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 2, or (at your option)
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, write to the Free Software Foundation,
18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
20 /* Written by David MacKenzie <djm@ai.mit.edu> */
22 /* The ASCII mode string is compiled into an array of `struct
23 modechange', which can then be applied to each file to be changed.
24 We do this instead of re-parsing the ASCII string for each file
25 because the compiled form requires less computation to use; when
26 changing the mode of many files, this probably results in a
31 #include "modechange.h"
33 #include "stat-macros.h"
37 /* The traditional octal values corresponding to each mode bit. */
50 #define ALLM 07777 /* all octal mode bits */
52 /* Convert OCTAL, which uses one of the traditional octal values, to
53 an internal mode_t value. */
55 octal_to_mode (unsigned int octal)
57 /* Help the compiler optimize the usual case where mode_t uses
58 the traditional octal representation. */
59 return ((S_ISUID == SUID && S_ISGID == SGID && S_ISVTX == SVTX
60 && S_IRUSR == RUSR && S_IWUSR == WUSR && S_IXUSR == XUSR
61 && S_IRGRP == RGRP && S_IWGRP == WGRP && S_IXGRP == XGRP
62 && S_IROTH == ROTH && S_IWOTH == WOTH && S_IXOTH == XOTH)
64 : (mode_t) ((octal & SUID ? S_ISUID : 0)
65 | (octal & SGID ? S_ISGID : 0)
66 | (octal & SVTX ? S_ISVTX : 0)
67 | (octal & RUSR ? S_IRUSR : 0)
68 | (octal & WUSR ? S_IWUSR : 0)
69 | (octal & XUSR ? S_IXUSR : 0)
70 | (octal & RGRP ? S_IRGRP : 0)
71 | (octal & WGRP ? S_IWGRP : 0)
72 | (octal & XGRP ? S_IXGRP : 0)
73 | (octal & ROTH ? S_IROTH : 0)
74 | (octal & WOTH ? S_IWOTH : 0)
75 | (octal & XOTH ? S_IXOTH : 0)));
78 /* Special operations flags. */
81 /* For the sentinel at the end of the mode changes array. */
84 /* The typical case. */
87 /* In addition to the typical case, affect the execute bits if at
88 least one execute bit is set already, or if the file is a
92 /* Instead of the typical case, copy some existing permissions for
93 u, g, or o onto the other two. Which of u, g, or o is copied
94 is determined by which bits are set in the `value' field. */
98 /* Description of a mode change. */
101 char op; /* One of "=+-". */
102 char flag; /* Special operations flag. */
103 mode_t affected; /* Set for u, g, o, or a. */
104 mode_t value; /* Bits to add/remove. */
105 mode_t mentioned; /* Bits explicitly mentioned. */
108 /* Return a mode_change array with the specified `=ddd'-style
109 mode change operation, where NEW_MODE is `ddd' and MENTIONED
110 contains the bits explicitly mentioned in the mode are MENTIONED. */
112 static struct mode_change *
113 make_node_op_equals (mode_t new_mode, mode_t mentioned)
115 struct mode_change *p = xmalloc (2 * sizeof *p);
117 p->flag = MODE_ORDINARY_CHANGE;
118 p->affected = CHMOD_MODE_BITS;
120 p->mentioned = mentioned;
121 p[1].flag = MODE_DONE;
125 /* Return a pointer to an array of file mode change operations created from
126 MODE_STRING, an ASCII string that contains either an octal number
127 specifying an absolute mode, or symbolic mode change operations with
129 [ugoa...][[+-=][rwxXstugo...]...][,...]
