fs/ext4/crypto_policy.c - kernel/bruno - Git at Google

 /*
  * 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 (!inode_owner_or_capable(inode))
 		return -EACCES;

 	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;
 }
	/*
	* 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 (!inode_owner_or_capable(inode))
	return -EACCES;

	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;
	}