#!/usr/bin/env python3 # Copyright (c) 2015-2020 The Bitcoin Core developers # Distributed under the MIT software license, see the accompanying # file COPYING or http://www.opensource.org/licenses/mit-license.php. ''' Perform basic security checks on a series of executables. Exit status will be 0 if successful, and the program will be silent. Otherwise the exit status will be 1 and it will log which executables failed which checks. ''' import sys from typing import List import lief def check_ELF_RELRO(binary) -> bool: ''' Check for read-only relocations. GNU_RELRO program header must exist Dynamic section must have BIND_NOW flag ''' have_gnu_relro = False for segment in binary.segments: # Note: not checking p_flags == PF_R: here as linkers set the permission differently # This does not affect security: the permission flags of the GNU_RELRO program # header are ignored, the PT_LOAD header determines the effective permissions. # However, the dynamic linker need to write to this area so these are RW. # Glibc itself takes care of mprotecting this area R after relocations are finished. # See also https://marc.info/?l=binutils&m=1498883354122353 if segment.type == lief.ELF.SEGMENT_TYPES.GNU_RELRO: have_gnu_relro = True have_bindnow = False try: flags = binary.get(lief.ELF.DYNAMIC_TAGS.FLAGS) if flags.value & lief.ELF.DYNAMIC_FLAGS.BIND_NOW: have_bindnow = True except: have_bindnow = False return have_gnu_relro and have_bindnow def check_ELF_Canary(binary) -> bool: ''' Check for use of stack canary ''' return binary.has_symbol('__stack_chk_fail') def check_ELF_separate_code(binary): ''' Check that sections are appropriately separated in virtual memory, based on their permissions. This checks for missing -Wl,-z,separate-code and potentially other problems. ''' R = lief.ELF.SEGMENT_FLAGS.R W = lief.ELF.SEGMENT_FLAGS.W E = lief.ELF.SEGMENT_FLAGS.X EXPECTED_FLAGS = { # Read + execute '.init': R | E, '.plt': R | E, '.plt.got': R | E, '.plt.sec': R | E, '.text': R | E, '.fini': R | E, # Read-only data '.interp': R, '.note.gnu.property': R, '.note.gnu.build-id': R, '.note.ABI-tag': R, '.gnu.hash': R, '.dynsym': R, '.dynstr': R, '.gnu.version': R, '.gnu.version_r': R, '.rela.dyn': R, '.rela.plt': R, '.rodata': R, '.eh_frame_hdr': R, '.eh_frame': R, '.qtmetadata': R, '.gcc_except_table': R, '.stapsdt.base': R, # Writable data '.init_array': R | W, '.fini_array': R | W, '.dynamic': R | W, '.got': R | W, '.data': R | W, '.bss': R | W, } if binary.header.machine_type == lief.ELF.ARCH.PPC64: # .plt is RW on ppc64 even with separate-code EXPECTED_FLAGS['.plt'] = R | W # For all LOAD program headers get mapping to the list of sections, # and for each section, remember the flags of the associated program header. flags_per_section = {} for segment in binary.segments: if segment.type == lief.ELF.SEGMENT_TYPES.LOAD: for section in segment.sections: flags_per_section[section.name] = segment.flags # Spot-check ELF LOAD program header flags per section # If these sections exist, check them against the expected R/W/E flags for (section, flags) in flags_per_section.items(): if section in EXPECTED_FLAGS: if int(EXPECTED_FLAGS[section]) != int(flags): return False return True def check_ELF_control_flow(binary) -> bool: ''' Check for control flow instrumentation ''' main = binary.get_function_address('main') content = binary.get_content_from_virtual_address(main, 4, lief.Binary.VA_TYPES.AUTO) if content == [243, 15, 30, 250]: # endbr64 return True return False def check_PE_DYNAMIC_BASE(binary) -> bool: '''PIE: DllCharacteristics bit 0x40 signifies dynamicbase (ASLR)''' return