[mirror_ubuntu-artful-kernel.git] / fs / crypto / keyinfo.c

/*
 * 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
0adda907	1	/*
0b81d077	2	* key management facility for FS encryption support.
0adda907 JK	3	*
	4	* Copyright (C) 2015, Google, Inc.
	5	*
0b81d077	6	* This contains encryption key functions.
0adda907 JK	7	*
	8	* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
	9	*/
0b81d077	10
0adda907	11	#include <keys/user-type.h>
0adda907	12	#include <linux/scatterlist.h>
b7e7cf7a DW	13	#include <linux/ratelimit.h>
	14	#include <crypto/aes.h>
	15	#include <crypto/sha.h>
3325bea5	16	#include "fscrypt_private.h"
0adda907	17
b7e7cf7a DW	18	static struct crypto_shash *essiv_hash_tfm;
b7e7cf7a DW	19
0adda907 JK	20	static void derive_crypt_complete(struct crypto_async_request *req, int rc)
0adda907 JK	21	{
0b81d077	22	struct fscrypt_completion_result *ecr = req->data;
0adda907 JK	23
	24	if (rc == -EINPROGRESS)
	25	return;
	26
	27	ecr->res = rc;
	28	complete(&ecr->completion);
	29	}
	30
	31	/**
0b81d077	32	* derive_key_aes() - Derive a key using AES-128-ECB
0fac2d50	33	* @deriving_key: Encryption key used for derivation.
0adda907	34	* @source_key: Source key to which to apply derivation.
b7e7cf7a	35	* @derived_raw_key: Derived raw key.
0adda907 JK	36	*
	37	* Return: Zero on success; non-zero otherwise.
	38	*/
0b81d077	39	static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
b7e7cf7a DW	40	const struct fscrypt_key *source_key,
b7e7cf7a DW	41	u8 derived_raw_key[FS_MAX_KEY_SIZE])
0adda907 JK	42	{
0adda907 JK	43	int res = 0;
d407574e	44	struct skcipher_request *req = NULL;
0b81d077	45	DECLARE_FS_COMPLETION_RESULT(ecr);
0adda907	46	struct scatterlist src_sg, dst_sg;
d407574e	47	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
0adda907 JK	48
	49	if (IS_ERR(tfm)) {
	50	res = PTR_ERR(tfm);
	51	tfm = NULL;
	52	goto out;
	53	}
d407574e LT	54	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
d407574e LT	55	req = skcipher_request_alloc(tfm, GFP_NOFS);
0adda907 JK	56	if (!req) {
	57	res = -ENOMEM;
	58	goto out;
	59	}
d407574e	60	skcipher_request_set_callback(req,
0adda907 JK	61	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
0adda907 JK	62	derive_crypt_complete, &ecr);
d407574e	63	res = crypto_skcipher_setkey(tfm, deriving_key,
0b81d077	64	FS_AES_128_ECB_KEY_SIZE);
0adda907 JK	65	if (res < 0)
	66	goto out;
	67
b7e7cf7a DW	68	sg_init_one(&src_sg, source_key->raw, source_key->size);
	69	sg_init_one(&dst_sg, derived_raw_key, source_key->size);
	70	skcipher_request_set_crypt(req, &src_sg, &dst_sg, source_key->size,
	71	NULL);
d407574e	72	res = crypto_skcipher_encrypt(req);
0adda907	73	if (res == -EINPROGRESS \|\| res == -EBUSY) {
0adda907 JK	74	wait_for_completion(&ecr.completion);
	75	res = ecr.res;
	76	}
	77	out:
d407574e LT	78	skcipher_request_free(req);
d407574e LT	79	crypto_free_skcipher(tfm);
0adda907 JK	80	return res;
	81	}
	82
b5a7aef1 JK	83	static int validate_user_key(struct fscrypt_info *crypt_info,
b5a7aef1 JK	84	struct fscrypt_context ctx, u8 raw_key,
b7e7cf7a	85	const char *prefix, int min_keysize)
b5a7aef1	86	{
a5d431ef	87	char *description;
b5a7aef1 JK	88	struct key *keyring_key;
	89	struct fscrypt_key *master_key;
	90	const struct user_key_payload *ukp;
b5a7aef1 JK	91	int res;
b5a7aef1 JK	92
a5d431ef EB	93	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
	94	FS_KEY_DESCRIPTOR_SIZE,
	95	ctx->master_key_descriptor);
	96	if (!description)
b5a7aef1 JK	97	return -ENOMEM;
b5a7aef1 JK	98
a5d431ef EB	99	keyring_key = request_key(&key_type_logon, description, NULL);
