[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 <crypto/skcipher.h>
#include "fscrypt_private.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, 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) ||
		    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)
{
	put_crypt_info(inode->i_crypt_info);
	inode->i_crypt_info = NULL;
}
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>
a575784c	17	#include <crypto/skcipher.h>
3325bea5	18	#include "fscrypt_private.h"
0adda907	19
b7e7cf7a DW	20	static struct crypto_shash *essiv_hash_tfm;
b7e7cf7a DW	21
0adda907	22	/**
0b81d077	23	* derive_key_aes() - Derive a key using AES-128-ECB
0fac2d50	24	* @deriving_key: Encryption key used for derivation.
0adda907	25	* @source_key: Source key to which to apply derivation.
b7e7cf7a	26	* @derived_raw_key: Derived raw key.
0adda907 JK	27	*
	28	* Return: Zero on success; non-zero otherwise.
	29	*/
0b81d077	30	static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
b7e7cf7a DW	31	const struct fscrypt_key *source_key,
b7e7cf7a DW	32	u8 derived_raw_key[FS_MAX_KEY_SIZE])
0adda907 JK	33	{
0adda907 JK	34	int res = 0;
d407574e	35	struct skcipher_request *req = NULL;
d0082e1a	36	DECLARE_CRYPTO_WAIT(wait);
0adda907	37	struct scatterlist src_sg, dst_sg;
d407574e	38	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
0adda907 JK	39
	40	if (IS_ERR(tfm)) {
	41	res = PTR_ERR(tfm);
	42	tfm = NULL;
	43	goto out;
	44	}
d407574e LT	45	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
d407574e LT	46	req = skcipher_request_alloc(tfm, GFP_NOFS);
0adda907 JK	47	if (!req) {
	48	res = -ENOMEM;
	49	goto out;
	50	}
d407574e	51	skcipher_request_set_callback(req,
0adda907	52	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
d0082e1a	53	crypto_req_done, &wait);
d407574e	54	res = crypto_skcipher_setkey(tfm, deriving_key,
0b81d077	55	FS_AES_128_ECB_KEY_SIZE);
0adda907 JK	56	if (res < 0)
	57	goto out;
	58
b7e7cf7a DW	59	sg_init_one(&src_sg, source_key->raw, source_key->size);
	60	sg_init_one(&dst_sg, derived_raw_key, source_key->size);
	61	skcipher_request_set_crypt(req, &src_sg, &dst_sg, source_key->size,
	62	NULL);
d0082e1a	63	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
0adda907	64	out:
d407574e LT	65	skcipher_request_free(req);
d407574e LT	66	crypto_free_skcipher(tfm);
0adda907 JK	67	return res;
	68	}
	69
b5a7aef1 JK	70	static int validate_user_key(struct fscrypt_info *crypt_info,
b5a7aef1 JK	71	struct fscrypt_context ctx, u8 raw_key,
b7e7cf7a	72	const char *prefix, int min_keysize)
b5a7aef1	73	{
a5d431ef	74	char *description;
b5a7aef1 JK	75	struct key *keyring_key;
	76	struct fscrypt_key *master_key;
	77	const struct user_key_payload *ukp;
b5a7aef1 JK	78	int res;
b5a7aef1 JK	79
a5d431ef EB	80	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
	81	FS_KEY_DESCRIPTOR_SIZE,
	82	ctx->master_key_descriptor);
	83	if (!description)
b5a7aef1 JK	84	return -ENOMEM;
b5a7aef1 JK	85
a5d431ef EB	86	keyring_key = request_key(&key_type_logon, description, NULL);
a5d431ef EB	87	kfree(description);
b5a7aef1 JK	88	if (IS_ERR(keyring_key))
b5a7aef1 JK	89	return PTR_ERR(keyring_key);
1b53cf98	90	down_read(&keyring_key->sem);
b5a7aef1 JK	91
	92	if (keyring_key->type != &key_type_logon) {
	93	printk_once(KERN_WARNING
	94	"%s: key type must be logon\n", __func__);
	95	res = -ENOKEY;
	96	goto out;
	97	}
0837e49a	98	ukp = user_key_payload_locked(keyring_key);
d60b5b78 EB	99	if (!ukp) {
	100	/* key was revoked before we acquired its semaphore */
	101	res = -EKEYREVOKED;
	102	goto out;
	103	}
b5a7aef1 JK	104	if (ukp->datalen != sizeof(struct fscrypt_key)) {
b5a7aef1 JK	105	res = -EINVAL;
b5a7aef1 JK	106	goto out;
	107	}
	108	master_key = (struct fscrypt_key *)ukp->data;
	109	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);
