1 /* modechange.c -- file mode manipulation
3 Copyright (C) 1989, 1990, 1997, 1998, 1999, 2001, 2003, 2004, 2005,
4 2006 Free Software Foundation, Inc.
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 <http://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;
140 if ('0' <= *mode_string && *mode_string < '8')
142 unsigned int octal_mode = 0;
148 octal_mode = 8 * octal_mode + *mode_string++ - '0';
149 if (ALLM < octal_mode)
152 while ('0' <= *mode_string && *mode_string < '8');
157 mode = octal_to_mode (octal_mode);
158 mentioned = (mode & (S_ISUID | S_ISGID)) | S_ISVTX | S_IRWXUGO;
159 return make_node_op_equals (mode, mentioned);
162 /* Allocate enough space to hold the result. */
166 for (p = mode_string; *p; p++)
167 needed += (*p == '=' || *p == '+' || *p == '-');
168 mc = xnmalloc (needed, sizeof *mc);
171 /* One loop iteration for each `[ugoa]*([-+=]([rwxXst]*|[ugo]))+'. */
172 for (;; mode_string++)
174 /* Which bits in the mode are operated on. */
177 /* Turn on all the bits in `affected' for each group given. */
178 for (;; mode_string++)
179 switch (*mode_string)
184 affected |= S_ISUID | S_IRWXU;
187 affected |= S_ISGID | S_IRWXG;
190 affected |= S_ISVTX | S_IRWXO;
193 affected |= CHMOD_MODE_BITS;
195 case '=': case '+': case '-':
196 goto no_more_affected;
202 char op = *mode_string++;
204 char flag = MODE_COPY_EXISTING;
205 struct mode_change *change;
207 switch (*mode_string++)
210 /* Set the affected bits to the value of the `u' bits
215 /* Set the affected bits to the value of the `g' bits
220 /* Set the affected bits to the value of the `o' bits
227 flag = MODE_ORDINARY_CHANGE;
229 for (mode_string--;; mode_string++)
230 switch (*mode_string)
233 value |= S_IRUSR | S_IRGRP | S_IROTH;
236 value |= S_IWUSR | S_IWGRP | S_IWOTH;
239 value |= S_IXUSR | S_IXGRP | S_IXOTH;
242 flag = MODE_X_IF_ANY_X;
245 /* Set the setuid/gid bits if `u' or `g' is selected. */
246 value |= S_ISUID | S_ISGID;
249 /* Set the "save text image" bit if `o' is selected. */
258 change = &mc[used++];
261 change->affected = affected;
262 change->value = value;
263 change->mentioned = (affected ? affected & value : value);
265 while (*mode_string == '=' || *mode_string == '+'
266 || *mode_string == '-');
268 if (*mode_string != ',')
272 if (*mode_string == 0)
274 mc[used].flag = MODE_DONE;
283 /* Return a file mode change operation that sets permissions to match those
284 of REF_FILE. Return NULL (setting errno) if REF_FILE can't be accessed. */
287 mode_create_from_ref (const char *ref_file)
289 struct stat ref_stats;
291 if (stat (ref_file, &ref_stats) != 0)
293 return make_node_op_equals (ref_stats.st_mode, CHMOD_MODE_BITS);
296 /* Return the file mode bits of OLDMODE (which is the mode of a
297 directory if DIR), assuming the umask is UMASK_VALUE, adjusted as
298 indicated by the list of change operations CHANGES. If DIR, the
299 type 'X' change affects the returned value even if no execute bits
300 were set in OLDMODE, and set user and group ID bits are preserved
301 unless CHANGES mentioned them. If PMODE_BITS is not null, store into
302 *PMODE_BITS a mask denoting file mode bits that are affected by
305 The returned value and *PMODE_BITS contain only file mode bits.
306 For example, they have the S_IFMT bits cleared on a standard
310 mode_adjust (mode_t oldmode, bool dir, mode_t umask_value,
311 struct mode_change const *changes, mode_t *pmode_bits)
313 /* The adjusted mode. */
314 mode_t newmode = oldmode & CHMOD_MODE_BITS;
316 /* File mode bits that CHANGES cares about. */
317 mode_t mode_bits = 0;
319 for (; changes->flag != MODE_DONE; changes++)
321 mode_t affected = changes->affected;
323 (dir ? S_ISUID | S_ISGID : 0) & ~ changes->mentioned;
324 mode_t value = changes->value;
326 switch (changes->flag)
328 case MODE_ORDINARY_CHANGE:
331 case MODE_COPY_EXISTING:
332 /* Isolate in `value' the bits in `newmode' to copy. */
335 /* Copy the isolated bits to the other two parts. */
336 value |= ((value & (S_IRUSR | S_IRGRP | S_IROTH)
337 ? S_IRUSR | S_IRGRP | S_IROTH : 0)
338 | (value & (S_IWUSR | S_IWGRP | S_IWOTH)
339 ? S_IWUSR | S_IWGRP | S_IWOTH : 0)
340 | (value & (S_IXUSR | S_IXGRP | S_IXOTH)
341 ? S_IXUSR | S_IXGRP | S_IXOTH : 0));
344 case MODE_X_IF_ANY_X:
345 /* Affect the execute bits if execute bits are already set
346 or if the file is a directory. */
347 if ((newmode & (S_IXUSR | S_IXGRP | S_IXOTH)) | dir)
348 value |= S_IXUSR | S_IXGRP | S_IXOTH;
352 /* If WHO was specified, limit the change to the affected bits.
353 Otherwise, apply the umask. Either way, omit changes as
355 value &= (affected ? affected : ~umask_value) & ~ omit_change;
360 /* If WHO was specified, preserve the previous values of
361 bits that are not affected by this change operation.
362 Otherwise, clear all the bits. */
364 mode_t preserved = (affected ? ~affected : 0) | omit_change;
365 mode_bits |= CHMOD_MODE_BITS & ~preserved;
366 newmode = (newmode & preserved) | value;
383 *pmode_bits = mode_bits;