>From b4ca84ba9ab76c6db83ad5b6c5580fb7a6673720 Mon Sep 17 00:00:00 2001
From: Nils Goroll <nils.goroll@uplex.de>
Date: Thu, 9 Jan 2014 18:17:45 +0100
Subject: [PATCH] autocrap auto-hardening

Automatically determine possible compiler/linker hardening options for additional
stack and buffer overflow protection and memory protection.

This adds the --enable-hardening configure option, which is default.

Use --disable-hardening to disable.

based upon work documented here: http://mainisusuallyafunction.blogspot.de/2012/05/automatic-binary-hardening-with.html

Changes to the above:

- removed CXX support
- replaced -fstack-protector-all with -fstack-protector-strong and fallback to
  -fstack-protector
- removed -Wstack-protector (XXXLATER: disable for specific functions only?)

DEVELOPER_CFLAGS:
- -fstack-protector removed
- -Wno-unused-parameter removed (because it is overridden by -Wunused-parameter later)
- -Wno-pointer-sign removed - this seems to be a useful warning
- -Wno-address added to avoid gcc "can't be NULL" warnings for use of REPLACE() with
  local variables
---
 build-aux/wrap-compiler-for-flag-check |   22 ++++++++
 configure.ac                           |   84 +++++++++++++++++++++++++++++++-
 m4/ax_check_link_flag.m4               |   73 +++++++++++++++++++++++++++
 3 files changed, 178 insertions(+), 1 deletions(-)
 create mode 100755 build-aux/wrap-compiler-for-flag-check
 create mode 100644 m4/ax_check_link_flag.m4

diff --git a/build-aux/wrap-compiler-for-flag-check b/build-aux/wrap-compiler-for-flag-check
new file mode 100755
index 0000000..579f577
--- /dev/null
+++ b/build-aux/wrap-compiler-for-flag-check
@@ -0,0 +1,22 @@
+#!/bin/sh
+
+# There is no way to make clang's "argument unused" warning fatal.  So when
+# configure checks for supported flags, it runs $CC, $CXX, $LD via this
+# wrapper.
+#
+# Ideally the search string would also include 'clang: ' but this output might
+# depend on clang's argv[0].
+
+if out=`"$@" 2>&1`; then
+  echo "$out"
+  if echo "$out" | grep 'warning: argument unused' >/dev/null; then
+    echo "$0: found clang warning"
+    exit 1
+  else
+    exit 0
+  fi
+else
+  code=$?
+  echo "$out"
+  exit $code
+fi
diff --git a/configure.ac b/configure.ac
index ea2039a..90dac09 100644
--- a/configure.ac
+++ b/configure.ac
@@ -48,6 +48,88 @@ LIBS="$PTHREAD_LIBS $LIBS"
 CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
 CC="$PTHREAD_CC"
 
