[linux-2.6-block.git] / fs / crypto / keyinfo.c

// 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 "fscrypt_private.h"

static struct crypto_shash *essiv_hash_tfm;

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

	if (rc == -EINPROGRESS)
		return;

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

/**
 * 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_FS_COMPLETION_RESULT(ecr);
	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,
			derive_crypt_complete, &ecr);
	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_skcipher_encrypt(req);
	if (res == -EINPROGRESS || res == -EBUSY) {
		wait_for_completion(&ecr.completion);
		res = ecr.res;
	}
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, u8 *raw_key,
			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, raw_key);
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 },
};

static int determine_cipher_type(struct fscrypt_info *ci, struct inode *inode,
				 const char **cipher_str_ret, int *keysize_ret)
{
	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)) {
		mode = ci->ci_data_mode;
	} else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) {
		mode = ci->ci_filename_mode;
	} 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);
	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);
}

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;
	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) ||
		    inode->i_sb->s_cop->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));

	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
	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;
	raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
	if (!raw_key)
		goto out;

	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX,
				keysize);
	if (res && inode->i_sb->s_cop->key_prefix) {
		int res2 = validate_user_key(crypt_info, &ctx, raw_key,
					     inode->i_sb->s_cop->key_prefix,
					     keysize);
		if (res2) {
			if (res2 == -ENOKEY)
				res = -ENOKEY;
			goto out;
		}
	} else if (res) {
		goto out;
	}
	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, 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, raw_key, keysize);
		if (res) {
			pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
				 __func__, res, inode->i_ino);
			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, struct fscrypt_info *ci)
{
	struct fscrypt_info *prev;

	if (ci == NULL)
		ci = ACCESS_ONCE(inode->i_crypt_info);
	if (ci == NULL)
		return;

