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contrib: Parse ELF directly for symbol and security checks 

Instead of the ever-messier text parsing of the output of the readelf
tool (which is clearly meant for human consumption not to be machine
parseable), parse the ELF binaries directly.

Add a small dependency-less ELF parser specific to the checks.

This is slightly more secure, too, because it removes potential
ambiguity due to misparsing and changes in the output format of `elfread`. It
also allows for stricter and more specific ELF format checks in the future.

This removes the build-time dependency for `readelf`.

It passes the test-security-check for me locally, though I haven't
checked on all platforms.
This commit is contained in:
Wladimir J. van der Laan 2020-11-20 09:15:44 +01:00
parent fdd068507d
commit 634f6ec4eb
6 changed files with 413 additions and 169 deletions
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3
Makefile.am
View File

@ -52,7 +52,8 @@ DIST_SHARE = \
$(top_srcdir)/share/rpcauth
BIN_CHECKS=$(top_srcdir)/contrib/devtools/symbol-check.py \
$(top_srcdir)/contrib/devtools/security-check.py
$(top_srcdir)/contrib/devtools/security-check.py \
$(top_srcdir)/contrib/devtools/pixie.py
WINDOWS_PACKAGING = $(top_srcdir)/share/pixmaps/bitcoin.ico \
$(top_srcdir)/share/pixmaps/nsis-header.bmp \

1
configure.ac
View File

@ -104,7 +104,6 @@ AC_PATH_PROG([GIT], [git])
AC_PATH_PROG(CCACHE,ccache)
AC_PATH_PROG(XGETTEXT,xgettext)
AC_PATH_PROG(HEXDUMP,hexdump)
AC_PATH_TOOL(READELF, readelf)
AC_PATH_TOOL(CPPFILT, c++filt)
AC_PATH_TOOL(OBJCOPY, objcopy)
AC_PATH_PROG(DOXYGEN, doxygen)

