File: security-check.py

package info (click to toggle)
litecoin 0.17.1-1
  • links: PTS, VCS
  • area: main
  • in suites: sid
  • size: 23,076 kB
  • sloc: cpp: 120,253; python: 22,203; ansic: 14,322; sh: 4,390; makefile: 1,509; asm: 730; java: 438
file content (215 lines) | stat: -rwxr-xr-x 8,250 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
#!/usr/bin/env python3
# Copyright (c) 2015-2018 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 ELF 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) and `objdump` (for PE).
'''
import subprocess
import sys
import os

READELF_CMD = os.getenv('READELF', '/usr/bin/readelf')
OBJDUMP_CMD = os.getenv('OBJDUMP', '/usr/bin/objdump')
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 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, 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

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)
]
}

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 = []
            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)