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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. */
+
+#include <config.h>
+
+#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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