crypto/cfb.c - linux - Git at Google

 //SPDX-License-Identifier: GPL-2.0
 /*
  * CFB: Cipher FeedBack mode
  *
  * Copyright (c) 2018 James.Bottomley@HansenPartnership.com
  *
  * CFB is a stream cipher mode which is layered on to a block
  * encryption scheme.  It works very much like a one time pad where
  * the pad is generated initially from the encrypted IV and then
  * subsequently from the encrypted previous block of ciphertext.  The
  * pad is XOR'd into the plain text to get the final ciphertext.
  *
  * The scheme of CFB is best described by wikipedia:
  *
  * https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#CFB
  *
  * Note that since the pad for both encryption and decryption is
  * generated by an encryption operation, CFB never uses the block
  * decryption function.
  */

 #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>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/types.h>

 struct crypto_cfb_ctx {
 	struct crypto_cipher *child;
 };

 static unsigned int crypto_cfb_bsize(struct crypto_skcipher *tfm)
 {
 	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
 	struct crypto_cipher *child = ctx->child;

 	return crypto_cipher_blocksize(child);
 }

 static void crypto_cfb_encrypt_one(struct crypto_skcipher *tfm,
 					  const u8 *src, u8 *dst)
 {
 	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);

 	crypto_cipher_encrypt_one(ctx->child, dst, src);
 }

 /* final encrypt and decrypt is the same */
 static void crypto_cfb_final(struct skcipher_walk *walk,
 			     struct crypto_skcipher *tfm)
 {
 	const unsigned long alignmask = crypto_skcipher_alignmask(tfm);
 	u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
 	u8 *stream = PTR_ALIGN(tmp + 0, alignmask + 1);
 	u8 *src = walk->src.virt.addr;
 	u8 *dst = walk->dst.virt.addr;
 	u8 *iv = walk->iv;
 	unsigned int nbytes = walk->nbytes;

 	crypto_cfb_encrypt_one(tfm, iv, stream);
 	crypto_xor_cpy(dst, stream, src, nbytes);
 }

 static int crypto_cfb_encrypt_segment(struct skcipher_walk *walk,
 				      struct crypto_skcipher *tfm)
 {
 	const unsigned int bsize = crypto_cfb_bsize(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
 	u8 *dst = walk->dst.virt.addr;
 	u8 *iv = walk->iv;

 	do {
 		crypto_cfb_encrypt_one(tfm, iv, dst);
 		crypto_xor(dst, src, bsize);
 		memcpy(iv, dst, bsize);

 		src += bsize;
 		dst += bsize;
 	} while ((nbytes -= bsize) >= bsize);

 	return nbytes;
 }

 static int crypto_cfb_encrypt_inplace(struct skcipher_walk *walk,
 				      struct crypto_skcipher *tfm)
 {
 	const unsigned int bsize = crypto_cfb_bsize(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
 	u8 *iv = walk->iv;
 	u8 tmp[MAX_CIPHER_BLOCKSIZE];

 	do {
 		crypto_cfb_encrypt_one(tfm, iv, tmp);
 		crypto_xor(src, tmp, bsize);
 		iv = src;

 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);

 	memcpy(walk->iv, iv, bsize);

 	return nbytes;
 }

 static int crypto_cfb_encrypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct skcipher_walk walk;
 	unsigned int bsize = crypto_cfb_bsize(tfm);
 	int err;

 	err = skcipher_walk_virt(&walk, req, false);

 	while (walk.nbytes >= bsize) {
 		if (walk.src.virt.addr == walk.dst.virt.addr)
 			err = crypto_cfb_encrypt_inplace(&walk, tfm);
 		else
 			err = crypto_cfb_encrypt_segment(&walk, tfm);
 		err = skcipher_walk_done(&walk, err);
 	}

 	if (walk.nbytes) {
 		crypto_cfb_final(&walk, tfm);
 		err = skcipher_walk_done(&walk, 0);
 	}