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

	put_crypt_info(ci);
}
EXPORT_SYMBOL(fscrypt_put_encryption_info);
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
0adda907	2	/*
0b81d077	3	* key management facility for FS encryption support.
0adda907 JK	4	*
	5	* Copyright (C) 2015, Google, Inc.
	6	*
0b81d077	7	* This contains encryption key functions.
0adda907 JK	8	*
	9	* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
	10	*/
0b81d077	11
0adda907	12	#include <keys/user-type.h>
0adda907	13	#include <linux/scatterlist.h>
b7e7cf7a DW	14	#include <linux/ratelimit.h>
	15	#include <crypto/aes.h>
	16	#include <crypto/sha.h>
3325bea5	17	#include "fscrypt_private.h"
0adda907	18
b7e7cf7a DW	19	static struct crypto_shash *essiv_hash_tfm;
b7e7cf7a DW	20
0adda907 JK	21	static void derive_crypt_complete(struct crypto_async_request *req, int rc)
0adda907 JK	22	{
0b81d077	23	struct fscrypt_completion_result *ecr = req->data;
0adda907 JK	24
	25	if (rc == -EINPROGRESS)
	26	return;
	27
	28	ecr->res = rc;
	29	complete(&ecr->completion);
	30	}
	31
	32	/**
0b81d077	33	* derive_key_aes() - Derive a key using AES-128-ECB
0fac2d50	34	* @deriving_key: Encryption key used for derivation.
0adda907	35	* @source_key: Source key to which to apply derivation.
b7e7cf7a	36	* @derived_raw_key: Derived raw key.
0adda907 JK	37	*
	38	* Return: Zero on success; non-zero otherwise.
	39	*/
0b81d077	40	static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
b7e7cf7a DW	41	const struct fscrypt_key *source_key,
b7e7cf7a DW	42	u8 derived_raw_key[FS_MAX_KEY_SIZE])
0adda907 JK	43	{
0adda907 JK	44	int res = 0;
d407574e	45	struct skcipher_request *req = NULL;
0b81d077	46	DECLARE_FS_COMPLETION_RESULT(ecr);
0adda907	47	struct scatterlist src_sg, dst_sg;
d407574e	48	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
0adda907 JK	49
	50	if (IS_ERR(tfm)) {
	51	res = PTR_ERR(tfm);
	52	tfm = NULL;
	53	goto out;
	54	}
d407574e LT	55	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
d407574e LT	56	req = skcipher_request_alloc(tfm, GFP_NOFS);
0adda907 JK	57	if (!req) {
	58	res = -ENOMEM;
	59	goto out;
	60	}
d407574e	61	skcipher_request_set_callback(req,
0adda907 JK	62	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
0adda907 JK	63	derive_crypt_complete, &ecr);
d407574e	64	res = crypto_skcipher_setkey(tfm, deriving_key,
0b81d077	65	FS_AES_128_ECB_KEY_SIZE);
0adda907 JK	66	if (res < 0)
	67	goto out;
	68
b7e7cf7a DW	69	sg_init_one(&src_sg, source_key->raw, source_key->size);
	70	sg_init_one(&dst_sg, derived_raw_key, source_key->size);
	71	skcipher_request_set_crypt(req, &src_sg, &dst_sg, source_key->size,
	72	NULL);
d407574e	73	res = crypto_skcipher_encrypt(req);
0adda907	74	if (res == -EINPROGRESS \|\| res == -EBUSY) {
0adda907 JK	75	wait_for_completion(&ecr.completion);
	76	res = ecr.res;
	77	}
	78	out:
d407574e LT	79	skcipher_request_free(req);
d407574e LT	80	crypto_free_skcipher(tfm);
0adda907 JK	81	return res;
	82	}
	83
b5a7aef1 JK	84	static int validate_user_key(struct fscrypt_info *crypt_info,
b5a7aef1 JK	85	struct fscrypt_context ctx, u8 raw_key,
b7e7cf7a	86	const char *prefix, int min_keysize)
b5a7aef1	87	{
a5d431ef	88	char *description;
b5a7aef1 JK	89	struct key *keyring_key;
	90	struct fscrypt_key *master_key;
	91	const struct user_key_payload *ukp;
b5a7aef1 JK	92	int res;
b5a7aef1 JK	93
a5d431ef EB	94	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
	95	FS_KEY_DESCRIPTOR_SIZE,
	96	ctx->master_key_descriptor);
	97	if (!description)
b5a7aef1 JK	98	return -ENOMEM;
b5a7aef1 JK	99
a5d431ef EB	100	keyring_key = request_key(&key_type_logon, description, NULL);
a5d431ef EB	101	kfree(description);
b5a7aef1 JK	102	if (IS_ERR(keyring_key))
b5a7aef1 JK	103	return PTR_ERR(keyring_key);
1b53cf98	104	down_read(&keyring_key->sem);
b5a7aef1 JK	105
	106	if (keyring_key->type != &key_type_logon) {
	107	printk_once(KERN_WARNING
	108	"%s: key type must be logon\n", __func__);
	109	res = -ENOKEY;
	110	goto out;
	111	}
0837e49a	112	ukp = user_key_payload_locked(keyring_key);
d60b5b78 EB	113	if (!ukp) {
	114	/* key was revoked before we acquired its semaphore */
	115	res = -EKEYREVOKED;
	116	goto out;
	117	}
b5a7aef1 JK	118	if (ukp->datalen != sizeof(struct fscrypt_key)) {
b5a7aef1 JK	119	res = -EINVAL;
b5a7aef1 JK	120	goto out;
	121	}
	122	master_key = (struct fscrypt_key *)ukp->data;
	123	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);
