268 lines
8.3 KiB
C
268 lines
8.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Encryption policy functions for per-file encryption support.
|
|
*
|
|
* Copyright (C) 2015, Google, Inc.
|
|
* Copyright (C) 2015, Motorola Mobility.
|
|
*
|
|
* Written by Michael Halcrow, 2015.
|
|
* Modified by Jaegeuk Kim, 2015.
|
|
*/
|
|
|
|
#include <linux/random.h>
|
|
#include <linux/string.h>
|
|
#include <linux/mount.h>
|
|
#include "fscrypt_private.h"
|
|
|
|
/*
|
|
* check whether an encryption policy is consistent with an encryption context
|
|
*/
|
|
static bool is_encryption_context_consistent_with_policy(
|
|
const struct fscrypt_context *ctx,
|
|
const struct fscrypt_policy *policy)
|
|
{
|
|
return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor,
|
|
FS_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 create_encryption_context_from_policy(struct inode *inode,
|
|
const struct fscrypt_policy *policy)
|
|
{
|
|
struct fscrypt_context ctx;
|
|
|
|
ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
|
|
memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
|
|
FS_KEY_DESCRIPTOR_SIZE);
|
|
|
|
if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
|
|
policy->filenames_encryption_mode))
|
|
return -EINVAL;
|
|
|
|
if (policy->flags & ~FS_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) != FS_KEY_DERIVATION_NONCE_SIZE);
|
|
get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
|
|
|
|
return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
|
|
}
|
|
|
|
int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
|
|
{
|
|
struct fscrypt_policy policy;
|
|
struct inode *inode = file_inode(filp);
|
|
int ret;
|
|
struct fscrypt_context ctx;
|
|
|
|
if (copy_from_user(&policy, arg, sizeof(policy)))
|
|
return -EFAULT;
|
|
|
|
if (!inode_owner_or_capable(inode))
|
|
return -EACCES;
|
|
|
|
if (policy.version != 0)
|
|
return -EINVAL;
|
|
|
|
ret = mnt_want_write_file(filp);
|
|
if (ret)
|
|
return ret;
|
|
|
|
inode_lock(inode);
|
|
|
|
ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
|
|
if (ret == -ENODATA) {
|
|
if (!S_ISDIR(inode->i_mode))
|
|
ret = -ENOTDIR;
|
|
else if (!inode->i_sb->s_cop->empty_dir(inode))
|
|
ret = -ENOTEMPTY;
|
|
else
|
|
ret = create_encryption_context_from_policy(inode,
|
|
&policy);
|
|
} else if (ret == sizeof(ctx) &&
|
|
is_encryption_context_consistent_with_policy(&ctx,
|
|
&policy)) {
|
|
/* The file already uses the same encryption policy. */
|
|
ret = 0;
|
|
} else if (ret >= 0 || ret == -ERANGE) {
|
|
/* The file already uses a different encryption policy. */
|
|
ret = -EEXIST;
|
|
}
|
|
|
|
inode_unlock(inode);
|
|
|
|
mnt_drop_write_file(filp);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
|
|
|
|
int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
|
|
{
|
|
struct inode *inode = file_inode(filp);
|
|
struct fscrypt_context ctx;
|
|
struct fscrypt_policy policy;
|
|
int res;
|
|
|
|
if (!IS_ENCRYPTED(inode))
|
|
return -ENODATA;
|
|
|
|
res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
|
|
if (res < 0 && res != -ERANGE)
|
|
return res;
|
|
if (res != sizeof(ctx))
|
|
return -EINVAL;
|
|
if (ctx.format != FS_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,
|
|
FS_KEY_DESCRIPTOR_SIZE);
|
|
|
|
if (copy_to_user(arg, &policy, sizeof(policy)))
|
|
return -EFAULT;
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
|
|
|
|
/**
|
|
* fscrypt_has_permitted_context() - is a file's encryption policy permitted
|
|
* within its directory?
|
|
*
|
|
* @parent: inode for parent directory
|
|
* @child: inode for file being looked up, opened, or linked into @parent
|
|
*
|
|
* Filesystems must call this before permitting access to an inode in a
|
|
* situation where the parent directory is encrypted (either before allowing
|
|
* ->lookup() to succeed, or for a regular file before allowing it to be opened)
|
|
* and before any operation that involves linking an inode into an encrypted
|
|
* directory, including link, rename, and cross rename. It enforces the
|
|
* constraint that within a given encrypted directory tree, all files use the
|
|
* same encryption policy. The pre-access check is needed to detect potentially
|
|
* malicious offline violations of this constraint, while the link and rename
|
|
* checks are needed to prevent online violations of this constraint.
