[linux-2.6-block.git] / fs / ext4 / crypto_key.c

/*
 * 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 <crypto/skcipher.h>
#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_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_key:  Derived key.
 *
 * Return: Zero on success; non-zero otherwise.
 */
static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
			       char source_key[EXT4_AES_256_XTS_KEY_SIZE],
			       char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
{
	int res = 0;
	struct skcipher_request *req = NULL;
	DECLARE_EXT4_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,
				     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);
	skcipher_request_set_crypt(req, &src_sg, &dst_sg,
				   EXT4_AES_256_XTS_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;
}

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_skcipher(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_skcipher *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;
	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_aes(ctx.nonce, master_key->raw,
				  raw_key);
	up_read(&keyring_key->sem);
	if (res)
		goto out;
got_key:
	ctfm = crypto_alloc_skcipher(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_skcipher_clear_flags(ctfm, ~0);
	crypto_tfm_set_flags(crypto_skcipher_tfm(ctfm),
			     CRYPTO_TFM_REQ_WEAK_KEY);
	res = crypto_skcipher_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);
}
Commit	Line	Data
88bd6ccd MH	1	/*
	2	* linux/fs/ext4/crypto_key.c
	3	*
	4	* Copyright (C) 2015, Google, Inc.
	5	*
	6	* This contains encryption key functions for ext4
	7	*
	8	* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
	9	*/
	10
3f32a5be	11	#include <crypto/skcipher.h>
88bd6ccd MH	12	#include <keys/encrypted-type.h>
	13	#include <keys/user-type.h>
	14	#include <linux/random.h>
	15	#include <linux/scatterlist.h>
	16	#include <uapi/linux/keyctl.h>
	17
	18	#include "ext4.h"
	19	#include "xattr.h"
	20
	21	static void derive_crypt_complete(struct crypto_async_request *req, int rc)
	22	{
	23	struct ext4_completion_result *ecr = req->data;
	24
	25	if (rc == -EINPROGRESS)
	26	return;
	27
	28	ecr->res = rc;
	29	complete(&ecr->completion);
	30	}
	31
	32	/**
	33	* ext4_derive_key_aes() - Derive a key using AES-128-ECB
bb9a4e7e	34	* @deriving_key: Encryption key used for derivation.
88bd6ccd MH	35	* @source_key: Source key to which to apply derivation.
	36	* @derived_key: Derived key.
	37	*
	38	* Return: Zero on success; non-zero otherwise.
	39	*/
	40	static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
	41	char source_key[EXT4_AES_256_XTS_KEY_SIZE],
	42	char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
	43	{
	44	int res = 0;
3f32a5be	45	struct skcipher_request *req = NULL;
88bd6ccd MH	46	DECLARE_EXT4_COMPLETION_RESULT(ecr);
88bd6ccd MH	47	struct scatterlist src_sg, dst_sg;
3f32a5be	48	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
88bd6ccd MH	49
	50	if (IS_ERR(tfm)) {
	51	res = PTR_ERR(tfm);
	52	tfm = NULL;
	53	goto out;
	54	}
3f32a5be HX	55	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
3f32a5be HX	56	req = skcipher_request_alloc(tfm, GFP_NOFS);
88bd6ccd MH	57	if (!req) {
	58	res = -ENOMEM;
	59	goto out;
	60	}
3f32a5be	61	skcipher_request_set_callback(req,
88bd6ccd MH	62	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
88bd6ccd MH	63	derive_crypt_complete, &ecr);
3f32a5be HX	64	res = crypto_skcipher_setkey(tfm, deriving_key,
3f32a5be HX	65	EXT4_AES_128_ECB_KEY_SIZE);
88bd6ccd MH	66	if (res < 0)
	67	goto out;
	68	sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
