsigned int nbytes = walk->nbytes;
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u8 *src = walk->src.virt.addr;
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u8 *dst = walk->dst.virt.addr;
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u8 *iv = walk->iv;
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do {
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crypto_cfb_encrypt_one(tfm, iv, dst);
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crypto_xor(dst, src, bsize);
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iv = src;
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src += bsize;
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dst += bsize;
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} while ((nbytes -= bsize) >= bsize);
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memcpy(walk->iv, iv, bsize);
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return nbytes;
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}
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static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
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struct crypto_skcipher *tfm)
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{
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const unsigned int bsize = crypto_cfb_bsize(tfm);
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unsigned int nbytes = walk->nbytes;
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u8 *src = walk->src.virt.addr;
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u8 * const iv = walk->iv;
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u8 tmp[MAX_CIPHER_BLOCKSIZE];
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do {
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crypto_cfb_encrypt_one(tfm, iv, tmp);
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memcpy(iv, src, bsize);
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crypto_xor(src, tmp, bsize);
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src += bsize;
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} while ((nbytes -= bsize) >= bsize);
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return nbytes;
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}
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static int crypto_cfb_decrypt_blocks(struct skcipher_walk *walk,
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struct crypto_skcipher *tfm)
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{
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if (walk->src.virt.addr == walk->dst.virt.addr)
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return crypto_cfb_decrypt_inplace(walk, tfm);
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else
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return crypto_cfb_decrypt_segment(walk, tfm);
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}
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static int crypto_cfb_decrypt(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 skcipher_walk walk;
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const unsigned int bsize = crypto_cfb_bsize(tfm);
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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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err = crypto_cfb_decrypt_blocks(&walk, tfm);
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err = skcipher_walk_done(&walk, err);
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}
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if (walk.nbytes) {
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crypto_cfb_final(&walk, tfm);
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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_cfb_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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/* CFB 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_cfb_encrypt;
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inst->alg.decrypt = crypto_cfb_decrypt;
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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_cfb_tmpl = {
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.name = "cfb",
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.create = crypto_cfb_create,
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.module = THIS_MODULE,
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};
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static int __init crypto_cfb_module_init(void)
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{
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return crypto_register_template(&crypto_cfb_tmpl);
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}
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static void __exit crypto_cfb_module_exit(void)
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{
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crypto_unregister_template(&crypto_cfb_tmpl);
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}
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subsys_initcall(crypto_cfb_module_init);
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module_exit(crypto_cfb_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("CFB block cipher mode of operation");
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MODULE_ALIAS_CRYPTO("cfb");
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MODULE_IMPORT_NS(CRYPTO_INTERNAL);
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