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-rw-r--r--lib/modechange.c388
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diff --git a/lib/modechange.c b/lib/modechange.c
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-/* modechange.c -- file mode manipulation
-
- Copyright (C) 1989, 1990, 1997, 1998, 1999, 2001, 2003, 2004, 2005,
- 2006 Free Software Foundation, Inc.
-
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2, or (at your option)
- any later version.
-
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software Foundation,
- Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
-
-/* Written by David MacKenzie <djm@ai.mit.edu> */
-
-/* The ASCII mode string is compiled into an array of `struct
- modechange', which can then be applied to each file to be changed.
- We do this instead of re-parsing the ASCII string for each file
- because the compiled form requires less computation to use; when
- changing the mode of many files, this probably results in a
- performance gain. */
-
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
-
-#include "modechange.h"
-#include <sys/stat.h>
-#include "stat-macros.h"
-#include "xalloc.h"
-#include <stdlib.h>
-
-/* The traditional octal values corresponding to each mode bit. */
-#define SUID 04000
-#define SGID 02000
-#define SVTX 01000
-#define RUSR 00400
-#define WUSR 00200
-#define XUSR 00100
-#define RGRP 00040
-#define WGRP 00020
-#define XGRP 00010
-#define ROTH 00004
-#define WOTH 00002
-#define XOTH 00001
-#define ALLM 07777 /* all octal mode bits */
-
-/* Convert OCTAL, which uses one of the traditional octal values, to
- an internal mode_t value. */
-static mode_t
-octal_to_mode (unsigned int octal)
-{
- /* Help the compiler optimize the usual case where mode_t uses
- the traditional octal representation. */
- return ((S_ISUID == SUID && S_ISGID == SGID && S_ISVTX == SVTX
- && S_IRUSR == RUSR && S_IWUSR == WUSR && S_IXUSR == XUSR
- && S_IRGRP == RGRP && S_IWGRP == WGRP && S_IXGRP == XGRP
- && S_IROTH == ROTH && S_IWOTH == WOTH && S_IXOTH == XOTH)
- ? octal
- : (mode_t) ((octal & SUID ? S_ISUID : 0)
- | (octal & SGID ? S_ISGID : 0)
- | (octal & SVTX ? S_ISVTX : 0)
- | (octal & RUSR ? S_IRUSR : 0)
- | (octal & WUSR ? S_IWUSR : 0)
- | (octal & XUSR ? S_IXUSR : 0)
- | (octal & RGRP ? S_IRGRP : 0)
- | (octal & WGRP ? S_IWGRP : 0)
- | (octal & XGRP ? S_IXGRP : 0)
- | (octal & ROTH ? S_IROTH : 0)
- | (octal & WOTH ? S_IWOTH : 0)
- | (octal & XOTH ? S_IXOTH : 0)));
-}
-
-/* Special operations flags. */
-enum
- {
- /* For the sentinel at the end of the mode changes array. */
- MODE_DONE,
-
- /* The typical case. */
- MODE_ORDINARY_CHANGE,
-
- /* In addition to the typical case, affect the execute bits if at
- least one execute bit is set already, or if the file is a
- directory. */
- MODE_X_IF_ANY_X,
-
- /* Instead of the typical case, copy some existing permissions for
- u, g, or o onto the other two. Which of u, g, or o is copied
- is determined by which bits are set in the `value' field. */
- MODE_COPY_EXISTING
- };
-
-/* Description of a mode change. */
-struct mode_change
-{
- char op; /* One of "=+-". */
- char flag; /* Special operations flag. */
- mode_t affected; /* Set for u, g, o, or a. */
- mode_t value; /* Bits to add/remove. */
- mode_t mentioned; /* Bits explicitly mentioned. */
-};
-
-/* Return a mode_change array with the specified `=ddd'-style
- mode change operation, where NEW_MODE is `ddd' and MENTIONED
- contains the bits explicitly mentioned in the mode are MENTIONED. */
-
-static struct mode_change *
-make_node_op_equals (mode_t new_mode, mode_t mentioned)
-{
- struct mode_change *p = xmalloc (2 * sizeof *p);
- p->op = '=';
- p->flag = MODE_ORDINARY_CHANGE;
- p->affected = CHMOD_MODE_BITS;
- p->value = new_mode;
- p->mentioned = mentioned;
- p[1].flag = MODE_DONE;
- return p;
-}
-
-/* Return a pointer to an array of file mode change operations created from
- MODE_STRING, an ASCII string that contains either an octal number
- specifying an absolute mode, or symbolic mode change operations with
- the form:
- [ugoa...][[+-=][rwxXstugo...]...][,...]
