* sysdeps/mach/hurd/check_fds.c: New file. Implements file descriptor checking in SUID programs for the Hurd.

* sysdeps/mach/hurd/check_fds.c: New file.  Implements
	file descriptor checking in SUID programs for the Hurd.

ChangeLog

@@ -1,5 +1,8 @@
 2000-07-10  Mark Kettenis  <kettenis@gnu.org>
 
+	* sysdeps/mach/hurd/check_fds.c: New file.  Implements
+	file descriptor checking in SUID programs for the Hurd.
+
 	* resolv/nss_dns/dns-host.c (_nss_dns_gethostbyname2_r): Use
 	res_hostalias instead of __hostalias for thread-safety.
 

sysdeps/mach/hurd/check_fds.c

@@ -0,0 +1,108 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#include <fcntl.h>
+#include <paths.h>
+#include <unistd.h>
+
+#include <hurd.h>
+#include <hurd/fd.h>
+
+#include <set-hooks.h>
+
+/* Try to get a machine dependent instruction which will make the
+   program crash.  This is used in case everything else fails.  */
+#include <abort-instr.h>
+#ifndef ABORT_INSTRUCTION
+/* No such instruction is available.  */
+# define ABORT_INSTRUCTION
+#endif
+
+static void
+check_one_fd (int fd, int mode)
+{
+  struct hurd_fd *d;
+
+  d = _hurd_fd_get (fd);
+  if (d == NULL)
+    {
+      /* This descriptor hasn't been opened.  We try to allocate the
+         descriptor and open /dev/null on it so that the SUID program
+         we are about to start does not accidently use this
+         descriptor.  */
+      d = _hurd_alloc_fd (NULL, fd);
+      if (d != NULL)
+	{
+	  mach_port_t port;
+
+	  port = __file_name_lookup (_PATH_DEVNULL, mode, 0);
+	  if (port)
+	    {
+	      /* Since /dev/null isn't supposed to be a terminal, we
+		 avoid any ctty magic.  */
+	      d->port.port = port;
+	      d->flags = 0;
+
+	      __spin_unlock (&d->port.lock);
+	      return;
+	    }
+	}
+      
+      /* We cannot even give an error message here since it would run
+	 into the same problems.  */
+      while (1)
+	/* Try for ever and ever.  */
+	ABORT_INSTRUCTION;
+    }
+}
+
+static void
+check_standard_fds (void)
+{
+  /* Check all three standard file descriptors.  */
+  check_one_fd (STDIN_FILENO, O_RDONLY);
+  check_one_fd (STDOUT_FILENO, O_RDWR);
+  check_one_fd (STDERR_FILENO, O_RDWR);
+}
+
+static void
+init_standard_fds (void)
+{
+  /* Now that we have FDs, make sure that, if this is a SUID program,
+     FDs 0, 1 and 2 are allocated.  If necessary we'll set them up
+     ourselves.  If that's not possible we stop the program.  */
+  if (__builtin_expect (__libc_enable_secure, 0))
+    check_standard_fds ();
+
+  (void) &init_standard_fds;	/* Avoid "defined but not used" warning.  */
+}
+text_set_element (_hurd_fd_subinit, init_standard_fds);
+
+
+#ifndef SHARED
+void
+__libc_check_standard_fds (void)
+{
+  /* We don't check the standard file descriptors here.  They will be
+     checked when we initialize the file descriptor table, as part of
+     the _hurd_fd_subinit hook.
+     
+     This function is only present to make sure that this module gets
+     linked in when part of the static libc.  */
+}
+#endif