1 /* modechange.c -- file mode manipulation
3 Copyright (C) 1989-1990, 1997-1999, 2001, 2003-2006, 2009-2017 Free Software
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <https://www.gnu.org/licenses/>. */
19 /* Written by David MacKenzie <djm@ai.mit.edu> */
21 /* The ASCII mode string is compiled into an array of 'struct
22 modechange', which can then be applied to each file to be changed.
23 We do this instead of re-parsing the ASCII string for each file
24 because the compiled form requires less computation to use; when
25 changing the mode of many files, this probably results in a
30 #include "modechange.h"
32 #include "stat-macros.h"
36 /* The traditional octal values corresponding to each mode bit. */
49 #define ALLM 07777 /* all octal mode bits */
51 /* Convert OCTAL, which uses one of the traditional octal values, to
52 an internal mode_t value. */
54 octal_to_mode (unsigned int octal
)
56 /* Help the compiler optimize the usual case where mode_t uses
57 the traditional octal representation. */
58 return ((S_ISUID
== SUID
&& S_ISGID
== SGID
&& S_ISVTX
== SVTX
59 && S_IRUSR
== RUSR
&& S_IWUSR
== WUSR
&& S_IXUSR
== XUSR
60 && S_IRGRP
== RGRP
&& S_IWGRP
== WGRP
&& S_IXGRP
== XGRP
61 && S_IROTH
== ROTH
&& S_IWOTH
== WOTH
&& S_IXOTH
== XOTH
)
63 : (mode_t
) ((octal
& SUID
? S_ISUID
: 0)
64 | (octal
& SGID
? S_ISGID
: 0)
65 | (octal
& SVTX
? S_ISVTX
: 0)
66 | (octal
& RUSR
? S_IRUSR
: 0)
67 | (octal
& WUSR
? S_IWUSR
: 0)
68 | (octal
& XUSR
? S_IXUSR
: 0)
69 | (octal
& RGRP
? S_IRGRP
: 0)
70 | (octal
& WGRP
? S_IWGRP
: 0)
71 | (octal
& XGRP
? S_IXGRP
: 0)
72 | (octal
& ROTH
? S_IROTH
: 0)
73 | (octal
& WOTH
? S_IWOTH
: 0)
74 | (octal
& XOTH
? S_IXOTH
: 0)));
77 /* Special operations flags. */
80 /* For the sentinel at the end of the mode changes array. */
83 /* The typical case. */
86 /* In addition to the typical case, affect the execute bits if at
87 least one execute bit is set already, or if the file is a
91 /* Instead of the typical case, copy some existing permissions for
92 u, g, or o onto the other two. Which of u, g, or o is copied
93 is determined by which bits are set in the 'value' field. */
97 /* Description of a mode change. */
100 char op
; /* One of "=+-". */
101 char flag
; /* Special operations flag. */
102 mode_t affected
; /* Set for u, g, o, or a. */
103 mode_t value
; /* Bits to add/remove. */
104 mode_t mentioned
; /* Bits explicitly mentioned. */
107 /* Return a mode_change array with the specified "=ddd"-style
108 mode change operation, where NEW_MODE is "ddd" and MENTIONED
109 contains the bits explicitly mentioned in the mode are MENTIONED. */
111 static struct mode_change
*
112 make_node_op_equals (mode_t new_mode
, mode_t mentioned
)
114 struct mode_change
*p
= xmalloc (2 * sizeof *p
);
116 p
->flag
= MODE_ORDINARY_CHANGE
;
117 p
->affected
= CHMOD_MODE_BITS
;
119 p
->mentioned
= mentioned
;
120 p
[1].flag
= MODE_DONE
;
124 /* Return a pointer to an array of file mode change operations created from
125 MODE_STRING, an ASCII string that contains either an octal number
126 specifying an absolute mode, or symbolic mode change operations with
128 [ugoa...][[+-=][rwxXstugo...]...][,...]
