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146 lines
3.8 KiB
C
146 lines
3.8 KiB
C
/* euidaccess-stat -- check if effective user id can access lstat'd file
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This function is probably useful only for choosing whether to issue
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a prompt in an implementation of POSIX-specified rm.
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Copyright (C) 2005 Free Software 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 2, or (at your option)
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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 along
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with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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/* Adapted for use in GNU remove.c by Jim Meyering. */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include "euidaccess-stat.h"
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#include <unistd.h>
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#ifndef F_OK
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# define F_OK 0
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# define X_OK 1
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# define W_OK 2
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# define R_OK 4
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#endif
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#include "group-member.h"
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#include "stat-macros.h"
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/* Return true if the current user has permission of type MODE
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on the file from which stat buffer *ST was obtained, ignoring
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ACLs, attributes, `read-only'ness, etc...
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Otherwise, return false.
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Like the reentrant version of euidaccess, but starting with
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a stat buffer rather than a file name. Hence, this function
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never calls access or accessx, and doesn't take into account
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whether the file has ACLs or other attributes, or resides on
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a read-only file system. */
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bool
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euidaccess_stat (struct stat const *st, int mode)
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{
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uid_t euid;
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unsigned int granted;
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/* Convert the mode to traditional form, clearing any bogus bits. */
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if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
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mode &= 7;
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else
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mode = ((mode & R_OK ? 4 : 0)
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+ (mode & W_OK ? 2 : 0)
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+ (mode & X_OK ? 1 : 0));
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if (mode == 0)
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return true; /* The file exists. */
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euid = geteuid ();
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/* The super-user can read and write any file, and execute any file
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that anyone can execute. */
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if (euid == 0 && ((mode & X_OK) == 0
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|| (st->st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
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return true;
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/* Convert the file's permission bits to traditional form. */
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if ( S_IRUSR == (4 << 6)
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&& S_IWUSR == (2 << 6)
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&& S_IXUSR == (1 << 6)
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&& S_IRGRP == (4 << 3)
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&& S_IWGRP == (2 << 3)
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&& S_IXGRP == (1 << 3)
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&& S_IROTH == (4 << 0)
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&& S_IWOTH == (2 << 0)
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&& S_IXOTH == (1 << 0))
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granted = st->st_mode;
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else
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granted = ( (st->st_mode & S_IRUSR ? 4 << 6 : 0)
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+ (st->st_mode & S_IWUSR ? 2 << 6 : 0)
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+ (st->st_mode & S_IXUSR ? 1 << 6 : 0)
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+ (st->st_mode & S_IRGRP ? 4 << 3 : 0)
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+ (st->st_mode & S_IWGRP ? 2 << 3 : 0)
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+ (st->st_mode & S_IXGRP ? 1 << 3 : 0)
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+ (st->st_mode & S_IROTH ? 4 << 0 : 0)
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+ (st->st_mode & S_IWOTH ? 2 << 0 : 0)
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+ (st->st_mode & S_IXOTH ? 1 << 0 : 0));
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if (euid == st->st_uid)
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granted >>= 6;
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else
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{
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gid_t egid = getegid ();
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if (egid == st->st_gid || group_member (st->st_gid))
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granted >>= 3;
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}
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if ((mode & ~granted) == 0)
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return true;
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return false;
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}
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#ifdef TEST
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# include <errno.h>
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# include <stdio.h>
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# include <stdlib.h>
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# include "error.h"
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# define _(msg) msg
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char *program_name;
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int
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main (int argc, char **argv)
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{
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char *file;
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int mode;
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bool ok;
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struct stat st;
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program_name = argv[0];
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if (argc < 3)
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abort ();
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file = argv[1];
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mode = atoi (argv[2]);
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if (lstat (file, &st) != 0)
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error (EXIT_FAILURE, errno, _("cannot stat %s"), file);
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ok = euidaccess_stat (&st, mode);
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printf ("%s: %s\n", file, ok ? "y" : "n");
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exit (0);
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}
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#endif
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