Support for building an hardened OpenWRT

Introduce configuration options to build an "hardened" OpenWRT.

Options to enable Stack-Smashing Protection, FORTIFY_SOURCE and RELRO
have been introduced.

uClibc makefile now automatically detects if SSP support is necessary.

hostapd makefile has been fixed to use "^" as sed separator since
using a comma was problematic when using "-Wl,-z,now" and the like in
TARGET_CFLAGS.

Currently enabling SSP on user space depends on enabling SSP kernel
side, this is due to the fact that TARGET_CFLAGS are used to build
kernel modules (at least). Suggestions on how to avoid this are welcome.
Using "select" instead of "depends on" doesn't seem to work with choice
entries.

Tested with a lantiq (WBMR) router, GCC 4.8, uClibc and a subset of
the available packages.
Needs to be tested with GCC 4.9 and the remaining packages.
PIE not currently included.

Signed-off-by: Alessandro Di Federico <ale+owrt@clearmind.me>

SVN-Revision: 44005

4 files changed, 117 insertions, 10 deletions

diff --git a/config/Config-build.in b/config/Config-build.in
index 89cf964a8e..280f71923b 100644
--- a/config/Config-build.in
+++ b/config/Config-build.in
@@ -97,15 +97,6 @@ menu "Global build settings"
 
 		  If you are unsure, select N.
 
-	config PKG_CHECK_FORMAT_SECURITY
-		bool
-		prompt "Enable gcc format-security"
-		default n
-		help
-		  Add -Wformat -Werror=format-security to the CFLAGS.  You can disable
-		  this per package by adding PKG_CHECK_FORMAT_SECURITY:=0 in the package
-		  Makefile.
-
 	config PKG_BUILD_USE_JOBSERVER
 		bool
 		prompt "Use top-level make jobserver for packages"
@@ -216,4 +207,83 @@ menu "Global build settings"
 			bool "libstdc++"
 	endchoice
 
+	comment "Hardening build options"
+
+	config PKG_CHECK_FORMAT_SECURITY
+		bool
+		prompt "Enable gcc format-security"
+		default n
+		help
+		  Add -Wformat -Werror=format-security to the CFLAGS.  You can disable
+		  this per package by adding PKG_CHECK_FORMAT_SECURITY:=0 in the package
+		  Makefile.
+
+	choice
+		prompt "User space Stack-Smashing Protection"
+		default PKG_CC_STACKPROTECTOR_NONE
+		help
+		  Enable GCC Stack Smashing Protection (SSP) for userspace applications
+		config PKG_CC_STACKPROTECTOR_NONE
+			bool "None"
+		config PKG_CC_STACKPROTECTOR_REGULAR
+			bool "Regular"
+			select SSP_SUPPORT
+			depends on KERNEL_CC_STACKPROTECTOR_REGULAR
+		config PKG_CC_STACKPROTECTOR_STRONG
+			bool "Strong"
+			select SSP_SUPPORT
+			depends on GCC_VERSION_4_9_LINARO
+			depends on KERNEL_CC_STACKPROTECTOR_STRONG
+	endchoice
+
+	choice
+		prompt "Kernel space Stack-Smashing Protection"
+		default KERNEL_CC_STACKPROTECTOR_NONE
+		help
+		  Enable GCC Stack-Smashing Protection (SSP) for the kernel
+		config KERNEL_CC_STACKPROTECTOR_NONE
+			bool "None"
+		config KERNEL_CC_STACKPROTECTOR_REGULAR
+			bool "Regular"
+		config KERNEL_CC_STACKPROTECTOR_STRONG
+			depends on GCC_VERSION_4_9_LINARO
+			bool "Strong"
+	endchoice
+
+	choice
+		prompt "Enable buffer-overflows detction (FORTIFY_SOURCE)"
+		help
+		  Enable the _FORTIFY_SOURCE macro which introduces additional
+		  checks to detect buffer-overflows in the following standard library
+		  functions: memcpy, mempcpy, memmove, memset, strcpy, stpcpy,
+		  strncpy, strcat, strncat, sprintf, vsprintf, snprintf, vsnprintf,
+		  gets.  "Conservative" (_FORTIFY_SOURCE set to 1) only introduces
+		  checks that sholdn't change the behavior of conforming programs,
+		  while "aggressive" (_FORTIFY_SOURCES set to 2) some more checking is
+		  added, but some conforming programs might fail.
+		config PKG_FORTIFY_SOURCE_NONE
+			bool "None"
+		config PKG_FORTIFY_SOURCE_1
+			bool "Conservative"
+		config PKG_FORTIFY_SOURCE_2
+			bool "Aggressive"
+	endchoice
+
+	choice
+		prompt "Enable RELRO protection"
+		help
+		  Enable a link-time protection know as RELRO (Relocation Read Only)
+		  which helps to protect from certain type of exploitation techniques
+		  altering the content of some ELF sections. "Partial" RELRO makes the
+		  .dynamic section not writeable after initialization, introducing
+		  almost no performance penalty, while "full" RELRO also marks the GOT
+		  as read-only at the cost of initializing all of it at startup.
+		config PKG_RELRO_NONE
+			bool "None"
+		config PKG_RELRO_PARTIAL
+			bool "Partial"
+		config PKG_RELRO_FULL
+			bool "Full"
+	endchoice
+
 endmenu
diff --git a/include/package.mk b/include/package.mk
index a1b90da38a..2c34a5850c 100644
--- a/include/package.mk
+++ b/include/package.mk
@@ -15,6 +15,12 @@ PKG_MD5SUM ?= unknown
 PKG_BUILD_PARALLEL ?=
 PKG_USE_MIPS16 ?= 1
 PKG_CHECK_FORMAT_SECURITY ?= 1
+PKG_CC_STACKPROTECTOR_REGULAR ?= 1
+PKG_CC_STACKPROTECTOR_STRONG ?= 1
+PKG_FORTIFY_SOURCE_1 ?= 1
+PKG_FORTIFY_SOURCE_2 ?= 1
+PKG_RELRO_PARTIAL ?= 1
+PKG_RELRO_FULL ?= 1
 