	110
b7e7cf7a DW	111	if (master_key->size < min_keysize \|\| master_key->size > FS_MAX_KEY_SIZE
b7e7cf7a DW	112	\|\| master_key->size % AES_BLOCK_SIZE != 0) {
b5a7aef1 JK	113	printk_once(KERN_WARNING
	114	"%s: key size incorrect: %d\n",
	115	__func__, master_key->size);
	116	res = -ENOKEY;
b5a7aef1 JK	117	goto out;
b5a7aef1 JK	118	}
b7e7cf7a	119	res = derive_key_aes(ctx->nonce, master_key, raw_key);
b5a7aef1	120	out:
1b53cf98	121	up_read(&keyring_key->sem);
b5a7aef1 JK	122	key_put(keyring_key);
	123	return res;
	124	}
	125
b7e7cf7a DW	126	static const struct {
	127	const char *cipher_str;
	128	int keysize;
	129	} available_modes[] = {
	130	[FS_ENCRYPTION_MODE_AES_256_XTS] = { "xts(aes)",
	131	FS_AES_256_XTS_KEY_SIZE },
	132	[FS_ENCRYPTION_MODE_AES_256_CTS] = { "cts(cbc(aes))",
	133	FS_AES_256_CTS_KEY_SIZE },
	134	[FS_ENCRYPTION_MODE_AES_128_CBC] = { "cbc(aes)",
	135	FS_AES_128_CBC_KEY_SIZE },
	136	[FS_ENCRYPTION_MODE_AES_128_CTS] = { "cts(cbc(aes))",
	137	FS_AES_128_CTS_KEY_SIZE },
	138	};
	139
8f39850d EB	140	static int determine_cipher_type(struct fscrypt_info ci, struct inode inode,
	141	const char *cipher_str_ret, int keysize_ret)
	142	{
b7e7cf7a DW	143	u32 mode;
	144
	145	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
	146	pr_warn_ratelimited("fscrypt: inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)\n",
	147	inode->i_ino,
	148	ci->ci_data_mode, ci->ci_filename_mode);
	149	return -EINVAL;
8f39850d EB	150	}
8f39850d EB	151
b7e7cf7a DW	152	if (S_ISREG(inode->i_mode)) {
	153	mode = ci->ci_data_mode;
	154	} else if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode)) {
	155	mode = ci->ci_filename_mode;
	156	} else {
	157	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
	158	inode->i_ino, (inode->i_mode & S_IFMT));
	159	return -EINVAL;
8f39850d EB	160	}
8f39850d EB	161
b7e7cf7a DW	162	*cipher_str_ret = available_modes[mode].cipher_str;
	163	*keysize_ret = available_modes[mode].keysize;
	164	return 0;
8f39850d EB	165	}
8f39850d EB	166
0b81d077	167	static void put_crypt_info(struct fscrypt_info *ci)
0adda907	168	{
0adda907 JK	169	if (!ci)
	170	return;
	171
d407574e	172	crypto_free_skcipher(ci->ci_ctfm);
b7e7cf7a	173	crypto_free_cipher(ci->ci_essiv_tfm);
0b81d077	174	kmem_cache_free(fscrypt_info_cachep, ci);
0adda907 JK	175	}
0adda907 JK	176
b7e7cf7a DW	177	static int derive_essiv_salt(const u8 key, int keysize, u8 salt)
	178	{
	179	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
	180
	181	/* init hash transform on demand */
	182	if (unlikely(!tfm)) {
	183	struct crypto_shash *prev_tfm;
	184
	185	tfm = crypto_alloc_shash("sha256", 0, 0);
	186	if (IS_ERR(tfm)) {
	187	pr_warn_ratelimited("fscrypt: error allocating SHA-256 transform: %ld\n",
	188	PTR_ERR(tfm));
	189	return PTR_ERR(tfm);
	190	}
	191	prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
	192	if (prev_tfm) {
	193	crypto_free_shash(tfm);
	194	tfm = prev_tfm;
	195	}
	196	}
	197
	198	{
	199	SHASH_DESC_ON_STACK(desc, tfm);
	200	desc->tfm = tfm;
	201	desc->flags = 0;
	202
	203	return crypto_shash_digest(desc, key, keysize, salt);
	204	}
	205	}
	206
	207	static int init_essiv_generator(struct fscrypt_info ci, const u8 raw_key,
	208	int keysize)
	209	{
	210	int err;
	211	struct crypto_cipher *essiv_tfm;
	212	u8 salt[SHA256_DIGEST_SIZE];
	213
	214	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
	215	if (IS_ERR(essiv_tfm))
	216	return PTR_ERR(essiv_tfm);
	217
	218	ci->ci_essiv_tfm = essiv_tfm;
	219
	220	err = derive_essiv_salt(raw_key, keysize, salt);
	221	if (err)
	222	goto out;
	223
	224	/*
	225	* Using SHA256 to derive the salt/key will result in AES-256 being
	226	* used for IV generation. File contents encryption will still use the
	227	* configured keysize (AES-128) nevertheless.
