[deliverable/linux.git] / fs / ext4 / crypto_policy.c

/*
 * linux/fs/ext4/crypto_policy.c
 *
 * Copyright (C) 2015, Google, Inc.
 *
 * This contains encryption policy functions for ext4
 *
 * Written by Michael Halcrow, 2015.
 */

#include <linux/random.h>
#include <linux/string.h>
#include <linux/types.h>

#include "ext4_jbd2.h"
#include "ext4.h"
#include "xattr.h"

static int ext4_inode_has_encryption_context(struct inode *inode)
{
	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
				 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
	return (res > 0);
}

/*
 * check whether the policy is consistent with the encryption context
 * for the inode
 */
static int ext4_is_encryption_context_consistent_with_policy(
	struct inode *inode, const struct ext4_encryption_policy *policy)
{
	struct ext4_encryption_context ctx;
	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
				 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
				 sizeof(ctx));
	if (res != sizeof(ctx))
		return 0;
	return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
			EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
		(ctx.flags ==
		 policy->flags) &&
		(ctx.contents_encryption_mode ==
		 policy->contents_encryption_mode) &&
		(ctx.filenames_encryption_mode ==
		 policy->filenames_encryption_mode));
}

static int ext4_create_encryption_context_from_policy(
	struct inode *inode, const struct ext4_encryption_policy *policy)
{
	struct ext4_encryption_context ctx;
	handle_t *handle;
	int res, res2;

	res = ext4_convert_inline_data(inode);
	if (res)
		return res;

	ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
	       EXT4_KEY_DESCRIPTOR_SIZE);
	if (!ext4_valid_contents_enc_mode(policy->contents_encryption_mode)) {
		printk(KERN_WARNING
		       "%s: Invalid contents encryption mode %d\n", __func__,
			policy->contents_encryption_mode);
		return -EINVAL;
	}
	if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
		printk(KERN_WARNING
		       "%s: Invalid filenames encryption mode %d\n", __func__,
			policy->filenames_encryption_mode);
		return -EINVAL;
	}
	if (policy->flags & ~EXT4_POLICY_FLAGS_VALID)
		return -EINVAL;
	ctx.contents_encryption_mode = policy->contents_encryption_mode;
	ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
	ctx.flags = policy->flags;
	BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);

	handle = ext4_journal_start(inode, EXT4_HT_MISC,
				    ext4_jbd2_credits_xattr(inode));
	if (IS_ERR(handle))
		return PTR_ERR(handle);
	res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
			     EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
			     sizeof(ctx), 0);
	if (!res) {
		ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
		res = ext4_mark_inode_dirty(handle, inode);
		if (res)
			EXT4_ERROR_INODE(inode, "Failed to mark inode dirty");
	}
	res2 = ext4_journal_stop(handle);
	if (!res)
		res = res2;
	return res;
}

int ext4_process_policy(const struct ext4_encryption_policy *policy,
			struct inode *inode)
{
	if (policy->version != 0)
		return -EINVAL;

	if (!ext4_inode_has_encryption_context(inode)) {
		if (!S_ISDIR(inode->i_mode))
			return -EINVAL;
		if (!ext4_empty_dir(inode))
			return -ENOTEMPTY;
		return ext4_create_encryption_context_from_policy(inode,
								  policy);
	}

	if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
		return 0;

	printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
	       __func__);
	return -EINVAL;
}

int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy)
{
	struct ext4_encryption_context ctx;

