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/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#ifndef ISC_FSACCESS_H
#define ISC_FSACCESS_H 1
/*! \file isc/fsaccess.h
* \brief The ISC filesystem access module encapsulates the setting of file
* and directory access permissions into one API that is meant to be
* portable to multiple operating systems.
*
* The two primary operating system flavors that are initially accommodated
* are POSIX and Windows NT 4.0 and later. The Windows NT access model is
* considerable more flexible than POSIX's model (as much as I am loathe to
* admit it), and so the ISC API has a higher degree of complexity than would
* be needed to simply address POSIX's needs.
*
* The full breadth of NT's flexibility is not available either, for the
* present time. Much of it is to provide compatibility with what Unix
* programmers are expecting. This is also due to not yet really needing all
* of the functionality of an NT system (or, for that matter, a POSIX system)
* in BIND9, and so resolving how to handle the various incompatibilities has
* been a purely theoretical exercise with no operational experience to
* indicate how flawed the thinking may be.
*
* Some of the more notable dumbing down of NT for this API includes:
*
*\li Each of FILE_READ_DATA and FILE_READ_EA are set with #ISC_FSACCESS_READ.
*
* \li All of FILE_WRITE_DATA, FILE_WRITE_EA and FILE_APPEND_DATA are
* set with #ISC_FSACCESS_WRITE. FILE_WRITE_ATTRIBUTES is not set
* so as to be consistent with Unix, where only the owner of the file
* or the superuser can change the attributes/mode of a file.
*
* \li Both of FILE_ADD_FILE and FILE_ADD_SUBDIRECTORY are set with
* #ISC_FSACCESS_CREATECHILD. This is similar to setting the WRITE
* permission on a Unix directory.
*
* \li SYNCHRONIZE is always set for files and directories, unless someone
* can give me a reason why this is a bad idea.
*
* \li READ_CONTROL and FILE_READ_ATTRIBUTES are always set; this is
* consistent with Unix, where any file or directory can be stat()'d
* unless the directory path disallows complete access somewhere along
* the way.
*
* \li WRITE_DAC is only set for the owner. This too is consistent with
* Unix, and is tighter security than allowing anyone else to be
* able to set permissions.
*
* \li DELETE is only set for the owner. On Unix the ability to delete
* a file is controlled by the directory permissions, but it isn't
* currently clear to me what happens on NT if the directory has
* FILE_DELETE_CHILD set but a file within it does not have DELETE
* set. Always setting DELETE on the file/directory for the owner
* gives maximum flexibility to the owner without exposing the
* file to deletion by others.
*
* \li WRITE_OWNER is never set. This too is consistent with Unix,
* and is also tighter security than allowing anyone to change the
* ownership of the file apart from the superu..ahem, Administrator.
*
* \li Inheritance is set to NO_INHERITANCE.
*
* Unix's dumbing down includes:
*
* \li The sticky bit cannot be set.
*
* \li setuid and setgid cannot be set.
*
* \li Only regular files and directories can be set.
*
* The rest of this comment discusses a few of the incompatibilities
* between the two systems that need more thought if this API is to
* be extended to accommodate them.
*
* The Windows standard access right "DELETE" doesn't have a direct
* equivalent in the Unix world, so it isn't clear what should be done
* with it.
*
* The Unix sticky bit is not supported. While NT does have a concept
* of allowing users to create files in a directory but not delete or
* rename them, it does not have a concept of allowing them to be deleted
* if they are owned by the user trying to delete/rename. While it is
* probable that something could be cobbled together in NT 5 with inheritance,
* it can't really be done in NT 4 as a single property that you could
* set on a directory. You'd need to coordinate something with file creation
* so that every file created had DELETE set for the owner but no one else.
*
* On Unix systems, setting #ISC_FSACCESS_LISTDIRECTORY sets READ.
* ... setting either #ISC_FSACCESS_CREATECHILD or #ISC_FSACCESS_DELETECHILD
* sets WRITE.
* ... setting #ISC_FSACCESS_ACCESSCHILD sets EXECUTE.
*
* On NT systems, setting #ISC_FSACCESS_LISTDIRECTORY sets FILE_LIST_DIRECTORY.
* ... setting #ISC_FSACCESS_CREATECHILD sets FILE_CREATE_CHILD independently.
* ... setting #ISC_FSACCESS_DELETECHILD sets FILE_DELETE_CHILD independently.
* ... setting #ISC_FSACCESS_ACCESSCHILD sets FILE_TRAVERSE.
*
* Unresolved: XXXDCL
* \li What NT access right controls the ability to rename a file?
* \li How does DELETE work? If a directory has FILE_DELETE_CHILD but a
* file or directory within it does not have DELETE, is that file
* or directory deletable?
* \li To implement isc_fsaccess_get(), mapping an existing Unix permission
* mode_t back to an isc_fsaccess_t is pretty trivial; however, mapping
* an NT DACL could be impossible to do in a responsible way.
* \li Similarly, trying to implement the functionality of being able to
* say "add group writability to whatever permissions already exist"
* could be tricky on NT because of the order-of-entry issue combined
* with possibly having one or more matching ACEs already explicitly
* granting or denying access. Because this functionality is
* not yet needed by the ISC, no code has been written to try to
* solve this problem.
*/
#include <inttypes.h>
#include <isc/lang.h>
#include <isc/types.h>
/*
* Trustees.
*/
#define ISC_FSACCESS_OWNER 0x1 /*%< User account. */
#define ISC_FSACCESS_GROUP 0x2 /*%< Primary group owner. */
#define ISC_FSACCESS_OTHER 0x4 /*%< Not the owner or the group owner. */
#define ISC_FSACCESS_WORLD 0x7 /*%< User, Group, Other. */
/*
* Types of permission.
*/
#define ISC_FSACCESS_READ 0x00000001 /*%< File only. */
#define ISC_FSACCESS_WRITE 0x00000002 /*%< File only. */
#define ISC_FSACCESS_EXECUTE 0x00000004 /*%< File only. */
#define ISC_FSACCESS_CREATECHILD 0x00000008 /*%< Dir only. */
#define ISC_FSACCESS_DELETECHILD 0x00000010 /*%< Dir only. */
#define ISC_FSACCESS_LISTDIRECTORY 0x00000020 /*%< Dir only. */
#define ISC_FSACCESS_ACCESSCHILD 0x00000040 /*%< Dir only. */
/*%
* Adding any permission bits beyond 0x200 would mean typedef'ing
* isc_fsaccess_t as uint64_t, and redefining this value to
* reflect the new range of permission types, Probably to 21 for
* maximum flexibility. The number of bits has to accommodate all of
* the permission types, and three full sets of them have to fit
* within an isc_fsaccess_t.
*/
#define ISC__FSACCESS_PERMISSIONBITS 10
ISC_LANG_BEGINDECLS
void
isc_fsaccess_add(int trustee, int permission, isc_fsaccess_t *access);
void
isc_fsaccess_remove(int trustee, int permission, isc_fsaccess_t *access);
isc_result_t
isc_fsaccess_set(const char *path, isc_fsaccess_t access);
ISC_LANG_ENDDECLS
#endif /* ISC_FSACCESS_H */
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