fs/ext4/crypto_key.c - kernel/common.git - Git at Google

 /*
  * linux/fs/ext4/crypto_key.c
  *
  * Copyright (C) 2015, Google, Inc.
  *
  * This contains encryption key functions for ext4
  *
  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
  */

 #include <keys/encrypted-type.h>
 #include <keys/user-type.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 #include <uapi/linux/keyctl.h>

 #include "ext4.h"
 #include "xattr.h"

 static void derive_crypt_complete(struct crypto_async_request *req, int rc)
 {
 	struct ext4_completion_result *ecr = req->data;

 	if (rc == -EINPROGRESS)
 		return;

 	ecr->res = rc;
 	complete(&ecr->completion);
 }

 /**
  * ext4_derive_key_v1() - Derive a key using AES-128-ECB
  * @deriving_key: Encryption key used for derivation.
  * @source_key:   Source key to which to apply derivation.
  * @derived_key:  Derived key.
  *
  * Return: 0 on success, -errno on failure
  */
 static int ext4_derive_key_v1(const char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
 			      const char source_key[EXT4_AES_256_XTS_KEY_SIZE],
 			      char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
 {
 	int res = 0;
 	struct ablkcipher_request *req = NULL;
 	DECLARE_EXT4_COMPLETION_RESULT(ecr);
 	struct scatterlist src_sg, dst_sg;
 	struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
 								0);

 	if (IS_ERR(tfm)) {
 		res = PTR_ERR(tfm);
 		tfm = NULL;
 		goto out;
 	}
 	crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
 	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		res = -ENOMEM;
 		goto out;
 	}
 	ablkcipher_request_set_callback(req,
 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 			derive_crypt_complete, &ecr);
 	res = crypto_ablkcipher_setkey(tfm, deriving_key,
 				       EXT4_AES_128_ECB_KEY_SIZE);
 	if (res < 0)
 		goto out;
 	sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
 	sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
 	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
 				     EXT4_AES_256_XTS_KEY_SIZE, NULL);
 	res = crypto_ablkcipher_encrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}

 out:
 	if (req)
 		ablkcipher_request_free(req);
 	if (tfm)
 		crypto_free_ablkcipher(tfm);
 	return res;
 }

 /**
  * ext4_derive_key_v2() - Derive a key non-reversibly
  * @nonce: the nonce associated with the file
  * @master_key: the master key referenced by the file
  * @derived_key: (output) the resulting derived key
  *
  * This function computes the following:
  *	 derived_key[0:127]   = AES-256-ENCRYPT(master_key[0:255], nonce)
  *	 derived_key[128:255] = AES-256-ENCRYPT(master_key[0:255], nonce ^ 0x01)
  *	 derived_key[256:383] = AES-256-ENCRYPT(master_key[256:511], nonce)
  *	 derived_key[384:511] = AES-256-ENCRYPT(master_key[256:511], nonce ^ 0x01)
  *
  * 'nonce ^ 0x01' denotes flipping the low order bit of the last byte.
  *
  * Unlike the v1 algorithm, the v2 algorithm is "non-reversible", meaning that
  * compromising a derived key does not also compromise the master key.
  *
  * Return: 0 on success, -errno on failure
  */
 static int ext4_derive_key_v2(const char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE],
 			      const char master_key[EXT4_MAX_KEY_SIZE],
 			      char derived_key[EXT4_MAX_KEY_SIZE])
 {
 	const int noncelen = EXT4_KEY_DERIVATION_NONCE_SIZE;
 	struct crypto_cipher *tfm;
 	int err;
 	int i;

 	/*
 	 * Since we only use each transform for a small number of encryptions,
 	 * requesting just "aes" turns out to be significantly faster than
 	 * "ecb(aes)", by about a factor of two.
 	 */
 	tfm = crypto_alloc_cipher("aes", 0, 0);
 	if (IS_ERR(tfm))
 		return PTR_ERR(tfm);

