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/*
* copied from linux/fs/ext4/crypto_policy.c
*
* Copyright (C) 2015, Google, Inc.
* Copyright (C) 2015, Motorola Mobility.
*
* This contains encryption policy functions for f2fs with some modifications
* to support f2fs-specific xattr APIs.
*
* Written by Michael Halcrow, 2015.
* Modified by Jaegeuk Kim, 2015.
*/
#include <linux/random.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/f2fs_fs.h>
#include "f2fs.h"
#include "xattr.h"
static int f2fs_inode_has_encryption_context(struct inode *inode)
{
int res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0, NULL);
return (res > 0);
}
/*
* check whether the policy is consistent with the encryption context
* for the inode
*/
static int f2fs_is_encryption_context_consistent_with_policy(
struct inode *inode, const struct f2fs_encryption_policy *policy)
{
struct f2fs_encryption_context ctx;
int res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
sizeof(ctx), NULL);
if (res != sizeof(ctx))
return 0;
return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
F2FS_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 f2fs_create_encryption_context_from_policy(
struct inode *inode, const struct f2fs_encryption_policy *policy)
{
struct f2fs_encryption_context ctx;
ctx.format = F2FS_ENCRYPTION_CONTEXT_FORMAT_V1;
memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
F2FS_KEY_DESCRIPTOR_SIZE);
if (!f2fs_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 (!f2fs_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 & ~F2FS_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) != F2FS_KEY_DERIVATION_NONCE_SIZE);
get_random_bytes(ctx.nonce, F2FS_KEY_DERIVATION_NONCE_SIZE);
return f2fs_setxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
sizeof(ctx), NULL, XATTR_CREATE);
}
int f2fs_process_policy(const struct f2fs_encryption_policy *policy,
struct inode *inode)
{
if (!inode_owner_or_capable(inode))
return -EACCES;
if (policy->version != 0)
return -EINVAL;
if (!S_ISDIR(inode->i_mode))
return -EINVAL;
if (!f2fs_inode_has_encryption_context(inode)) {
if (!f2fs_empty_dir(inode))
return -ENOTEMPTY;
return f2fs_create_encryption_context_from_policy(inode,
policy);
}
if (f2fs_is_encryption_context_consistent_with_policy(inode, policy))
return 0;
printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
__func__);
return -EINVAL;
}
int f2fs_get_policy(struct inode *inode, struct f2fs_encryption_policy *policy)
{
struct f2fs_encryption_context ctx;
int res;
if (!f2fs_encrypted_inode(inode))
return -ENODATA;
res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
&ctx, sizeof(ctx), NULL);
if (res != sizeof(ctx))
return -ENODATA;
if (ctx.format != F2FS_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,
F2FS_KEY_DESCRIPTOR_SIZE);
return 0;
}
int f2fs_is_child_context_consistent_with_parent(struct inode *parent,
struct inode *child)
{
struct f2fs_crypt_info *parent_ci, *child_ci;
int res;
if ((parent == NULL) || (child == NULL)) {
pr_err("parent %p child %p\n", parent, child);
BUG_ON(1);
}
/* No restrictions on file types which are never encrypted */
if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
!S_ISLNK(child->i_mode))
return 1;
/* no restrictions if the parent directory is not encrypted */
if (!f2fs_encrypted_inode(parent))
return 1;
/* if the child directory is not encrypted, this is always a problem */
if (!f2fs_encrypted_inode(child))
return 0;
res = f2fs_get_encryption_info(parent);
if (res)
return 0;
res = f2fs_get_encryption_info(child);
if (res)
return 0;
parent_ci = F2FS_I(parent)->i_crypt_info;
child_ci = F2FS_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,
F2FS_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));
}
/**
* f2fs_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 f2fs_inherit_context(struct inode *parent, struct inode *child,
struct page *ipage)
{
struct f2fs_encryption_context ctx;
struct f2fs_crypt_info *ci;
int res;
res = f2fs_get_encryption_info(parent);
if (res < 0)
return res;
ci = F2FS_I(parent)->i_crypt_info;
BUG_ON(ci == NULL);
ctx.format = F2FS_ENCRYPTION_CONTEXT_FORMAT_V1;
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,
F2FS_KEY_DESCRIPTOR_SIZE);
get_random_bytes(ctx.nonce, F2FS_KEY_DERIVATION_NONCE_SIZE);
return f2fs_setxattr(child, F2FS_XATTR_INDEX_ENCRYPTION,
F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
sizeof(ctx), ipage, XATTR_CREATE);
}
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