dash/contrib/devtools/security-check.py
Wladimir J. van der Laan 33c473a8e3
Merge #18796: scripts: security-check.py refactors
eacedfb0230978748cbcfb13817fed7e7c756ba7 scripts: add additional type annotations to security-check.py (fanquake)
83d063e9541cc9ea41ea86919eb9435c73efb14e scripts: add run_command to security-check.py (fanquake)
13f606b4f940e5820ff21ea62fc27a5a91774b05 scripts: remove NONFATAL from security-check.py (fanquake)
061acf62a15ad3dbb9f055b7c2569b9832ed623a scripts: no-longer check for 32 bit windows in security-check.py (fanquake)

Pull request description:

  * Remove 32-bit Windows checks.
  * Remove NONFATAL checking. Added in #8249, however unused since #13764.
  * Add `run_command` to de-duplicate all of the subprocess calls. Mentioned in #18713.
  * Add additional type annotations.
  * Print stderr when there is an issue running a command.

ACKs for top commit:
  laanwj:
    ACK eacedfb0230978748cbcfb13817fed7e7c756ba7

Tree-SHA512: 69a7ccfdf346ee202b3e8f940634c5daed1d2b5a5d15ac9800252866ba3284ec66e391a66a0b341f5a4e5e8482fe1b614d4671e8e766112ff059405081184a85
2022-06-18 22:14:03 -07:00

