fs/crypto/keyinfo.c - kernel/msm-4.9 - Gitiles

 /*
  * 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"
 #include "fscrypt_ice.h"

 static struct crypto_shash *essiv_hash_tfm;

 /**
  * derive_key_aes() - Derive a key using AES-128-ECB
  * @deriving_key: Encryption key used for derivation.
  * @source_key:   Source key to which to apply derivation.
  * @derived_raw_key:  Derived raw key.
  *
  * Return: Zero on success; non-zero otherwise.
  */
 static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
 				const struct fscrypt_key *source_key,
 				u8 derived_raw_key[FS_MAX_KEY_SIZE])
 {
 	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, deriving_key,
 					FS_AES_128_ECB_KEY_SIZE);
 	if (res < 0)
 		goto out;

 	sg_init_one(&src_sg, source_key->raw, source_key->size);
 	sg_init_one(&dst_sg, derived_raw_key, source_key->size);
 	skcipher_request_set_crypt(req, &src_sg, &dst_sg, source_key->size,
 				   NULL);
 	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
 out:
 	skcipher_request_free(req);
 	crypto_free_skcipher(tfm);
 	return res;
 }

 static int validate_user_key(struct fscrypt_info *crypt_info,
 			struct fscrypt_context *ctx,
 			const char *prefix, int min_keysize)
 {
 	char *description;
 	struct key *keyring_key;
 	struct fscrypt_key *master_key;
 	const struct user_key_payload *ukp;
 	int res;

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

 	keyring_key = request_key(&key_type_logon, description, NULL);
 	kfree(description);
 	if (IS_ERR(keyring_key))
 		return PTR_ERR(keyring_key);
 	down_read(&keyring_key->sem);

 	if (keyring_key->type != &key_type_logon) {
 		printk_once(KERN_WARNING
 				"%s: key type must be logon\n", __func__);
 		res = -ENOKEY;
 		goto out;
 	}
 	ukp = user_key_payload_locked(keyring_key);
 	if (!ukp) {
 		/* key was revoked before we acquired its semaphore */
 		res = -EKEYREVOKED;
 		goto out;
 	}
 	if (ukp->datalen != sizeof(struct fscrypt_key)) {
 		res = -EINVAL;
 		goto out;
 	}
 	master_key = (struct fscrypt_key *)ukp->data;
 	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);

 	if (master_key->size < min_keysize || master_key->size > FS_MAX_KEY_SIZE
 	    || master_key->size % AES_BLOCK_SIZE != 0) {
 		printk_once(KERN_WARNING
 				"%s: key size incorrect: %d\n",
 				__func__, master_key->size);
 		res = -ENOKEY;
 		goto out;
 	}
 	res = derive_key_aes(ctx->nonce, master_key, crypt_info->ci_raw_key);
 	/* If we don't need to derive, we still want to do everything
 	 * up until now to validate the key. It's cleaner to fail now
 	 * than to fail in block I/O.
 	if (!is_private_data_mode(crypt_info)) {
 		res = derive_key_aes(ctx->nonce, master_key,
 				crypt_info->ci_raw_key);
 	} else {
 		 * Inline encryption: no key derivation required because IVs are
 		 * assigned based on iv_sector.

 		BUILD_BUG_ON(sizeof(crypt_info->ci_raw_key) !=
 				sizeof(master_key->raw));
 		memcpy(crypt_info->ci_raw_key,
 			master_key->raw, sizeof(crypt_info->ci_raw_key));
 		res = 0;
 	}
 	 */
 out:
 	up_read(&keyring_key->sem);
 	key_put(keyring_key);
 	return res;
 }

 static const struct {
 	const char *cipher_str;
 	int keysize;
 } available_modes[] = {
 	[FS_ENCRYPTION_MODE_AES_256_XTS] = { "xts(aes)",
 					     FS_AES_256_XTS_KEY_SIZE },
 	[FS_ENCRYPTION_MODE_AES_256_CTS] = { "cts(cbc(aes))",
 					     FS_AES_256_CTS_KEY_SIZE },
 	[FS_ENCRYPTION_MODE_AES_128_CBC] = { "cbc(aes)",
 					     FS_AES_128_CBC_KEY_SIZE },
 	[FS_ENCRYPTION_MODE_AES_128_CTS] = { "cts(cbc(aes))",
 					     FS_AES_128_CTS_KEY_SIZE },
 	[FS_ENCRYPTION_MODE_PRIVATE]	 = { "bugon",
 					     FS_AES_256_XTS_KEY_SIZE },
 };

 static int determine_cipher_type(struct fscrypt_info *ci, struct inode *inode,
 		const char **cipher_str_ret, int *keysize_ret, int *fname)
 {
 	u32 mode;