 	return err;
 }

 static int crypto_cfb_decrypt_segment(struct skcipher_walk *walk,
 				      struct crypto_skcipher *tfm)
 {
 	const unsigned int bsize = crypto_cfb_bsize(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
 	u8 *dst = walk->dst.virt.addr;
 	u8 *iv = walk->iv;

 	do {
 		crypto_cfb_encrypt_one(tfm, iv, dst);
 		crypto_xor(dst, src, bsize);
 		iv = src;

 		src += bsize;
 		dst += bsize;
 	} while ((nbytes -= bsize) >= bsize);

 	memcpy(walk->iv, iv, bsize);

 	return nbytes;
 }

 static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
 				      struct crypto_skcipher *tfm)
 {
 	const unsigned int bsize = crypto_cfb_bsize(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
 	u8 *iv = walk->iv;
 	u8 tmp[MAX_CIPHER_BLOCKSIZE];

 	do {
 		crypto_cfb_encrypt_one(tfm, iv, tmp);
 		memcpy(iv, src, bsize);
 		crypto_xor(src, tmp, bsize);
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);

 	memcpy(walk->iv, iv, bsize);

 	return nbytes;
 }

 static int crypto_cfb_decrypt_blocks(struct skcipher_walk *walk,
 				     struct crypto_skcipher *tfm)
 {
 	if (walk->src.virt.addr == walk->dst.virt.addr)
 		return crypto_cfb_decrypt_inplace(walk, tfm);
 	else
 		return crypto_cfb_decrypt_segment(walk, tfm);
 }

 static int crypto_cfb_setkey(struct crypto_skcipher *parent, const u8 *key,
 			     unsigned int keylen)
 {
 	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(parent);
 	struct crypto_cipher *child = ctx->child;
 	int err;

 	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 	crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) &
 				       CRYPTO_TFM_REQ_MASK);
 	err = crypto_cipher_setkey(child, key, keylen);
 	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
 					  CRYPTO_TFM_RES_MASK);
 	return err;
 }

 static int crypto_cfb_decrypt(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct skcipher_walk walk;
 	const unsigned int bsize = crypto_cfb_bsize(tfm);
 	int err;

 	err = skcipher_walk_virt(&walk, req, false);

 	while (walk.nbytes >= bsize) {
 		err = crypto_cfb_decrypt_blocks(&walk, tfm);
 		err = skcipher_walk_done(&walk, err);
 	}

 	if (walk.nbytes) {
 		crypto_cfb_final(&walk, tfm);
 		err = skcipher_walk_done(&walk, 0);
 	}

 	return err;
 }

 static int crypto_cfb_init_tfm(struct crypto_skcipher *tfm)
 {
 	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 	struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
 	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
 	struct crypto_cipher *cipher;

 	cipher = crypto_spawn_cipher(spawn);
 	if (IS_ERR(cipher))
 		return PTR_ERR(cipher);

 	ctx->child = cipher;
 	return 0;
 }

 static void crypto_cfb_exit_tfm(struct crypto_skcipher *tfm)
 {
 	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);

 	crypto_free_cipher(ctx->child);
 }

 static void crypto_cfb_free(struct skcipher_instance *inst)
 {
 	crypto_drop_skcipher(skcipher_instance_ctx(inst));
 	kfree(inst);
 }

 static int crypto_cfb_create(struct crypto_template *tmpl, struct rtattr **tb)
 {
 	struct skcipher_instance *inst;
 	struct crypto_attr_type *algt;
 	struct crypto_spawn *spawn;
 	struct crypto_alg *alg;
 	u32 mask;
 	int err;

 	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER);
 	if (err)
 		return err;

 	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 	if (!inst)
 		return -ENOMEM;

 	algt = crypto_get_attr_type(tb);
 	err = PTR_ERR(algt);
 	if (IS_ERR(algt))
 		goto err_free_inst;

 	mask = CRYPTO_ALG_TYPE_MASK |
 		crypto_requires_off(algt->type, algt->mask,
 				    CRYPTO_ALG_NEED_FALLBACK);

