security hardening: add RELFO, FORTIFY options

This enables a user to build a complete system using these
options.  It is important to note that not all packages will
build correctly to start with.

Modeled after OpenWRT approach
https://github.com/openwrt/openwrt/blob/master/config/Config-build.in#L176

A good testing tool to check a target's elf files for compliance
to an array of hardening techniques can be found here:
https://github.com/slimm609/checksec.sh

[Peter: reword fortify help texts, glibc comment]
Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

diff --git a/Config.in b/Config.in
index e7e5c2d077e8d9b0e6aff18c74444df1321aefd7..0002df51767f52d8b9aef3a295fefcde5ade080e 100644 (file)
--- a/Config.in
+++ b/Config.in
@@ -734,6 +734,76 @@ endchoice
 comment "Stack Smashing Protection needs a toolchain w/ SSP"
        depends on !BR2_TOOLCHAIN_HAS_SSP
 
+choice
+       bool "RELRO Protection"
+       depends on BR2_SHARED_LIBS
+       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.
+
+config BR2_RELRO_NONE
+       bool "None"
+       help
+         Disables Relocation link-time protections.
+
+config BR2_RELRO_PARTIAL
+       bool "Partial"
+       help
+         This option makes the dynamic section not writeable after
+         initialization (with almost no performance penalty).
+
+config BR2_RELRO_FULL
+       bool "Full"
+       help
+         This option includes the partial configuration, but also
+         marks the GOT as read-only at the cost of initialization time
+         during program loading, i.e every time an executable is started.
+
+endchoice
+
+comment "RELocation Read Only (RELRO) needs shared libraries"
+       depends on !BR2_SHARED_LIBS
+
+choice
+       bool "Buffer-overflow Detection (FORTIFY_SOURCE)"
+       depends on BR2_TOOLCHAIN_USES_GLIBC
+       depends on !BR2_OPTIMIZE_0
+       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.
+
+         NOTE: This feature requires an optimization level of s/1/2/3/g
+
+         Support for this feature has been present since GCC 4.x.
+
+config BR2_FORTIFY_SOURCE_NONE
+       bool "None"
+       help
+         Disables additional checks to detect buffer-overflows.
+
+config BR2_FORTIFY_SOURCE_1
+       bool "Conservative"
+       help
+         This option sets _FORTIFY_SOURCE to 1 and only introduces
+         checks that shouldn't change the behavior of conforming
+         programs.  Adds checks at compile-time only.
+
+config BR2_FORTIFY_SOURCE_2
+       bool "Aggressive"
+       help
+         This option sets _FORTIFY_SOURCES to 2 and some more
+         checking is added, but some conforming programs might fail.
+         Also adds checks at run-time (detected buffer overflow
+         terminates the program)
+
+endchoice
+
+comment "Fortify Source needs a glibc toolchain and optimization"
+       depends on (!BR2_TOOLCHAIN_USES_GLIBC || BR2_OPTIMIZE_0)
 endmenu
 
 source "toolchain/Config.in"

diff --git a/package/Makefile.in b/package/Makefile.in
index 61f0a8f9d0f15ab7b3842dbdd4b2346db20bde08..e387ce67feebf93272393a80a69e380b1d6aa369 100644 (file)
--- a/package/Makefile.in
+++ b/package/Makefile.in
@@ -138,11 +138,37 @@ ifeq ($(BR2_DEBUG_3),y)
 TARGET_DEBUGGING = -g3
 endif
 
+TARGET_CFLAGS_RELRO = -Wl,-z,relro
+TARGET_CFLAGS_RELRO_FULL = -Wl,-z,now $(TARGET_CFLAGS_RELRO)
+
+TARGET_LDFLAGS = $(call qstrip,$(BR2_TARGET_LDFLAGS))
+
+ifeq ($(BR2_SSP_REGULAR),y)
+TARGET_CPPFLAGS += -fstack-protector
+else ifeq ($(BR2_SSP_STRONG),y)
+TARGET_CPPFLAGS += -fstack-protector-strong
+else ifeq ($(BR2_SSP_ALL),y)
+TARGET_CPPFLAGS += -fstack-protector-all
+endif
+
+ifeq ($(BR2_RELRO_PARTIAL),y)
+TARGET_CPPFLAGS += $(TARGET_CFLAGS_RELRO)
+TARGET_LDFLAGS += $(TARGET_CFLAGS_RELRO)
+else ifeq ($(BR2_RELRO_FULL),y)
+TARGET_CPPFLAGS += -fPIE $(TARGET_CFLAGS_RELRO_FULL)
+TARGET_LDFLAGS += -pie
+endif
+
+ifeq ($(BR2_FORTIFY_SOURCE_1),y)
+TARGET_CPPFLAGS += -D_FORTIFY_SOURCE=1
+else ifeq ($(BR2_FORTIFY_SOURCE_2),y)
+TARGET_CPPFLAGS += -D_FORTIFY_SOURCE=2
+endif
+
 TARGET_CPPFLAGS += -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
 TARGET_CFLAGS = $(TARGET_CPPFLAGS) $(TARGET_ABI) $(TARGET_OPTIMIZATION) $(TARGET_DEBUGGING)
 TARGET_CXXFLAGS = $(TARGET_CFLAGS)
 TARGET_FCFLAGS = $(TARGET_ABI) $(TARGET_OPTIMIZATION) $(TARGET_DEBUGGING)
-TARGET_LDFLAGS = $(call qstrip,$(BR2_TARGET_LDFLAGS))
 
 ifeq ($(BR2_BINFMT_FLAT),y)
 TARGET_CFLAGS += $(if $($(PKG)_FLAT_STACKSIZE),-Wl$(comma)-elf2flt=-s$($(PKG)_FLAT_STACKSIZE),\
@@ -167,20 +193,6 @@ TARGET_FCFLAGS += -msep-data
 TARGET_CXXFLAGS += -msep-data
 endif
 
-ifeq ($(BR2_SSP_REGULAR),y)
-TARGET_CFLAGS += -fstack-protector
-TARGET_CXXFLAGS += -fstack-protector
-TARGET_FCFLAGS += -fstack-protector
-else ifeq ($(BR2_SSP_STRONG),y)
-TARGET_CFLAGS += -fstack-protector-strong
-TARGET_CXXFLAGS += -fstack-protector-strong
-TARGET_FCFLAGS += -fstack-protector-strong
-else ifeq ($(BR2_SSP_ALL),y)
-TARGET_CFLAGS += -fstack-protector-all
-TARGET_CXXFLAGS += -fstack-protector-all
-TARGET_FCFLAGS += -fstack-protector-all
-endif
-
 ifeq ($(BR2_TOOLCHAIN_BUILDROOT),y)
 TARGET_CROSS = $(HOST_DIR)/bin/$(GNU_TARGET_NAME)-
 else