	69	sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
3f32a5be HX	70	skcipher_request_set_crypt(req, &src_sg, &dst_sg,
	71	EXT4_AES_256_XTS_KEY_SIZE, NULL);
	72	res = crypto_skcipher_encrypt(req);
88bd6ccd	73	if (res == -EINPROGRESS \|\| res == -EBUSY) {
88bd6ccd MH	74	wait_for_completion(&ecr.completion);
	75	res = ecr.res;
	76	}
	77
	78	out:
3f32a5be HX	79	skcipher_request_free(req);
3f32a5be HX	80	crypto_free_skcipher(tfm);
88bd6ccd MH	81	return res;
	82	}
	83
c936e1ec	84	void ext4_free_crypt_info(struct ext4_crypt_info *ci)
b7236e21	85	{
b7236e21 TT	86	if (!ci)
	87	return;
	88
	89	if (ci->ci_keyring_key)
	90	key_put(ci->ci_keyring_key);
3f32a5be	91	crypto_free_skcipher(ci->ci_ctfm);
8ee03714	92	kmem_cache_free(ext4_crypt_info_cachep, ci);
c936e1ec TT	93	}
	94
	95	void ext4_free_encryption_info(struct inode *inode,
	96	struct ext4_crypt_info *ci)
	97	{
	98	struct ext4_inode_info *ei = EXT4_I(inode);
	99	struct ext4_crypt_info *prev;
	100
	101	if (ci == NULL)
	102	ci = ACCESS_ONCE(ei->i_crypt_info);
	103	if (ci == NULL)
	104	return;
	105	prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
	106	if (prev != ci)
	107	return;
	108
	109	ext4_free_crypt_info(ci);
b7236e21 TT	110	}
	111
	112	int _ext4_get_encryption_info(struct inode *inode)
88bd6ccd MH	113	{
88bd6ccd MH	114	struct ext4_inode_info *ei = EXT4_I(inode);
b7236e21	115	struct ext4_crypt_info *crypt_info;
88bd6ccd MH	116	char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
	117	(EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
	118	struct key *keyring_key = NULL;
	119	struct ext4_encryption_key *master_key;
	120	struct ext4_encryption_context ctx;
146aa8b1	121	const struct user_key_payload *ukp;
6ddb2447	122	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
3f32a5be	123	struct crypto_skcipher *ctfm;
c936e1ec TT	124	const char *cipher_str;
	125	char raw_key[EXT4_MAX_KEY_SIZE];
	126	char mode;
b7236e21	127	int res;
88bd6ccd	128
8ee03714 TT	129	if (!ext4_read_workqueue) {
	130	res = ext4_init_crypto();
	131	if (res)
	132	return res;
	133	}
	134
c936e1ec TT	135	retry:
	136	crypt_info = ACCESS_ONCE(ei->i_crypt_info);
	137	if (crypt_info) {
	138	if (!crypt_info->ci_keyring_key \|\|
	139	key_validate(crypt_info->ci_keyring_key) == 0)
b7236e21	140	return 0;
c936e1ec TT	141	ext4_free_encryption_info(inode, crypt_info);
c936e1ec TT	142	goto retry;
88bd6ccd	143	}
b7236e21 TT	144
	145	res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	146	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
	147	&ctx, sizeof(ctx));
	148	if (res < 0) {
	149	if (!DUMMY_ENCRYPTION_ENABLED(sbi))
	150	return res;
	151	ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
	152	ctx.filenames_encryption_mode =
	153	EXT4_ENCRYPTION_MODE_AES_256_CTS;
	154	ctx.flags = 0;
	155	} else if (res != sizeof(ctx))
	156	return -EINVAL;
88bd6ccd MH	157	res = 0;
88bd6ccd MH	158
8ee03714	159	crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL);
b7236e21 TT	160	if (!crypt_info)
	161	return -ENOMEM;
	162
b7236e21 TT	163	crypt_info->ci_flags = ctx.flags;
	164	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
	165	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
	166	crypt_info->ci_ctfm = NULL;
c936e1ec	167	crypt_info->ci_keyring_key = NULL;
b7236e21 TT	168	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
b7236e21 TT	169	sizeof(crypt_info->ci_master_key));
6ddb2447	170	if (S_ISREG(inode->i_mode))
c936e1ec	171	mode = crypt_info->ci_data_mode;
6ddb2447	172	else if (S_ISDIR(inode->i_mode) \|\| S_ISLNK(inode->i_mode))
c936e1ec	173	mode = crypt_info->ci_filename_mode;
