fs/crypto/keyinfo.c - linux-mtk - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * key management facility for FS encryption support.
  *
  * Copyright (C) 2015, Google, Inc.
  *
  * This contains encryption key functions.
  *
  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
  */

 #include <keys/user-type.h>
 #include <linux/scatterlist.h>
 #include <linux/ratelimit.h>
 #include <crypto/aes.h>
 #include <crypto/sha.h>
 #include <crypto/skcipher.h>
 #include "fscrypt_private.h"

 static struct crypto_shash *essiv_hash_tfm;

 /*
  * Key derivation function.  This generates the derived key by encrypting the
  * master key with AES-128-ECB using the inode's nonce as the AES key.
  *
  * The master key must be at least as long as the derived key.  If the master
  * key is longer, then only the first 'derived_keysize' bytes are used.
  */
 static int derive_key_aes(const u8 *master_key,
 			  const struct fscrypt_context *ctx,
 			  u8 *derived_key, unsigned int derived_keysize)
 {
 	int res = 0;
 	struct skcipher_request *req = NULL;
 	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist src_sg, dst_sg;
 	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);

 	if (IS_ERR(tfm)) {
 		res = PTR_ERR(tfm);
 		tfm = NULL;
 		goto out;
 	}
 	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
 	req = skcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		res = -ENOMEM;
 		goto out;
 	}
 	skcipher_request_set_callback(req,
 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 			crypto_req_done, &wait);
 	res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce));
 	if (res < 0)
 		goto out;

 	sg_init_one(&src_sg, master_key, derived_keysize);
 	sg_init_one(&dst_sg, derived_key, derived_keysize);
 	skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
 				   NULL);
 	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
 out:
 	skcipher_request_free(req);
 	crypto_free_skcipher(tfm);
 	return res;
 }

 /*
  * Search the current task's subscribed keyrings for a "logon" key with
  * description prefix:descriptor, and if found acquire a read lock on it and
  * return a pointer to its validated payload in *payload_ret.
  */
 static struct key *
 find_and_lock_process_key(const char *prefix,
 			  const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE],
 			  unsigned int min_keysize,
 			  const struct fscrypt_key **payload_ret)
 {
 	char *description;
 	struct key *key;
 	const struct user_key_payload *ukp;
 	const struct fscrypt_key *payload;

 	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
 				FS_KEY_DESCRIPTOR_SIZE, descriptor);
 	if (!description)
 		return ERR_PTR(-ENOMEM);

 	key = request_key(&key_type_logon, description, NULL);
 	kfree(description);
 	if (IS_ERR(key))
 		return key;

 	down_read(&key->sem);
 	ukp = user_key_payload_locked(key);

 	if (!ukp) /* was the key revoked before we acquired its semaphore? */
 		goto invalid;

 	payload = (const struct fscrypt_key *)ukp->data;

 	if (ukp->datalen != sizeof(struct fscrypt_key) ||
 	    payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) {
 		fscrypt_warn(NULL,
 			     "key with description '%s' has invalid payload",
 			     key->description);
 		goto invalid;
 	}

 	if (payload->size < min_keysize) {
 		fscrypt_warn(NULL,
 			     "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
 			     key->description, payload->size, min_keysize);
 		goto invalid;
 	}

 	*payload_ret = payload;
 	return key;

 invalid:
 	up_read(&key->sem);
 	key_put(key);
 	return ERR_PTR(-ENOKEY);
 }

 /* Find the master key, then derive the inode's actual encryption key */
 static int find_and_derive_key(const struct inode *inode,
 			       const struct fscrypt_context *ctx,
 			       u8 *derived_key, unsigned int derived_keysize)
 {
 	struct key *key;
 	const struct fscrypt_key *payload;
 	int err;

 	key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
 					ctx->master_key_descriptor,
 					derived_keysize, &payload);
 	if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
 		key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
 						ctx->master_key_descriptor,
 						derived_keysize, &payload);
 	}
 	if (IS_ERR(key))
 		return PTR_ERR(key);
 	err = derive_key_aes(payload->raw, ctx, derived_key, derived_keysize);
 	up_read(&key->sem);
 	key_put(key);
 	return err;
 }

