--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2010-03-21  Bruno Haible  <bruno@clisp.org>
+
+	New module 'pt_chown'.
+	* lib/pt_chown.c: New file, from glibc with modifications.
+	* lib/pty-private.h: New file, from glibc with modifications.
+	* modules/pt_chown: New file.
+	* config/srclist.txt: Add pt_chown.c, pty-private.h (commented).
+
 2010-03-21  Bruno Haible  <bruno@clisp.org>
 
 	Tests for module 'ptsname'.

--- a/config/srclist.txt
+++ b/config/srclist.txt
@@ -174,6 +174,8 @@
 #$LIBCSRC/locale/programs/xmalloc.c	lib gpl
 #$LIBCSRC/locale/programs/xstrdup.c	lib gpl
 #
+#$LIBCSRC/login/programs/pt_chown.c	lib gpl
+#
 # http://sources.redhat.com/bugzilla/show_bug.cgi?id=321
 #$LIBCSRC/malloc/obstack.c		lib gpl
 #
@@ -209,6 +211,7 @@
 #$LIBCSRC/string/strcspn.c		lib gpl
 #$LIBCSRC/string/strpbrk.c		lib gpl
 #$LIBCSRC/string/strstr.c		lib gpl
+#$LIBCSRC/sysdeps/generic/pty-private.h	lib gpl
 #$LIBCSRC/sysdeps/posix/dup2.c		lib gpl
 #$LIBCSRC/sysdeps/posix/euidaccess.c	lib gpl
 #$LIBCSRC/sysdeps/posix/tempname.c	lib gpl

new file mode 100644
--- /dev/null
+++ b/lib/pt_chown.c
@@ -0,0 +1,164 @@
+/* pt_chown - helper program for `grantpt'.
+   Copyright (C) 1998, 1999, 2009, 2010 Free Software Foundation, Inc.
+   Contributed by C. Scott Ananian <cananian@alumni.princeton.edu>, 1998.
+
+   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 <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include <errno.h>
+#include <grp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "idpriv.h"
+#include "pty-private.h"
+
+/* For security reasons, we try to minimize the dependencies on libraries
+   outside libc.  This means, in particular:
+     - No use of gettext(), since it's usually implemented in libintl.
+     - No use of error() or argp, since they rely on gettext by default.  */
+
+
+static int
+do_pt_chown (void)
+{
+  char *pty;
+  struct stat st;
+  struct group *p;
+  gid_t gid;
+
+  /* Check that PTY_FILENO is a valid master pseudo terminal.  */
+  pty = ptsname (PTY_FILENO);
+  if (pty == NULL)
+    return errno == EBADF ? FAIL_EBADF : FAIL_EINVAL;
+
+  /* Check that the returned slave pseudo terminal is a
+     character device.  */
+  if (stat (pty, &st) < 0 || !S_ISCHR (st.st_mode))
+    return FAIL_EINVAL;
+
+  /* Get the group ID of the special `tty' group.  */
+  p = getgrnam (TTY_GROUP);
+  gid = p ? p->gr_gid : getgid ();
+
+  /* Set the owner to the real user ID, and the group to that special
+     group ID.  */
+  if (st.st_gid != gid && chown (pty, getuid (), gid) < 0)
+    return FAIL_EACCES;
+
+  /* Set the permission mode to readable and writable by the owner,
+     and writable by the group.  */
+  if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != (S_IRUSR|S_IWUSR|S_IWGRP)
+      && chmod (pty, S_IRUSR|S_IWUSR|S_IWGRP) < 0)
+    return FAIL_EACCES;
+
+  return 0;
+}
+
+
+int
+main (int argc, char *argv[])
+{
+  uid_t euid = geteuid ();
+
+  if (argc == 1 && euid == 0)
+    {
+      /* Normal invocation of this program is with no arguments and
+         with privileges.  */
+      return do_pt_chown ();
+    }
+
+  /* We aren't going to be using privileges, so drop them right now. */
+  if (idpriv_drop () < 0)
+    return EXIT_FAILURE;
+
+  {
+    int do_help = 0;
+    int do_version = 0;
+    int remaining;
+
+    for (remaining = 1; remaining < argc; remaining++)
+      {
+        const char *arg = argv[remaining];
+
+        if (arg[0] == '-')
+          {
+            if (strcmp (arg, "--") == 0)
+              {
+                remaining++;
+                break;
+              }
+            else if (strcmp (arg, "--help") == 0)
+              do_help = 1;
+            else if (strcmp (arg, "--version") == 0)
+              do_version = 1;
+            else
+              {
+                fprintf (stderr, "pt_chown: invalid option: %s\n", arg);
+                return EXIT_FAILURE;
+              }
+          }
+        else
+          break;
+      }
+
+    if (remaining < argc)
+      {
+        fprintf (stderr, "pt_chown: too many arguments\n");
+        return EXIT_FAILURE;
+      }
+
+    if (do_help)
+      {
+        printf ("Usage: pt_chown [OPTION...]\n");
+        printf ("Set the owner, group and access permission of the slave pseudo terminal\n"
+                "corresponding to the master pseudo terminal passed on file descriptor %d.\n"
+                "This is the helper program for the 'grantpt' function.  It is not intended\n"
+                "to be run directly from the command line.\n",
+                PTY_FILENO);
+        printf ("\n");
+        printf ("  --help                     Give this help list\n");
+        printf ("  --version                  Print program version\n");
+        printf ("\n");
+        printf ("The owner is set to the current user, the group is set to '%s', and the\n"
+                "access permission is set to '%o'.\n",
+                TTY_GROUP, S_IRUSR|S_IWUSR|S_IWGRP);
+        printf ("Please report bugs to <bug-gnulib@gnu.org>.\n");
+        return EXIT_SUCCESS;
+      }
+
+    if (do_version)
+      {
+        printf ("pt_chown (GNU %s) %s\n", "libc", "2.11");
+        printf ("Copyright (C) %s Free Software Foundation, Inc.\n"
+                "This is free software; see the source for copying conditions.  There is NO\n"
+                "warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n",
+                "1999");
+        return EXIT_SUCCESS;
+      }
+  }
+
+  /* Check if we are properly installed.  */
+  if (euid != 0)
+    {
+      fprintf (stderr, "pt_chown: needs to be installed setuid 'root'\n");
+      return FAIL_EXEC;
+    }
+
+  return EXIT_SUCCESS;
+}