278 lines
9.1 KiB
Python
Executable File

#!/usr/bin/env python3
# Copyright (c) 2015-2016 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.
Needs `readelf` (for ELF), `objdump` (for PE) and `otool` (for MACHO).
'''
import subprocess
import sys
import os
from typing import List, Optional
READELF_CMD = os.getenv('READELF', '/usr/bin/readelf')
OBJDUMP_CMD = os.getenv('OBJDUMP', '/usr/bin/objdump')
OTOOL_CMD = os.getenv('OTOOL', '/usr/bin/otool')
def run_command(command) -> str:
p = subprocess.run(command, stdout=subprocess.PIPE, check=True, universal_newlines=True)
return p.stdout
def check_ELF_PIE(executable) -> bool:
'''
Check for position independent executable (PIE), allowing for address space randomization.
'''
stdout = run_command([READELF_CMD, '-h', '-W', executable])
ok = False
for line in stdout.splitlines():
tokens = line.split()
if len(line)>=2 and tokens[0] == 'Type:' and tokens[1] == 'DYN':
ok = True
return ok
def get_ELF_program_headers(executable):
'''Return type and flags for ELF program headers'''
stdout = run_command([READELF_CMD, '-l', '-W', executable])
in_headers = False
count = 0
headers = []
for line in stdout.splitlines():
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) -> bool:
'''
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) -> bool:
'''
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 https://marc.info/?l=binutils&m=1498883354122353
if typ == 'GNU_RELRO':
have_gnu_relro = True
have_bindnow = False
stdout = run_command([READELF_CMD, '-d', '-W', executable])
for line in stdout.splitlines():
tokens = line.split()
if len(tokens)>1 and tokens[1] == '(BIND_NOW)' or (len(tokens)>2 and tokens[1] == '(FLAGS)' and 'BIND_NOW' in tokens[2:]):
have_bindnow = True
return have_gnu_relro and have_bindnow
def check_ELF_Canary(executable) -> bool:
'''
Check for use of stack canary
'''
stdout = run_command([READELF_CMD, '--dyn-syms', '-W', executable])
ok = False
for line in stdout.splitlines():
if '__stack_chk_fail' in line:
ok = True
return ok
def get_PE_dll_characteristics(executable) -> int:
'''Get PE DllCharacteristics bits'''
stdout = run_command([OBJDUMP_CMD, '-x', executable])
bits = 0
for line in stdout.splitlines():
tokens = line.split()
if len(tokens)>=2 and tokens[0] == 'DllCharacteristics':
bits = int(tokens[1],16)
return bits
IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA = 0x0020
IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE = 0x0040
IMAGE_DLL_CHARACTERISTICS_NX_COMPAT = 0x0100
def check_PE_DYNAMIC_BASE(executable) -> bool:
'''PIE: DllCharacteristics bit 0x40 signifies dynamicbase (ASLR)'''
bits = get_PE_dll_characteristics(executable)
return (bits & IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE) == IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE
# 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(executable) -> bool:
'''PIE: DllCharacteristics bit 0x20 signifies high-entropy ASLR'''
bits = get_PE_dll_characteristics(executable)
return (bits & IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA) == IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA
def check_PE_RELOC_SECTION(executable) -> bool:
'''Check for a reloc section. This is required for functional ASLR.'''
stdout = run_command([OBJDUMP_CMD, '-h', executable])
for line in stdout.splitlines():
if '.reloc' in line:
return True
return False
def check_PE_NX(executable) -> bool:
'''NX: DllCharacteristics bit 0x100 signifies nxcompat (DEP)'''
bits = get_PE_dll_characteristics(executable)
return (bits & IMAGE_DLL_CHARACTERISTICS_NX_COMPAT) == IMAGE_DLL_CHARACTERISTICS_NX_COMPAT
def get_MACHO_executable_flags(executable) -> List[str]:
stdout = run_command([OTOOL_CMD, '-vh', executable])
flags = []
for line in stdout.splitlines():
tokens = line.split()
# filter first two header lines
if 'magic' in tokens or 'Mach' in tokens:
continue
# filter ncmds and sizeofcmds values
flags += [t for t in tokens if not t.isdigit()]
return flags
def check_MACHO_PIE(executable) -> bool:
'''
Check for position independent executable (PIE), allowing for address space randomization.
'''
flags = get_MACHO_executable_flags(executable)
if 'PIE' in flags:
return True
return False
def check_MACHO_NOUNDEFS(executable) -> bool:
'''
Check for no undefined references.
'''
flags = get_MACHO_executable_flags(executable)
if 'NOUNDEFS' in flags:
return True
return False
def check_MACHO_NX(executable) -> bool:
'''
Check for no stack execution
'''
flags = get_MACHO_executable_flags(executable)
if 'ALLOW_STACK_EXECUTION' in flags:
return False
return True
def check_MACHO_LAZY_BINDINGS(executable) -> bool:
'''
Check for no lazy bindings.
We don't use or check for MH_BINDATLOAD. See #18295.
'''
stdout = run_command([OTOOL_CMD, '-l', executable])
for line in stdout.splitlines():
tokens = line.split()
if 'lazy_bind_off' in tokens or 'lazy_bind_size' in tokens:
if tokens[1] != '0':
return False
return True
def check_MACHO_Canary(executable) -> bool:
'''
Check for use of stack canary
'''
stdout = run_command([OTOOL_CMD, '-Iv', executable])
ok = False
for line in stdout.splitlines():
if '___stack_chk_fail' in line:
ok = True
return ok
CHECKS = {
'ELF': [
('PIE', check_ELF_PIE),
('NX', check_ELF_NX),
('RELRO', check_ELF_RELRO),
('Canary', check_ELF_Canary)
],
'PE': [
('DYNAMIC_BASE', check_PE_DYNAMIC_BASE),
('HIGH_ENTROPY_VA', check_PE_HIGH_ENTROPY_VA),
('NX', check_PE_NX),
('RELOC_SECTION', check_PE_RELOC_SECTION)
],
'MACHO': [
('PIE', check_MACHO_PIE),
('NOUNDEFS', check_MACHO_NOUNDEFS),
('NX', check_MACHO_NX),
('LAZY_BINDINGS', check_MACHO_LAZY_BINDINGS),
('Canary', check_MACHO_Canary)
]
}
def identify_executable(executable) -> Optional[str]:
with open(filename, 'rb') as f:
magic = f.read(4)
if magic.startswith(b'MZ'):
return 'PE'
elif magic.startswith(b'\x7fELF'):
return 'ELF'
elif magic.startswith(b'\xcf\xfa'):
return 'MACHO'
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
sys.exit(retval)