 static struct fscrypt_mode {
 	const char *friendly_name;
 	const char *cipher_str;
 	int keysize;
 	bool logged_impl_name;
 } available_modes[] = {
 	[FS_ENCRYPTION_MODE_AES_256_XTS] = {
 		.friendly_name = "AES-256-XTS",
 		.cipher_str = "xts(aes)",
 		.keysize = 64,
 	},
 	[FS_ENCRYPTION_MODE_AES_256_CTS] = {
 		.friendly_name = "AES-256-CTS-CBC",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 32,
 	},
 	[FS_ENCRYPTION_MODE_AES_128_CBC] = {
 		.friendly_name = "AES-128-CBC",
 		.cipher_str = "cbc(aes)",
 		.keysize = 16,
 	},
 	[FS_ENCRYPTION_MODE_AES_128_CTS] = {
 		.friendly_name = "AES-128-CTS-CBC",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 16,
 	},
 };

 static struct fscrypt_mode *
 select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
 {
 	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
 		fscrypt_warn(inode->i_sb,
 			     "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)",
 			     inode->i_ino, ci->ci_data_mode,
 			     ci->ci_filename_mode);
 		return ERR_PTR(-EINVAL);
 	}

 	if (S_ISREG(inode->i_mode))
 		return &available_modes[ci->ci_data_mode];

 	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
 		return &available_modes[ci->ci_filename_mode];

 	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
 		  inode->i_ino, (inode->i_mode & S_IFMT));
 	return ERR_PTR(-EINVAL);
 }

 static void put_crypt_info(struct fscrypt_info *ci)
 {
 	if (!ci)
 		return;

 	crypto_free_skcipher(ci->ci_ctfm);
 	crypto_free_cipher(ci->ci_essiv_tfm);
 	kmem_cache_free(fscrypt_info_cachep, ci);
 }

 static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
 {
 	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);

 	/* init hash transform on demand */
 	if (unlikely(!tfm)) {
 		struct crypto_shash *prev_tfm;

 		tfm = crypto_alloc_shash("sha256", 0, 0);
 		if (IS_ERR(tfm)) {
 			fscrypt_warn(NULL,
 				     "error allocating SHA-256 transform: %ld",
 				     PTR_ERR(tfm));
 			return PTR_ERR(tfm);
 		}
 		prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
 		if (prev_tfm) {
 			crypto_free_shash(tfm);
 			tfm = prev_tfm;
 		}
 	}

 	{
 		SHASH_DESC_ON_STACK(desc, tfm);
 		desc->tfm = tfm;
 		desc->flags = 0;

 		return crypto_shash_digest(desc, key, keysize, salt);
 	}
 }

 static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
 				int keysize)
 {
 	int err;
 	struct crypto_cipher *essiv_tfm;
 	u8 salt[SHA256_DIGEST_SIZE];

 	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
 	if (IS_ERR(essiv_tfm))
 		return PTR_ERR(essiv_tfm);

 	ci->ci_essiv_tfm = essiv_tfm;

 	err = derive_essiv_salt(raw_key, keysize, salt);
 	if (err)
 		goto out;

 	/*
 	 * Using SHA256 to derive the salt/key will result in AES-256 being
 	 * used for IV generation. File contents encryption will still use the
 	 * configured keysize (AES-128) nevertheless.
 	 */
 	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
 	if (err)
 		goto out;

 out:
 	memzero_explicit(salt, sizeof(salt));
 	return err;
 }

 void __exit fscrypt_essiv_cleanup(void)
 {
 	crypto_free_shash(essiv_hash_tfm);
 }

 int fscrypt_get_encryption_info(struct inode *inode)
 {
 	struct fscrypt_info *crypt_info;
 	struct fscrypt_context ctx;
 	struct crypto_skcipher *ctfm;
 	struct fscrypt_mode *mode;
 	u8 *raw_key = NULL;
 	int res;

 	if (inode->i_crypt_info)
 		return 0;

 	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
 	if (res)
 		return res;

 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
 	if (res < 0) {
 		if (!fscrypt_dummy_context_enabled(inode) ||
 		    IS_ENCRYPTED(inode))
 			return res;
 		/* Fake up a context for an unencrypted directory */
 		memset(&ctx, 0, sizeof(ctx));
 		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
 		ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
 		ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
 		memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
 	} else if (res != sizeof(ctx)) {
 		return -EINVAL;
 	}

 	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
 		return -EINVAL;

 	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
 		return -EINVAL;

 	crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
 	if (!crypt_info)
 		return -ENOMEM;

 	crypt_info->ci_flags = ctx.flags;
 	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
 	crypt_info->ci_ctfm = NULL;
 	crypt_info->ci_essiv_tfm = NULL;
 	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
 				sizeof(crypt_info->ci_master_key));

 	mode = select_encryption_mode(crypt_info, inode);
 	if (IS_ERR(mode)) {
 		res = PTR_ERR(mode);
 		goto out;
 	}

