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devtools: Check for high-entropy ASLR in 64-bit PE executables

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check_PE_PIE only checked for DYNAMIC_BASE, this is not enough
for (secure) ASLR on 64-bit.
This commit is contained in:
Wladimir J. van der Laan 2016-06-23 16:52:12 +02:00
parent 08338942b5
commit 9a75d29b6f
1 changed files with 40 additions and 8 deletions
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48
contrib/devtools/security-check.py
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@ -12,6 +12,7 @@ import os
READELF_CMD = os.getenv('READELF', '/usr/bin/readelf')
OBJDUMP_CMD = os.getenv('OBJDUMP', '/usr/bin/objdump')
NONFATAL = {'HIGH_ENTROPY_VA'} # checks which are non-fatal for now but only generate a warning
def check_ELF_PIE(executable):
'''
@ -114,26 +115,50 @@ def check_ELF_Canary(executable):
def get_PE_dll_characteristics(executable):
'''
Get PE DllCharacteristics bits
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)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
arch = ''
bits = 0
for line in stdout.split('\n'):
tokens = line.split()
if len(tokens)>=2 and tokens[0] == 'architecture:':
arch = tokens[1].rstrip(',')
if len(tokens)>=2 and tokens[0] == 'DllCharacteristics':
return int(tokens[1],16)
return 0
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_PIE(executable):
def check_PE_DYNAMIC_BASE(executable):
'''PIE: DllCharacteristics bit 0x40 signifies dynamicbase (ASLR)'''
return bool(get_PE_dll_characteristics(executable) & 0x40)
(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)'''
return bool(get_PE_dll_characteristics(executable) & 0x100)
(arch,bits) = get_PE_dll_characteristics(executable)
return (bits & IMAGE_DLL_CHARACTERISTICS_NX_COMPAT) == IMAGE_DLL_CHARACTERISTICS_NX_COMPAT
CHECKS = {
'ELF': [
@ -143,7 +168,8 @@ CHECKS = {
('Canary', check_ELF_Canary)
],
'PE': [
('PIE', check_PE_PIE),
('DYNAMIC_BASE', check_PE_DYNAMIC_BASE),
('HIGH_ENTROPY_VA', check_PE_HIGH_ENTROPY_VA),
('NX', check_PE_NX)
]
}
@ -168,12 +194,18 @@ if __name__ == '__main__':
continue
failed = []
warning = []
for (name, func) in CHECKS[etype]:
if not func(filename):
failed.append(name)
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