 	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);
 	err = PTR_ERR(alg);
 	if (IS_ERR(alg))
 		goto err_free_inst;

 	spawn = skcipher_instance_ctx(inst);
 	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
 				CRYPTO_ALG_TYPE_MASK);
 	if (err)
 		goto err_put_alg;

 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cfb", alg);
 	if (err)
 		goto err_drop_spawn;

 	inst->alg.base.cra_priority = alg->cra_priority;
 	/* we're a stream cipher independend of the crypto cra_blocksize */
 	inst->alg.base.cra_blocksize = 1;
 	inst->alg.base.cra_alignmask = alg->cra_alignmask;

 	inst->alg.ivsize = alg->cra_blocksize;
 	inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
 	inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;

 	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cfb_ctx);

 	inst->alg.init = crypto_cfb_init_tfm;
 	inst->alg.exit = crypto_cfb_exit_tfm;

 	inst->alg.setkey = crypto_cfb_setkey;
 	inst->alg.encrypt = crypto_cfb_encrypt;
 	inst->alg.decrypt = crypto_cfb_decrypt;

 	inst->free = crypto_cfb_free;

 	err = skcipher_register_instance(tmpl, inst);
 	if (err)
 		goto err_drop_spawn;
 	crypto_mod_put(alg);

 out:
 	return err;

 err_drop_spawn:
 	crypto_drop_spawn(spawn);
 err_put_alg:
 	crypto_mod_put(alg);
 err_free_inst:
 	kfree(inst);
 	goto out;
 }

 static struct crypto_template crypto_cfb_tmpl = {
 	.name = "cfb",
 	.create = crypto_cfb_create,
 	.module = THIS_MODULE,
 };

 static int __init crypto_cfb_module_init(void)
 {
 	return crypto_register_template(&crypto_cfb_tmpl);
 }

 static void __exit crypto_cfb_module_exit(void)
 {
 	crypto_unregister_template(&crypto_cfb_tmpl);
 }

 module_init(crypto_cfb_module_init);
 module_exit(crypto_cfb_module_exit);

 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("CFB block cipher algorithm");
 MODULE_ALIAS_CRYPTO("cfb");
	//SPDX-License-Identifier: GPL-2.0
	/*
	* CFB: Cipher FeedBack mode
	*
	* Copyright (c) 2018 James.Bottomley@HansenPartnership.com
	*
	* CFB is a stream cipher mode which is layered on to a block
	* encryption scheme. It works very much like a one time pad where
	* the pad is generated initially from the encrypted IV and then
	* subsequently from the encrypted previous block of ciphertext. The
	* pad is XOR'd into the plain text to get the final ciphertext.
	*
	* The scheme of CFB is best described by wikipedia:
	*
	* https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#CFB
	*
	* Note that since the pad for both encryption and decryption is
	* generated by an encryption operation, CFB never uses the block
	* decryption function.
	*/

	#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>
	#include <linux/slab.h>
	#include <linux/string.h>
	#include <linux/types.h>

	struct crypto_cfb_ctx {
	struct crypto_cipher *child;
	};

	static unsigned int crypto_cfb_bsize(struct crypto_skcipher *tfm)
	{
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_cipher *child = ctx->child;

	return crypto_cipher_blocksize(child);
	}

	static void crypto_cfb_encrypt_one(struct crypto_skcipher *tfm,
	const u8 src, u8 dst)
	{
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);

	crypto_cipher_encrypt_one(ctx->child, dst, src);
	}

	/* final encrypt and decrypt is the same */
	static void crypto_cfb_final(struct skcipher_walk *walk,
	struct crypto_skcipher *tfm)
	{
	const unsigned long alignmask = crypto_skcipher_alignmask(tfm);
	u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
	u8 *stream = PTR_ALIGN(tmp + 0, alignmask + 1);
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	u8 *iv = walk->iv;
	unsigned int nbytes = walk->nbytes;