323
contrib/devtools/pixie.py Normal file
View File

@ -0,0 +1,323 @@
#!/usr/bin/env python3
# Copyright (c) 2020 Wladimir J. van der Laan
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
'''
Compact, self-contained ELF implementation for bitcoin-core security checks.
'''
import struct
import types
from typing import Dict, List, Optional, Union, Tuple
# you can find all these values in elf.h
EI_NIDENT = 16
# Byte indices in e_ident
EI_CLASS = 4 # ELFCLASSxx
EI_DATA = 5 # ELFDATAxxxx
ELFCLASS32 = 1 # 32-bit
ELFCLASS64 = 2 # 64-bit
ELFDATA2LSB = 1 # little endian
ELFDATA2MSB = 2 # big endian
# relevant values for e_machine
EM_386 = 3
EM_PPC64 = 21
EM_ARM = 40
EM_AARCH64 = 183
EM_X86_64 = 62
EM_RISCV = 243
# relevant values for e_type
ET_DYN = 3
# relevant values for sh_type
SHT_PROGBITS = 1
SHT_STRTAB = 3
SHT_DYNAMIC = 6
SHT_DYNSYM = 11
SHT_GNU_verneed = 0x6ffffffe
SHT_GNU_versym = 0x6fffffff
# relevant values for p_type
PT_LOAD = 1
PT_GNU_STACK = 0x6474e551
PT_GNU_RELRO = 0x6474e552
# relevant values for p_flags
PF_X = (1 << 0)
PF_W = (1 << 1)
PF_R = (1 << 2)
# relevant values for d_tag
DT_NEEDED = 1
DT_FLAGS = 30
# relevant values of `d_un.d_val' in the DT_FLAGS entry
DF_BIND_NOW = 0x00000008
# relevant d_tags with string payload
STRING_TAGS = {DT_NEEDED}
# rrlevant values for ST_BIND subfield of st_info (symbol binding)
STB_LOCAL = 0
class ELFRecord(types.SimpleNamespace):
'''Unified parsing for ELF records.'''
def __init__(self, data: bytes, offset: int, eh: 'ELFHeader', total_size: Optional[int]) -> None:
hdr_struct = self.STRUCT[eh.ei_class][0][eh.ei_data]
if total_size is not None and hdr_struct.size > total_size:
raise ValueError(f'{self.__class__.__name__} header size too small ({total_size} < {hdr_struct.size})')
for field, value in zip(self.STRUCT[eh.ei_class][1], hdr_struct.unpack(data[offset:offset + hdr_struct.size])):
setattr(self, field, value)
def BiStruct(chars: str) -> Dict[int, struct.Struct]:
'''Compile a struct parser for both endians.'''
return {
ELFDATA2LSB: struct.Struct('<' + chars),
ELFDATA2MSB: struct.Struct('>' + chars),
}
class ELFHeader(ELFRecord):
FIELDS = ['e_type', 'e_machine', 'e_version', 'e_entry', 'e_phoff', 'e_shoff', 'e_flags', 'e_ehsize', 'e_phentsize', 'e_phnum', 'e_shentsize', 'e_shnum', 'e_shstrndx']
STRUCT = {
ELFCLASS32: (BiStruct('HHIIIIIHHHHHH'), FIELDS),
ELFCLASS64: (BiStruct('HHIQQQIHHHHHH'), FIELDS),
}
def __init__(self, data: bytes, offset: int) -> None:
self.e_ident = data[offset:offset + EI_NIDENT]
if self.e_ident[0:4] != b'\x7fELF':
raise ValueError('invalid ELF magic')
self.ei_class = self.e_ident[EI_CLASS]
self.ei_data = self.e_ident[EI_DATA]
super().__init__(data, offset + EI_NIDENT, self, None)
def __repr__(self) -> str:
return f'Header(e_ident={self.e_ident!r}, e_type={self.e_type}, e_machine={self.e_machine}, e_version={self.e_version}, e_entry={self.e_entry}, e_phoff={self.e_phoff}, e_shoff={self.e_shoff}, e_flags={self.e_flags}, e_ehsize={self.e_ehsize}, e_phentsize={self.e_phentsize}, e_phnum={self.e_phnum}, e_shentsize={self.e_shentsize}, e_shnum={self.e_shnum}, e_shstrndx={self.e_shstrndx})'
class Section(ELFRecord):
name: Optional[bytes] = None
FIELDS = ['sh_name', 'sh_type', 'sh_flags', 'sh_addr', 'sh_offset', 'sh_size', 'sh_link', 'sh_info', 'sh_addralign', 'sh_entsize']
STRUCT = {
ELFCLASS32: (BiStruct('IIIIIIIIII'), FIELDS),
ELFCLASS64: (BiStruct('IIQQQQIIQQ'), FIELDS),
}
def __init__(self, data: bytes, offset: int, eh: ELFHeader) -> None:
super().__init__(data, offset, eh, eh.e_shentsize)
self._data = data
def __repr__(self) -> str:
return f'Section(sh_name={self.sh_name}({self.name!r}), sh_type=0x{self.sh_type:x}, sh_flags={self.sh_flags}, sh_addr=0x{self.sh_addr:x}, sh_offset=0x{self.sh_offset:x}, sh_size={self.sh_size}, sh_link={self.sh_link}, sh_info={self.sh_info}, sh_addralign={self.sh_addralign}, sh_entsize={self.sh_entsize})'
def contents(self) -> bytes:
'''Return section contents.'''
return self._data[self.sh_offset:self.sh_offset + self.sh_size]
class ProgramHeader(ELFRecord):
STRUCT = {
# different ELF classes have the same fields, but in a different order to optimize space versus alignment
ELFCLASS32: (BiStruct('IIIIIIII'), ['p_type', 'p_offset', 'p_vaddr', 'p_paddr', 'p_filesz', 'p_memsz', 'p_flags', 'p_align']),
ELFCLASS64: (BiStruct('IIQQQQQQ'), ['p_type', 'p_flags', 'p_offset', 'p_vaddr', 'p_paddr', 'p_filesz', 'p_memsz', 'p_align']),
}
def __init__(self, data: bytes, offset: int, eh: ELFHeader) -> None:
super().__init__(data, offset, eh, eh.e_phentsize)
def __repr__(self) -> str:
return f'ProgramHeader(p_type={self.p_type}, p_offset={self.p_offset}, p_vaddr={self.p_vaddr}, p_paddr={self.p_paddr}, p_filesz={self.p_filesz}, p_memsz={self.p_memsz}, p_flags={self.p_flags}, p_align={self.p_align})'
class Symbol(ELFRecord):
STRUCT = {
