dash/contrib/devtools/security-check.py
fanquake bd7b5a3ad4
Merge #18713: scripts: Add MACHO stack canary check to security-check.py
8334ee31f868f0f9baf0920d14d20174ed889dbe scripts: add MACHO LAZY_BINDINGS test to test-security-check.py (fanquake)
7b99c7454cdb74cd9cd7a5eedc2fb9d0a19df456 scripts: add MACHO Canary check to security-check.py (fanquake)

Pull request description:

  7b99c7454cdb74cd9cd7a5eedc2fb9d0a19df456 uses `otool -Iv` to check for `___stack_chk_fail` in the macOS binaries. Similar to the [ELF check](https://github.com/bitcoin/bitcoin/blob/master/contrib/devtools/security-check.py#L105). Note that looking for a triple underscore prefixed function (as opposed to two for ELF) is correct for the macOS binaries. i.e:
  ```bash
  otool -Iv bitcoind | grep chk
  0x00000001006715b8   509 ___memcpy_chk
  0x00000001006715be   510 ___snprintf_chk
  0x00000001006715c4   511 ___sprintf_chk
  0x00000001006715ca   512 ___stack_chk_fail
  0x00000001006715d6   517 ___vsnprintf_chk
  0x0000000100787898   513 ___stack_chk_guard
  ```

  8334ee31f868f0f9baf0920d14d20174ed889dbe is a follow up to #18295 and adds test cases to `test-security-check.py` that for some reason I didn't add at the time. I'll sort out #18434 so that we can run these tests in the CI.

ACKs for top commit:
  practicalswift:
    ACK 8334ee31f868f0f9baf0920d14d20174ed889dbe: Mitigations are important. Important things are worth asserting :)
  jonasschnelli:
    utACK 8334ee31f868f0f9baf0920d14d20174ed889dbe.

Tree-SHA512: 1aa5ded34bbd187eddb112b27278deb328bfc21ac82316b20fab6ad894f223b239a76b53dab0ac1770d194c1760fcc40d4da91ec09959ba4fc8eadedb173936a
2022-06-18 22:14:03 -07:00

300 lines
11 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
READELF_CMD = os.getenv('READELF', '/usr/bin/readelf')
OBJDUMP_CMD = os.getenv('OBJDUMP', '/usr/bin/objdump')
OTOOL_CMD = os.getenv('OTOOL', '/usr/bin/otool')
NONFATAL = {} # checks which are non-fatal for now but only generate a warning
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, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
ok = False
for line in stdout.splitlines():
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, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
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):
'''
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 https://marc.info/?l=binutils&m=1498883354122353
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, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
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):
'''
Check for use of stack canary
'''
p = subprocess.Popen([READELF_CMD, '--dyn-syms', '-W', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
ok = False
for line in stdout.splitlines():
if '__stack_chk_fail' in line:
ok = True
return ok
def get_PE_dll_characteristics(executable):
'''
Get PE DllCharacteristics bits.
Returns a tuple (arch,bits) where arch is 'i386:x86-64' or 'i386'
and bits is the DllCharacteristics value.
'''
p = subprocess.Popen([OBJDUMP_CMD, '-x', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
arch = ''
bits = 0
for line in stdout.splitlines():
tokens = line.split()
if len(tokens)>=2 and tokens[0] == 'architecture:':
arch = tokens[1].rstrip(',')
if len(tokens)>=2 and tokens[0] == 'DllCharacteristics':
bits = int(tokens[1],16)
return (arch,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):
'''PIE: DllCharacteristics bit 0x40 signifies dynamicbase (ASLR)'''
(arch,bits) = get_PE_dll_characteristics(executable)
reqbits = IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE
return (bits & reqbits) == reqbits
# On 64 bit, 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):
'''PIE: DllCharacteristics bit 0x20 signifies high-entropy ASLR'''
(arch,bits) = get_PE_dll_characteristics(executable)
if arch == 'i386:x86-64':
reqbits = IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA
else: # Unnecessary on 32-bit
assert(arch == 'i386')
reqbits = 0
return (bits & reqbits) == reqbits
def check_PE_NX(executable):
'''NX: DllCharacteristics bit 0x100 signifies nxcompat (DEP)'''
(arch,bits) = get_PE_dll_characteristics(executable)
return (bits & IMAGE_DLL_CHARACTERISTICS_NX_COMPAT) == IMAGE_DLL_CHARACTERISTICS_NX_COMPAT
def get_MACHO_executable_flags(executable):
p = subprocess.Popen([OTOOL_CMD, '-vh', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
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.
'''
p = subprocess.Popen([OTOOL_CMD, '-l', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
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
'''
p = subprocess.Popen([OTOOL_CMD, '-Iv', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
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)
],
'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):
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 = []
warning = []
for (name, func) in CHECKS[etype]:
if not func(filename):
if name in NONFATAL:
warning.append(name)
else:
failed.append(name)
if failed:
print('%s: failed %s' % (filename, ' '.join(failed)))
retval = 1
if warning:
print('%s: warning %s' % (filename, ' '.join(warning)))
except IOError:
print('%s: cannot open' % filename)
retval = 1
sys.exit(retval)