 	/*
 	 * This cannot be a stack buffer because it is passed to the scatterlist
 	 * crypto API as part of key derivation.
 	 */
 	res = -ENOMEM;
 	raw_key = kmalloc(mode->keysize, GFP_NOFS);
 	if (!raw_key)
 		goto out;

 	res = find_and_derive_key(inode, &ctx, raw_key, mode->keysize);
 	if (res)
 		goto out;

 	ctfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
 	if (IS_ERR(ctfm)) {
 		res = PTR_ERR(ctfm);
 		fscrypt_warn(inode->i_sb,
 			     "error allocating '%s' transform for inode %lu: %d",
 			     mode->cipher_str, inode->i_ino, res);
 		goto out;
 	}
 	if (unlikely(!mode->logged_impl_name)) {
 		/*
 		 * fscrypt performance can vary greatly depending on which
 		 * crypto algorithm implementation is used.  Help people debug
 		 * performance problems by logging the ->cra_driver_name the
 		 * first time a mode is used.  Note that multiple threads can
 		 * race here, but it doesn't really matter.
 		 */
 		mode->logged_impl_name = true;
 		pr_info("fscrypt: %s using implementation \"%s\"\n",
 			mode->friendly_name,
 			crypto_skcipher_alg(ctfm)->base.cra_driver_name);
 	}
 	crypt_info->ci_ctfm = ctfm;
 	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
 	res = crypto_skcipher_setkey(ctfm, raw_key, mode->keysize);
 	if (res)
 		goto out;

 	if (S_ISREG(inode->i_mode) &&
 	    crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
 		res = init_essiv_generator(crypt_info, raw_key, mode->keysize);
 		if (res) {
 			fscrypt_warn(inode->i_sb,
 				     "error initializing ESSIV generator for inode %lu: %d",
 				     inode->i_ino, res);
 			goto out;
 		}
 	}
 	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
 		crypt_info = NULL;
 out:
 	if (res == -ENOKEY)
 		res = 0;
 	put_crypt_info(crypt_info);
 	kzfree(raw_key);
 	return res;
 }
 EXPORT_SYMBOL(fscrypt_get_encryption_info);

 void fscrypt_put_encryption_info(struct inode *inode)
 {
 	put_crypt_info(inode->i_crypt_info);
 	inode->i_crypt_info = NULL;
 }
 EXPORT_SYMBOL(fscrypt_put_encryption_info);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* key management facility for FS encryption support.
	*
	* Copyright (C) 2015, Google, Inc.
	*
	* This contains encryption key functions.
	*
	* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
	*/

	#include <keys/user-type.h>
	#include <linux/scatterlist.h>
	#include <linux/ratelimit.h>
	#include <crypto/aes.h>
	#include <crypto/sha.h>
	#include <crypto/skcipher.h>
	#include "fscrypt_private.h"

	static struct crypto_shash *essiv_hash_tfm;

	/*
	* Key derivation function. This generates the derived key by encrypting the
	* master key with AES-128-ECB using the inode's nonce as the AES key.
	*
	* The master key must be at least as long as the derived key. If the master
	* key is longer, then only the first 'derived_keysize' bytes are used.
	*/
	static int derive_key_aes(const u8 *master_key,
	const struct fscrypt_context *ctx,
	u8 *derived_key, unsigned int derived_keysize)
	{
	int res = 0;
	struct skcipher_request *req = NULL;
	DECLARE_CRYPTO_WAIT(wait);
	struct scatterlist src_sg, dst_sg;
	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);

	if (IS_ERR(tfm)) {
	res = PTR_ERR(tfm);
	tfm = NULL;
	goto out;
	}
	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
	req = skcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	res = -ENOMEM;
	goto out;
	}
	skcipher_request_set_callback(req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	crypto_req_done, &wait);
	res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce));
	if (res < 0)
	goto out;

	sg_init_one(&src_sg, master_key, derived_keysize);
	sg_init_one(&dst_sg, derived_key, derived_keysize);
	skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
	NULL);
	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
	out:
	skcipher_request_free(req);
	crypto_free_skcipher(tfm);
	return res;
	}

	/*
	* Search the current task's subscribed keyrings for a "logon" key with
	* description prefix:descriptor, and if found acquire a read lock on it and
	* return a pointer to its validated payload in *payload_ret.
	*/
	static struct key *
	find_and_lock_process_key(const char *prefix,
	const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE],
	unsigned int min_keysize,
	const struct fscrypt_key **payload_ret)
	{
	char *description;
	struct key *key;
	const struct user_key_payload *ukp;
	const struct fscrypt_key *payload;

