415 lines
13 KiB
C
415 lines
13 KiB
C
/* modechange.c -- file mode manipulation
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Copyright (C) 1989-1990, 1997-1999, 2001, 2003-2006, 2009-2020 Free Software
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Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by David MacKenzie <djm@ai.mit.edu> */
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/* The ASCII mode string is compiled into an array of 'struct
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modechange', which can then be applied to each file to be changed.
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We do this instead of re-parsing the ASCII string for each file
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because the compiled form requires less computation to use; when
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changing the mode of many files, this probably results in a
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performance gain. */
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#include <config.h>
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#include "modechange.h"
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#include <sys/stat.h>
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#include "stat-macros.h"
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#include "xalloc.h"
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#include <stdlib.h>
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/* The traditional octal values corresponding to each mode bit. */
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#define SUID 04000
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#define SGID 02000
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#define SVTX 01000
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#define RUSR 00400
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#define WUSR 00200
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#define XUSR 00100
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#define RGRP 00040
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#define WGRP 00020
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#define XGRP 00010
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#define ROTH 00004
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#define WOTH 00002
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#define XOTH 00001
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#define ALLM 07777 /* all octal mode bits */
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/* Convert OCTAL, which uses one of the traditional octal values, to
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an internal mode_t value. */
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static mode_t
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octal_to_mode (unsigned int octal)
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{
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/* Help the compiler optimize the usual case where mode_t uses
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the traditional octal representation. */
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return ((S_ISUID == SUID && S_ISGID == SGID && S_ISVTX == SVTX
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&& S_IRUSR == RUSR && S_IWUSR == WUSR && S_IXUSR == XUSR
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&& S_IRGRP == RGRP && S_IWGRP == WGRP && S_IXGRP == XGRP
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&& S_IROTH == ROTH && S_IWOTH == WOTH && S_IXOTH == XOTH)
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? octal
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: (mode_t) ((octal & SUID ? S_ISUID : 0)
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| (octal & SGID ? S_ISGID : 0)
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| (octal & SVTX ? S_ISVTX : 0)
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| (octal & RUSR ? S_IRUSR : 0)
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| (octal & WUSR ? S_IWUSR : 0)
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| (octal & XUSR ? S_IXUSR : 0)
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| (octal & RGRP ? S_IRGRP : 0)
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| (octal & WGRP ? S_IWGRP : 0)
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| (octal & XGRP ? S_IXGRP : 0)
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| (octal & ROTH ? S_IROTH : 0)
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| (octal & WOTH ? S_IWOTH : 0)
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| (octal & XOTH ? S_IXOTH : 0)));
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}
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/* Special operations flags. */
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enum
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{
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/* For the sentinel at the end of the mode changes array. */
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MODE_DONE,
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/* The typical case. */
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MODE_ORDINARY_CHANGE,
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/* In addition to the typical case, affect the execute bits if at
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least one execute bit is set already, or if the file is a
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directory. */
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MODE_X_IF_ANY_X,
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/* Instead of the typical case, copy some existing permissions for
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u, g, or o onto the other two. Which of u, g, or o is copied
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is determined by which bits are set in the 'value' field. */
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MODE_COPY_EXISTING
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};
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/* Description of a mode change. */
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struct mode_change
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{
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char op; /* One of "=+-". */
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char flag; /* Special operations flag. */
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mode_t affected; /* Set for u, g, o, or a. */
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mode_t value; /* Bits to add/remove. */
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mode_t mentioned; /* Bits explicitly mentioned. */
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};
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/* Return a mode_change array with the specified "=ddd"-style
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mode change operation, where NEW_MODE is "ddd" and MENTIONED
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contains the bits explicitly mentioned in the mode are MENTIONED. */
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static struct mode_change *
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make_node_op_equals (mode_t new_mode, mode_t mentioned)
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{
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struct mode_change *p = xmalloc (2 * sizeof *p);
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p->op = '=';
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p->flag = MODE_ORDINARY_CHANGE;
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p->affected = CHMOD_MODE_BITS;
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p->value = new_mode;
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p->mentioned = mentioned;
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p[1].flag = MODE_DONE;
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return p;
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}
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/* Return a pointer to an array of file mode change operations created from
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MODE_STRING, an ASCII string that contains either an octal number
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specifying an absolute mode, or symbolic mode change operations with
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the form:
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[ugoa...][[+-=][rwxXstugo...]...][,...]