-
- Return NULL if `mode_string' does not contain a valid
- representation of file mode change operations. */
-
-struct mode_change *
-mode_compile (char const *mode_string)
-{
- /* The array of mode-change directives to be returned. */
- struct mode_change *mc;
- size_t used = 0;
-
- if ('0' <= *mode_string && *mode_string < '8')
- {
- unsigned int octal_mode = 0;
- mode_t mode;
- mode_t mentioned;
-
- do
- {
- octal_mode = 8 * octal_mode + *mode_string++ - '0';
- if (ALLM < octal_mode)
- return NULL;
- }
- while ('0' <= *mode_string && *mode_string < '8');
-
- if (*mode_string)
- return NULL;
-
- mode = octal_to_mode (octal_mode);
- mentioned = (mode & (S_ISUID | S_ISGID)) | S_ISVTX | S_IRWXUGO;
- return make_node_op_equals (mode, mentioned);
- }
-
- /* Allocate enough space to hold the result. */
- {
- size_t needed = 1;
- char const *p;
- for (p = mode_string; *p; p++)
- needed += (*p == '=' || *p == '+' || *p == '-');
- mc = xnmalloc (needed, sizeof *mc);
- }
-
- /* One loop iteration for each `[ugoa]*([-+=]([rwxXst]*|[ugo]))+'. */
- for (;; mode_string++)
- {
- /* Which bits in the mode are operated on. */
- mode_t affected = 0;
-
- /* Turn on all the bits in `affected' for each group given. */
- for (;; mode_string++)
- switch (*mode_string)
- {
- default:
- goto invalid;
- case 'u':
- affected |= S_ISUID | S_IRWXU;
- break;
- case 'g':
- affected |= S_ISGID | S_IRWXG;
- break;
- case 'o':
- affected |= S_ISVTX | S_IRWXO;
- break;
- case 'a':
- affected |= CHMOD_MODE_BITS;
- break;
- case '=': case '+': case '-':
- goto no_more_affected;
- }
- no_more_affected:;
-
- do
- {
- char op = *mode_string++;
- mode_t value;
- char flag = MODE_COPY_EXISTING;
- struct mode_change *change;
-
- switch (*mode_string++)
- {
- case 'u':
- /* Set the affected bits to the value of the `u' bits
- on the same file. */
- value = S_IRWXU;
- break;
- case 'g':
- /* Set the affected bits to the value of the `g' bits
- on the same file. */
- value = S_IRWXG;
- break;
- case 'o':
- /* Set the affected bits to the value of the `o' bits
- on the same file. */
- value = S_IRWXO;
- break;
-
- default:
- value = 0;
- flag = MODE_ORDINARY_CHANGE;
-
- for (mode_string--;; mode_string++)
- switch (*mode_string)
- {
- case 'r':
- value |= S_IRUSR | S_IRGRP | S_IROTH;
- break;
- case 'w':
- value |= S_IWUSR | S_IWGRP | S_IWOTH;
- break;
- case 'x':
- value |= S_IXUSR | S_IXGRP | S_IXOTH;
- break;
- case 'X':
- flag = MODE_X_IF_ANY_X;
- break;
- case 's':
- /* Set the setuid/gid bits if `u' or `g' is selected. */
- value |= S_ISUID | S_ISGID;
- break;
- case 't':
- /* Set the "save text image" bit if `o' is selected. */
- value |= S_ISVTX;
- break;
- default:
- goto no_more_values;
- }
- no_more_values:;
- }
-
- change = &mc[used++];
- change->op = op;
- change->flag = flag;
- change->affected = affected;
- change->value = value;
- change->mentioned = (affected ? affected & value : value);
- }
- while (*mode_string == '=' || *mode_string == '+'
- || *mode_string == '-');
-
- if (*mode_string != ',')
- break;
- }
-
- if (*mode_string == 0)
- {
- mc[used].flag = MODE_DONE;
