[Buildroot] [git commit] security hardening: add RELFO, FORTIFY options
Peter Korsgaard
peter at korsgaard.com
Sun Jan 28 14:21:14 UTC 2018
commit: https://git.buildroot.net/buildroot/commit/?id=20a4583ebf7fe97ea22a1ea11621dd44a8114ca5
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/master
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 at rockwellcollins.com>
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
Config.in | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
package/Makefile.in | 42 ++++++++++++++++++++------------
2 files changed, 97 insertions(+), 15 deletions(-)
diff --git a/Config.in b/Config.in
index e7e5c2d..0002df5 100644
--- 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 61f0a8f..e387ce6 100644
--- 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
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