	crypto_cfb_encrypt_one(tfm, iv, stream);
	crypto_xor_cpy(dst, stream, src, nbytes);
	}

	static int crypto_cfb_encrypt_segment(struct skcipher_walk *walk,
	struct crypto_skcipher *tfm)
	{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	u8 *iv = walk->iv;

	do {
	crypto_cfb_encrypt_one(tfm, iv, dst);
	crypto_xor(dst, src, bsize);
	memcpy(iv, dst, bsize);

	src += bsize;
	dst += bsize;
	} while ((nbytes -= bsize) >= bsize);

	return nbytes;
	}

	static int crypto_cfb_encrypt_inplace(struct skcipher_walk *walk,
	struct crypto_skcipher *tfm)
	{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *iv = walk->iv;
	u8 tmp[MAX_CIPHER_BLOCKSIZE];

	do {
	crypto_cfb_encrypt_one(tfm, iv, tmp);
	crypto_xor(src, tmp, bsize);
	iv = src;

	src += bsize;
	} while ((nbytes -= bsize) >= bsize);

	memcpy(walk->iv, iv, bsize);

	return nbytes;
	}

	static int crypto_cfb_encrypt(struct skcipher_request *req)
	{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct skcipher_walk walk;
	unsigned int bsize = crypto_cfb_bsize(tfm);
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while (walk.nbytes >= bsize) {
	if (walk.src.virt.addr == walk.dst.virt.addr)
	err = crypto_cfb_encrypt_inplace(&walk, tfm);
	else
	err = crypto_cfb_encrypt_segment(&walk, tfm);
	err = skcipher_walk_done(&walk, err);
	}

	if (walk.nbytes) {
	crypto_cfb_final(&walk, tfm);
	err = skcipher_walk_done(&walk, 0);
	}

	return err;
	}

	static int crypto_cfb_decrypt_segment(struct skcipher_walk *walk,
	struct crypto_skcipher *tfm)
	{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *dst = walk->dst.virt.addr;
	u8 *iv = walk->iv;

	do {
	crypto_cfb_encrypt_one(tfm, iv, dst);
	crypto_xor(dst, src, bsize);
	iv = src;

	src += bsize;
	dst += bsize;
	} while ((nbytes -= bsize) >= bsize);

	memcpy(walk->iv, iv, bsize);

	return nbytes;
	}

	static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
	struct crypto_skcipher *tfm)
	{
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	unsigned int nbytes = walk->nbytes;
	u8 *src = walk->src.virt.addr;
	u8 *iv = walk->iv;
	u8 tmp[MAX_CIPHER_BLOCKSIZE];

	do {
	crypto_cfb_encrypt_one(tfm, iv, tmp);
	memcpy(iv, src, bsize);
	crypto_xor(src, tmp, bsize);
	src += bsize;
	} while ((nbytes -= bsize) >= bsize);

	memcpy(walk->iv, iv, bsize);

	return nbytes;
	}

	static int crypto_cfb_decrypt_blocks(struct skcipher_walk *walk,
	struct crypto_skcipher *tfm)
	{
	if (walk->src.virt.addr == walk->dst.virt.addr)
	return crypto_cfb_decrypt_inplace(walk, tfm);
	else
	return crypto_cfb_decrypt_segment(walk, tfm);
	}

	static int crypto_cfb_setkey(struct crypto_skcipher parent, const u8 key,
	unsigned int keylen)
	{
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(parent);
	struct crypto_cipher *child = ctx->child;
	int err;