 	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
 		pr_warn_ratelimited("fscrypt: inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)\n",
 				    inode->i_ino,
 				    ci->ci_data_mode, ci->ci_filename_mode);
 		return -EINVAL;
 	}

 	if (S_ISREG(inode->i_mode)) {
 		ci->ci_mode = CI_DATA_MODE;
 		mode = ci->ci_data_mode;
 	} else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) {
 		ci->ci_mode = CI_FNAME_MODE;
 		mode = ci->ci_filename_mode;
 		*fname = 1;
 	} else {
 		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 -EINVAL;
 	}

 	*cipher_str_ret = available_modes[mode].cipher_str;
 	*keysize_ret = available_modes[mode].keysize;
 	return 0;
 }

 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);
 	memset(ci, 0, sizeof(*ci)); /* sanitizes ->ci_raw_key */
 	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)) {
 			pr_warn_ratelimited("fscrypt: error allocating SHA-256 transform: %ld\n",
 					    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);
 }

 static int fscrypt_data_encryption_mode(struct inode *inode)
 {
 	return fscrypt_should_be_processed_by_ice(inode) ?
 	FS_ENCRYPTION_MODE_PRIVATE : FS_ENCRYPTION_MODE_AES_256_XTS;
 }

 int fscrypt_get_encryption_info(struct inode *inode)
 {
 	struct fscrypt_info *crypt_info;
 	struct fscrypt_context ctx;
 	struct crypto_skcipher *ctfm;
 	const char *cipher_str;
 	int keysize;
 	int res;
 	int fname = 0;

 	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 =
 			fscrypt_data_encryption_mode(inode);
 		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));

 	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize,
 				&fname);
 	if (res)
 		goto out;

 	/*
 	 * This cannot be a stack buffer because it is passed to the scatterlist
 	 * crypto API as part of key derivation.
 	 */
 	res = -ENOMEM;

 	res = validate_user_key(crypt_info, &ctx, FS_KEY_DESC_PREFIX,
 				keysize);
 	if (res && inode->i_sb->s_cop->key_prefix) {
 		int res2 = validate_user_key(crypt_info, &ctx,
 					     inode->i_sb->s_cop->key_prefix,
 					     keysize);
 		if (res2) {
 			if (res2 == -ENOKEY)
 				res = -ENOKEY;
 			goto out;
 		}
 		res = 0;
 	} else if (res) {
 		goto out;
 	}

 	if (is_private_data_mode(crypt_info)) {
 		if (!fscrypt_is_ice_capable(inode->i_sb)) {
 			pr_warn("%s: ICE support not available\n",
 					__func__);
 			res = -EINVAL;
 			goto out;
 		}
 		/* Let's encrypt/decrypt by ICE */
 		goto do_ice;
 	}


 	ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
 	if (!ctfm || IS_ERR(ctfm)) {
 		res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
 		pr_debug("%s: error %d (inode %lu) allocating crypto tfm\n",
 			 __func__, res, inode->i_ino);
 		goto out;
 	}
 	crypt_info->ci_ctfm = ctfm;
 	crypto_skcipher_clear_flags(ctfm, ~0);
 	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
 	/*
 	 * if the provided key is longer than keysize, we use the first
 	 * keysize bytes of the derived key only
 	 */
 	res = crypto_skcipher_setkey(ctfm, crypt_info->ci_raw_key, 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, crypt_info->ci_raw_key,
 						keysize);
 		if (res) {
 			pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
 				 __func__, res, inode->i_ino);
 			goto out;
 		}
 	}
 	memzero_explicit(crypt_info->ci_raw_key,
 		sizeof(crypt_info->ci_raw_key));
 do_ice:
 	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
 		crypt_info = NULL;
 out:
 	if (res == -ENOKEY)
 		res = 0;
 	put_crypt_info(crypt_info);
 	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);
	/*
	* 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"
	#include "fscrypt_ice.h"

	static struct crypto_shash *essiv_hash_tfm;

