1 files changed, 142 insertions, 0 deletions
diff --git a/lib/fchmodat.c b/lib/fchmodat.c
new file mode 100644
index 0000000..a7b70a2
--- /dev/null
+++ b/lib/fchmodat.c
@@ -0,0 +1,142 @@
+/* Change the protections of file relative to an open directory.
+   Copyright (C) 2006, 2009-2023 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 and Paul Eggert */
+
+/* If the user's config.h happens to include <sys/stat.h>, let it include only
+   the system's <sys/stat.h> here, so that orig_fchmodat doesn't recurse to
+   rpl_fchmodat.  */
+#define __need_system_sys_stat_h
+#include <config.h>
+
+/* Specification.  */
+#include <sys/stat.h>
+#undef __need_system_sys_stat_h
+
+#if HAVE_FCHMODAT
+static int
+orig_fchmodat (int dir, char const *file, mode_t mode, int flags)
+{
+  return fchmodat (dir, file, mode, flags);
+}
+#endif
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifdef __osf__
+/* Write "sys/stat.h" here, not <sys/stat.h>, otherwise OSF/1 5.1 DTK cc
+   eliminates this include because of the preliminary #include <sys/stat.h>
+   above.  */
+# include "sys/stat.h"
+#else
+# include <sys/stat.h>
+#endif
+
+#include <intprops.h>
+
+/* Invoke chmod or lchmod on FILE, using mode MODE, in the directory
+   open on descriptor FD.  If possible, do it without changing the
+   working directory.  Otherwise, resort to using save_cwd/fchdir,
+   then (chmod|lchmod)/restore_cwd.  If either the save_cwd or the
+   restore_cwd fails, then give a diagnostic and exit nonzero.
+   Note that an attempt to use a FLAG value of AT_SYMLINK_NOFOLLOW
+   on a system without lchmod support causes this function to fail.  */
+
+#if HAVE_FCHMODAT
+int
+fchmodat (int dir, char const *file, mode_t mode, int flags)
+{
+# if HAVE_NEARLY_WORKING_FCHMODAT
+  /* Correct the trailing slash handling.  */
+  size_t len = strlen (file);
+  if (len && file[len - 1] == '/')
+    {
+      struct stat st;
+      if (fstatat (dir, file, &st, flags & AT_SYMLINK_NOFOLLOW) < 0)
+        return -1;
+      if (!S_ISDIR (st.st_mode))
+        {
+          errno = ENOTDIR;
+          return -1;
+        }
+    }
+# endif
+
+# if NEED_FCHMODAT_NONSYMLINK_FIX
+  if (flags == AT_SYMLINK_NOFOLLOW)
+    {
+#  if HAVE_READLINKAT
+      char readlink_buf[1];
+
+#   ifdef O_PATH
+      /* Open a file descriptor with O_NOFOLLOW, to make sure we don't
+         follow symbolic links, if /proc is mounted.  O_PATH is used to
+         avoid a failure if the file is not readable.
+         Cf. <https://sourceware.org/bugzilla/show_bug.cgi?id=14578>  */
+      int fd = openat (dir, file, O_PATH | O_NOFOLLOW | O_CLOEXEC);
+      if (fd < 0)
+        return fd;
+
+      int err;
+      if (0 <= readlinkat (fd, "", readlink_buf, sizeof readlink_buf))
+        err = EOPNOTSUPP;
+      else if (errno == EINVAL)
+        {
+          static char const fmt[] = "/proc/self/fd/%d";
+          char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)];
+          sprintf (buf, fmt, fd);
+          err = chmod (buf, mode) == 0 ? 0 : errno == ENOENT ? -1 : errno;
+        }
+      else
+        err = errno == ENOENT ? -1 : errno;
+
+      close (fd);
+
+      errno = err;
+      if (0 <= err)
+        return err == 0 ? 0 : -1;
+#   endif
+
+      /* O_PATH + /proc is not supported.  */
+
+      if (0 <= readlinkat (dir, file, readlink_buf, sizeof readlink_buf))
+        {
+          errno = EOPNOTSUPP;
+          return -1;
+        }
+#  endif
+
+      /* Fall back on orig_fchmodat with no flags, despite a possible race.  */
+      flags = 0;
+    }
+# endif
+
+  return orig_fchmodat (dir, file, mode, flags);
+}
+#else
+# define AT_FUNC_NAME fchmodat
+# define AT_FUNC_F1 lchmod
+# define AT_FUNC_F2 chmod
+# define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
+# define AT_FUNC_POST_FILE_PARAM_DECLS , mode_t mode, int flag
+# define AT_FUNC_POST_FILE_ARGS        , mode
+# include "at-func.c"
+#endif