 	BUILD_BUG_ON(4 * EXT4_KEY_DERIVATION_NONCE_SIZE != EXT4_MAX_KEY_SIZE);
 	BUILD_BUG_ON(2 * EXT4_AES_256_ECB_KEY_SIZE != EXT4_MAX_KEY_SIZE);
 	for (i = 0; i < 2; i++) {
 		memcpy(derived_key, nonce, noncelen);
 		memcpy(derived_key + noncelen, nonce, noncelen);
 		derived_key[2 * noncelen - 1] ^= 0x01;
 		err = crypto_cipher_setkey(tfm, master_key,
 					   EXT4_AES_256_ECB_KEY_SIZE);
 		if (err)
 			break;
 		crypto_cipher_encrypt_one(tfm, derived_key, derived_key);
 		crypto_cipher_encrypt_one(tfm, derived_key + noncelen,
 					  derived_key + noncelen);
 		master_key += EXT4_AES_256_ECB_KEY_SIZE;
 		derived_key += 2 * noncelen;
 	}
 	crypto_free_cipher(tfm);
 	return err;
 }

 /**
  * ext4_derive_key() - Derive a per-file key from a nonce and master key
  * @ctx: the encryption context associated with the file
  * @master_key: the master key referenced by the file
  * @derived_key: (output) the resulting derived key
  *
  * Return: 0 on success, -errno on failure
  */
 static int ext4_derive_key(const struct ext4_encryption_context *ctx,
 			   const char master_key[EXT4_MAX_KEY_SIZE],
 			   char derived_key[EXT4_MAX_KEY_SIZE])
 {
 	BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != EXT4_KEY_DERIVATION_NONCE_SIZE);
 	BUILD_BUG_ON(EXT4_AES_256_XTS_KEY_SIZE != EXT4_MAX_KEY_SIZE);

 	/*
 	 * Although the key derivation algorithm is logically independent of the
 	 * choice of encryption modes, in this kernel it is bundled with HEH
 	 * encryption of filenames, which is another crypto improvement that
 	 * requires an on-disk format change and requires userspace to specify
 	 * different encryption policies.
 	 */
 	if (ctx->filenames_encryption_mode == EXT4_ENCRYPTION_MODE_AES_256_HEH)
 		return ext4_derive_key_v2(ctx->nonce, master_key, derived_key);
 	else
 		return ext4_derive_key_v1(ctx->nonce, master_key, derived_key);
 }

 void ext4_free_crypt_info(struct ext4_crypt_info *ci)
 {
 	if (!ci)
 		return;

 	if (ci->ci_keyring_key)
 		key_put(ci->ci_keyring_key);
 	crypto_free_ablkcipher(ci->ci_ctfm);
 	kmem_cache_free(ext4_crypt_info_cachep, ci);
 }

 void ext4_free_encryption_info(struct inode *inode,
 			       struct ext4_crypt_info *ci)
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	struct ext4_crypt_info *prev;

 	if (ci == NULL)
 		ci = ACCESS_ONCE(ei->i_crypt_info);
 	if (ci == NULL)
 		return;
 	prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
 	if (prev != ci)
 		return;

 	ext4_free_crypt_info(ci);
 }

 int _ext4_get_encryption_info(struct inode *inode)
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	struct ext4_crypt_info *crypt_info;
 	char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
 				 (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
 	struct key *keyring_key = NULL;
 	struct ext4_encryption_key *master_key;
 	struct ext4_encryption_context ctx;
 	const struct user_key_payload *ukp;
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	struct crypto_ablkcipher *ctfm;
 	const char *cipher_str;
 	char raw_key[EXT4_MAX_KEY_SIZE];
 	char mode;
 	int res;

 	if (!ext4_read_workqueue) {
 		res = ext4_init_crypto();
 		if (res)
 			return res;
 	}