	/**
	* derive_key_aes() - Derive a key using AES-128-ECB
	* @deriving_key: Encryption key used for derivation.
	* @source_key: Source key to which to apply derivation.
	* @derived_raw_key: Derived raw key.
	*
	* Return: Zero on success; non-zero otherwise.
	*/
	static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
	const struct fscrypt_key *source_key,
	u8 derived_raw_key[FS_MAX_KEY_SIZE])
	{
	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, deriving_key,
	FS_AES_128_ECB_KEY_SIZE);
	if (res < 0)
	goto out;

	sg_init_one(&src_sg, source_key->raw, source_key->size);
	sg_init_one(&dst_sg, derived_raw_key, source_key->size);
	skcipher_request_set_crypt(req, &src_sg, &dst_sg, source_key->size,
	NULL);
	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
	out:
	skcipher_request_free(req);
	crypto_free_skcipher(tfm);
	return res;
	}

	static int validate_user_key(struct fscrypt_info *crypt_info,
	struct fscrypt_context *ctx,
	const char *prefix, int min_keysize)
	{
	char *description;
	struct key *keyring_key;
	struct fscrypt_key *master_key;
	const struct user_key_payload *ukp;
	int res;

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

	keyring_key = request_key(&key_type_logon, description, NULL);
	kfree(description);
	if (IS_ERR(keyring_key))
	return PTR_ERR(keyring_key);
	down_read(&keyring_key->sem);

	if (keyring_key->type != &key_type_logon) {
	printk_once(KERN_WARNING
	"%s: key type must be logon\n", __func__);
	res = -ENOKEY;
	goto out;
	}
	ukp = user_key_payload_locked(keyring_key);
	if (!ukp) {
	/* key was revoked before we acquired its semaphore */
	res = -EKEYREVOKED;
	goto out;
	}
	if (ukp->datalen != sizeof(struct fscrypt_key)) {
	res = -EINVAL;
	goto out;
	}
	master_key = (struct fscrypt_key *)ukp->data;
	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);

	if (master_key->size < min_keysize \|\| master_key->size > FS_MAX_KEY_SIZE
	\|\| master_key->size % AES_BLOCK_SIZE != 0) {
	printk_once(KERN_WARNING
	"%s: key size incorrect: %d\n",
	__func__, master_key->size);
	res = -ENOKEY;
	goto out;
	}
	res = derive_key_aes(ctx->nonce, master_key, crypt_info->ci_raw_key);
	/* If we don't need to derive, we still want to do everything
	* up until now to validate the key. It's cleaner to fail now
	* than to fail in block I/O.
	if (!is_private_data_mode(crypt_info)) {
	res = derive_key_aes(ctx->nonce, master_key,
	crypt_info->ci_raw_key);
	} else {
	* Inline encryption: no key derivation required because IVs are
	* assigned based on iv_sector.

	BUILD_BUG_ON(sizeof(crypt_info->ci_raw_key) !=
	sizeof(master_key->raw));
	memcpy(crypt_info->ci_raw_key,
	master_key->raw, sizeof(crypt_info->ci_raw_key));
	res = 0;
	}
	*/
	out:
	up_read(&keyring_key->sem);
	key_put(keyring_key);
	return res;
	}

	static const struct {
	const char *cipher_str;
	int keysize;
	} available_modes[] = {
	[FS_ENCRYPTION_MODE_AES_256_XTS] = { "xts(aes)",
	FS_AES_256_XTS_KEY_SIZE },
	[FS_ENCRYPTION_MODE_AES_256_CTS] = { "cts(cbc(aes))",
	FS_AES_256_CTS_KEY_SIZE },
	[FS_ENCRYPTION_MODE_AES_128_CBC] = { "cbc(aes)",
	FS_AES_128_CBC_KEY_SIZE },
	[FS_ENCRYPTION_MODE_AES_128_CTS] = { "cts(cbc(aes))",
	FS_AES_128_CTS_KEY_SIZE },
	[FS_ENCRYPTION_MODE_PRIVATE] = { "bugon",
	FS_AES_256_XTS_KEY_SIZE },
	};

	static int determine_cipher_type(struct fscrypt_info ci, struct inode inode,
	const char *cipher_str_ret, int keysize_ret, int *fname)
	{
	u32 mode;