+####
+## BEGIN autoharden configure.ac
+##
+## based upon:
+##     http://mainisusuallyafunction.blogspot.com/2012/05/automatic-binary-hardening-with.html
+##     https://github.com/kmcallister/autoharden
+##
+## changes
+## - removed CXX support
+## - replaced -fstack-protector-all with -fstack-protector-strong and fallback to -fstack-protector
+## - removed -Wstack-protector (XXXLATER: disable for specific functions only?)
+
+# We want to check for compiler flag support, but there is no way to make
+# clang's "argument unused" warning fatal.  So we invoke the compiler through a
+# wrapper script that greps for this message.
+saved_CC="$CC"
+saved_LD="$LD"
+flag_wrap="$srcdir/build-aux/wrap-compiler-for-flag-check"
+CC="$flag_wrap $CC"
+LD="$flag_wrap $LD"
+
+# We use the same hardening flags for C.  We must check that each flag
+# is supported by both compilers.
+AC_DEFUN([check_cc_flag],
+ [AX_CHECK_COMPILE_FLAG([$1], [$2], [$3], [-Werror $4])])
+AC_DEFUN([check_link_flag],
+ [AX_CHECK_LINK_FLAG([$1], [$2], [$3], [-Werror $4])])
+
+AC_ARG_ENABLE([hardening],
+  [AS_HELP_STRING([--enable-hardening],
+    [Enable compiler and linker options to frustrate memory corruption exploits @<:@yes@:>@])],
+  [hardening="$enableval"],
+  [hardening="yes"])
+
+HARDEN_CFLAGS=""
+HARDEN_LDFLAGS=""
+AS_IF([test x"$hardening" != x"no"], [
+  check_cc_flag([-fno-strict-overflow], [HARDEN_CFLAGS="$HARDEN_CFLAGS -fno-strict-overflow"])
+
+  # This one will likely succeed, even on platforms where it does nothing.
+  check_cc_flag([-D_FORTIFY_SOURCE=2], [HARDEN_CFLAGS="$HARDEN_CFLAGS -D_FORTIFY_SOURCE=2"])
+
+  check_cc_flag([-fstack-protector-strong],
+   [check_link_flag([-fstack-protector-strong],
+     [HARDEN_CFLAGS="$HARDEN_CFLAGS -fstack-protector-strong"
+      check_cc_flag([--param ssp-buffer-size=1], [HARDEN_CFLAGS="$HARDEN_CFLAGS --param ssp-buffer-size=1"],
+        [], [-fstack-protector-strong])])],
+   [check_link_flag([-fstack-protector],
+     [HARDEN_CFLAGS="$HARDEN_CFLAGS -fstack-protector"
+      check_cc_flag([--param ssp-buffer-size=1], [HARDEN_CFLAGS="$HARDEN_CFLAGS --param ssp-buffer-size=1"],
+        [], [-fstack-protector])])])
+
+		
+
+  # At the link step, we might want -pie (GCC) or -Wl,-pie (Clang on OS X)
+  #
+  # The linker checks also compile code, so we need to include -fPIE as well.
+  check_cc_flag([-fPIE],
+   [check_link_flag([-fPIE -pie],
+     [HARDEN_CFLAGS="$HARDEN_CFLAGS -fPIE"
+      HARDEN_LDFLAGS="$HARDEN_LDFLAGS -pie"],
+     [check_link_flag([-fPIE -Wl,-pie],
+       [HARDEN_CFLAGS="$HARDEN_CFLAGS -fPIE"
+        HARDEN_LDFLAGS="$HARDEN_LDFLAGS -Wl,-pie"])])])
+
+  check_link_flag([-Wl,-z,relro],
+   [HARDEN_LDFLAGS="$HARDEN_LDFLAGS -Wl,-z,relro"
+    check_link_flag([-Wl,-z,now], [HARDEN_LDFLAGS="$HARDEN_LDFLAGS -Wl,-z,now"])])])
+AC_SUBST([HARDEN_CFLAGS])
+AC_SUBST([HARDEN_LDFLAGS])
+
+# End of flag tests.
+CC="$saved_CC"
+LD="$saved_LD"
+
+## END autoharden configure.ac
+####
+
+CFLAGS="${CFLAGS} ${HARDEN_CFLAGS}" 
+LDFLAGS="${LDFLAGS} ${HARDEN_LDFLAGS}" 
+
+
 AC_PROG_INSTALL
 AC_PROG_MAKE_SET
 AC_ARG_WITH([rst2man],
@@ -465,7 +547,7 @@ AX_CHECK_COMPILE_FLAG([-Werror=unused-result],
       OCFLAGS="${OCFLAGS} -Wno-unused-result"])])
 
 # This corresponds to FreeBSD's WARNS level 6
-DEVELOPER_CFLAGS="-fstack-protector -Werror -Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wunused-parameter -Wcast-align -Wchar-subscripts -Wnested-externs -Wno-pointer-sign -Wextra -Wno-missing-field-initializers -Wno-sign-compare"
+DEVELOPER_CFLAGS="-Werror -Wall -Wno-format-y2k -W -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wunused-parameter -Wcast-align -Wchar-subscripts -Wnested-externs -Wextra -Wno-missing-field-initializers -Wno-sign-compare -Wno-address "
 
 # These are not compliable yet
 DEVELOPER_GCC_CFLAGS="-Wold-style-definition -Wredundant-decls "
diff --git a/m4/ax_check_link_flag.m4 b/m4/ax_check_link_flag.m4
new file mode 100644
index 0000000..db899dd
--- /dev/null
+++ b/m4/ax_check_link_flag.m4
@@ -0,0 +1,73 @@
+# ===========================================================================
+#    http://www.gnu.org/software/autoconf-archive/ax_check_link_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_LINK_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   Check whether the given FLAG works with the linker or gives an error.
+#   (Warnings, however, are ignored)
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   If EXTRA-FLAGS is defined, it is added to the linker's default flags
+#   when the check is done.  The check is thus made with the flags: "LDFLAGS
+#   EXTRA-FLAGS FLAG".  This can for example be used to force the linker to
+#   issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_LINK_IFELSE.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{PREPROC,COMPILE}_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   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/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 3
+
+AC_DEFUN([AX_CHECK_LINK_FLAG],
+[AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_ldflags_$4_$1])dnl
+AC_CACHE_CHECK([whether the linker accepts $1], CACHEVAR, [
+  ax_check_save_flags=$LDFLAGS
+  LDFLAGS="$LDFLAGS $4 $1"
+  AC_LINK_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  LDFLAGS=$ax_check_save_flags])
+AS_IF([test x"AS_VAR_GET(CACHEVAR)" = xyes],
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
+AS_VAR_POPDEF([CACHEVAR])dnl
+])dnl AX_CHECK_LINK_FLAGS
-- 
1.5.6.5