lief.PE.DLL_CHARACTERISTICS.DYNAMIC_BASE in binary.optional_header.dll_characteristics_lists # Must support high-entropy 64-bit address space layout randomization # in addition to DYNAMIC_BASE to have secure ASLR. def check_PE_HIGH_ENTROPY_VA(binary) -> bool: '''PIE: DllCharacteristics bit 0x20 signifies high-entropy ASLR''' return lief.PE.DLL_CHARACTERISTICS.HIGH_ENTROPY_VA in binary.optional_header.dll_characteristics_lists def check_PE_RELOC_SECTION(binary) -> bool: '''Check for a reloc section. This is required for functional ASLR.''' return binary.has_relocations def check_PE_control_flow(binary) -> bool: ''' Check for control flow instrumentation ''' main = binary.get_symbol('main').value section_addr = binary.section_from_rva(main).virtual_address virtual_address = binary.optional_header.imagebase + section_addr + main content = binary.get_content_from_virtual_address(virtual_address, 4, lief.Binary.VA_TYPES.VA) if content == [243, 15, 30, 250]: # endbr64 return True return False def check_MACHO_NOUNDEFS(binary) -> bool: ''' Check for no undefined references. ''' return binary.header.has(lief.MachO.HEADER_FLAGS.NOUNDEFS) def check_MACHO_LAZY_BINDINGS(binary) -> bool: ''' Check for no lazy bindings. We don't use or check for MH_BINDATLOAD. See #18295. ''' return binary.dyld_info.lazy_bind == (0,0) def check_MACHO_Canary(binary) -> bool: ''' Check for use of stack canary ''' return binary.has_symbol('___stack_chk_fail') def check_PIE(binary) -> bool: ''' Check for position independent executable (PIE), allowing for address space randomization. ''' return binary.is_pie def check_NX(binary) -> bool: ''' Check for no stack execution ''' return binary.has_nx def check_MACHO_control_flow(binary) -> bool: ''' Check for control flow instrumentation ''' content = binary.get_content_from_virtual_address(binary.entrypoint, 4, lief.Binary.VA_TYPES.AUTO) if content == [243, 15, 30, 250]: # endbr64 return True return False BASE_ELF = [ ('PIE', check_PIE), ('NX', check_NX), ('RELRO', check_ELF_RELRO), ('Canary', check_ELF_Canary), ('separate_code', check_ELF_separate_code), ] BASE_PE = [ ('PIE', check_PIE), ('DYNAMIC_BASE', check_PE_DYNAMIC_BASE), ('HIGH_ENTROPY_VA', check_PE_HIGH_ENTROPY_VA), ('NX', check_NX), ('RELOC_SECTION', check_PE_RELOC_SECTION), ('CONTROL_FLOW', check_PE_control_flow), ] BASE_MACHO = [ ('NOUNDEFS', check_MACHO_NOUNDEFS), ('LAZY_BINDINGS', check_MACHO_LAZY_BINDINGS), ('Canary', check_MACHO_Canary), ] CHECKS = { lief.EXE_FORMATS.ELF: { lief.ARCHITECTURES.X86: BASE_ELF + [('CONTROL_FLOW', check_ELF_control_flow)], lief.ARCHITECTURES.ARM: BASE_ELF, lief.ARCHITECTURES.ARM64: BASE_ELF, lief.ARCHITECTURES.PPC: BASE_ELF, lief.ARCHITECTURES.RISCV: BASE_ELF, }, lief.EXE_FORMATS.PE: { lief.ARCHITECTURES.X86: BASE_PE, }, lief.EXE_FORMATS.MACHO: { lief.ARCHITECTURES.X86: BASE_MACHO + [('PIE', check_PIE), ('NX', check_NX), ('CONTROL_FLOW', check_MACHO_control_flow)], lief.ARCHITECTURES.ARM64: BASE_MACHO, } } if __name__ == '__main__': retval: int = 0 for filename in sys.argv[1:]: try: binary = lief.parse(filename) etype = binary.format arch = binary.abstract.header.architecture binary.concrete if etype == lief.EXE_FORMATS.UNKNOWN: print(f'{filename}: unknown executable format') retval = 1 continue if arch == lief.ARCHITECTURES.NONE: print(f'{filename}: unknown architecture') retval = 1 continue failed: List[str] = [] for (name, func) in CHECKS[etype][arch]: if not func(binary): failed.append(name) if failed: print(f'{filename}: failed {" ".join(failed)}') retval = 1 except IOError: print(f'{filename}: cannot open') retval = 1 sys.exit(retval)