	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
	pr_warn_ratelimited("fscrypt: inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)\n",
	inode->i_ino,
	ci->ci_data_mode, ci->ci_filename_mode);
	return -EINVAL;
	}

	if (S_ISREG(inode->i_mode)) {
	ci->ci_mode = CI_DATA_MODE;
	mode = ci->ci_data_mode;
	} else if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode)) {
	ci->ci_mode = CI_FNAME_MODE;
	mode = ci->ci_filename_mode;
	*fname = 1;
	} else {
	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 -EINVAL;
	}

	*cipher_str_ret = available_modes[mode].cipher_str;
	*keysize_ret = available_modes[mode].keysize;
	return 0;
	}

	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);
	memset(ci, 0, sizeof(ci)); / sanitizes ->ci_raw_key */
	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)) {
	pr_warn_ratelimited("fscrypt: error allocating SHA-256 transform: %ld\n",
	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);
	}

	static int fscrypt_data_encryption_mode(struct inode *inode)
	{
	return fscrypt_should_be_processed_by_ice(inode) ?
	FS_ENCRYPTION_MODE_PRIVATE : FS_ENCRYPTION_MODE_AES_256_XTS;
	}

	int fscrypt_get_encryption_info(struct inode *inode)
	{
	struct fscrypt_info *crypt_info;
	struct fscrypt_context ctx;
	struct crypto_skcipher *ctfm;
	const char *cipher_str;
	int keysize;
	int res;
	int fname = 0;

	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 =
	fscrypt_data_encryption_mode(inode);
	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));

	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize,
	&fname);
	if (res)
	goto out;

	/*
	* This cannot be a stack buffer because it is passed to the scatterlist
	* crypto API as part of key derivation.
	*/
	res = -ENOMEM;

	res = validate_user_key(crypt_info, &ctx, FS_KEY_DESC_PREFIX,
	keysize);
	if (res && inode->i_sb->s_cop->key_prefix) {
	int res2 = validate_user_key(crypt_info, &ctx,
	inode->i_sb->s_cop->key_prefix,
	keysize);
	if (res2) {
	if (res2 == -ENOKEY)
	res = -ENOKEY;
	goto out;
	}
	res = 0;
	} else if (res) {
	goto out;
	}

	if (is_private_data_mode(crypt_info)) {
	if (!fscrypt_is_ice_capable(inode->i_sb)) {
	pr_warn("%s: ICE support not available\n",
	__func__);
	res = -EINVAL;
	goto out;
	}
	/* Let's encrypt/decrypt by ICE */
	goto do_ice;
	}


	ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
	if (!ctfm \|\| IS_ERR(ctfm)) {
	res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
	pr_debug("%s: error %d (inode %lu) allocating crypto tfm\n",
	__func__, res, inode->i_ino);
	goto out;
	}
	crypt_info->ci_ctfm = ctfm;
	crypto_skcipher_clear_flags(ctfm, ~0);
	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
	/*
	* if the provided key is longer than keysize, we use the first
	* keysize bytes of the derived key only
	*/
	res = crypto_skcipher_setkey(ctfm, crypt_info->ci_raw_key, 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, crypt_info->ci_raw_key,
	keysize);
	if (res) {
	pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
	__func__, res, inode->i_ino);
	goto out;
	}
	}
	memzero_explicit(crypt_info->ci_raw_key,
	sizeof(crypt_info->ci_raw_key));
	do_ice:
	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
	crypt_info = NULL;
	out:
	if (res == -ENOKEY)
	res = 0;
	put_crypt_info(crypt_info);
	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);