152 lines
4.3 KiB
C
152 lines
4.3 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, 2004-2007, 2009-2022 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file 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 Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser 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 Jim Meyering */
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#include <config.h>
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/* Specification. */
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#include <unistd.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <string.h>
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#include <sys/stat.h>
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#if !HAVE_CHOWN
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/* Simple stub that always fails with ENOSYS, for mingw. */
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int
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chown (_GL_UNUSED const char *file, _GL_UNUSED uid_t uid,
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_GL_UNUSED gid_t gid)
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{
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errno = ENOSYS;
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return -1;
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}
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#else /* HAVE_CHOWN */
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/* Below we refer to the system's chown(). */
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# undef chown
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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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struct stat st;
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bool stat_valid = false;
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int result;
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# if CHOWN_CHANGE_TIME_BUG
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if (gid != (gid_t) -1 || uid != (uid_t) -1)
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{
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if (stat (file, &st))
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return -1;
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stat_valid = true;
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}
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# endif
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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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/* Stat file to get id(s) that should remain unchanged. */
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if (!stat_valid && stat (file, &st))
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return -1;
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if (gid == (gid_t) -1)
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gid = st.st_gid;
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if (uid == (uid_t) -1)
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uid = st.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 open_flags = O_NONBLOCK | O_NOCTTY | O_CLOEXEC;
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int fd = open (file, O_RDONLY | open_flags);
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if (0 <= fd
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|| (errno == EACCES
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&& 0 <= (fd = open (file, O_WRONLY | open_flags))))
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{
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int saved_errno;
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bool fchown_socket_failure;
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result = fchown (fd, uid, gid);
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saved_errno = errno;
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/* POSIX says fchown can fail with errno == EINVAL on sockets
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and pipes, so fall back on chown in that case. */
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fchown_socket_failure =
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(result != 0 && saved_errno == EINVAL
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&& fstat (fd, &st) == 0
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&& (S_ISFIFO (st.st_mode) || S_ISSOCK (st.st_mode)));
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close (fd);
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if (! fchown_socket_failure)
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{
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errno = saved_errno;
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return result;
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}
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}
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else if (errno != EACCES)
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return -1;
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}
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# endif
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# if CHOWN_TRAILING_SLASH_BUG
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if (!stat_valid)
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{
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size_t len = strlen (file);
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if (len && file[len - 1] == '/' && stat (file, &st))
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return -1;
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}
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# endif
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result = chown (file, uid, gid);
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# if CHOWN_CHANGE_TIME_BUG
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if (result == 0 && stat_valid
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&& (uid == st.st_uid || uid == (uid_t) -1)
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&& (gid == st.st_gid || gid == (gid_t) -1))
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{
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/* No change in ownership, but at least one argument was not -1,
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so we are required to update ctime. Since chown succeeded,
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we assume that chmod will do likewise. Fortunately, on all
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known systems where a 'no-op' chown skips the ctime update, a
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'no-op' chmod still does the trick. */
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result = chmod (file, st.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO
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| S_ISUID | S_ISGID | S_ISVTX));
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}
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# endif
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return result;
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}
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#endif /* HAVE_CHOWN */
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