	124
b7e7cf7a DW	125	if (master_key->size < min_keysize \|\| master_key->size > FS_MAX_KEY_SIZE
b7e7cf7a DW	126	\|\| master_key->size % AES_BLOCK_SIZE != 0) {
b5a7aef1 JK	127	printk_once(KERN_WARNING
	128	"%s: key size incorrect: %d\n",
	129	__func__, master_key->size);
	130	res = -ENOKEY;
b5a7aef1 JK	131	goto out;
b5a7aef1 JK	132	}
b7e7cf7a	133	res = derive_key_aes(ctx->nonce, master_key, raw_key);
b5a7aef1	134	out:
1b53cf98	135	up_read(&keyring_key->sem);
b5a7aef1 JK	136	key_put(keyring_key);
	137	return res;
	138	}
	139
b7e7cf7a DW	140	static const struct {
	141	const char *cipher_str;
	142	int keysize;
	143	} available_modes[] = {
	144	[FS_ENCRYPTION_MODE_AES_256_XTS] = { "xts(aes)",
	145	FS_AES_256_XTS_KEY_SIZE },
	146	[FS_ENCRYPTION_MODE_AES_256_CTS] = { "cts(cbc(aes))",
	147	FS_AES_256_CTS_KEY_SIZE },
	148	[FS_ENCRYPTION_MODE_AES_128_CBC] = { "cbc(aes)",
	149	FS_AES_128_CBC_KEY_SIZE },
	150	[FS_ENCRYPTION_MODE_AES_128_CTS] = { "cts(cbc(aes))",
	151	FS_AES_128_CTS_KEY_SIZE },
	152	};
	153
8f39850d EB	154	static int determine_cipher_type(struct fscrypt_info ci, struct inode inode,
	155	const char *cipher_str_ret, int keysize_ret)
	156	{
b7e7cf7a DW	157	u32 mode;
	158
	159	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
	160	pr_warn_ratelimited("fscrypt: inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)\n",
	161	inode->i_ino,
	162	ci->ci_data_mode, ci->ci_filename_mode);
	163	return -EINVAL;
8f39850d EB	164	}
8f39850d EB	165
b7e7cf7a DW	166	if (S_ISREG(inode->i_mode)) {
	167	mode = ci->ci_data_mode;
	168	} else if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode)) {
	169	mode = ci->ci_filename_mode;
	170	} else {
	171	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
	172	inode->i_ino, (inode->i_mode & S_IFMT));
	173	return -EINVAL;
8f39850d EB	174	}
8f39850d EB	175
b7e7cf7a DW	176	*cipher_str_ret = available_modes[mode].cipher_str;
	177	*keysize_ret = available_modes[mode].keysize;
	178	return 0;
8f39850d EB	179	}
8f39850d EB	180
0b81d077	181	static void put_crypt_info(struct fscrypt_info *ci)
0adda907	182	{
0adda907 JK	183	if (!ci)
	184	return;
	185
d407574e	186	crypto_free_skcipher(ci->ci_ctfm);
b7e7cf7a	187	crypto_free_cipher(ci->ci_essiv_tfm);
0b81d077	188	kmem_cache_free(fscrypt_info_cachep, ci);
0adda907 JK	189	}
0adda907 JK	190
b7e7cf7a DW	191	static int derive_essiv_salt(const u8 key, int keysize, u8 salt)
	192	{
	193	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
	194
	195	/* init hash transform on demand */
	196	if (unlikely(!tfm)) {
	197	struct crypto_shash *prev_tfm;
	198
	199	tfm = crypto_alloc_shash("sha256", 0, 0);
	200	if (IS_ERR(tfm)) {
	201	pr_warn_ratelimited("fscrypt: error allocating SHA-256 transform: %ld\n",
	202	PTR_ERR(tfm));
	203	return PTR_ERR(tfm);
	204	}
	205	prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
	206	if (prev_tfm) {
	207	crypto_free_shash(tfm);
	208	tfm = prev_tfm;
	209	}
	210	}
	211
	212	{
	213	SHASH_DESC_ON_STACK(desc, tfm);
	214	desc->tfm = tfm;
	215	desc->flags = 0;
	216
	217	return crypto_shash_digest(desc, key, keysize, salt);
	218	}
	219	}
	220
	221	static int init_essiv_generator(struct fscrypt_info ci, const u8 raw_key,
	222	int keysize)
	223	{
	224	int err;
	225	struct crypto_cipher *essiv_tfm;
	226	u8 salt[SHA256_DIGEST_SIZE];
	227
	228	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
	229	if (IS_ERR(essiv_tfm))
	230	return PTR_ERR(essiv_tfm);
	231
	232	ci->ci_essiv_tfm = essiv_tfm;
	233
	234	err = derive_essiv_salt(raw_key, keysize, salt);
	235	if (err)
	236	goto out;
	237
	238	/*
	239	* Using SHA256 to derive the salt/key will result in AES-256 being
	240	* used for IV generation. File contents encryption will still use the
	241	* configured keysize (AES-128) nevertheless.
	242	*/
	243	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
	244	if (err)
	245	goto out;
	246
	247	out:
	248	memzero_explicit(salt, sizeof(salt));
	249	return err;
	250	}
	251
	252	void __exit fscrypt_essiv_cleanup(void)
	253	{
	254	crypto_free_shash(essiv_hash_tfm);
255	}
256
1b53cf98	257	int fscrypt_get_encryption_info(struct inode *inode)
0adda907	258	{
0b81d077	259	struct fscrypt_info *crypt_info;
0b81d077	260	struct fscrypt_context ctx;
d407574e	261	struct crypto_skcipher *ctfm;
26bf3dc7	262	const char *cipher_str;
8f39850d	263	int keysize;
a6e08912	264	u8 *raw_key = NULL;
0adda907 JK	265	int res;
0adda907 JK	266
