[linux-2.6-block.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.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;
	int res = 0;

	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);

	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);
	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 (!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_encryption_context parent_ctx, child_ctx;
	int res;

	if ((parent == NULL) || (child == NULL)) {
		pr_err("parent %p child %p\n", parent, child);
		BUG_ON(1);
	}
	/* no restrictions if the parent directory is not encrypted */
	if (!ext4_encrypted_inode(parent))
		return 1;
	res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
			     EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
			     &parent_ctx, sizeof(parent_ctx));
	if (res != sizeof(parent_ctx))
		return 0;
	/* if the child directory is not encrypted, this is always a problem */
	if (!ext4_encrypted_inode(child))
		return 0;
	res = ext4_xattr_get(child, EXT4_XATTR_INDEX_ENCRYPTION,
			     EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
			     &child_ctx, sizeof(child_ctx));
	if (res != sizeof(child_ctx))
		return 0;
	return (memcmp(parent_ctx.master_key_descriptor,
		       child_ctx.master_key_descriptor,
		       EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
		(parent_ctx.contents_encryption_mode ==
		 child_ctx.contents_encryption_mode) &&
		(parent_ctx.filenames_encryption_mode ==
		 child_ctx.filenames_encryption_mode));
}

/**
 * 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;
	int res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
				 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
				 &ctx, sizeof(ctx));