- return mc;
- }
-
-invalid:
- free (mc);
- return NULL;
-}
-
-/* Return a file mode change operation that sets permissions to match those
- of REF_FILE. Return NULL (setting errno) if REF_FILE can't be accessed. */
-
-struct mode_change *
-mode_create_from_ref (const char *ref_file)
-{
- struct stat ref_stats;
-
- if (stat (ref_file, &ref_stats) != 0)
- return NULL;
- return make_node_op_equals (ref_stats.st_mode, CHMOD_MODE_BITS);
-}
-
-/* Return the file mode bits of OLDMODE (which is the mode of a
- directory if DIR), assuming the umask is UMASK_VALUE, adjusted as
- indicated by the list of change operations CHANGES. If DIR, the
- type 'X' change affects the returned value even if no execute bits
- were set in OLDMODE, and set user and group ID bits are preserved
- unless CHANGES mentioned them. If PMODE_BITS is not null, store into
- *PMODE_BITS a mask denoting file mode bits that are affected by
- CHANGES.
-
- The returned value and *PMODE_BITS contain only file mode bits.
- For example, they have the S_IFMT bits cleared on a standard
- Unix-like host. */
-
-mode_t
-mode_adjust (mode_t oldmode, bool dir, mode_t umask_value,
- struct mode_change const *changes, mode_t *pmode_bits)
-{
- /* The adjusted mode. */
- mode_t newmode = oldmode & CHMOD_MODE_BITS;
-
- /* File mode bits that CHANGES cares about. */
- mode_t mode_bits = 0;
-
- for (; changes->flag != MODE_DONE; changes++)
- {
- mode_t affected = changes->affected;
- mode_t omit_change =
- (dir ? S_ISUID | S_ISGID : 0) & ~ changes->mentioned;
- mode_t value = changes->value;
-
- switch (changes->flag)
- {
- case MODE_ORDINARY_CHANGE:
- break;
-
- case MODE_COPY_EXISTING:
- /* Isolate in `value' the bits in `newmode' to copy. */
- value &= newmode;
-
- /* Copy the isolated bits to the other two parts. */
- value |= ((value & (S_IRUSR | S_IRGRP | S_IROTH)
- ? S_IRUSR | S_IRGRP | S_IROTH : 0)
- | (value & (S_IWUSR | S_IWGRP | S_IWOTH)
- ? S_IWUSR | S_IWGRP | S_IWOTH : 0)
- | (value & (S_IXUSR | S_IXGRP | S_IXOTH)
- ? S_IXUSR | S_IXGRP | S_IXOTH : 0));
- break;
-
- case MODE_X_IF_ANY_X:
- /* Affect the execute bits if execute bits are already set
- or if the file is a directory. */
- if ((newmode & (S_IXUSR | S_IXGRP | S_IXOTH)) | dir)
- value |= S_IXUSR | S_IXGRP | S_IXOTH;
- break;
- }
-
- /* If WHO was specified, limit the change to the affected bits.
- Otherwise, apply the umask. Either way, omit changes as
- requested. */
- value &= (affected ? affected : ~umask_value) & ~ omit_change;
-
- switch (changes->op)
- {
- case '=':
- /* If WHO was specified, preserve the previous values of
- bits that are not affected by this change operation.
- Otherwise, clear all the bits. */
- {
- mode_t preserved = (affected ? ~affected : 0) | omit_change;
- mode_bits |= CHMOD_MODE_BITS & ~preserved;
- newmode = (newmode & preserved) | value;
- break;
- }
-
- case '+':
- mode_bits |= value;
- newmode |= value;
- break;
-
- case '-':
- mode_bits |= value;
- newmode &= ~value;
- break;
- }
- }
-
- if (pmode_bits)
- *pmode_bits = mode_bits;
- return newmode;
-}
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