a5d431ef EB	100	kfree(description);
b5a7aef1 JK	101	if (IS_ERR(keyring_key))
b5a7aef1 JK	102	return PTR_ERR(keyring_key);
1b53cf98	103	down_read(&keyring_key->sem);
b5a7aef1 JK	104
	105	if (keyring_key->type != &key_type_logon) {
	106	printk_once(KERN_WARNING
	107	"%s: key type must be logon\n", __func__);
	108	res = -ENOKEY;
	109	goto out;
	110	}
0837e49a	111	ukp = user_key_payload_locked(keyring_key);
3ec6d5ae EB	112	if (!ukp) {
	113	/* key was revoked before we acquired its semaphore */
	114	res = -EKEYREVOKED;
	115	goto out;
	116	}
b5a7aef1 JK	117	if (ukp->datalen != sizeof(struct fscrypt_key)) {
b5a7aef1 JK	118	res = -EINVAL;
b5a7aef1 JK	119	goto out;
	120	}
	121	master_key = (struct fscrypt_key *)ukp->data;
	122	BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);
	123
b7e7cf7a DW	124	if (master_key->size < min_keysize \|\| master_key->size > FS_MAX_KEY_SIZE
b7e7cf7a DW	125	\|\| master_key->size % AES_BLOCK_SIZE != 0) {
b5a7aef1 JK	126	printk_once(KERN_WARNING
	127	"%s: key size incorrect: %d\n",
	128	__func__, master_key->size);
	129	res = -ENOKEY;
b5a7aef1 JK	130	goto out;
b5a7aef1 JK	131	}
b7e7cf7a	132	res = derive_key_aes(ctx->nonce, master_key, raw_key);
b5a7aef1	133	out:
1b53cf98	134	up_read(&keyring_key->sem);
b5a7aef1 JK	135	key_put(keyring_key);
	136	return res;
	137	}
	138
b7e7cf7a DW	139	static const struct {
	140	const char *cipher_str;
	141	int keysize;
	142	} available_modes[] = {
	143	[FS_ENCRYPTION_MODE_AES_256_XTS] = { "xts(aes)",
	144	FS_AES_256_XTS_KEY_SIZE },
	145	[FS_ENCRYPTION_MODE_AES_256_CTS] = { "cts(cbc(aes))",
	146	FS_AES_256_CTS_KEY_SIZE },
	147	[FS_ENCRYPTION_MODE_AES_128_CBC] = { "cbc(aes)",
	148	FS_AES_128_CBC_KEY_SIZE },
	149	[FS_ENCRYPTION_MODE_AES_128_CTS] = { "cts(cbc(aes))",
	150	FS_AES_128_CTS_KEY_SIZE },
	151	};
	152
8f39850d EB	153	static int determine_cipher_type(struct fscrypt_info ci, struct inode inode,
	154	const char *cipher_str_ret, int keysize_ret)
	155	{
b7e7cf7a DW	156	u32 mode;
	157
	158	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
	159	pr_warn_ratelimited("fscrypt: inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)\n",
	160	inode->i_ino,
	161	ci->ci_data_mode, ci->ci_filename_mode);
	162	return -EINVAL;
8f39850d EB	163	}
8f39850d EB	164
b7e7cf7a DW	165	if (S_ISREG(inode->i_mode)) {
	166	mode = ci->ci_data_mode;
	167	} else if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode)) {
	168	mode = ci->ci_filename_mode;
	169	} else {
	170	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
	171	inode->i_ino, (inode->i_mode & S_IFMT));
	172	return -EINVAL;
8f39850d EB	173	}
8f39850d EB	174
b7e7cf7a DW	175	*cipher_str_ret = available_modes[mode].cipher_str;
	176	*keysize_ret = available_modes[mode].keysize;
	177	return 0;
8f39850d EB	178	}
8f39850d EB	179
0b81d077	180	static void put_crypt_info(struct fscrypt_info *ci)
0adda907	181	{
0adda907 JK	182	if (!ci)
	183	return;
	184
d407574e	185	crypto_free_skcipher(ci->ci_ctfm);
b7e7cf7a	186	crypto_free_cipher(ci->ci_essiv_tfm);
0b81d077	187	kmem_cache_free(fscrypt_info_cachep, ci);
0adda907 JK	188	}
0adda907 JK	189
b7e7cf7a DW	190	static int derive_essiv_salt(const u8 key, int keysize, u8 salt)
	191	{
	192	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
	193
	194	/* init hash transform on demand */
	195	if (unlikely(!tfm)) {
	196	struct crypto_shash *prev_tfm;
	197
	198	tfm = crypto_alloc_shash("sha256", 0, 0);
	199	if (IS_ERR(tfm)) {
	200	pr_warn_ratelimited("fscrypt: error allocating SHA-256 transform: %ld\n",
	201	PTR_ERR(tfm));