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Return NULL if 'mode_string' does not contain a valid
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representation of file mode change operations. */
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struct mode_change *
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mode_compile (char const *mode_string)
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{
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/* The array of mode-change directives to be returned. */
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struct mode_change *mc;
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size_t used = 0;
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char const *p;
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if ('0' <= *mode_string && *mode_string < '8')
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{
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unsigned int octal_mode = 0;
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mode_t mode;
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mode_t mentioned;
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p = mode_string;
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do
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{
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octal_mode = 8 * octal_mode + *p++ - '0';
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if (ALLM < octal_mode)
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return NULL;
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}
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while ('0' <= *p && *p < '8');
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if (*p)
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return NULL;
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mode = octal_to_mode (octal_mode);
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mentioned = (p - mode_string < 5
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? (mode & (S_ISUID | S_ISGID)) | S_ISVTX | S_IRWXUGO
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: CHMOD_MODE_BITS);
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return make_node_op_equals (mode, mentioned);
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}
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/* Allocate enough space to hold the result. */
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{
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size_t needed = 1;
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for (p = mode_string; *p; p++)
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needed += (*p == '=' || *p == '+' || *p == '-');
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mc = xnmalloc (needed, sizeof *mc);
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}
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/* One loop iteration for each
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'[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. */
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for (p = mode_string; ; p++)
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{
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/* Which bits in the mode are operated on. */
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mode_t affected = 0;
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/* Turn on all the bits in 'affected' for each group given. */
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for (;; p++)
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switch (*p)
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{
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default:
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goto invalid;
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case 'u':
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affected |= S_ISUID | S_IRWXU;
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break;
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case 'g':
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affected |= S_ISGID | S_IRWXG;
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break;
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case 'o':
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affected |= S_ISVTX | S_IRWXO;
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break;
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case 'a':
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affected |= CHMOD_MODE_BITS;
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break;
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case '=': case '+': case '-':
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goto no_more_affected;
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}
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no_more_affected:;
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do
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{
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char op = *p++;
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mode_t value;
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mode_t mentioned = 0;
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char flag = MODE_COPY_EXISTING;
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struct mode_change *change;
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switch (*p)
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{
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case '0': case '1': case '2': case '3':
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case '4': case '5': case '6': case '7':
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{
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unsigned int octal_mode = 0;
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do
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{
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octal_mode = 8 * octal_mode + *p++ - '0';
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if (ALLM < octal_mode)
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goto invalid;
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}
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while ('0' <= *p && *p < '8');
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if (affected || (*p && *p != ','))
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goto invalid;
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affected = mentioned = CHMOD_MODE_BITS;
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value = octal_to_mode (octal_mode);
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flag = MODE_ORDINARY_CHANGE;
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break;
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}
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case 'u':
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/* Set the affected bits to the value of the "u" bits
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on the same file. */
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value = S_IRWXU;
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p++;
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break;
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case 'g':
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/* Set the affected bits to the value of the "g" bits
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on the same file. */
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value = S_IRWXG;
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p++;
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break;
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case 'o':
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/* Set the affected bits to the value of the "o" bits
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on the same file. */
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value = S_IRWXO;
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p++;
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break;
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default:
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value = 0;
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flag = MODE_ORDINARY_CHANGE;
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for (;; p++)
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switch (*p)
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{
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case 'r':
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value |= S_IRUSR | S_IRGRP | S_IROTH;
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break;
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case 'w':
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value |= S_IWUSR | S_IWGRP | S_IWOTH;
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break;
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case 'x':
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value |= S_IXUSR | S_IXGRP | S_IXOTH;
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break;
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case 'X':
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flag = MODE_X_IF_ANY_X;
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break;
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case 's':
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/* Set the setuid/gid bits if 'u' or 'g' is selected. */
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value |= S_ISUID | S_ISGID;