	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
				 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
				 &ctx, sizeof(ctx));
	if (res != sizeof(ctx))
		return -ENOENT;
	if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
		return -EINVAL;
	policy->version = 0;
	policy->contents_encryption_mode = ctx.contents_encryption_mode;
	policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
	policy->flags = ctx.flags;
	memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
	       EXT4_KEY_DESCRIPTOR_SIZE);
	return 0;
}

int ext4_is_child_context_consistent_with_parent(struct inode *parent,
						 struct inode *child)
{
	struct ext4_crypt_info *parent_ci, *child_ci;
	int res;

	if ((parent == NULL) || (child == NULL)) {
		pr_err("parent %p child %p\n", parent, child);
		WARN_ON(1);	/* Should never happen */
		return 0;
	}
	/* no restrictions if the parent directory is not encrypted */
	if (!ext4_encrypted_inode(parent))
		return 1;
	/* if the child directory is not encrypted, this is always a problem */
	if (!ext4_encrypted_inode(child))
		return 0;
	res = ext4_get_encryption_info(parent);
	if (res)
		return 0;
	res = ext4_get_encryption_info(child);
	if (res)
		return 0;
	parent_ci = EXT4_I(parent)->i_crypt_info;
	child_ci = EXT4_I(child)->i_crypt_info;
	if (!parent_ci && !child_ci)
		return 1;
	if (!parent_ci || !child_ci)
		return 0;

	return (memcmp(parent_ci->ci_master_key,
		       child_ci->ci_master_key,
		       EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
		(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
		(parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
		(parent_ci->ci_flags == child_ci->ci_flags));
}

/**
 * ext4_inherit_context() - Sets a child context from its parent
 * @parent: Parent inode from which the context is inherited.
 * @child:  Child inode that inherits the context from @parent.
 *
 * Return: Zero on success, non-zero otherwise
 */
int ext4_inherit_context(struct inode *parent, struct inode *child)
{
	struct ext4_encryption_context ctx;
	struct ext4_crypt_info *ci;
	int res;

	res = ext4_get_encryption_info(parent);
	if (res < 0)
		return res;
	ci = EXT4_I(parent)->i_crypt_info;
	if (ci == NULL)
		return -ENOKEY;

	ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
	if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
		ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
		ctx.filenames_encryption_mode =
			EXT4_ENCRYPTION_MODE_AES_256_CTS;
		ctx.flags = 0;
		memset(ctx.master_key_descriptor, 0x42,
		       EXT4_KEY_DESCRIPTOR_SIZE);
		res = 0;
	} else {
		ctx.contents_encryption_mode = ci->ci_data_mode;
		ctx.filenames_encryption_mode = ci->ci_filename_mode;
		ctx.flags = ci->ci_flags;
		memcpy(ctx.master_key_descriptor, ci->ci_master_key,
		       EXT4_KEY_DESCRIPTOR_SIZE);
	}
	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
	res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
			     EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
			     sizeof(ctx), 0);
	if (!res) {
		ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
		ext4_clear_inode_state(child, EXT4_STATE_MAY_INLINE_DATA);
		res = ext4_get_encryption_info(child);
	}
	return res;
}
Commit	Line	Data
9bd8212f MH	1	/*
	2	* linux/fs/ext4/crypto_policy.c
	3	*
	4	* Copyright (C) 2015, Google, Inc.
	5	*
	6	* This contains encryption policy functions for ext4
	7	*
	8	* Written by Michael Halcrow, 2015.
	9	*/
	10
	11	#include <linux/random.h>
	12	#include <linux/string.h>
	13	#include <linux/types.h>
	14
806c24ad	15	#include "ext4_jbd2.h"
9bd8212f MH	16	#include "ext4.h"
	17	#include "xattr.h"
	18
	19	static int ext4_inode_has_encryption_context(struct inode *inode)
	20	{
	21	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	22	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
	23	return (res > 0);
	24	}
	25
	26	/*
	27	* check whether the policy is consistent with the encryption context
	28	* for the inode
	29	*/
	30	static int ext4_is_encryption_context_consistent_with_policy(
	31	struct inode inode, const struct ext4_encryption_policy policy)
	32	{
	33	struct ext4_encryption_context ctx;
	34	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	35	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
	36	sizeof(ctx));
	37	if (res != sizeof(ctx))
	38	return 0;
	39	return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
	40	EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
a44cd7a0 TT	41	(ctx.flags ==
a44cd7a0 TT	42	policy->flags) &&
9bd8212f MH	43	(ctx.contents_encryption_mode ==
	44	policy->contents_encryption_mode) &&
	45	(ctx.filenames_encryption_mode ==
	46	policy->filenames_encryption_mode));
	47	}
	48
	49	static int ext4_create_encryption_context_from_policy(
	50	struct inode inode, const struct ext4_encryption_policy policy)
	51	{
	52	struct ext4_encryption_context ctx;
806c24ad TT	53	handle_t *handle;
806c24ad TT	54	int res, res2;
9bd8212f	55
f5aed2c2 TT	56	res = ext4_convert_inline_data(inode);
	57	if (res)
	58	return res;
	59
9bd8212f MH	60	ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
	61	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
	62	EXT4_KEY_DESCRIPTOR_SIZE);
b30ab0e0 MH	63	if (!ext4_valid_contents_enc_mode(policy->contents_encryption_mode)) {
	64	printk(KERN_WARNING
	65	"%s: Invalid contents encryption mode %d\n", __func__,
	66	policy->contents_encryption_mode);
a44cd7a0	67	return -EINVAL;
b30ab0e0	68	}
d5d0e8c7 MH	69	if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
	70	printk(KERN_WARNING
	71	"%s: Invalid filenames encryption mode %d\n", __func__,
	72	policy->filenames_encryption_mode);
a44cd7a0	73	return -EINVAL;
d5d0e8c7	74	}
a44cd7a0 TT	75	if (policy->flags & ~EXT4_POLICY_FLAGS_VALID)
a44cd7a0 TT	76	return -EINVAL;
9bd8212f MH	77	ctx.contents_encryption_mode = policy->contents_encryption_mode;
9bd8212f MH	78	ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
a44cd7a0	79	ctx.flags = policy->flags;
9bd8212f MH	80	BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
	81	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
	82
806c24ad TT	83	handle = ext4_journal_start(inode, EXT4_HT_MISC,
	84	ext4_jbd2_credits_xattr(inode));
	85	if (IS_ERR(handle))
	86	return PTR_ERR(handle);
9bd8212f MH	87	res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	88	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
	89	sizeof(ctx), 0);
806c24ad	90	if (!res) {
9bd8212f	91	ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
806c24ad TT	92	res = ext4_mark_inode_dirty(handle, inode);
	93	if (res)
	94	EXT4_ERROR_INODE(inode, "Failed to mark inode dirty");
	95	}
	96	res2 = ext4_journal_stop(handle);
	97	if (!res)
	98	res = res2;
9bd8212f MH	99	return res;
	100	}
	101
	102	int ext4_process_policy(const struct ext4_encryption_policy *policy,