	if (res != sizeof(ctx)) {
		if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
			ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
			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 {
			goto out;
		}
	}
	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);
out:
	if (!res)
		ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
	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
	15	#include "ext4.h"
	16	#include "xattr.h"
	17
	18	static int ext4_inode_has_encryption_context(struct inode *inode)
	19	{
	20	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	21	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
	22	return (res > 0);
	23	}
	24
	25	/*
	26	* check whether the policy is consistent with the encryption context
	27	* for the inode
	28	*/
	29	static int ext4_is_encryption_context_consistent_with_policy(
	30	struct inode inode, const struct ext4_encryption_policy policy)
	31	{
	32	struct ext4_encryption_context ctx;
	33	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	34	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
	35	sizeof(ctx));
	36	if (res != sizeof(ctx))
	37	return 0;
	38	return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
	39	EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
a44cd7a0 TT	40	(ctx.flags ==
a44cd7a0 TT	41	policy->flags) &&
9bd8212f MH	42	(ctx.contents_encryption_mode ==
	43	policy->contents_encryption_mode) &&
	44	(ctx.filenames_encryption_mode ==
	45	policy->filenames_encryption_mode));
	46	}
	47
	48	static int ext4_create_encryption_context_from_policy(
	49	struct inode inode, const struct ext4_encryption_policy policy)
	50	{
	51	struct ext4_encryption_context ctx;
	52	int res = 0;
	53
	54	ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
	55	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
	56	EXT4_KEY_DESCRIPTOR_SIZE);
b30ab0e0 MH	57	if (!ext4_valid_contents_enc_mode(policy->contents_encryption_mode)) {
	58	printk(KERN_WARNING
	59	"%s: Invalid contents encryption mode %d\n", __func__,
	60	policy->contents_encryption_mode);
a44cd7a0	61	return -EINVAL;
b30ab0e0	62	}
d5d0e8c7 MH	63	if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
	64	printk(KERN_WARNING
	65	"%s: Invalid filenames encryption mode %d\n", __func__,
	66	policy->filenames_encryption_mode);
a44cd7a0	67	return -EINVAL;
d5d0e8c7	68	}
a44cd7a0 TT	69	if (policy->flags & ~EXT4_POLICY_FLAGS_VALID)
a44cd7a0 TT	70	return -EINVAL;
9bd8212f MH	71	ctx.contents_encryption_mode = policy->contents_encryption_mode;
9bd8212f MH	72	ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
a44cd7a0	73	ctx.flags = policy->flags;
9bd8212f MH	74	BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
	75	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
	76
	77	res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	78	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
	79	sizeof(ctx), 0);
	80	if (!res)
	81	ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
	82	return res;
	83	}
	84
	85	int ext4_process_policy(const struct ext4_encryption_policy *policy,
	86	struct inode *inode)
	87	{
	88	if (policy->version != 0)
	89	return -EINVAL;
	90
	91	if (!ext4_inode_has_encryption_context(inode)) {
	92	if (!ext4_empty_dir(inode))
	93	return -ENOTEMPTY;
	94	return ext4_create_encryption_context_from_policy(inode,
	95	policy);
	96	}
	97
	98	if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
	99	return 0;
	100
	101	printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
	102	__func__);
	103	return -EINVAL;
	104	}
	105
	106	int ext4_get_policy(struct inode inode, struct ext4_encryption_policy policy)
	107	{
	108	struct ext4_encryption_context ctx;
	109
	110	int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
	111	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
	112	&ctx, sizeof(ctx));
	113	if (res != sizeof(ctx))
	114	return -ENOENT;
	115	if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
	116	return -EINVAL;
	117	policy->version = 0;
	118	policy->contents_encryption_mode = ctx.contents_encryption_mode;
	119	policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
a44cd7a0	120	policy->flags = ctx.flags;
9bd8212f MH	121	memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
	122	EXT4_KEY_DESCRIPTOR_SIZE);
	123	return 0;
	124	}
	125
	126	int ext4_is_child_context_consistent_with_parent(struct inode *parent,
	127	struct inode *child)
	128	{
	129	struct ext4_encryption_context parent_ctx, child_ctx;
	130	int res;
	131
	132	if ((parent == NULL) \|\| (child == NULL)) {
	133	pr_err("parent %p child %p\n", parent, child);
	134	BUG_ON(1);
	135	}
	136	/* no restrictions if the parent directory is not encrypted */
	137	if (!ext4_encrypted_inode(parent))
	138	return 1;
	139	res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
	140	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
	141	&parent_ctx, sizeof(parent_ctx));
	142	if (res != sizeof(parent_ctx))
	143	return 0;
	144	/* if the child directory is not encrypted, this is always a problem */
	145	if (!ext4_encrypted_inode(child))
	146	return 0;
	147	res = ext4_xattr_get(child, EXT4_XATTR_INDEX_ENCRYPTION,
	148	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
	149	&child_ctx, sizeof(child_ctx));
	150	if (res != sizeof(child_ctx))
	151	return 0;
	152	return (memcmp(parent_ctx.master_key_descriptor,
	153	child_ctx.master_key_descriptor,
	154	EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
	155	(parent_ctx.contents_encryption_mode ==
	156	child_ctx.contents_encryption_mode) &&
	157	(parent_ctx.filenames_encryption_mode ==
	158	child_ctx.filenames_encryption_mode));
	159	}
	160
	161	/**
	162	* ext4_inherit_context() - Sets a child context from its parent
	163	* @parent: Parent inode from which the context is inherited.
	164	* @child: Child inode that inherits the context from @parent.
	165	*
	166	* Return: Zero on success, non-zero otherwise
	167	*/
	168	int ext4_inherit_context(struct inode parent, struct inode child)
	169	{
	170	struct ext4_encryption_context ctx;
	171	int res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
	172	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
	173	&ctx, sizeof(ctx));
	174
6ddb2447 TT	175	if (res != sizeof(ctx)) {
	176	if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
	177	ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
	178	ctx.contents_encryption_mode =
	179	EXT4_ENCRYPTION_MODE_AES_256_XTS;
	180	ctx.filenames_encryption_mode =
	181	EXT4_ENCRYPTION_MODE_AES_256_CTS;
a44cd7a0	182	ctx.flags = 0;
6ddb2447 TT	183	memset(ctx.master_key_descriptor, 0x42,
	184	EXT4_KEY_DESCRIPTOR_SIZE);
	185	res = 0;
	186	} else {
	187	goto out;
	188	}
	189	}
9bd8212f MH	190	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
	191	res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
	192	EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
	193	sizeof(ctx), 0);
6ddb2447	194	out:
9bd8212f MH	195	if (!res)
	196	ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
	197	return res;
	198	}