 retry:
 	crypt_info = ACCESS_ONCE(ei->i_crypt_info);
 	if (crypt_info) {
 		if (!crypt_info->ci_keyring_key ||
 		    key_validate(crypt_info->ci_keyring_key) == 0)
 			return 0;
 		ext4_free_encryption_info(inode, crypt_info);
 		goto retry;
 	}

 	res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
 				 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
 				 &ctx, sizeof(ctx));
 	if (res < 0) {
 		if (!DUMMY_ENCRYPTION_ENABLED(sbi))
 			return res;
 		ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
 		ctx.filenames_encryption_mode =
 			EXT4_ENCRYPTION_MODE_AES_256_CTS;
 		ctx.flags = 0;
 	} else if (res != sizeof(ctx))
 		return -EINVAL;
 	res = 0;

 	crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL);
 	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_keyring_key = NULL;
 	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
 	       sizeof(crypt_info->ci_master_key));
 	if (S_ISREG(inode->i_mode))
 		mode = crypt_info->ci_data_mode;
 	else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
 		mode = crypt_info->ci_filename_mode;
 	else
 		BUG();
 	switch (mode) {
 	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
 		cipher_str = "xts(aes)";
 		break;
 	case EXT4_ENCRYPTION_MODE_AES_256_CTS:
 		cipher_str = "cts(cbc(aes))";
 		break;
 	case EXT4_ENCRYPTION_MODE_AES_256_HEH:
 		cipher_str = "heh(aes)";
 		break;
 	default:
 		printk_once(KERN_WARNING
 			    "ext4: unsupported key mode %d (ino %u)\n",
 			    mode, (unsigned) inode->i_ino);
 		res = -ENOKEY;
 		goto out;
 	}
 	if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
 		memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
 		goto got_key;
 	}
 	memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
 	       EXT4_KEY_DESC_PREFIX_SIZE);
 	sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
 		"%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
 		ctx.master_key_descriptor);
 	full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
 			    (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
 	keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
 	if (IS_ERR(keyring_key)) {
 		res = PTR_ERR(keyring_key);
 		keyring_key = NULL;
 		goto out;
 	}
 	crypt_info->ci_keyring_key = keyring_key;
 	if (keyring_key->type != &key_type_logon) {
 		printk_once(KERN_WARNING
 			    "ext4: key type must be logon\n");
 		res = -ENOKEY;
 		goto out;
 	}
 	down_read(&keyring_key->sem);
 	ukp = user_key_payload(keyring_key);
 	if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
 		res = -EINVAL;
 		up_read(&keyring_key->sem);
 		goto out;
 	}
 	master_key = (struct ext4_encryption_key *)ukp->data;
 	BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
 		     EXT4_KEY_DERIVATION_NONCE_SIZE);
 	if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) {
 		printk_once(KERN_WARNING
 			    "ext4: key size incorrect: %d\n",
 			    master_key->size);
 		res = -ENOKEY;
 		up_read(&keyring_key->sem);
 		goto out;
 	}
 	res = ext4_derive_key(&ctx, master_key->raw, raw_key);
 	up_read(&keyring_key->sem);
 	if (res)
 		goto out;
 got_key:
 	ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
 	if (!ctfm || IS_ERR(ctfm)) {
 		res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
 		printk(KERN_DEBUG
 		       "%s: error %d (inode %u) allocating crypto tfm\n",
 		       __func__, res, (unsigned) inode->i_ino);
 		goto out;
 	}
 	crypt_info->ci_ctfm = ctfm;
 	crypto_ablkcipher_clear_flags(ctfm, ~0);
 	crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
 			     CRYPTO_TFM_REQ_WEAK_KEY);
 	res = crypto_ablkcipher_setkey(ctfm, raw_key,
 				       ext4_encryption_key_size(mode));
 	if (res)
 		goto out;
 	memzero_explicit(raw_key, sizeof(raw_key));
 	if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
 		ext4_free_crypt_info(crypt_info);
 		goto retry;
 	}
 	return 0;

 out:
 	if (res == -ENOKEY)
 		res = 0;
 	ext4_free_crypt_info(crypt_info);
 	memzero_explicit(raw_key, sizeof(raw_key));
 	return res;
 }

 int ext4_has_encryption_key(struct inode *inode)
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);

 	return (ei->i_crypt_info != NULL);
 }
	/*
	* linux/fs/ext4/crypto_key.c
	*
	* Copyright (C) 2015, Google, Inc.
	*
	* This contains encryption key functions for ext4
	*
	* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
	*/