	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
	FS_KEY_DESCRIPTOR_SIZE, descriptor);
	if (!description)
	return ERR_PTR(-ENOMEM);

	key = request_key(&key_type_logon, description, NULL);
	kfree(description);
	if (IS_ERR(key))
	return key;

	down_read(&key->sem);
	ukp = user_key_payload_locked(key);

	if (!ukp) /* was the key revoked before we acquired its semaphore? */
	goto invalid;

	payload = (const struct fscrypt_key *)ukp->data;

	if (ukp->datalen != sizeof(struct fscrypt_key) \|\|
	payload->size < 1 \|\| payload->size > FS_MAX_KEY_SIZE) {
	fscrypt_warn(NULL,
	"key with description '%s' has invalid payload",
	key->description);
	goto invalid;
	}

	if (payload->size < min_keysize) {
	fscrypt_warn(NULL,
	"key with description '%s' is too short (got %u bytes, need %u+ bytes)",
	key->description, payload->size, min_keysize);
	goto invalid;
	}

	*payload_ret = payload;
	return key;

	invalid:
	up_read(&key->sem);
	key_put(key);
	return ERR_PTR(-ENOKEY);
	}

	/* Find the master key, then derive the inode's actual encryption key */
	static int find_and_derive_key(const struct inode *inode,
	const struct fscrypt_context *ctx,
	u8 *derived_key, unsigned int derived_keysize)
	{
	struct key *key;
	const struct fscrypt_key *payload;
	int err;

	key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
	ctx->master_key_descriptor,
	derived_keysize, &payload);
	if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
	key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
	ctx->master_key_descriptor,
	derived_keysize, &payload);
	}
	if (IS_ERR(key))
	return PTR_ERR(key);
	err = derive_key_aes(payload->raw, ctx, derived_key, derived_keysize);
	up_read(&key->sem);
	key_put(key);
	return err;
	}

	static struct fscrypt_mode {
	const char *friendly_name;
	const char *cipher_str;
	int keysize;
	bool logged_impl_name;
	} available_modes[] = {
	[FS_ENCRYPTION_MODE_AES_256_XTS] = {
	.friendly_name = "AES-256-XTS",
	.cipher_str = "xts(aes)",
	.keysize = 64,
	},
	[FS_ENCRYPTION_MODE_AES_256_CTS] = {
	.friendly_name = "AES-256-CTS-CBC",
	.cipher_str = "cts(cbc(aes))",
	.keysize = 32,
	},
	[FS_ENCRYPTION_MODE_AES_128_CBC] = {
	.friendly_name = "AES-128-CBC",
	.cipher_str = "cbc(aes)",
	.keysize = 16,
	},
	[FS_ENCRYPTION_MODE_AES_128_CTS] = {
	.friendly_name = "AES-128-CTS-CBC",
	.cipher_str = "cts(cbc(aes))",
	.keysize = 16,
	},
	};

	static struct fscrypt_mode *
	select_encryption_mode(const struct fscrypt_info ci, const struct inode inode)
	{
	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
	fscrypt_warn(inode->i_sb,
	"inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)",
	inode->i_ino, ci->ci_data_mode,
	ci->ci_filename_mode);
	return ERR_PTR(-EINVAL);
	}

	if (S_ISREG(inode->i_mode))
	return &available_modes[ci->ci_data_mode];

	if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode))
	return &available_modes[ci->ci_filename_mode];

	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
	inode->i_ino, (inode->i_mode & S_IFMT));
	return ERR_PTR(-EINVAL);
	}

	static void put_crypt_info(struct fscrypt_info *ci)
	{
	if (!ci)
	return;

	crypto_free_skcipher(ci->ci_ctfm);
	crypto_free_cipher(ci->ci_essiv_tfm);
	kmem_cache_free(fscrypt_info_cachep, ci);
	}

	static int derive_essiv_salt(const u8 key, int keysize, u8 salt)
	{
	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);

	/* init hash transform on demand */
	if (unlikely(!tfm)) {
	struct crypto_shash *prev_tfm;

	tfm = crypto_alloc_shash("sha256", 0, 0);
	if (IS_ERR(tfm)) {
	fscrypt_warn(NULL,
	"error allocating SHA-256 transform: %ld",
	PTR_ERR(tfm));
	return PTR_ERR(tfm);
	}
	prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
	if (prev_tfm) {
	crypto_free_shash(tfm);
	tfm = prev_tfm;
	}
	}