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break;
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case 't':
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/* Set the "save text image" bit if 'o' is selected. */
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value |= S_ISVTX;
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break;
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default:
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goto no_more_values;
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}
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no_more_values:;
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}
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change = &mc[used++];
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change->op = op;
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change->flag = flag;
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change->affected = affected;
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change->value = value;
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change->mentioned =
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(mentioned ? mentioned : affected ? affected & value : value);
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}
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while (*p == '=' || *p == '+' || *p == '-');
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if (*p != ',')
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break;
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}
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if (*p == 0)
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{
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mc[used].flag = MODE_DONE;
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return mc;
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}
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invalid:
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free (mc);
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return NULL;
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}
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/* Return a file mode change operation that sets permissions to match those
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of REF_FILE. Return NULL (setting errno) if REF_FILE can't be accessed. */
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struct mode_change *
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mode_create_from_ref (const char *ref_file)
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{
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struct stat ref_stats;
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if (stat (ref_file, &ref_stats) != 0)
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return NULL;
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return make_node_op_equals (ref_stats.st_mode, CHMOD_MODE_BITS);
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}
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/* Return the file mode bits of OLDMODE (which is the mode of a
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directory if DIR), assuming the umask is UMASK_VALUE, adjusted as
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indicated by the list of change operations CHANGES. If DIR, the
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type 'X' change affects the returned value even if no execute bits
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were set in OLDMODE, and set user and group ID bits are preserved
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unless CHANGES mentioned them. If PMODE_BITS is not null, store into
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*PMODE_BITS a mask denoting file mode bits that are affected by
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CHANGES.
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The returned value and *PMODE_BITS contain only file mode bits.
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For example, they have the S_IFMT bits cleared on a standard
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Unix-like host. */
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mode_t
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mode_adjust (mode_t oldmode, bool dir, mode_t umask_value,
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struct mode_change const *changes, mode_t *pmode_bits)
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{
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/* The adjusted mode. */
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mode_t newmode = oldmode & CHMOD_MODE_BITS;
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/* File mode bits that CHANGES cares about. */
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mode_t mode_bits = 0;
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for (; changes->flag != MODE_DONE; changes++)
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{
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mode_t affected = changes->affected;
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mode_t omit_change =
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(dir ? S_ISUID | S_ISGID : 0) & ~ changes->mentioned;
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mode_t value = changes->value;
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switch (changes->flag)
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{
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case MODE_ORDINARY_CHANGE:
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break;
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case MODE_COPY_EXISTING:
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/* Isolate in 'value' the bits in 'newmode' to copy. */
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value &= newmode;
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/* Copy the isolated bits to the other two parts. */
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value |= ((value & (S_IRUSR | S_IRGRP | S_IROTH)
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? S_IRUSR | S_IRGRP | S_IROTH : 0)
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| (value & (S_IWUSR | S_IWGRP | S_IWOTH)
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? S_IWUSR | S_IWGRP | S_IWOTH : 0)
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| (value & (S_IXUSR | S_IXGRP | S_IXOTH)
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? S_IXUSR | S_IXGRP | S_IXOTH : 0));
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break;
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case MODE_X_IF_ANY_X:
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/* Affect the execute bits if execute bits are already set
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or if the file is a directory. */
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if ((newmode & (S_IXUSR | S_IXGRP | S_IXOTH)) | dir)
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value |= S_IXUSR | S_IXGRP | S_IXOTH;
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break;
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}
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/* If WHO was specified, limit the change to the affected bits.
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Otherwise, apply the umask. Either way, omit changes as
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requested. */
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value &= (affected ? affected : ~umask_value) & ~ omit_change;
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switch (changes->op)
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{
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case '=':
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/* If WHO was specified, preserve the previous values of
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bits that are not affected by this change operation.
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Otherwise, clear all the bits. */
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{
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mode_t preserved = (affected ? ~affected : 0) | omit_change;
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mode_bits |= CHMOD_MODE_BITS & ~preserved;
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newmode = (newmode & preserved) | value;
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break;
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}
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case '+':
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mode_bits |= value;
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newmode |= value;
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break;
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case '-':
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mode_bits |= value;
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newmode &= ~value;
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break;
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}
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}
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if (pmode_bits)
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*pmode_bits = mode_bits;
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return newmode;
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}
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