	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
	crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) &
	CRYPTO_TFM_REQ_MASK);
	err = crypto_cipher_setkey(child, key, keylen);
	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
	CRYPTO_TFM_RES_MASK);
	return err;
	}

	static int crypto_cfb_decrypt(struct skcipher_request *req)
	{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct skcipher_walk walk;
	const unsigned int bsize = crypto_cfb_bsize(tfm);
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while (walk.nbytes >= bsize) {
	err = crypto_cfb_decrypt_blocks(&walk, tfm);
	err = skcipher_walk_done(&walk, err);
	}

	if (walk.nbytes) {
	crypto_cfb_final(&walk, tfm);
	err = skcipher_walk_done(&walk, 0);
	}

	return err;
	}

	static int crypto_cfb_init_tfm(struct crypto_skcipher *tfm)
	{
	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
	struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);
	struct crypto_cipher *cipher;

	cipher = crypto_spawn_cipher(spawn);
	if (IS_ERR(cipher))
	return PTR_ERR(cipher);

	ctx->child = cipher;
	return 0;
	}

	static void crypto_cfb_exit_tfm(struct crypto_skcipher *tfm)
	{
	struct crypto_cfb_ctx *ctx = crypto_skcipher_ctx(tfm);

	crypto_free_cipher(ctx->child);
	}

	static void crypto_cfb_free(struct skcipher_instance *inst)
	{
	crypto_drop_skcipher(skcipher_instance_ctx(inst));
	kfree(inst);
	}

	static int crypto_cfb_create(struct crypto_template tmpl, struct rtattr *tb)
	{
	struct skcipher_instance *inst;
	struct crypto_attr_type *algt;
	struct crypto_spawn *spawn;
	struct crypto_alg *alg;
	u32 mask;
	int err;

	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER);
	if (err)
	return err;

	inst = kzalloc(sizeof(inst) + sizeof(spawn), GFP_KERNEL);
	if (!inst)
	return -ENOMEM;

	algt = crypto_get_attr_type(tb);
	err = PTR_ERR(algt);
	if (IS_ERR(algt))
	goto err_free_inst;

	mask = CRYPTO_ALG_TYPE_MASK \|
	crypto_requires_off(algt->type, algt->mask,
	CRYPTO_ALG_NEED_FALLBACK);

	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);
	err = PTR_ERR(alg);
	if (IS_ERR(alg))
	goto err_free_inst;

	spawn = skcipher_instance_ctx(inst);
	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
	CRYPTO_ALG_TYPE_MASK);
	if (err)
	goto err_put_alg;

	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cfb", alg);
	if (err)
	goto err_drop_spawn;

	inst->alg.base.cra_priority = alg->cra_priority;
	/* we're a stream cipher independend of the crypto cra_blocksize */
	inst->alg.base.cra_blocksize = 1;
	inst->alg.base.cra_alignmask = alg->cra_alignmask;

	inst->alg.ivsize = alg->cra_blocksize;
	inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
	inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;

	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cfb_ctx);

	inst->alg.init = crypto_cfb_init_tfm;
	inst->alg.exit = crypto_cfb_exit_tfm;

	inst->alg.setkey = crypto_cfb_setkey;
	inst->alg.encrypt = crypto_cfb_encrypt;
	inst->alg.decrypt = crypto_cfb_decrypt;

	inst->free = crypto_cfb_free;

	err = skcipher_register_instance(tmpl, inst);
	if (err)
	goto err_drop_spawn;
	crypto_mod_put(alg);

	out:
	return err;

	err_drop_spawn:
	crypto_drop_spawn(spawn);
	err_put_alg:
	crypto_mod_put(alg);
	err_free_inst:
	kfree(inst);
	goto out;
	}

	static struct crypto_template crypto_cfb_tmpl = {
	.name = "cfb",
	.create = crypto_cfb_create,
	.module = THIS_MODULE,
	};

	static int __init crypto_cfb_module_init(void)
	{
	return crypto_register_template(&crypto_cfb_tmpl);
	}

	static void __exit crypto_cfb_module_exit(void)
	{
	crypto_unregister_template(&crypto_cfb_tmpl);
	}

	module_init(crypto_cfb_module_init);
	module_exit(crypto_cfb_module_exit);

	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("CFB block cipher algorithm");
	MODULE_ALIAS_CRYPTO("cfb");