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#THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#For more information, please refer to <https://unlicense.org/>

include(CheckCXXCompilerFlag)

function(determineSupportedHardeningFlags property)
	set(FLAGS_HARDENING "")
	foreach(flag ${ARGN})
		unset(var_name)
		string(REPLACE "=" "_eq_" var_name ${flag})
		string(REPLACE "," "_comma_" var_name ${var_name})
		set(var_name "SUPPORTS_HARDENING_${property}_${var_name}")
		check_cxx_compiler_flag(${flag} ${var_name})#since linker flags and other flags are in the form of compiler flags
		if(${${var_name}})
			list(APPEND FLAGS_HARDENING "${flag}")
		endif()
	endforeach(flag)
	string(REPLACE ";" " " FLAGS_HARDENING "${FLAGS_HARDENING}")
	#message(STATUS "FLAGS_HARDENING ${FLAGS_HARDENING}")
	set(HARDENING_${property} "${FLAGS_HARDENING}" CACHE STRING "Hardening flags")
endfunction(determineSupportedHardeningFlags)

function(processFlagsList target property)
	get_target_property(FLAGS_UNHARDENED ${target} ${property})
	if(FLAGS_UNHARDENED MATCHES "FLAGS_UNHARDENED-NOTFOUND")
		set(FLAGS_UNHARDENED "")
	endif()
	#message(STATUS "processFlagsList ${target} ${property} ${FLAGS_UNHARDENED}")
	#message(STATUS "HARDENING_${property} ${HARDENING_${property}}")
	if(HARDENING_${property})
	else()
		determineSupportedHardeningFlags(${property} ${ARGN})
	endif()
	
	set(FLAGS_HARDENED ${FLAGS_UNHARDENED})
	list(APPEND FLAGS_HARDENED ${HARDENING_${property}})
	string(REPLACE ";" " " FLAGS_HARDENED "${FLAGS_HARDENED}")
	#message(STATUS "${target} PROPERTIES ${property} ${FLAGS_HARDENED}")
	set_target_properties(${target} PROPERTIES ${property} "${FLAGS_HARDENED}")
endfunction(processFlagsList)

function(setupPIC target)
	set_property(TARGET ${target} PROPERTY POSITION_INDEPENDENT_CODE ON) # FUCK, doesn't work
	if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
		get_target_property(type ${target} TYPE)
		if(type STREQUAL "EXECUTABLE")
			list(APPEND HARDENING_COMPILER_FLAGS
				"-fPIE"
			)
		else()
			list(APPEND HARDENING_COMPILER_FLAGS
				"-fPIC"
			)
		endif()
		list(APPEND HARDENING_LINKER_FLAGS
			"-pie"
		)
	elseif(MSVC)
		list(APPEND HARDENING_COMPILER_FLAGS
			"/dynamicbase" "/HIGHENTROPYVA"
		)
	else()
		message(ERROR "The compiler is not supported")
	endif()
endfunction(setupPIC)

function(harden target)
	setupPIC("${target}")
	if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
		list(APPEND HARDENING_COMPILER_FLAGS
			"-Wall" "-Wextra" "-Wconversion" "-Wformat" "-Wformat-security" "-Werror=format-security"
			"-fno-strict-aliasing" "-fno-common"
			#"-fstack-check"
			#"-fcf-protection=full" # conflicts to "-mindirect-branch"
			"-fcf-runtime-abi=full"
			
			"-fstack-clash-protection"
			"-mcet"
			"-fsanitize=cfi"
			"-fsanitize=cfi-cast-strict"
			"-fsanitize=cfi-derived-cast"
			"-fsanitize=cfi-unrelated-cast"
			"-fsanitize=cfi-nvcall"
			"-fsanitize=cfi-vcall"
			"-fsanitize=cfi-icall"
			"-fsanitize=cfi-mfcall"
			
			# CLang-ish flags
			"-mretpoline"
			"-mspeculative-load-hardening"
			
			
			#"-fsanitize=safe-stack;compiler-rt" # https://clang.llvm.org/docs/SafeStack.html
			"-fsanitize=address" # https://clang.llvm.org/docs/AddressSanitizer.html
			
			# TODO implement compiler flag dependence on libs linking
			#"-fsanitize=undefined;ubsan" # https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html , gcc also has it
			