	#include <keys/encrypted-type.h>
	#include <keys/user-type.h>
	#include <linux/random.h>
	#include <linux/scatterlist.h>
	#include <uapi/linux/keyctl.h>

	#include "ext4.h"
	#include "xattr.h"

	static void derive_crypt_complete(struct crypto_async_request *req, int rc)
	{
	struct ext4_completion_result *ecr = req->data;

	if (rc == -EINPROGRESS)
	return;

	ecr->res = rc;
	complete(&ecr->completion);
	}

	/**
	* ext4_derive_key_v1() - Derive a key using AES-128-ECB
	* @deriving_key: Encryption key used for derivation.
	* @source_key: Source key to which to apply derivation.
	* @derived_key: Derived key.
	*
	* Return: 0 on success, -errno on failure
	*/
	static int ext4_derive_key_v1(const char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
	const char source_key[EXT4_AES_256_XTS_KEY_SIZE],
	char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
	{
	int res = 0;
	struct ablkcipher_request *req = NULL;
	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	struct scatterlist src_sg, dst_sg;
	struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
	0);

	if (IS_ERR(tfm)) {
	res = PTR_ERR(tfm);
	tfm = NULL;
	goto out;
	}
	crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	res = -ENOMEM;
	goto out;
	}
	ablkcipher_request_set_callback(req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	derive_crypt_complete, &ecr);
	res = crypto_ablkcipher_setkey(tfm, deriving_key,
	EXT4_AES_128_ECB_KEY_SIZE);
	if (res < 0)
	goto out;
	sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
	sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
	EXT4_AES_256_XTS_KEY_SIZE, NULL);
	res = crypto_ablkcipher_encrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}

	out:
	if (req)
	ablkcipher_request_free(req);
	if (tfm)
	crypto_free_ablkcipher(tfm);
	return res;
	}

	/**
	* ext4_derive_key_v2() - Derive a key non-reversibly
	* @nonce: the nonce associated with the file
	* @master_key: the master key referenced by the file
	* @derived_key: (output) the resulting derived key
	*
	* This function computes the following:
	* derived_key[0:127] = AES-256-ENCRYPT(master_key[0:255], nonce)
	* derived_key[128:255] = AES-256-ENCRYPT(master_key[0:255], nonce ^ 0x01)
	* derived_key[256:383] = AES-256-ENCRYPT(master_key[256:511], nonce)
	* derived_key[384:511] = AES-256-ENCRYPT(master_key[256:511], nonce ^ 0x01)
	*
	* 'nonce ^ 0x01' denotes flipping the low order bit of the last byte.
	*
	* Unlike the v1 algorithm, the v2 algorithm is "non-reversible", meaning that
	* compromising a derived key does not also compromise the master key.
	*
	* Return: 0 on success, -errno on failure
	*/
	static int ext4_derive_key_v2(const char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE],
	const char master_key[EXT4_MAX_KEY_SIZE],
	char derived_key[EXT4_MAX_KEY_SIZE])
	{
	const int noncelen = EXT4_KEY_DERIVATION_NONCE_SIZE;
	struct crypto_cipher *tfm;
	int err;
	int i;

	/*
	* Since we only use each transform for a small number of encryptions,
	* requesting just "aes" turns out to be significantly faster than
	* "ecb(aes)", by about a factor of two.
	*/
	tfm = crypto_alloc_cipher("aes", 0, 0);
	if (IS_ERR(tfm))
	return PTR_ERR(tfm);

