New unlinkdir module.

2 files changed, 97 insertions, 0 deletions

diff --git a/lib/unlinkdir.c b/lib/unlinkdir.c
new file mode 100644
index 000000000..c30aa1020
--- /dev/null
+++ b/lib/unlinkdir.c
@@ -0,0 +1,70 @@
+/* unlinkdir.c - determine (and maybe change) whether we can unlink directories
+
+   Copyright (C) 2005 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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Paul Eggert and Jim Meyering.  */
+
+#include <config.h>
+
+#include "unlinkdir.h"
+
+#if HAVE_PRIV_H
+# include <priv.h>
+#endif
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+
+#if ! UNLINK_CANNOT_UNLINK_DIR
+
+/* Return true if we cannot unlink directories, false if we might be
+   able to unlink directories.  If possible, tell the kernel we don't
+   want to be able to unlink directories, so that we can return true.  */
+
+bool
+cannot_unlink_dir (void)
+{
+  static bool initialized;
+  static bool cannot;
+
+  if (! initialized)
+    {
+# if defined PRIV_EFFECTIVE && defined PRIV_SYS_LINKDIR
+      /* We might be able to unlink directories if we cannot
+	 determine our privileges, or if we have the
+	 PRIV_SYS_LINKDIR privilege and cannot delete it.  */
+      priv_set_t *pset = priv_allocset ();
+      if (pset)
+	{
+	  cannot =
+	    (getppriv (PRIV_EFFECTIVE, pset) == 0
+	     && (! priv_ismember (pset, PRIV_SYS_LINKDIR)
+		 || (priv_delset (pset, PRIV_SYS_LINKDIR) == 0
+		     && setppriv (PRIV_SET, PRIV_EFFECTIVE, pset) == 0)));
+	  priv_freeset (pset);
+	}
+# else
+      /* In traditional Unix, only root can unlink directories.  */
+      cannot = (getuid () != 0);
+# endif
+    }
+
+  initialized = true;
+  return cannot;
+}
+
+#endif
diff --git a/lib/unlinkdir.h b/lib/unlinkdir.h
new file mode 100644
index 000000000..f705f1233
--- /dev/null
+++ b/lib/unlinkdir.h
@@ -0,0 +1,27 @@
+/* unlinkdir.h - determine (and maybe change) whether we can unlink directories
+
+   Copyright (C) 2005 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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Paul Eggert and Jim Meyering.  */
+
+#include <stdbool.h>
+
+#if UNLINK_CANNOT_UNLINK_DIR
+static bool cannot_unlink_dir (void) { return true; }
+#else
+bool cannot_unlink_dir (void);
+#endif