 ifneq ($(CONFIG_PKG_BUILD_USE_JOBSERVER),)
   MAKE_J:=$(if $(MAKE_JOBSERVER),$(MAKE_JOBSERVER) -j)
@@ -39,6 +45,36 @@ ifdef CONFIG_PKG_CHECK_FORMAT_SECURITY
     TARGET_CFLAGS += -Wformat -Werror=format-security
   endif
 endif
+ifdef CONFIG_PKG_CC_STACKPROTECTOR_REGULAR
+  ifeq ($(strip $(PKG_CC_STACKPROTECTOR_REGULAR)),1)
+    TARGET_CFLAGS += -fstack-protector
+  endif
+endif
+ifdef CONFIG_PKG_CC_STACKPROTECTOR_STRONG
+  ifeq ($(strip $(PKG_CC_STACKPROTECTOR_STRONG)),1)
+    TARGET_CFLAGS += -fstack-protector-strong
+  endif
+endif
+ifdef CONFIG_PKG_FORTIFY_SOURCE_1
+  ifeq ($(strip $(PKG_FORTIFY_SOURCE_1)),1)
+    TARGET_CFLAGS += -D_FORTIFY_SOURCE=1
+  endif
+endif
+ifdef CONFIG_PKG_FORTIFY_SOURCE_2
+  ifeq ($(strip $(PKG_FORTIFY_SOURCE_2)),1)
+    TARGET_CFLAGS += -D_FORTIFY_SOURCE=2
+  endif
+endif
+ifdef CONFIG_PKG_RELRO_PARTIAL
+  ifeq ($(strip $(PKG_RELRO_PARTIAL)),1)
+    TARGET_CFLAGS += -Wl,-z,relro
+  endif
+endif
+ifdef CONFIG_PKG_RELRO_FULL
+  ifeq ($(strip $(PKG_RELRO_FULL)),1)
+    TARGET_CFLAGS += -Wl,-z,now -Wl,-z,relro
+  endif
+endif
 
 include $(INCLUDE_DIR)/prereq.mk
 include $(INCLUDE_DIR)/host.mk
diff --git a/package/network/services/hostapd/Makefile b/package/network/services/hostapd/Makefile
index 19d536ecc0..6bdf5341e0 100644
--- a/package/network/services/hostapd/Makefile
+++ b/package/network/services/hostapd/Makefile
@@ -294,7 +294,7 @@ define Build/Compile/wpad
 	echo ` \
 		$(call Build/RunMake,hostapd,-s MULTICALL=1 dump_cflags); \
 		$(call Build/RunMake,wpa_supplicant,-s MULTICALL=1 dump_cflags) | \
-		sed -e 's,-n ,,g' -e 's,$(TARGET_CFLAGS),,' \
+		sed -e 's,-n ,,g' -e 's^$(TARGET_CFLAGS)^^' \
 	` > $(PKG_BUILD_DIR)/.cflags
 	+$(call Build/RunMake,hostapd, \
 		CFLAGS="$$$$(cat $(PKG_BUILD_DIR)/.cflags)" \
diff --git a/toolchain/uClibc/common.mk b/toolchain/uClibc/common.mk
index e507dc6fb0..435e4c2511 100644
--- a/toolchain/uClibc/common.mk
+++ b/toolchain/uClibc/common.mk
@@ -80,6 +80,7 @@ define Host/Configure
 		-e 's,^.*UCLIBC_HAS_SHADOW.*,UCLIBC_HAS_SHADOW=$(if $(CONFIG_SHADOW_PASSWORDS),y,n),g' \
 		-e 's,^.*UCLIBC_HAS_LOCALE.*,UCLIBC_HAS_LOCALE=$(if $(CONFIG_BUILD_NLS),y,n),g' \
 		-e 's,^.*UCLIBC_BUILD_ALL_LOCALE.*,UCLIBC_BUILD_ALL_LOCALE=$(if $(CONFIG_BUILD_NLS),y,n),g' \
+		-e 's,^.*UCLIBC_HAS_SSP.*,UCLIBC_HAS_SSP=$(if $(or $(CONFIG_PKG_CC_STACKPROTECTOR_REGULAR),$(CONFIG_PKG_CC_STACKPROTECTOR_STRONG)),y,n),g' \
 		$(HOST_BUILD_DIR)/.config.new
 	cmp -s $(HOST_BUILD_DIR)/.config.new $(HOST_BUILD_DIR)/.config.last || { \
 		cp $(HOST_BUILD_DIR)/.config.new $(HOST_BUILD_DIR)/.config && \