	202	return PTR_ERR(tfm);
	203	}
	204	prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
	205	if (prev_tfm) {
	206	crypto_free_shash(tfm);
	207	tfm = prev_tfm;
	208	}
	209	}
	210
	211	{
	212	SHASH_DESC_ON_STACK(desc, tfm);
	213	desc->tfm = tfm;
	214	desc->flags = 0;
	215
	216	return crypto_shash_digest(desc, key, keysize, salt);
	217	}
	218	}
	219
	220	static int init_essiv_generator(struct fscrypt_info ci, const u8 raw_key,
	221	int keysize)
	222	{
	223	int err;
	224	struct crypto_cipher *essiv_tfm;
	225	u8 salt[SHA256_DIGEST_SIZE];
	226
	227	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
	228	if (IS_ERR(essiv_tfm))
	229	return PTR_ERR(essiv_tfm);
	230
	231	ci->ci_essiv_tfm = essiv_tfm;
	232
	233	err = derive_essiv_salt(raw_key, keysize, salt);
	234	if (err)
	235	goto out;
	236
	237	/*
	238	* Using SHA256 to derive the salt/key will result in AES-256 being
	239	* used for IV generation. File contents encryption will still use the
	240	* configured keysize (AES-128) nevertheless.
	241	*/
	242	err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
	243	if (err)
	244	goto out;
	245
	246	out:
	247	memzero_explicit(salt, sizeof(salt));
	248	return err;
	249	}
	250
	251	void __exit fscrypt_essiv_cleanup(void)
	252	{
	253	crypto_free_shash(essiv_hash_tfm);
254	}
255
1b53cf98	256	int fscrypt_get_encryption_info(struct inode *inode)
0adda907	257	{
0b81d077	258	struct fscrypt_info *crypt_info;
0b81d077	259	struct fscrypt_context ctx;
d407574e	260	struct crypto_skcipher *ctfm;
26bf3dc7	261	const char *cipher_str;
8f39850d	262	int keysize;
a6e08912	263	u8 *raw_key = NULL;
0adda907 JK	264	int res;
0adda907 JK	265
1b53cf98 EB	266	if (inode->i_crypt_info)
	267	return 0;
	268
f32d7ac2	269	res = fscrypt_initialize(inode->i_sb->s_cop->flags);
cfc4d971 JK	270	if (res)
cfc4d971 JK	271	return res;
0b81d077	272
0b81d077 JK	273	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
0b81d077 JK	274	if (res < 0) {
5bbdcbbb TT	275	if (!fscrypt_dummy_context_enabled(inode) \|\|
5bbdcbbb TT	276	inode->i_sb->s_cop->is_encrypted(inode))
0b81d077	277	return res;
5bbdcbbb TT	278	/* Fake up a context for an unencrypted directory */
5bbdcbbb TT	279	memset(&ctx, 0, sizeof(ctx));
8f39850d	280	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
0b81d077 JK	281	ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
0b81d077 JK	282	ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
5bbdcbbb	283	memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
0b81d077	284	} else if (res != sizeof(ctx)) {
0adda907	285	return -EINVAL;
0b81d077	286	}
8f39850d EB	287
	288	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
	289	return -EINVAL;
	290
	291	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
	292	return -EINVAL;
0adda907	293
0b81d077	294	crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
0adda907 JK	295	if (!crypt_info)
	296	return -ENOMEM;
	297
	298	crypt_info->ci_flags = ctx.flags;
	299	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
	300	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
	301	crypt_info->ci_ctfm = NULL;
b7e7cf7a	302	crypt_info->ci_essiv_tfm = NULL;
0adda907 JK	303	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
0adda907 JK	304	sizeof(crypt_info->ci_master_key));
640778fb	305
8f39850d EB	306	res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
8f39850d EB	307	if (res)
26bf3dc7	308	goto out;
8f39850d	309
a6e08912 EB	310	/*
	311	* This cannot be a stack buffer because it is passed to the scatterlist
	312	* crypto API as part of key derivation.
