aboutsummaryrefslogtreecommitdiff
path: root/contrib/devtools/security-check.py
blob: 137fe377da94e33394911fb8278e4a1c002e4391 (plain)
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
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
#!/usr/bin/env python3
# Copyright (c) 2015-2021 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.
'''
import sys
from typing import List

import lief #type:ignore

# temporary constant, to be replaced with lief.ELF.ARCH.RISCV
# https://github.com/lief-project/LIEF/pull/562
LIEF_ELF_ARCH_RISCV = lief.ELF.ARCH(243)

def check_ELF_RELRO(binary) -> bool:
    '''
    Check for read-only relocations.
    GNU_RELRO program header must exist
    Dynamic section must have BIND_NOW flag
    '''
    have_gnu_relro = False
    for segment in binary.segments:
        # Note: not checking p_flags == PF_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 segment.type == lief.ELF.SEGMENT_TYPES.GNU_RELRO:
            have_gnu_relro = True

    have_bindnow = False
    try:
        flags = binary.get(lief.ELF.DYNAMIC_TAGS.FLAGS)
        if flags.value & lief.ELF.DYNAMIC_FLAGS.BIND_NOW:
            have_bindnow = True
    except:
        have_bindnow = False

    return have_gnu_relro and have_bindnow

def check_ELF_Canary(binary) -> bool:
    '''
    Check for use of stack canary
    '''
    return binary.has_symbol('__stack_chk_fail')

def check_ELF_separate_code(binary):
    '''
    Check that sections are appropriately separated in virtual memory,
    based on their permissions. This checks for missing -Wl,-z,separate-code
    and potentially other problems.
    '''
    R = lief.ELF.SEGMENT_FLAGS.R
    W = lief.ELF.SEGMENT_FLAGS.W
    E = lief.ELF.SEGMENT_FLAGS.X
    EXPECTED_FLAGS = {
        # Read + execute
        '.init': R | E,
        '.plt': R | E,
        '.plt.got': R | E,
        '.plt.sec': R | E,
        '.text': R | E,
        '.fini': R | E,
        # Read-only data
        '.interp': R,
        '.note.gnu.property': R,
        '.note.gnu.build-id': R,
        '.note.ABI-tag': R,
        '.gnu.hash': R,
        '.dynsym': R,
        '.dynstr': R,
        '.gnu.version': R,
        '.gnu.version_r': R,
        '.rela.dyn': R,
        '.rela.plt': R,
        '.rodata': R,
        '.eh_frame_hdr': R,
        '.eh_frame': R,
        '.qtmetadata': R,
        '.gcc_except_table': R,
        '.stapsdt.base': R,
        # Writable data
        '.init_array': R | W,
        '.fini_array': R | W,
        '.dynamic': R | W,
        '.got': R | W,
        '.data': R | W,
        '.bss': R | W,
    }
    if binary.header.machine_type == lief.ELF.ARCH.PPC64:
        # .plt is RW on ppc64 even with separate-code
        EXPECTED_FLAGS['.plt'] = R | W
    # For all LOAD program headers get mapping to the list of sections,
    # and for each section, remember the flags of the associated program header.
    flags_per_section = {}
    for segment in binary.segments:
        if segment.type ==  lief.ELF.SEGMENT_TYPES.LOAD:
            for section in segment.sections:
                assert(section.name not in flags_per_section)
                flags_per_section[section.name] = segment.flags
    # Spot-check ELF LOAD program header flags per section
    # If these sections exist, check them against the expected R/W/E flags
    for (section, flags) in flags_per_section.items():
        if section in EXPECTED_FLAGS:
            if int(EXPECTED_FLAGS[section]) != int(flags):
                return False
    return True

def check_PE_DYNAMIC_BASE(binary) -> bool:
    '''PIE: DllCharacteristics bit 0x40 signifies dynamicbase (ASLR)'''
    return lief.PE.DLL_CHARACTERISTICS.DYNAMIC_BASE in binary.optional_header.dll_characteristics_lists