131 Return NULL if `mode_string' does not contain a valid
132 representation of file mode change operations. */
135 mode_compile (char const *mode_string)
137 /* The array of mode-change directives to be returned. */
138 struct mode_change *mc;
141 if ('0' <= *mode_string && *mode_string < '8')
143 unsigned int octal_mode = 0;
149 octal_mode = 8 * octal_mode + *mode_string++ - '0';
150 if (ALLM < octal_mode)
153 while ('0' <= *mode_string && *mode_string < '8');
158 mode = octal_to_mode (octal_mode);
159 mentioned = (mode & (S_ISUID | S_ISGID)) | S_ISVTX | S_IRWXUGO;
160 return make_node_op_equals (mode, mentioned);
163 /* Allocate enough space to hold the result. */
167 for (p = mode_string; *p; p++)
168 needed += (*p == '=' || *p == '+' || *p == '-');
169 mc = xnmalloc (needed, sizeof *mc);
172 /* One loop iteration for each `[ugoa]*([-+=]([rwxXst]*|[ugo]))+'. */
173 for (;; mode_string++)
175 /* Which bits in the mode are operated on. */
178 /* Turn on all the bits in `affected' for each group given. */
179 for (;; mode_string++)
180 switch (*mode_string)
185 affected |= S_ISUID | S_IRWXU;
188 affected |= S_ISGID | S_IRWXG;
191 affected |= S_ISVTX | S_IRWXO;
194 affected |= CHMOD_MODE_BITS;
196 case '=': case '+': case '-':
197 goto no_more_affected;
203 char op = *mode_string++;
205 char flag = MODE_COPY_EXISTING;
206 struct mode_change *change;
208 switch (*mode_string++)
211 /* Set the affected bits to the value of the `u' bits
216 /* Set the affected bits to the value of the `g' bits
221 /* Set the affected bits to the value of the `o' bits
228 flag = MODE_ORDINARY_CHANGE;
230 for (mode_string--;; mode_string++)
231 switch (*mode_string)
234 value |= S_IRUSR | S_IRGRP | S_IROTH;
237 value |= S_IWUSR | S_IWGRP | S_IWOTH;
240 value |= S_IXUSR | S_IXGRP | S_IXOTH;
243 flag = MODE_X_IF_ANY_X;
246 /* Set the setuid/gid bits if `u' or `g' is selected. */
247 value |= S_ISUID | S_ISGID;
250 /* Set the "save text image" bit if `o' is selected. */
259 change = &mc[used++];
262 change->affected = affected;
263 change->value = value;
264 change->mentioned = (affected ? affected & value : value);
266 while (*mode_string == '=' || *mode_string == '+'
267 || *mode_string == '-');
269 if (*mode_string != ',')
273 if (*mode_string == 0)
275 mc[used].flag = MODE_DONE;
284 /* Return a file mode change operation that sets permissions to match those
285 of REF_FILE. Return NULL (setting errno) if REF_FILE can't be accessed. */
288 mode_create_from_ref (const char *ref_file)
290 struct stat ref_stats;
292 if (stat (ref_file, &ref_stats) != 0)
294 return make_node_op_equals (ref_stats.st_mode, CHMOD_MODE_BITS);
297 /* Return the file mode bits of OLDMODE (which is the mode of a
298 directory if DIR), assuming the umask is UMASK_VALUE, adjusted as
299 indicated by the list of change operations CHANGES. If DIR, the
300 type 'X' change affects the returned value even if no execute bits
301 were set in OLDMODE, and set user and group ID bits are preserved
302 unless CHANGES mentioned them. If PMODE_BITS is not null, store into
303 *PMODE_BITS a mask denoting file mode bits that are affected by
306 The returned value and *PMODE_BITS contain only file mode bits.
307 For example, they have the S_IFMT bits cleared on a standard
311 mode_adjust (mode_t oldmode, bool dir, mode_t umask_value,
312 struct mode_change const *changes, mode_t *pmode_bits)
314 /* The adjusted mode. */
315 mode_t newmode = oldmode & CHMOD_MODE_BITS;
317 /* File mode bits that CHANGES cares about. */
318 mode_t mode_bits = 0;
320 for (; changes->flag != MODE_DONE; changes++)
322 mode_t affected = changes->affected;
324 (dir ? S_ISUID | S_ISGID : 0) & ~ changes->mentioned;
325 mode_t value = changes->value;
327 switch (changes->flag)
329 case MODE_ORDINARY_CHANGE:
332 case MODE_COPY_EXISTING:
333 /* Isolate in `value' the bits in `newmode' to copy. */
336 /* Copy the isolated bits to the other two parts. */
337 value |= ((value & (S_IRUSR | S_IRGRP | S_IROTH)
338 ? S_IRUSR | S_IRGRP | S_IROTH : 0)
339 | (value & (S_IWUSR | S_IWGRP | S_IWOTH)
340 ? S_IWUSR | S_IWGRP | S_IWOTH : 0)
341 | (value & (S_IXUSR | S_IXGRP | S_IXOTH)
342 ? S_IXUSR | S_IXGRP | S_IXOTH : 0));
345 case MODE_X_IF_ANY_X:
346 /* Affect the execute bits if execute bits are already set
347 or if the file is a directory. */
348 if ((newmode & (S_IXUSR | S_IXGRP | S_IXOTH)) | dir)
349 value |= S_IXUSR | S_IXGRP | S_IXOTH;
353 /* If WHO was specified, limit the change to the affected bits.
354 Otherwise, apply the umask. Either way, omit changes as
356 value &= (affected ? affected : ~umask_value) & ~ omit_change;
361 /* If WHO was specified, preserve the previous values of
362 bits that are not affected by this change operation.
363 Otherwise, clear all the bits. */
365 mode_t preserved = (affected ? ~affected : 0) | omit_change;
366 mode_bits |= CHMOD_MODE_BITS & ~preserved;
367 newmode = (newmode & preserved) | value;
384 *pmode_bits = mode_bits;