	BUILD_BUG_ON(4 * EXT4_KEY_DERIVATION_NONCE_SIZE != EXT4_MAX_KEY_SIZE);
	BUILD_BUG_ON(2 * EXT4_AES_256_ECB_KEY_SIZE != EXT4_MAX_KEY_SIZE);
	for (i = 0; i < 2; i++) {
	memcpy(derived_key, nonce, noncelen);
	memcpy(derived_key + noncelen, nonce, noncelen);
	derived_key[2 * noncelen - 1] ^= 0x01;
	err = crypto_cipher_setkey(tfm, master_key,
	EXT4_AES_256_ECB_KEY_SIZE);
	if (err)
	break;
	crypto_cipher_encrypt_one(tfm, derived_key, derived_key);
	crypto_cipher_encrypt_one(tfm, derived_key + noncelen,
	derived_key + noncelen);
	master_key += EXT4_AES_256_ECB_KEY_SIZE;
	derived_key += 2 * noncelen;
	}
	crypto_free_cipher(tfm);
	return err;
	}

	/**
	* ext4_derive_key() - Derive a per-file key from a nonce and master key
	* @ctx: the encryption context associated with the file
	* @master_key: the master key referenced by the file
	* @derived_key: (output) the resulting derived key
	*
	* Return: 0 on success, -errno on failure
	*/
	static int ext4_derive_key(const struct ext4_encryption_context *ctx,
	const char master_key[EXT4_MAX_KEY_SIZE],
	char derived_key[EXT4_MAX_KEY_SIZE])
	{
	BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != EXT4_KEY_DERIVATION_NONCE_SIZE);
	BUILD_BUG_ON(EXT4_AES_256_XTS_KEY_SIZE != EXT4_MAX_KEY_SIZE);

	/*
	* Although the key derivation algorithm is logically independent of the
	* choice of encryption modes, in this kernel it is bundled with HEH
	* encryption of filenames, which is another crypto improvement that
	* requires an on-disk format change and requires userspace to specify
	* different encryption policies.
	*/
	if (ctx->filenames_encryption_mode == EXT4_ENCRYPTION_MODE_AES_256_HEH)
	return ext4_derive_key_v2(ctx->nonce, master_key, derived_key);
	else
	return ext4_derive_key_v1(ctx->nonce, master_key, derived_key);
	}

	void ext4_free_crypt_info(struct ext4_crypt_info *ci)
	{
	if (!ci)
	return;

	if (ci->ci_keyring_key)
	key_put(ci->ci_keyring_key);
	crypto_free_ablkcipher(ci->ci_ctfm);
	kmem_cache_free(ext4_crypt_info_cachep, ci);
	}

	void ext4_free_encryption_info(struct inode *inode,
	struct ext4_crypt_info *ci)
	{
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct ext4_crypt_info *prev;

	if (ci == NULL)
	ci = ACCESS_ONCE(ei->i_crypt_info);
	if (ci == NULL)
	return;
	prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
	if (prev != ci)
	return;

	ext4_free_crypt_info(ci);
	}

	int _ext4_get_encryption_info(struct inode *inode)
	{
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct ext4_crypt_info *crypt_info;
	char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
	(EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
	struct key *keyring_key = NULL;
	struct ext4_encryption_key *master_key;
	struct ext4_encryption_context ctx;
	const struct user_key_payload *ukp;
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct crypto_ablkcipher *ctfm;
	const char *cipher_str;
	char raw_key[EXT4_MAX_KEY_SIZE];
	char mode;
	int res;

	if (!ext4_read_workqueue) {
	res = ext4_init_crypto();
	if (res)
	return res;
	}

	retry:
	crypt_info = ACCESS_ONCE(ei->i_crypt_info);
	if (crypt_info) {
	if (!crypt_info->ci_keyring_key \|\|
	key_validate(crypt_info->ci_keyring_key) == 0)
	return 0;
	ext4_free_encryption_info(inode, crypt_info);
	goto retry;
	}