# 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(binary) -> bool:
    '''PIE: DllCharacteristics bit 0x20 signifies high-entropy ASLR'''
    return lief.PE.DLL_CHARACTERISTICS.HIGH_ENTROPY_VA in binary.optional_header.dll_characteristics_lists

def check_PE_RELOC_SECTION(binary) -> bool:
    '''Check for a reloc section. This is required for functional ASLR.'''
    return binary.has_relocations

def check_PE_control_flow(binary) -> bool:
    '''
    Check for control flow instrumentation
    '''
    main = binary.get_symbol('main').value

    section_addr = binary.section_from_rva(main).virtual_address
    virtual_address = binary.optional_header.imagebase + section_addr + main

    content = binary.get_content_from_virtual_address(virtual_address, 4, lief.Binary.VA_TYPES.VA)

    if content == [243, 15, 30, 250]: # endbr64
        return True
    return False

def check_MACHO_NOUNDEFS(binary) -> bool:
    '''
    Check for no undefined references.
    '''
    return binary.header.has(lief.MachO.HEADER_FLAGS.NOUNDEFS)

def check_MACHO_LAZY_BINDINGS(binary) -> bool:
    '''
    Check for no lazy bindings.
    We don't use or check for MH_BINDATLOAD. See #18295.
    '''
    return binary.dyld_info.lazy_bind == (0,0)

def check_MACHO_Canary(binary) -> bool:
    '''
    Check for use of stack canary
    '''
    return binary.has_symbol('___stack_chk_fail')

def check_PIE(binary) -> bool:
    '''
    Check for position independent executable (PIE),
    allowing for address space randomization.
    '''
    return binary.is_pie

def check_NX(binary) -> bool:
    '''
    Check for no stack execution
    '''
    return binary.has_nx

def check_control_flow(binary) -> bool:
    '''
    Check for control flow instrumentation
    '''
    content = binary.get_content_from_virtual_address(binary.entrypoint, 4, lief.Binary.VA_TYPES.AUTO)

    if content == [243, 15, 30, 250]: # endbr64
        return True
    return False

BASE_ELF = [
    ('PIE', check_PIE),
    ('NX', check_NX),
    ('RELRO', check_ELF_RELRO),
    ('Canary', check_ELF_Canary),
    ('separate_code', check_ELF_separate_code),
]

BASE_PE = [
    ('PIE', check_PIE),
    ('DYNAMIC_BASE', check_PE_DYNAMIC_BASE),
    ('HIGH_ENTROPY_VA', check_PE_HIGH_ENTROPY_VA),
    ('NX', check_NX),
    ('RELOC_SECTION', check_PE_RELOC_SECTION),
    ('CONTROL_FLOW', check_PE_control_flow),
]

BASE_MACHO = [
    ('PIE', check_PIE),
    ('NOUNDEFS', check_MACHO_NOUNDEFS),
    ('NX', check_NX),
    ('LAZY_BINDINGS', check_MACHO_LAZY_BINDINGS),
    ('Canary', check_MACHO_Canary),
    ('CONTROL_FLOW', check_control_flow),
]

CHECKS = {
    lief.EXE_FORMATS.ELF: {
        lief.ARCHITECTURES.X86: BASE_ELF,
        lief.ARCHITECTURES.ARM: BASE_ELF,
        lief.ARCHITECTURES.ARM64: BASE_ELF,
        lief.ARCHITECTURES.PPC: BASE_ELF,
        LIEF_ELF_ARCH_RISCV: BASE_ELF,
    },
    lief.EXE_FORMATS.PE: {
        lief.ARCHITECTURES.X86: BASE_PE,
    },
    lief.EXE_FORMATS.MACHO: {
        lief.ARCHITECTURES.X86: BASE_MACHO,
    }
}

if __name__ == '__main__':
    retval: int = 0
    for filename in sys.argv[1:]:
        try:
            binary = lief.parse(filename)
            etype = binary.format
            arch = binary.abstract.header.architecture
            binary.concrete

            if etype == lief.EXE_FORMATS.UNKNOWN:
                print(f'{filename}: unknown executable format')
                retval = 1
                continue

            if arch == lief.ARCHITECTURES.NONE:
                if binary.header.machine_type == LIEF_ELF_ARCH_RISCV:
                    arch = LIEF_ELF_ARCH_RISCV
                else:
                    print(f'{filename}: unknown architecture')
                    retval = 1
                    continue

            failed: List[str] = []
            for (name, func) in CHECKS[etype][arch]:
                if not func(binary):
                    failed.append(name)
            if failed:
                print(f'{filename}: failed {" ".join(failed)}')
                retval = 1
        except IOError:
            print(f'{filename}: cannot open')
            retval = 1
    sys.exit(retval)