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Edit File: fsaccess.h

/* * 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 */