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90 lines
2.6 KiB
C
90 lines
2.6 KiB
C
/* provide consistent interface to chown for systems that don't interpret
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an ID of -1 as meaning `don't change the corresponding ID'.
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Copyright (C) 1997, 2004, 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
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along 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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/* written by Jim Meyering */
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#include <config.h>
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/* Disable the definition of chown to rpl_chown (from config.h) in this
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file. Otherwise, we'd get conflicting prototypes for rpl_chown on
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most systems. */
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#undef chown
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#include <sys/types.h>
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#include <sys/stat.h>
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#if HAVE_UNISTD_H
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# include <unistd.h>
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#endif
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#if HAVE_FCNTL_H
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# include <fcntl.h>
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#else
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# include <sys/file.h>
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#endif
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#include <errno.h>
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/* Provide a more-closely POSIX-conforming version of chown on
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systems with one or both of the following problems:
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- chown doesn't treat an ID of -1 as meaning
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`don't change the corresponding ID'.
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- chown doesn't dereference symlinks. */
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int
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rpl_chown (const char *file, uid_t uid, gid_t gid)
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{
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#if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE
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if (gid == (gid_t) -1 || uid == (uid_t) -1)
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{
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struct stat file_stats;
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/* Stat file to get id(s) that should remain unchanged. */
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if (stat (file, &file_stats))
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return -1;
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if (gid == (gid_t) -1)
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gid = file_stats.st_gid;
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if (uid == (uid_t) -1)
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uid = file_stats.st_uid;
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}
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#endif
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#if CHOWN_MODIFIES_SYMLINK
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{
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/* Handle the case in which the system-supplied chown function
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does *not* follow symlinks. Instead, it changes permissions
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on the symlink itself. To work around that, we open the
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file (but this can fail due to lack of read or write permission) and
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use fchown on the resulting descriptor. */
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int fd = open (file, O_RDONLY | O_NONBLOCK | O_NOCTTY);
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if (fd < 0
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&& (fd = open (file, O_WRONLY | O_NONBLOCK | O_NOCTTY)) < 0)
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return -1;
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if (fchown (fd, uid, gid))
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{
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int saved_errno = errno;
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close (fd);
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errno = saved_errno;
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return -1;
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}
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return close (fd);
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}
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#else
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return chown (file, uid, gid);
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#endif
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}
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