	313	*/
	314	res = -ENOMEM;
	315	raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
	316	if (!raw_key)
	317	goto out;
	318
b7e7cf7a DW	319	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX,
b7e7cf7a DW	320	keysize);
b5a7aef1	321	if (res && inode->i_sb->s_cop->key_prefix) {
a5d431ef	322	int res2 = validate_user_key(crypt_info, &ctx, raw_key,
b7e7cf7a DW	323	inode->i_sb->s_cop->key_prefix,
b7e7cf7a DW	324	keysize);
b5a7aef1 JK	325	if (res2) {
	326	if (res2 == -ENOKEY)
	327	res = -ENOKEY;
	328	goto out;
	329	}
	330	} else if (res) {
66aa3e12 JK	331	goto out;
66aa3e12 JK	332	}
d407574e	333	ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
26bf3dc7 JK	334	if (!ctfm \|\| IS_ERR(ctfm)) {
26bf3dc7 JK	335	res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
b7e7cf7a DW	336	pr_debug("%s: error %d (inode %lu) allocating crypto tfm\n",
b7e7cf7a DW	337	__func__, res, inode->i_ino);
26bf3dc7	338	goto out;
0adda907	339	}
26bf3dc7	340	crypt_info->ci_ctfm = ctfm;
d407574e LT	341	crypto_skcipher_clear_flags(ctfm, ~0);
d407574e LT	342	crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
b7e7cf7a DW	343	/*
	344	* if the provided key is longer than keysize, we use the first
	345	* keysize bytes of the derived key only
	346	*/
8f39850d	347	res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
26bf3dc7 JK	348	if (res)
	349	goto out;
	350
b7e7cf7a DW	351	if (S_ISREG(inode->i_mode) &&
	352	crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
	353	res = init_essiv_generator(crypt_info, raw_key, keysize);
	354	if (res) {
	355	pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
	356	__func__, res, inode->i_ino);
	357	goto out;
	358	}
	359	}
1b53cf98 EB	360	if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
1b53cf98 EB	361	crypt_info = NULL;
26bf3dc7	362	out:
0b81d077	363	if (res == -ENOKEY)
26bf3dc7	364	res = 0;
0b81d077	365	put_crypt_info(crypt_info);
a6e08912	366	kzfree(raw_key);
0adda907 JK	367	return res;
0adda907 JK	368	}
1b53cf98	369	EXPORT_SYMBOL(fscrypt_get_encryption_info);
0adda907	370
0b81d077	371	void fscrypt_put_encryption_info(struct inode inode, struct fscrypt_info ci)
0adda907	372	{
0b81d077 JK	373	struct fscrypt_info *prev;
	374
	375	if (ci == NULL)
	376	ci = ACCESS_ONCE(inode->i_crypt_info);
	377	if (ci == NULL)
	378	return;
0adda907	379
0b81d077 JK	380	prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
	381	if (prev != ci)
	382	return;
	383
	384	put_crypt_info(ci);
	385	}
	386	EXPORT_SYMBOL(fscrypt_put_encryption_info);