	{
	SHASH_DESC_ON_STACK(desc, tfm);
	desc->tfm = tfm;
	desc->flags = 0;

	return crypto_shash_digest(desc, key, keysize, salt);
	}
	}

	static int init_essiv_generator(struct fscrypt_info ci, const u8 raw_key,
	int keysize)
	{
	int err;
	struct crypto_cipher *essiv_tfm;
	u8 salt[SHA256_DIGEST_SIZE];

	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
	if (IS_ERR(essiv_tfm))
	return PTR_ERR(essiv_tfm);

	ci->ci_essiv_tfm = essiv_tfm;

	err = derive_essiv_salt(raw_key, keysize, salt);
	if (err)
	goto out;

	/*
	* Using SHA256 to derive the salt/key will result in AES-256 being
	* used for IV generation. File contents encryption will still use the
	* configured keysize (AES-128) nevertheless.
	*/
	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
	if (err)
	goto out;

	out:
	memzero_explicit(salt, sizeof(salt));
	return err;
	}

	void __exit fscrypt_essiv_cleanup(void)
	{
	crypto_free_shash(essiv_hash_tfm);
	}

	int fscrypt_get_encryption_info(struct inode *inode)
	{
	struct fscrypt_info *crypt_info;
	struct fscrypt_context ctx;
	struct crypto_skcipher *ctfm;
	struct fscrypt_mode *mode;
	u8 *raw_key = NULL;
	int res;

	if (inode->i_crypt_info)
	return 0;

	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
	if (res)
	return res;

	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
	if (res < 0) {
	if (!fscrypt_dummy_context_enabled(inode) \|\|
	IS_ENCRYPTED(inode))
	return res;
	/* Fake up a context for an unencrypted directory */
	memset(&ctx, 0, sizeof(ctx));
	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
	ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
	ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
	memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
	} else if (res != sizeof(ctx)) {
	return -EINVAL;
	}

	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
	return -EINVAL;

	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
	return -EINVAL;

	crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
	if (!crypt_info)
	return -ENOMEM;

	crypt_info->ci_flags = ctx.flags;
	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
	crypt_info->ci_ctfm = NULL;
	crypt_info->ci_essiv_tfm = NULL;
	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
	sizeof(crypt_info->ci_master_key));

	mode = select_encryption_mode(crypt_info, inode);
	if (IS_ERR(mode)) {
	res = PTR_ERR(mode);
	goto out;
	}

	/*
	* This cannot be a stack buffer because it is passed to the scatterlist
	* crypto API as part of key derivation.
	*/
	res = -ENOMEM;
	raw_key = kmalloc(mode->keysize, GFP_NOFS);
	if (!raw_key)
	goto out;

	res = find_and_derive_key(inode, &ctx, raw_key, mode->keysize);
	if (res)
	goto out;

	ctfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
	if (IS_ERR(ctfm)) {
	res = PTR_ERR(ctfm);
	fscrypt_warn(inode->i_sb,
	"error allocating '%s' transform for inode %lu: %d",
	mode->cipher_str, inode->i_ino, res);
	goto out;
	}
	if (unlikely(!mode->logged_impl_name)) {
	/*
	* fscrypt performance can vary greatly depending on which
	* crypto algorithm implementation is used. Help people debug
	* performance problems by logging the ->cra_driver_name the
	* first time a mode is used. Note that multiple threads can
	* race here, but it doesn't really matter.
	*/
	mode->logged_impl_name = true;
	pr_info("fscrypt: %s using implementation \"%s\"\n",
	mode->friendly_name,
	crypto_skcipher_alg(ctfm)->base.cra_driver_name);
	}
	crypt_info->ci_ctfm = ctfm;
	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
	res = crypto_skcipher_setkey(ctfm, raw_key, mode->keysize);
	if (res)
	goto out;

	if (S_ISREG(inode->i_mode) &&
	crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
	res = init_essiv_generator(crypt_info, raw_key, mode->keysize);
	if (res) {
	fscrypt_warn(inode->i_sb,
	"error initializing ESSIV generator for inode %lu: %d",
	inode->i_ino, res);
	goto out;
	}
	}
	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
	crypt_info = NULL;
	out:
	if (res == -ENOKEY)
	res = 0;
	put_crypt_info(crypt_info);
	kzfree(raw_key);
	return res;
	}
	EXPORT_SYMBOL(fscrypt_get_encryption_info);

	void fscrypt_put_encryption_info(struct inode *inode)
	{
	put_crypt_info(inode->i_crypt_info);
	inode->i_crypt_info = NULL;
	}
	EXPORT_SYMBOL(fscrypt_put_encryption_info);