|
|
*
|
|
* Return: 1 if permitted, 0 if forbidden.
|
|
*/
|
|
int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
|
|
{
|
|
const struct fscrypt_operations *cops = parent->i_sb->s_cop;
|
|
const struct fscrypt_info *parent_ci, *child_ci;
|
|
struct fscrypt_context parent_ctx, child_ctx;
|
|
int res;
|
|
|
|
/* 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 unencrypted */
|
|
if (!IS_ENCRYPTED(parent))
|
|
return 1;
|
|
|
|
/* Encrypted directories must not contain unencrypted files */
|
|
if (!IS_ENCRYPTED(child))
|
|
return 0;
|
|
|
|
/*
|
|
* Both parent and child are encrypted, so verify they use the same
|
|
* encryption policy. Compare the fscrypt_info structs if the keys are
|
|
* available, otherwise retrieve and compare the fscrypt_contexts.
|
|
*
|
|
* Note that the fscrypt_context retrieval will be required frequently
|
|
* when accessing an encrypted directory tree without the key.
|
|
* Performance-wise this is not a big deal because we already don't
|
|
* really optimize for file access without the key (to the extent that
|
|
* such access is even possible), given that any attempted access
|
|
* already causes a fscrypt_context retrieval and keyring search.
|
|
*
|
|
* In any case, if an unexpected error occurs, fall back to "forbidden".
|
|
*/
|
|
|
|
res = fscrypt_get_encryption_info(parent);
|
|
if (res)
|
|
return 0;
|
|
res = fscrypt_get_encryption_info(child);
|
|
if (res)
|
|
return 0;
|
|
parent_ci = READ_ONCE(parent->i_crypt_info);
|
|
child_ci = READ_ONCE(child->i_crypt_info);
|
|
|
|
if (parent_ci && child_ci) {
|
|
return memcmp(parent_ci->ci_master_key_descriptor,
|
|
child_ci->ci_master_key_descriptor,
|
|
FS_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);
|
|
}
|
|
|
|
res = cops->get_context(parent, &parent_ctx, sizeof(parent_ctx));
|
|
if (res != sizeof(parent_ctx))
|
|
return 0;
|
|
|
|
res = cops->get_context(child, &child_ctx, sizeof(child_ctx));
|
|
if (res != sizeof(child_ctx))
|
|
return 0;
|
|
|
|
return memcmp(parent_ctx.master_key_descriptor,
|
|
child_ctx.master_key_descriptor,
|
|
FS_KEY_DESCRIPTOR_SIZE) == 0 &&
|
|
(parent_ctx.contents_encryption_mode ==
|
|
child_ctx.contents_encryption_mode) &&
|
|
(parent_ctx.filenames_encryption_mode ==
|
|
child_ctx.filenames_encryption_mode) &&
|
|
(parent_ctx.flags == child_ctx.flags);
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_has_permitted_context);
|
|
|
|
/**
|
|
* fscrypt_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.
|
|
* @fs_data: private data given by FS.
|
|
* @preload: preload child i_crypt_info if true
|
|
*
|
|
* Return: 0 on success, -errno on failure
|
|
*/
|
|
int fscrypt_inherit_context(struct inode *parent, struct inode *child,
|
|
void *fs_data, bool preload)
|
|
{
|
|
struct fscrypt_context ctx;
|
|
struct fscrypt_info *ci;
|
|
int res;
|
|
|
|
res = fscrypt_get_encryption_info(parent);
|
|
if (res < 0)
|
|
return res;
|
|
|
|
ci = READ_ONCE(parent->i_crypt_info);
|
|
if (ci == NULL)
|
|
return -ENOKEY;
|
|
|
|
ctx.format = FS_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_descriptor,
|
|
FS_KEY_DESCRIPTOR_SIZE);
|
|
get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
|
|
BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
|
|
res = parent->i_sb->s_cop->set_context(child, &ctx,
|
|
sizeof(ctx), fs_data);
|
|
if (res)
|
|
return res;
|
|
return preload ? fscrypt_get_encryption_info(child): 0;
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_inherit_context);
|