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