diff options
Diffstat (limited to 'contrib/devtools/security-check.py')
| -rwxr-xr-x | contrib/devtools/security-check.py | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/contrib/devtools/security-check.py b/contrib/devtools/security-check.py new file mode 100755 index 0000000000..e96eaa9c38 --- /dev/null +++ b/contrib/devtools/security-check.py @@ -0,0 +1,181 @@ +#!/usr/bin/python2 +''' +Perform basic ELF security checks on a series of executables. +Exit status will be 0 if succesful, and the program will be silent. +Otherwise the exit status will be 1 and it will log which executables failed which checks. +Needs `readelf` (for ELF) and `objdump` (for PE). +''' +from __future__ import division,print_function +import subprocess +import sys +import os + +READELF_CMD = os.getenv('READELF', '/usr/bin/readelf') +OBJDUMP_CMD = os.getenv('OBJDUMP', '/usr/bin/objdump') + +def check_ELF_PIE(executable): + ''' + Check for position independent executable (PIE), allowing for address space randomization. + ''' + p = subprocess.Popen([READELF_CMD, '-h', '-W', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE) + (stdout, stderr) = p.communicate() + if p.returncode: + raise IOError('Error opening file') + + ok = False + for line in stdout.split('\n'): + line = line.split() + if len(line)>=2 and line[0] == 'Type:' and line[1] == 'DYN': + ok = True + return ok + +def get_ELF_program_headers(executable): + '''Return type and flags for ELF program headers''' + p = subprocess.Popen([READELF_CMD, '-l', '-W', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE) + (stdout, stderr) = p.communicate() + if p.returncode: + raise IOError('Error opening file') + in_headers = False + count = 0 + headers = [] + for line in stdout.split('\n'): + if line.startswith('Program Headers:'): + in_headers = True + if line == '': + in_headers = False + if in_headers: + if count == 1: # header line + ofs_typ = line.find('Type') + ofs_offset = line.find('Offset') + ofs_flags = line.find('Flg') + ofs_align = line.find('Align') + if ofs_typ == -1 or ofs_offset == -1 or ofs_flags == -1 or ofs_align == -1: + raise ValueError('Cannot parse elfread -lW output') + elif count > 1: + typ = line[ofs_typ:ofs_offset].rstrip() + flags = line[ofs_flags:ofs_align].rstrip() + headers.append((typ, flags)) + count += 1 + return headers + +def check_ELF_NX(executable): + ''' + Check that no sections are writable and executable (including the stack) + ''' + have_wx = False + have_gnu_stack = False + for (typ, flags) in get_ELF_program_headers(executable): + if typ == 'GNU_STACK': + have_gnu_stack = True + if 'W' in flags and 'E' in flags: # section is both writable and executable + have_wx = True + return have_gnu_stack and not have_wx + +def check_ELF_RELRO(executable): + ''' + Check for read-only relocations. + GNU_RELRO program header must exist + Dynamic section must have BIND_NOW flag + ''' + have_gnu_relro = False + for (typ, flags) in get_ELF_program_headers(executable): + # Note: not checking flags == '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 http://permalink.gmane.org/gmane.comp.gnu.binutils/71347 + if typ == 'GNU_RELRO': + have_gnu_relro = True + + have_bindnow = False + p = subprocess.Popen([READELF_CMD, '-d', '-W', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE) + (stdout, stderr) = p.communicate() + if p.returncode: + raise IOError('Error opening file') + for line in stdout.split('\n'): + tokens = line.split() + if len(tokens)>1 and tokens[1] == '(BIND_NOW)': + have_bindnow = True + return have_gnu_relro and have_bindnow + +def check_ELF_Canary(executable): + ''' + Check for use of stack canary + ''' + p = subprocess.Popen([READELF_CMD, '--dyn-syms', '-W', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE) + (stdout, stderr) = p.communicate() + if p.returncode: + raise IOError('Error opening file') + ok = False + for line in stdout.split('\n'): + if '__stack_chk_fail' in line: + ok = True + return ok + +def get_PE_dll_characteristics(executable): + ''' + Get PE DllCharacteristics bits + ''' + p = subprocess.Popen([OBJDUMP_CMD, '-x', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE) + (stdout, stderr) = p.communicate() + if p.returncode: + raise IOError('Error opening file') + for line in stdout.split('\n'): + tokens = line.split() + if len(tokens)>=2 and tokens[0] == 'DllCharacteristics': + return int(tokens[1],16) + return 0 + + +def check_PE_PIE(executable): + '''PIE: DllCharacteristics bit 0x40 signifies dynamicbase (ASLR)''' + return bool(get_PE_dll_characteristics(executable) & 0x40) + +def check_PE_NX(executable): + '''NX: DllCharacteristics bit 0x100 signifies nxcompat (DEP)''' + return bool(get_PE_dll_characteristics(executable) & 0x100) + +CHECKS = { +'ELF': [ + ('PIE', check_ELF_PIE), + ('NX', check_ELF_NX), + ('RELRO', check_ELF_RELRO), + ('Canary', check_ELF_Canary) +], +'PE': [ + ('PIE', check_PE_PIE), + ('NX', check_PE_NX) +] +} + +def identify_executable(executable): + with open(filename, 'rb') as f: + magic = f.read(4) + if magic.startswith(b'MZ'): + return 'PE' + elif magic.startswith(b'\x7fELF'): + return 'ELF' + return None + +if __name__ == '__main__': + retval = 0 + for filename in sys.argv[1:]: + try: + etype = identify_executable(filename) + if etype is None: + print('%s: unknown format' % filename) + retval = 1 + continue + + failed = [] + for (name, func) in CHECKS[etype]: + if not func(filename): + failed.append(name) + if failed: + print('%s: failed %s' % (filename, ' '.join(failed))) + retval = 1 + except IOError: + print('%s: cannot open' % filename) + retval = 1 + exit(retval) + |