1aaa6e8b	174	else
6ddb2447	175	BUG();
c936e1ec TT	176	switch (mode) {
	177	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
	178	cipher_str = "xts(aes)";
	179	break;
	180	case EXT4_ENCRYPTION_MODE_AES_256_CTS:
	181	cipher_str = "cts(cbc(aes))";
	182	break;
	183	default:
	184	printk_once(KERN_WARNING
	185	"ext4: unsupported key mode %d (ino %u)\n",
	186	mode, (unsigned) inode->i_ino);
	187	res = -ENOKEY;
6ddb2447 TT	188	goto out;
6ddb2447 TT	189	}
c936e1ec TT	190	if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
	191	memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
	192	goto got_key;
	193	}
88bd6ccd MH	194	memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
	195	EXT4_KEY_DESC_PREFIX_SIZE);
	196	sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
	197	"%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
	198	ctx.master_key_descriptor);
	199	full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
	200	(2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
	201	keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
	202	if (IS_ERR(keyring_key)) {
	203	res = PTR_ERR(keyring_key);
	204	keyring_key = NULL;
	205	goto out;
	206	}
c936e1ec	207	crypt_info->ci_keyring_key = keyring_key;
687c3c36 TT	208	if (keyring_key->type != &key_type_logon) {
	209	printk_once(KERN_WARNING
	210	"ext4: key type must be logon\n");
	211	res = -ENOKEY;
	212	goto out;
	213	}
db7730e3	214	down_read(&keyring_key->sem);
146aa8b1	215	ukp = user_key_payload(keyring_key);
88bd6ccd MH	216	if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
88bd6ccd MH	217	res = -EINVAL;
db7730e3	218	up_read(&keyring_key->sem);
88bd6ccd MH	219	goto out;
	220	}
	221	master_key = (struct ext4_encryption_key *)ukp->data;
88bd6ccd MH	222	BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
88bd6ccd MH	223	EXT4_KEY_DERIVATION_NONCE_SIZE);
687c3c36 TT	224	if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) {
	225	printk_once(KERN_WARNING
	226	"ext4: key size incorrect: %d\n",
	227	master_key->size);
	228	res = -ENOKEY;
db7730e3	229	up_read(&keyring_key->sem);
687c3c36 TT	230	goto out;
687c3c36 TT	231	}
e2881b1b	232	res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
c936e1ec	233	raw_key);
db7730e3	234	up_read(&keyring_key->sem);
d76d99b2 LN	235	if (res)
d76d99b2 LN	236	goto out;
c936e1ec	237	got_key:
3f32a5be	238	ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
c936e1ec TT	239	if (!ctfm \|\| IS_ERR(ctfm)) {
	240	res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
	241	printk(KERN_DEBUG
	242	"%s: error %d (inode %u) allocating crypto tfm\n",
	243	__func__, res, (unsigned) inode->i_ino);
	244	goto out;
	245	}
	246	crypt_info->ci_ctfm = ctfm;
3f32a5be HX	247	crypto_skcipher_clear_flags(ctfm, ~0);
3f32a5be HX	248	crypto_tfm_set_flags(crypto_skcipher_tfm(ctfm),
c936e1ec	249	CRYPTO_TFM_REQ_WEAK_KEY);
3f32a5be HX	250	res = crypto_skcipher_setkey(ctfm, raw_key,
3f32a5be HX	251	ext4_encryption_key_size(mode));
c936e1ec TT	252	if (res)
	253	goto out;
	254	memzero_explicit(raw_key, sizeof(raw_key));
	255	if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
	256	ext4_free_crypt_info(crypt_info);
	257	goto retry;
b7236e21	258	}
c936e1ec TT	259	return 0;
	260
	261	out:
	262	if (res == -ENOKEY)
	263	res = 0;
	264	ext4_free_crypt_info(crypt_info);
	265	memzero_explicit(raw_key, sizeof(raw_key));
88bd6ccd MH	266	return res;
	267	}
	268
	269	int ext4_has_encryption_key(struct inode *inode)
	270	{
	271	struct ext4_inode_info *ei = EXT4_I(inode);
88bd6ccd	272
b7236e21	273	return (ei->i_crypt_info != NULL);
88bd6ccd	274	}