1b53cf98 EB	267	if (inode->i_crypt_info)
	268	return 0;
	269
f32d7ac2	270	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
cfc4d971 JK	271	if (res)
cfc4d971 JK	272	return res;
0b81d077	273
0b81d077 JK	274	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
0b81d077 JK	275	if (res < 0) {
5bbdcbbb TT	276	if (!fscrypt_dummy_context_enabled(inode) \|\|
5bbdcbbb TT	277	inode->i_sb->s_cop->is_encrypted(inode))
0b81d077	278	return res;
5bbdcbbb TT	279	/* Fake up a context for an unencrypted directory */
5bbdcbbb TT	280	memset(&ctx, 0, sizeof(ctx));
8f39850d	281	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
0b81d077 JK	282	ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
0b81d077 JK	283	ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
5bbdcbbb	284	memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
0b81d077	285	} else if (res != sizeof(ctx)) {
0adda907	286	return -EINVAL;
0b81d077	287	}
8f39850d EB	288
	289	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
	290	return -EINVAL;
	291
	292	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
	293	return -EINVAL;
0adda907	294
0b81d077	295	crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
0adda907 JK	296	if (!crypt_info)
	297	return -ENOMEM;
	298
	299	crypt_info->ci_flags = ctx.flags;
	300	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
	301	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
	302	crypt_info->ci_ctfm = NULL;
b7e7cf7a	303	crypt_info->ci_essiv_tfm = NULL;
0adda907 JK	304	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
0adda907 JK	305	sizeof(crypt_info->ci_master_key));
640778fb	306
8f39850d EB	307	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
8f39850d EB	308	if (res)
26bf3dc7	309	goto out;
8f39850d	310
a6e08912 EB	311	/*
	312	* This cannot be a stack buffer because it is passed to the scatterlist
	313	* crypto API as part of key derivation.
	314	*/
	315	res = -ENOMEM;
	316	raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
	317	if (!raw_key)
	318	goto out;
	319
b7e7cf7a DW	320	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX,
b7e7cf7a DW	321	keysize);
b5a7aef1	322	if (res && inode->i_sb->s_cop->key_prefix) {
a5d431ef	323	int res2 = validate_user_key(crypt_info, &ctx, raw_key,
b7e7cf7a DW	324	inode->i_sb->s_cop->key_prefix,
b7e7cf7a DW	325	keysize);
b5a7aef1 JK	326	if (res2) {
	327	if (res2 == -ENOKEY)
	328	res = -ENOKEY;
	329	goto out;
	330	}
	331	} else if (res) {
66aa3e12 JK	332	goto out;
66aa3e12 JK	333	}
d407574e	334	ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
26bf3dc7 JK	335	if (!ctfm \|\| IS_ERR(ctfm)) {
26bf3dc7 JK	336	res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
b7e7cf7a DW	337	pr_debug("%s: error %d (inode %lu) allocating crypto tfm\n",
b7e7cf7a DW	338	__func__, res, inode->i_ino);
26bf3dc7	339	goto out;
0adda907	340	}
26bf3dc7	341	crypt_info->ci_ctfm = ctfm;
d407574e LT	342	crypto_skcipher_clear_flags(ctfm, ~0);
d407574e LT	343	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
b7e7cf7a DW	344	/*
	345	* if the provided key is longer than keysize, we use the first
	346	* keysize bytes of the derived key only
	347	*/
8f39850d	348	res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
26bf3dc7 JK	349	if (res)
	350	goto out;
	351
b7e7cf7a DW	352	if (S_ISREG(inode->i_mode) &&
	353	crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
	354	res = init_essiv_generator(crypt_info, raw_key, keysize);
	355	if (res) {
	356	pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
	357	__func__, res, inode->i_ino);
	358	goto out;
	359	}
	360	}
1b53cf98 EB	361	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
1b53cf98 EB	362	crypt_info = NULL;
26bf3dc7	363	out:
0b81d077	364	if (res == -ENOKEY)
26bf3dc7	365	res = 0;
0b81d077	366	put_crypt_info(crypt_info);
a6e08912	367	kzfree(raw_key);
0adda907 JK	368	return res;
0adda907 JK	369	}
1b53cf98	370	EXPORT_SYMBOL(fscrypt_get_encryption_info);
0adda907	371
0b81d077	372	void fscrypt_put_encryption_info(struct inode inode, struct fscrypt_info ci)
0adda907	373	{
0b81d077 JK	374	struct fscrypt_info *prev;
	375
	376	if (ci == NULL)
	377	ci = ACCESS_ONCE(inode->i_crypt_info);
	378	if (ci == NULL)
	379	return;
0adda907	380
0b81d077 JK	381	prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
	382	if (prev != ci)
	383	return;
	384
	385	put_crypt_info(ci);
	386	}
	387	EXPORT_SYMBOL(fscrypt_put_encryption_info);