	res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
	&ctx, sizeof(ctx));
	if (res < 0) {
	if (!DUMMY_ENCRYPTION_ENABLED(sbi))
	return res;
	ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
	ctx.filenames_encryption_mode =
	EXT4_ENCRYPTION_MODE_AES_256_CTS;
	ctx.flags = 0;
	} else if (res != sizeof(ctx))
	return -EINVAL;
	res = 0;

	crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL);
	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_keyring_key = NULL;
	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
	sizeof(crypt_info->ci_master_key));
	if (S_ISREG(inode->i_mode))
	mode = crypt_info->ci_data_mode;
	else if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode))
	mode = crypt_info->ci_filename_mode;
	else
	BUG();
	switch (mode) {
	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
	cipher_str = "xts(aes)";
	break;
	case EXT4_ENCRYPTION_MODE_AES_256_CTS:
	cipher_str = "cts(cbc(aes))";
	break;
	case EXT4_ENCRYPTION_MODE_AES_256_HEH:
	cipher_str = "heh(aes)";
	break;
	default:
	printk_once(KERN_WARNING
	"ext4: unsupported key mode %d (ino %u)\n",
	mode, (unsigned) inode->i_ino);
	res = -ENOKEY;
	goto out;
	}
	if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
	memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
	goto got_key;
	}
	memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
	EXT4_KEY_DESC_PREFIX_SIZE);
	sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
	"%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
	ctx.master_key_descriptor);
	full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
	(2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
	keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
	if (IS_ERR(keyring_key)) {
	res = PTR_ERR(keyring_key);
	keyring_key = NULL;
	goto out;
	}
	crypt_info->ci_keyring_key = keyring_key;
	if (keyring_key->type != &key_type_logon) {
	printk_once(KERN_WARNING
	"ext4: key type must be logon\n");
	res = -ENOKEY;
	goto out;
	}
	down_read(&keyring_key->sem);
	ukp = user_key_payload(keyring_key);
	if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
	res = -EINVAL;
	up_read(&keyring_key->sem);
	goto out;
	}
	master_key = (struct ext4_encryption_key *)ukp->data;
	BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
	EXT4_KEY_DERIVATION_NONCE_SIZE);
	if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) {
	printk_once(KERN_WARNING
	"ext4: key size incorrect: %d\n",
	master_key->size);
	res = -ENOKEY;
	up_read(&keyring_key->sem);
	goto out;
	}
	res = ext4_derive_key(&ctx, master_key->raw, raw_key);
	up_read(&keyring_key->sem);
	if (res)
	goto out;
	got_key:
	ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
	if (!ctfm \|\| IS_ERR(ctfm)) {
	res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
	printk(KERN_DEBUG
	"%s: error %d (inode %u) allocating crypto tfm\n",
	__func__, res, (unsigned) inode->i_ino);
	goto out;
	}
	crypt_info->ci_ctfm = ctfm;
	crypto_ablkcipher_clear_flags(ctfm, ~0);
	crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
	CRYPTO_TFM_REQ_WEAK_KEY);
	res = crypto_ablkcipher_setkey(ctfm, raw_key,
	ext4_encryption_key_size(mode));
	if (res)
	goto out;
	memzero_explicit(raw_key, sizeof(raw_key));
	if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
	ext4_free_crypt_info(crypt_info);
	goto retry;
	}
	return 0;

	out:
	if (res == -ENOKEY)
	res = 0;
	ext4_free_crypt_info(crypt_info);
	memzero_explicit(raw_key, sizeof(raw_key));
	return res;
	}

	int ext4_has_encryption_key(struct inode *inode)
	{
	struct ext4_inode_info *ei = EXT4_I(inode);

	return (ei->i_crypt_info != NULL);
	}