130 Return NULL if 'mode_string' does not contain a valid
131 representation of file mode change operations. */
134 mode_compile (char const *mode_string
)
136 /* The array of mode-change directives to be returned. */
137 struct mode_change
*mc
;
141 if ('0' <= *mode_string
&& *mode_string
< '8')
143 unsigned int octal_mode
= 0;
150 octal_mode
= 8 * octal_mode
+ *p
++ - '0';
151 if (ALLM
< octal_mode
)
154 while ('0' <= *p
&& *p
< '8');
159 mode
= octal_to_mode (octal_mode
);
160 mentioned
= (p
- mode_string
< 5
161 ? (mode
& (S_ISUID
| S_ISGID
)) | S_ISVTX
| S_IRWXUGO
163 return make_node_op_equals (mode
, mentioned
);
166 /* Allocate enough space to hold the result. */
169 for (p
= mode_string
; *p
; p
++)
170 needed
+= (*p
== '=' || *p
== '+' || *p
== '-');
171 mc
= xnmalloc (needed
, sizeof *mc
);
174 /* One loop iteration for each
175 '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. */
176 for (p
= mode_string
; ; p
++)
178 /* Which bits in the mode are operated on. */
181 /* Turn on all the bits in 'affected' for each group given. */
188 affected
|= S_ISUID
| S_IRWXU
;
191 affected
|= S_ISGID
| S_IRWXG
;
194 affected
|= S_ISVTX
| S_IRWXO
;
197 affected
|= CHMOD_MODE_BITS
;
199 case '=': case '+': case '-':
200 goto no_more_affected
;
208 mode_t mentioned
= 0;
209 char flag
= MODE_COPY_EXISTING
;
210 struct mode_change
*change
;
214 case '0': case '1': case '2': case '3':
215 case '4': case '5': case '6': case '7':
217 unsigned int octal_mode
= 0;
221 octal_mode
= 8 * octal_mode
+ *p
++ - '0';
222 if (ALLM
< octal_mode
)
225 while ('0' <= *p
&& *p
< '8');
227 if (affected
|| (*p
&& *p
!= ','))
229 affected
= mentioned
= CHMOD_MODE_BITS
;
230 value
= octal_to_mode (octal_mode
);
231 flag
= MODE_ORDINARY_CHANGE
;
236 /* Set the affected bits to the value of the "u" bits
242 /* Set the affected bits to the value of the "g" bits
248 /* Set the affected bits to the value of the "o" bits
256 flag
= MODE_ORDINARY_CHANGE
;
262 value
|= S_IRUSR
| S_IRGRP
| S_IROTH
;
265 value
|= S_IWUSR
| S_IWGRP
| S_IWOTH
;
268 value
|= S_IXUSR
| S_IXGRP
| S_IXOTH
;
271 flag
= MODE_X_IF_ANY_X
;
274 /* Set the setuid/gid bits if 'u' or 'g' is selected. */
275 value
|= S_ISUID
| S_ISGID
;
278 /* Set the "save text image" bit if 'o' is selected. */
287 change
= &mc
[used
++];
290 change
->affected
= affected
;
291 change
->value
= value
;
293 (mentioned
? mentioned
: affected
? affected
& value
: value
);
295 while (*p
== '=' || *p
== '+' || *p
== '-');
303 mc
[used
].flag
= MODE_DONE
;
312 /* Return a file mode change operation that sets permissions to match those
313 of REF_FILE. Return NULL (setting errno) if REF_FILE can't be accessed. */
316 mode_create_from_ref (const char *ref_file
)
318 struct stat ref_stats
;
320 if (stat (ref_file
, &ref_stats
) != 0)
322 return make_node_op_equals (ref_stats
.st_mode
, CHMOD_MODE_BITS
);
325 /* Return the file mode bits of OLDMODE (which is the mode of a
326 directory if DIR), assuming the umask is UMASK_VALUE, adjusted as
327 indicated by the list of change operations CHANGES. If DIR, the
328 type 'X' change affects the returned value even if no execute bits
329 were set in OLDMODE, and set user and group ID bits are preserved
330 unless CHANGES mentioned them. If PMODE_BITS is not null, store into
331 *PMODE_BITS a mask denoting file mode bits that are affected by
334 The returned value and *PMODE_BITS contain only file mode bits.
335 For example, they have the S_IFMT bits cleared on a standard
339 mode_adjust (mode_t oldmode
, bool dir
, mode_t umask_value
,
340 struct mode_change
const *changes
, mode_t
*pmode_bits
)
342 /* The adjusted mode. */
343 mode_t newmode
= oldmode
& CHMOD_MODE_BITS
;
345 /* File mode bits that CHANGES cares about. */
346 mode_t mode_bits
= 0;
348 for (; changes
->flag
!= MODE_DONE
; changes
++)
350 mode_t affected
= changes
->affected
;
352 (dir
? S_ISUID
| S_ISGID
: 0) & ~ changes
->mentioned
;
353 mode_t value
= changes
->value
;
355 switch (changes
->flag
)
357 case MODE_ORDINARY_CHANGE
:
360 case MODE_COPY_EXISTING
:
361 /* Isolate in 'value' the bits in 'newmode' to copy. */
364 /* Copy the isolated bits to the other two parts. */
365 value
|= ((value
& (S_IRUSR
| S_IRGRP
| S_IROTH
)
366 ? S_IRUSR
| S_IRGRP
| S_IROTH
: 0)
367 | (value
& (S_IWUSR
| S_IWGRP
| S_IWOTH
)
368 ? S_IWUSR
| S_IWGRP
| S_IWOTH
: 0)
369 | (value
& (S_IXUSR
| S_IXGRP
| S_IXOTH
)
370 ? S_IXUSR
| S_IXGRP
| S_IXOTH
: 0));
373 case MODE_X_IF_ANY_X
:
374 /* Affect the execute bits if execute bits are already set
375 or if the file is a directory. */
376 if ((newmode
& (S_IXUSR
| S_IXGRP
| S_IXOTH
)) | dir
)
377 value
|= S_IXUSR
| S_IXGRP
| S_IXOTH
;
381 /* If WHO was specified, limit the change to the affected bits.
382 Otherwise, apply the umask. Either way, omit changes as
384 value
&= (affected
? affected
: ~umask_value
) & ~ omit_change
;
389 /* If WHO was specified, preserve the previous values of
390 bits that are not affected by this change operation.
391 Otherwise, clear all the bits. */
393 mode_t preserved
= (affected
? ~affected
: 0) | omit_change
;
394 mode_bits
|= CHMOD_MODE_BITS
& ~preserved
;
395 newmode
= (newmode
& preserved
) | value
;
412 *pmode_bits
= mode_bits
;