#* CVE-2013-2207 Incorrectly granting access to another user's pseudo-terminal

#  has been fixed by disabling the use of pt_chown (Bugzilla #15755).

#  Distributions can re-enable building and using pt_chown via the new configure

#  option `--enable-pt_chown'.  Enabling the use of pt_chown carries with it

#  considerable security risks and should only be used if the distribution

#  understands and accepts the risks.

#

#2013-07-21  Siddhesh Poyarekar  <siddhesh@redhat.com>

#	    Andreas Schwab  <schwab@suse.de>

#	    Roland McGrath  <roland@hack.frob.com>

#	    Joseph Myers  <joseph@codesourcery.com>

#	    Carlos O'Donell  <carlos@redhat.com>

#

#	[BZ #15755]

#	* config.h.in: Define HAVE_PT_CHOWN.

#	* config.make.in (build-pt-chown): New variable.

#	* configure.in (--enable-pt_chown): New configure option.

#	* configure: Regenerate.

#	* login/Makefile: Include Makeconfig.  Build pt_chown only if

#	build-pt-chown is enabled.

#	* sysdeps/unix/grantpt.c (grantpt) [HAVE_PT_CHOWN]: Spawn

#	pt_chown to fix pty ownership.

#	* sysdeps/unix/sysv/linux/grantpt.c [HAVE_PT_CHOWN]: Define

#	CLOSE_ALL_FDS.

#	* manual/install.texi (Configuring and compiling): Mention

#	--enable-pt_chown. Add @findex for grantpt.

#	* INSTALL: Regenerate.

#

diff -Nrup a/config.h.in b/config.h.in

--- a/config.h.in	2012-12-24 22:02:13.000000000 -0500

+++ b/config.h.in	2013-07-24 00:20:07.651301252 -0400

@@ -232,4 +232,7 @@

 /* The ARM hard-float ABI is being used.  */

 #undef HAVE_ARM_PCS_VFP

+/* The pt_chown binary is being built and used by grantpt.  */

+#undef HAVE_PT_CHOWN

+

 #endif

diff -Nrup a/config.make.in b/config.make.in

--- a/config.make.in	2012-12-24 22:02:13.000000000 -0500

+++ b/config.make.in	2013-07-24 00:21:15.244176098 -0400

@@ -101,6 +101,7 @@ force-install = @force_install@

 link-obsolete-rpc = @link_obsolete_rpc@

 build-nscd = @build_nscd@

 use-nscd = @use_nscd@

+build-pt-chown = @build_pt_chown@

 # Build tools.

 CC = @CC@

diff -Nrup a/configure b/configure

--- a/configure	2013-07-24 00:25:10.090174244 -0400

+++ b/configure	2013-07-24 00:20:07.769174345 -0400

@@ -653,6 +653,7 @@ multi_arch

 base_machine

 add_on_subdirs

 add_ons

+build_pt_chown

 build_nscd

 link_obsolete_rpc

 libc_cv_nss_crypt

@@ -759,6 +760,7 @@ enable_obsolete_rpc

 enable_systemtap

 enable_build_nscd

 enable_nscd

+enable_pt_chown

 with_cpu

 '

       ac_precious_vars='build_alias

@@ -1419,6 +1421,7 @@ Optional Features:

   --enable-systemtap      enable systemtap static probe points [default=no]

   --disable-build-nscd    disable building and installing the nscd daemon

   --disable-nscd          library functions will not contact the nscd daemon

+  --enable-pt_chown       Enable building and installing pt_chown

 Optional Packages:

   --with-PACKAGE[=ARG]    use PACKAGE [ARG=yes]

@@ -3934,6 +3937,19 @@ else

 fi

+# Check whether --enable-pt_chown was given.

+if test "${enable_pt_chown+set}" = set; then :

+  enableval=$enable_pt_chown; build_pt_chown=$enableval

+else

+  build_pt_chown=no

+fi

+

+

+if test $build_pt_chown = yes; then

+  $as_echo "#define HAVE_PT_CHOWN 1" >>confdefs.h

+

+fi

+

 # The way shlib-versions is used to generate soversions.mk uses a

 # fairly simplistic model for name recognition that can't distinguish

 # i486-pc-linux-gnu fully from i486-pc-gnu.  So we mutate a $host_os

diff -Nrup a/configure.in b/configure.in

--- a/configure.in	2012-12-24 22:02:13.000000000 -0500

+++ b/configure.in	2013-07-24 00:20:07.658298658 -0400

@@ -315,6 +315,16 @@ AC_ARG_ENABLE([nscd],

 	      [use_nscd=$enableval],

 	      [use_nscd=yes])

+AC_ARG_ENABLE([pt_chown],

+	      [AS_HELP_STRING([--enable-pt_chown],

+	       [Enable building and installing pt_chown])],

+	      [build_pt_chown=$enableval],

+	      [build_pt_chown=no])

+AC_SUBST(build_pt_chown)

+if test $build_pt_chown = yes; then

+  AC_DEFINE(HAVE_PT_CHOWN)

+fi

+

 # The way shlib-versions is used to generate soversions.mk uses a

 # fairly simplistic model for name recognition that can't distinguish

 # i486-pc-linux-gnu fully from i486-pc-gnu.  So we mutate a $host_os

diff -Nrup a/INSTALL b/INSTALL

--- a/INSTALL	2012-12-24 22:02:13.000000000 -0500

+++ b/INSTALL	2013-07-24 00:20:07.650300624 -0400

@@ -128,6 +128,18 @@ will be used, and CFLAGS sets optimizati

      this can be prevented though there generally is no reason since it

      creates compatibility problems.