			#"-fsanitize=thread" # https://clang.llvm.org/docs/ThreadSanitizer.html , 15x slowdown and 10x memory overhead
			#"-fsanitize=memory" # https://clang.llvm.org/docs/MemorySanitizer.html 3x slowdown
			#"-fsanitize=dataflow" # https://clang.llvm.org/docs/DataFlowSanitizer.html, taint analysis, requires explicit annotation of code
			
			#"-fvtable-verify=std;vtv"
			
			# this conflicts with gcc which now has -fcf-protection=full hardcoded
			"-fcf-protection=none -mindirect-branch"
			"-fcf-protection=none -mindirect-branch=thunk-extern"
			"-fcf-protection=none -mindirect-branch=thunk-inline"
			"-fcf-protection=none -mindirect-return"
			"-fcf-protection=none -mindirect-branch-register"
			"-fcf-protection=none -mindirect-branch-loop"
			
			"-x86-speculative-load-hardening"
			"-mno-indirect-branch-register"
		)
		
		# some flags are bugged in GCC
		if(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
		else()
			list(APPEND HARDENING_COMPILER_FLAGS
				"-ftrapv" # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=35412
			)
		endif()
		
		# GCC 9 has removed these flags
		if(CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 9 AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10))
			message(STATUS "GCC 9 removes some hardening flags but doesn't fail if they are present, instead shows deprecation message. In order to not to put garbage into warnings we don't insert them. See the code of Harden.cmake for the details.")
		else()
			list(APPEND HARDENING_COMPILER_FLAGS
				"-mmitigate-rop" 
				"-fcheck-pointer-bounds"
				"-fchkp-treat-zero-size-reloc-as-infinite"
				"-fchkp-first-field-has-own-bounds"
				"-fchkp-narrow-bounds"
				"-fchkp-narrow-to-innermost-array"
				"-fchkp-optimize"
				"-fchkp-use-fast-string-functions"
				"-fchkp-use-nochk-string-functions"
				"-fchkp-use-static-const-bounds"
			)
		endif()
		
		list(APPEND HARDENING_LINKER_FLAGS
			"-Wl,-O1"
			"-Wl,--sort-common"
			"-Wl,--as-needed"
			"-Wl,-flto"
		)
		if(CMAKE_SYSTEM_NAME MATCHES "Windows")
			list(APPEND HARDENING_LINKER_FLAGS
				"-Wl,--export-all-symbols"
				"-Wl,--nxcompat"
				"-Wl,--dynamicbase"
			)
			if(CMAKE_SIZEOF_VOID_P EQUAL 8)
			#	list(APPEND HARDENING_LINKER_FLAGS "-Wl,--image-base,0x140000000") # doesn't work for this project
			endif()
		elseif(CMAKE_SYSTEM_NAME MATCHES "Linux") # other using ELF too?
			list(APPEND HARDENING_COMPILER_FLAGS
				# on MinGW hello world works, but more complex things just exit without any output or crash in the middle of execution
				"-fstack-protector"
				"-fstack-protector-strong"
			)
			list(APPEND HARDENING_LINKER_FLAGS
				# not present in MinGW
				"-Wl,-z,relro"
				"-Wl,-z,now"
				"-Wl,-z,ibtplt"
				"-Wl,-z,ibt"
				"-Wl,-z,shstk"
			)
		endif()
		list(APPEND HARDENING_MACRODEFS
			"-D_FORTIFY_SOURCE=2"
			"-D_GLIBCXX_ASSERTIONS"
		)
	elseif(MSVC)
		set(HARDENING_COMPILER_FLAGS "/sdl" "/GS" "/SafeSEH" "/guard:cf" "/HIGHENTROPYVA")
		set(HARDENING_LINKER_FLAGS "/guard:cf")
	else()
		message(ERROR "The compiler is not supported")
	endif()

	processFlagsList(${target} COMPILE_FLAGS ${HARDENING_COMPILER_FLAGS})
	processFlagsList(${target} LINK_FLAGS ${HARDENING_LINKER_FLAGS})
	
	#list(JOIN HARDENING_MACRODEFS " " HARDENING_MACRODEFS) # unneeded, list is needed, not string
	set(HARDENING_MACRODEFS "${HARDENING_MACRODEFS}" CACHE STRING "Hardening flags CMake list (not string!)")
	target_compile_definitions(${target} PRIVATE ${HARDENING_MACRODEFS})
endfunction(harden)