	228	*/
	229	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
	230	if (err)
	231	goto out;
	232
	233	out:
	234	memzero_explicit(salt, sizeof(salt));
	235	return err;
	236	}
	237
	238	void __exit fscrypt_essiv_cleanup(void)
	239	{
	240	crypto_free_shash(essiv_hash_tfm);
241	}
242
1b53cf98	243	int fscrypt_get_encryption_info(struct inode *inode)
0adda907	244	{
0b81d077	245	struct fscrypt_info *crypt_info;
0b81d077	246	struct fscrypt_context ctx;
d407574e	247	struct crypto_skcipher *ctfm;
26bf3dc7	248	const char *cipher_str;
8f39850d	249	int keysize;
a6e08912	250	u8 *raw_key = NULL;
0adda907 JK	251	int res;
0adda907 JK	252
1b53cf98 EB	253	if (inode->i_crypt_info)
	254	return 0;
	255
f32d7ac2	256	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
cfc4d971 JK	257	if (res)
cfc4d971 JK	258	return res;
0b81d077	259
0b81d077 JK	260	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
0b81d077 JK	261	if (res < 0) {
5bbdcbbb	262	if (!fscrypt_dummy_context_enabled(inode) \|\|
e0428a26	263	IS_ENCRYPTED(inode))
0b81d077	264	return res;
5bbdcbbb TT	265	/* Fake up a context for an unencrypted directory */
5bbdcbbb TT	266	memset(&ctx, 0, sizeof(ctx));
8f39850d	267	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
0b81d077 JK	268	ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
0b81d077 JK	269	ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
5bbdcbbb	270	memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
0b81d077	271	} else if (res != sizeof(ctx)) {
0adda907	272	return -EINVAL;
0b81d077	273	}
8f39850d EB	274
	275	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
	276	return -EINVAL;
	277
	278	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
	279	return -EINVAL;
0adda907	280
0b81d077	281	crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
0adda907 JK	282	if (!crypt_info)
	283	return -ENOMEM;
	284
	285	crypt_info->ci_flags = ctx.flags;
	286	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
	287	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
	288	crypt_info->ci_ctfm = NULL;
b7e7cf7a	289	crypt_info->ci_essiv_tfm = NULL;
0adda907 JK	290	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
0adda907 JK	291	sizeof(crypt_info->ci_master_key));
640778fb	292
8f39850d EB	293	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
8f39850d EB	294	if (res)
26bf3dc7	295	goto out;
8f39850d	296
a6e08912 EB	297	/*
	298	* This cannot be a stack buffer because it is passed to the scatterlist
	299	* crypto API as part of key derivation.
	300	*/
	301	res = -ENOMEM;
	302	raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
	303	if (!raw_key)
	304	goto out;
	305
b7e7cf7a DW	306	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX,
b7e7cf7a DW	307	keysize);
b5a7aef1	308	if (res && inode->i_sb->s_cop->key_prefix) {
a5d431ef	309	int res2 = validate_user_key(crypt_info, &ctx, raw_key,
b7e7cf7a DW	310	inode->i_sb->s_cop->key_prefix,
b7e7cf7a DW	311	keysize);
b5a7aef1 JK	312	if (res2) {
	313	if (res2 == -ENOKEY)
	314	res = -ENOKEY;
	315	goto out;
	316	}
	317	} else if (res) {
66aa3e12 JK	318	goto out;
66aa3e12 JK	319	}
d407574e	320	ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
26bf3dc7 JK	321	if (!ctfm \|\| IS_ERR(ctfm)) {
26bf3dc7 JK	322	res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
b7e7cf7a DW	323	pr_debug("%s: error %d (inode %lu) allocating crypto tfm\n",
b7e7cf7a DW	324	__func__, res, inode->i_ino);
26bf3dc7	325	goto out;
0adda907	326	}
26bf3dc7	327	crypt_info->ci_ctfm = ctfm;
d407574e LT	328	crypto_skcipher_clear_flags(ctfm, ~0);
d407574e LT	329	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
b7e7cf7a DW	330	/*
	331	* if the provided key is longer than keysize, we use the first
	332	* keysize bytes of the derived key only
	333	*/
8f39850d	334	res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
26bf3dc7 JK	335	if (res)
	336	goto out;
	337
b7e7cf7a DW	338	if (S_ISREG(inode->i_mode) &&
	339	crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
	340	res = init_essiv_generator(crypt_info, raw_key, keysize);
	341	if (res) {
	342	pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
	343	__func__, res, inode->i_ino);
	344	goto out;
	345	}
	346	}
1b53cf98 EB	347	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
1b53cf98 EB	348	crypt_info = NULL;
26bf3dc7	349	out:
0b81d077	350	if (res == -ENOKEY)
26bf3dc7	351	res = 0;
0b81d077	352	put_crypt_info(crypt_info);
a6e08912	353	kzfree(raw_key);
0adda907 JK	354	return res;
0adda907 JK	355	}
1b53cf98	356	EXPORT_SYMBOL(fscrypt_get_encryption_info);
0adda907	357
3d204e24	358	void fscrypt_put_encryption_info(struct inode *inode)
0adda907	359	{
3d204e24 EB	360	put_crypt_info(inode->i_crypt_info);
3d204e24 EB	361	inode->i_crypt_info = NULL;
0b81d077 JK	362	}
0b81d077 JK	363	EXPORT_SYMBOL(fscrypt_put_encryption_info);