new file mode 100644
--- /dev/null
+++ b/lib/pty-private.h
@@ -0,0 +1,46 @@
+/* Interface to the pt_chown program.
+   Copyright (C) 1998, 1999, 2009, 2010 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#ifndef _PTY_PRIVATE_H
+#define _PTY_PRIVATE_H 1
+
+/* The group slave pseudo terminals belong to.  */
+#define TTY_GROUP "tty"
+
+/* The file descriptor connected to the master pseudo terminal.  */
+#define PTY_FILENO 3
+
+/* Path to the helper program that implements `grantpt' in user space.  */
+#define _PATH_PT_CHOWN PKGLIBEXECDIR "/pt_chown"
+
+/* Test whether given TTY is really a Unix98 pseudo terminal.  */
+/* #define unix98_pseudo_p(Dev) ... */
+
+/* Exit codes for the helper program.  */
+enum  /* failure modes */
+{
+  FAIL_EBADF = 1,
+  FAIL_EINVAL,
+  FAIL_EACCES,
+  FAIL_EXEC,
+  FAIL_ENOMEM
+};
+
+#endif /* pty-private.h  */

new file mode 100644
--- /dev/null
+++ b/modules/pt_chown
@@ -0,0 +1,25 @@
+Description:
+Helper program for setting the owner of the slave side of a pseudo-terminal.
+
+Files:
+lib/pt_chown.c
+lib/pty-private.h
+
+Depends-on:
+idpriv-drop
+ptsname
+
+configure.ac:
+
+Makefile.am:
+# TODO: Add rules for installing as setuid root (chown root, chmod a=rx,u+s).
+pkglibexec_PROGRAMS = pt_chown
+pt_chown_LDADD = libgnu.a
+
+Include:
+
+License:
+LGPL
+
+Maintainer:
+glibc