diff options
Diffstat (limited to 'lib/chown.c')
| -rw-r--r-- | lib/chown.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/lib/chown.c b/lib/chown.c new file mode 100644 index 0000000..46e753e --- /dev/null +++ b/lib/chown.c @@ -0,0 +1,151 @@ +/* provide consistent interface to chown for systems that don't interpret + an ID of -1 as meaning "don't change the corresponding ID". + + Copyright (C) 1997, 2004-2007, 2009-2020 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 3 of the License, 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, see <https://www.gnu.org/licenses/>. */ + +/* written by Jim Meyering */ + +#include <config.h> + +/* Specification. */ +#include <unistd.h> + +#include <errno.h> +#include <fcntl.h> +#include <stdbool.h> +#include <string.h> +#include <sys/stat.h> + +#if !HAVE_CHOWN + +/* Simple stub that always fails with ENOSYS, for mingw. */ +int +chown (const char *file _GL_UNUSED, uid_t uid _GL_UNUSED, + gid_t gid _GL_UNUSED) +{ + errno = ENOSYS; + return -1; +} + +#else /* HAVE_CHOWN */ + +/* Below we refer to the system's chown(). */ +# undef chown + +/* Provide a more-closely POSIX-conforming version of chown on + systems with one or both of the following problems: + - chown doesn't treat an ID of -1 as meaning + "don't change the corresponding ID". + - chown doesn't dereference symlinks. */ + +int +rpl_chown (const char *file, uid_t uid, gid_t gid) +{ + struct stat st; + bool stat_valid = false; + int result; + +# if CHOWN_CHANGE_TIME_BUG + if (gid != (gid_t) -1 || uid != (uid_t) -1) + { + if (stat (file, &st)) + return -1; + stat_valid = true; + } +# endif + +# if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE + if (gid == (gid_t) -1 || uid == (uid_t) -1) + { + /* Stat file to get id(s) that should remain unchanged. */ + if (!stat_valid && stat (file, &st)) + return -1; + if (gid == (gid_t) -1) + gid = st.st_gid; + if (uid == (uid_t) -1) + uid = st.st_uid; + } +# endif + +# if CHOWN_MODIFIES_SYMLINK + { + /* Handle the case in which the system-supplied chown function + does *not* follow symlinks. Instead, it changes permissions + on the symlink itself. To work around that, we open the + file (but this can fail due to lack of read or write permission) and + use fchown on the resulting descriptor. */ + int open_flags = O_NONBLOCK | O_NOCTTY; + int fd = open (file, O_RDONLY | open_flags); + if (0 <= fd + || (errno == EACCES + && 0 <= (fd = open (file, O_WRONLY | open_flags)))) + { + int saved_errno; + bool fchown_socket_failure; + + result = fchown (fd, uid, gid); + saved_errno = errno; + + /* POSIX says fchown can fail with errno == EINVAL on sockets + and pipes, so fall back on chown in that case. */ + fchown_socket_failure = + (result != 0 && saved_errno == EINVAL + && fstat (fd, &st) == 0 + && (S_ISFIFO (st.st_mode) || S_ISSOCK (st.st_mode))); + + close (fd); + + if (! fchown_socket_failure) + { + errno = saved_errno; + return result; + } + } + else if (errno != EACCES) + return -1; + } +# endif + +# if CHOWN_TRAILING_SLASH_BUG + if (!stat_valid) + { + size_t len = strlen (file); + if (len && file[len - 1] == '/' && stat (file, &st)) + return -1; + } +# endif + + result = chown (file, uid, gid); + +# if CHOWN_CHANGE_TIME_BUG + if (result == 0 && stat_valid + && (uid == st.st_uid || uid == (uid_t) -1) + && (gid == st.st_gid || gid == (gid_t) -1)) + { + /* No change in ownership, but at least one argument was not -1, + so we are required to update ctime. Since chown succeeded, + we assume that chmod will do likewise. Fortunately, on all + known systems where a 'no-op' chown skips the ctime update, a + 'no-op' chmod still does the trick. */ + result = chmod (file, st.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO + | S_ISUID | S_ISGID | S_ISVTX)); + } +# endif + + return result; +} + +#endif /* HAVE_CHOWN */ |