	103	struct inode *inode)
	104	{
	105	if (policy->version != 0)
	106	return -EINVAL;
	107
	108	if (!ext4_inode_has_encryption_context(inode)) {
d87f6d78 TT	109	if (!S_ISDIR(inode->i_mode))
d87f6d78 TT	110	return -EINVAL;
9bd8212f MH	111	if (!ext4_empty_dir(inode))
	112	return -ENOTEMPTY;
	113	return ext4_create_encryption_context_from_policy(inode,
	114	policy);
	115	}
	116
	117	if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
	118	return 0;
	119
	120	printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
	121	__func__);
	122	return -EINVAL;
	123	}
	124
	125	int ext4_get_policy(struct inode inode, struct ext4_encryption_policy policy)
	126	{
	127	struct ext4_encryption_context ctx;
	128
	129	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	130	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
	131	&ctx, sizeof(ctx));
	132	if (res != sizeof(ctx))
	133	return -ENOENT;
	134	if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
	135	return -EINVAL;
	136	policy->version = 0;
	137	policy->contents_encryption_mode = ctx.contents_encryption_mode;
	138	policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
a44cd7a0	139	policy->flags = ctx.flags;
9bd8212f MH	140	memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
	141	EXT4_KEY_DESCRIPTOR_SIZE);
	142	return 0;
	143	}
	144
	145	int ext4_is_child_context_consistent_with_parent(struct inode *parent,
	146	struct inode *child)
	147	{
b7236e21	148	struct ext4_crypt_info parent_ci, child_ci;
9bd8212f MH	149	int res;
	150
	151	if ((parent == NULL) \|\| (child == NULL)) {
	152	pr_err("parent %p child %p\n", parent, child);
687c3c36 TT	153	WARN_ON(1); /* Should never happen */
687c3c36 TT	154	return 0;
9bd8212f MH	155	}
	156	/* no restrictions if the parent directory is not encrypted */
	157	if (!ext4_encrypted_inode(parent))
	158	return 1;
9bd8212f MH	159	/* if the child directory is not encrypted, this is always a problem */
	160	if (!ext4_encrypted_inode(child))
	161	return 0;
b7236e21 TT	162	res = ext4_get_encryption_info(parent);
	163	if (res)
	164	return 0;
	165	res = ext4_get_encryption_info(child);
	166	if (res)
	167	return 0;
	168	parent_ci = EXT4_I(parent)->i_crypt_info;
	169	child_ci = EXT4_I(child)->i_crypt_info;
	170	if (!parent_ci && !child_ci)
	171	return 1;
	172	if (!parent_ci \|\| !child_ci)
9bd8212f	173	return 0;
b7236e21 TT	174
	175	return (memcmp(parent_ci->ci_master_key,
	176	child_ci->ci_master_key,
9bd8212f	177	EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
b7236e21 TT	178	(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
	179	(parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
	180	(parent_ci->ci_flags == child_ci->ci_flags));
9bd8212f MH	181	}
	182
	183	/**
	184	* ext4_inherit_context() - Sets a child context from its parent
	185	* @parent: Parent inode from which the context is inherited.
	186	* @child: Child inode that inherits the context from @parent.
	187	*
	188	* Return: Zero on success, non-zero otherwise
	189	*/
	190	int ext4_inherit_context(struct inode parent, struct inode child)
	191	{
	192	struct ext4_encryption_context ctx;
b7236e21 TT	193	struct ext4_crypt_info *ci;
	194	int res;
	195
	196	res = ext4_get_encryption_info(parent);
	197	if (res < 0)
	198	return res;
	199	ci = EXT4_I(parent)->i_crypt_info;
abdd438b TT	200	if (ci == NULL)
abdd438b TT	201	return -ENOKEY;
9bd8212f	202
b7236e21 TT	203	ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
	204	if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
	205	ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
	206	ctx.filenames_encryption_mode =
	207	EXT4_ENCRYPTION_MODE_AES_256_CTS;
	208	ctx.flags = 0;
	209	memset(ctx.master_key_descriptor, 0x42,
	210	EXT4_KEY_DESCRIPTOR_SIZE);
	211	res = 0;
	212	} else {
	213	ctx.contents_encryption_mode = ci->ci_data_mode;
	214	ctx.filenames_encryption_mode = ci->ci_filename_mode;
	215	ctx.flags = ci->ci_flags;
	216	memcpy(ctx.master_key_descriptor, ci->ci_master_key,
	217	EXT4_KEY_DESCRIPTOR_SIZE);
6ddb2447	218	}
9bd8212f MH	219	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
	220	res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
	221	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
	222	sizeof(ctx), 0);
f5aed2c2	223	if (!res) {
9bd8212f	224	ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
f5aed2c2	225	ext4_clear_inode_state(child, EXT4_STATE_MAY_INLINE_DATA);
55557029	226	res = ext4_get_encryption_info(child);
f5aed2c2	227	}
9bd8212f MH	228	return res;
9bd8212f MH	229	}