+`--enable-pt_chown'

+     The file `pt_chown' is a helper binary for `grantpt' (*note

+     Pseudo-Terminals: Allocation.) that is installed setuid root to

+     fix up pseudo-terminal ownership.  It is not built by default

+     because systems using the Linux kernel are commonly built with the

+     `devpts' filesystem enabled and mounted at `/dev/pts', which

+     manages pseudo-terminal ownership automatically.  By using

+     `--enable-pt_chown', you may build `pt_chown' and install it

+     setuid and owned by `root'.  The use of `pt_chown' introduces

+     additional security risks to the system and you should enable it

+     only if you understand and accept those risks.

+

 `--build=BUILD-SYSTEM'

 `--host=HOST-SYSTEM'

      These options are for cross-compiling.  If you specify both

diff -Nrup a/login/Makefile b/login/Makefile

--- a/login/Makefile	2012-12-24 22:02:13.000000000 -0500

+++ b/login/Makefile	2013-07-24 00:20:07.660298670 -0400

@@ -29,9 +29,15 @@ routines := getutent getutent_r getutid 

 CFLAGS-grantpt.c = -DLIBEXECDIR='"$(libexecdir)"'

-others = utmpdump pt_chown

+others = utmpdump

+

+include ../Makeconfig

+

+ifeq (yes,$(build-pt-chown))

+others += pt_chown

 others-pie = pt_chown

 install-others-programs = $(inst_libexecdir)/pt_chown

+endif

 subdir-dirs = programs

 vpath %.c programs

diff -Nrup a/manual/install.texi b/manual/install.texi

--- a/manual/install.texi	2012-12-24 22:02:13.000000000 -0500

+++ b/manual/install.texi	2013-07-24 00:20:07.662298261 -0400

@@ -155,6 +155,20 @@ if the used tools support it.  By using 

 prevented though there generally is no reason since it creates

 compatibility problems.

+@pindex pt_chown

+@findex grantpt

+@item --enable-pt_chown

+The file @file{pt_chown} is a helper binary for @code{grantpt}

+(@pxref{Allocation, Pseudo-Terminals}) that is installed setuid root to

+fix up pseudo-terminal ownership.  It is not built by default because

+systems using the Linux kernel are commonly built with the @code{devpts}

+filesystem enabled and mounted at @file{/dev/pts}, which manages

+pseudo-terminal ownership automatically.  By using

+@samp{--enable-pt_chown}, you may build @file{pt_chown} and install it

+setuid and owned by @code{root}.  The use of @file{pt_chown} introduces

+additional security risks to the system and you should enable it only if

+you understand and accept those risks.

+

 @item --build=@var{build-system}

 @itemx --host=@var{host-system}

 These options are for cross-compiling.  If you specify both options and

diff -Nrup a/sysdeps/unix/grantpt.c b/sysdeps/unix/grantpt.c

--- a/sysdeps/unix/grantpt.c	2012-12-24 22:02:13.000000000 -0500

+++ b/sysdeps/unix/grantpt.c	2013-07-24 00:20:07.663299235 -0400

@@ -173,9 +173,10 @@ grantpt (int fd)

   retval = 0;

   goto cleanup;

-  /* We have to use the helper program.  */

+  /* We have to use the helper program if it is available.  */

  helper:;

+#ifdef HAVE_PT_CHOWN

   pid_t pid = __fork ();

   if (pid == -1)

     goto cleanup;

@@ -190,9 +191,9 @@ grantpt (int fd)

 	if (__dup2 (fd, PTY_FILENO) < 0)

 	  _exit (FAIL_EBADF);

-#ifdef CLOSE_ALL_FDS

+# ifdef CLOSE_ALL_FDS

       CLOSE_ALL_FDS ();

-#endif

+# endif

       execle (_PATH_PT_CHOWN, basename (_PATH_PT_CHOWN), NULL, NULL);

       _exit (FAIL_EXEC);

@@ -231,6 +232,7 @@ grantpt (int fd)

 	    assert(! "getpt: internal error: invalid exit code from pt_chown");

 	  }

     }

+#endif

  cleanup:

   if (buf != _buf)

diff -Nrup a/sysdeps/unix/sysv/linux/grantpt.c b/sysdeps/unix/sysv/linux/grantpt.c

--- a/sysdeps/unix/sysv/linux/grantpt.c	2012-12-24 22:02:13.000000000 -0500

+++ b/sysdeps/unix/sysv/linux/grantpt.c	2013-07-24 00:20:07.664298465 -0400

@@ -11,7 +11,7 @@

 #include "pty-private.h"

-

+#if HAVE_PT_CHOWN

 /* Close all file descriptors except the one specified.  */

 static void

 close_all_fds (void)

@@ -38,6 +38,7 @@ close_all_fds (void)

       __dup2 (STDOUT_FILENO, STDERR_FILENO);

     }

 }

-#define CLOSE_ALL_FDS() close_all_fds()

+# define CLOSE_ALL_FDS() close_all_fds()

+#endif

 #include <sysdeps/unix/grantpt.c>