# different ELF classes have the same fields, but in a different order to optimize space versus alignment
ELFCLASS32: (BiStruct('IIIBBH'), ['st_name', 'st_value', 'st_size', 'st_info', 'st_other', 'st_shndx']),
ELFCLASS64: (BiStruct('IBBHQQ'), ['st_name', 'st_info', 'st_other', 'st_shndx', 'st_value', 'st_size']),
}
def __init__(self, data: bytes, offset: int, eh: ELFHeader, symtab: Section, strings: bytes, version: Optional[bytes]) -> None:
super().__init__(data, offset, eh, symtab.sh_entsize)
self.name = _lookup_string(strings, self.st_name)
self.version = version
def __repr__(self) -> str:
return f'Symbol(st_name={self.st_name}({self.name!r}), st_value={self.st_value}, st_size={self.st_size}, st_info={self.st_info}, st_other={self.st_other}, st_shndx={self.st_shndx}, version={self.version!r})'
@property
def is_import(self) -> bool:
'''Returns whether the symbol is an imported symbol.'''
return self.st_bind != STB_LOCAL and self.st_shndx == 0
@property
def is_export(self) -> bool:
'''Returns whether the symbol is an exported symbol.'''
return self.st_bind != STB_LOCAL and self.st_shndx != 0
@property
def st_bind(self) -> int:
'''Returns STB_*.'''
return self.st_info >> 4
class Verneed(ELFRecord):
DEF = (BiStruct('HHIII'), ['vn_version', 'vn_cnt', 'vn_file', 'vn_aux', 'vn_next'])
STRUCT = { ELFCLASS32: DEF, ELFCLASS64: DEF }
def __init__(self, data: bytes, offset: int, eh: ELFHeader) -> None:
super().__init__(data, offset, eh, None)
def __repr__(self) -> str:
return f'Verneed(vn_version={self.vn_version}, vn_cnt={self.vn_cnt}, vn_file={self.vn_file}, vn_aux={self.vn_aux}, vn_next={self.vn_next})'
class Vernaux(ELFRecord):
DEF = (BiStruct('IHHII'), ['vna_hash', 'vna_flags', 'vna_other', 'vna_name', 'vna_next'])
STRUCT = { ELFCLASS32: DEF, ELFCLASS64: DEF }
def __init__(self, data: bytes, offset: int, eh: ELFHeader, strings: bytes) -> None:
super().__init__(data, offset, eh, None)
self.name = _lookup_string(strings, self.vna_name)
def __repr__(self) -> str:
return f'Veraux(vna_hash={self.vna_hash}, vna_flags={self.vna_flags}, vna_other={self.vna_other}, vna_name={self.vna_name}({self.name!r}), vna_next={self.vna_next})'
class DynTag(ELFRecord):
STRUCT = {
ELFCLASS32: (BiStruct('II'), ['d_tag', 'd_val']),
ELFCLASS64: (BiStruct('QQ'), ['d_tag', 'd_val']),
}
def __init__(self, data: bytes, offset: int, eh: ELFHeader, section: Section) -> None:
super().__init__(data, offset, eh, section.sh_entsize)
def __repr__(self) -> str:
return f'DynTag(d_tag={self.d_tag}, d_val={self.d_val})'
def _lookup_string(data: bytes, index: int) -> bytes:
'''Look up string by offset in ELF string table.'''
endx = data.find(b'\x00', index)
assert endx != -1
return data[index:endx]
VERSYM_S = BiStruct('H') # .gnu_version section has a single 16-bit integer per symbol in the linked section
def _parse_symbol_table(section: Section, strings: bytes, eh: ELFHeader, versym: bytes, verneed: Dict[int, bytes]) -> List[Symbol]:
'''Parse symbol table, return a list of symbols.'''
data = section.contents()
symbols = []
versym_iter = (verneed.get(v[0]) for v in VERSYM_S[eh.ei_data].iter_unpack(versym))
for ofs, version in zip(range(0, len(data), section.sh_entsize), versym_iter):
symbols.append(Symbol(data, ofs, eh, section, strings, version))
return symbols
def _parse_verneed(section: Section, strings: bytes, eh: ELFHeader) -> Dict[int, bytes]:
'''Parse .gnu.version_r section, return a dictionary of {versym: 'GLIBC_...'}.'''
data = section.contents()
ofs = 0
result = {}
while True:
verneed = Verneed(data, ofs, eh)
aofs = verneed.vn_aux
while True:
vernaux = Vernaux(data, aofs, eh, strings)
result[vernaux.vna_other] = vernaux.name
if not vernaux.vna_next:
break
aofs += vernaux.vna_next
if not verneed.vn_next:
break
ofs += verneed.vn_next
return result
def _parse_dyn_tags(section: Section, strings: bytes, eh: ELFHeader) -> List[Tuple[int, Union[bytes, int]]]:
'''Parse dynamic tags. Return array of tuples.'''
data = section.contents()
ofs = 0
result = []
for ofs in range(0, len(data), section.sh_entsize):
tag = DynTag(data, ofs, eh, section)
val = _lookup_string(strings, tag.d_val) if tag.d_tag in STRING_TAGS else tag.d_val
result.append((tag.d_tag, val))
return result
class ELFFile:
sections: List[Section]
program_headers: List[ProgramHeader]
dyn_symbols: List[Symbol]
dyn_tags: List[Tuple[int, Union[bytes, int]]]
def __init__(self, data: bytes) -> None:
self.data = data
self.hdr = ELFHeader(self.data, 0)
self._load_sections()
self._load_program_headers()
self._load_dyn_symbols()
self._load_dyn_tags()
self._section_to_segment_mapping()
def _load_sections(self) -> None:
self.sections = []
for idx in range(self.hdr.e_shnum):
offset = self.hdr.e_shoff + idx * self.hdr.e_shentsize
self.sections.append(Section(self.data, offset, self.hdr))
shstr = self.sections[self.hdr.e_shstrndx].contents()
for section in self.sections:
section.name = _lookup_string(shstr, section.sh_name)
def _load_program_headers(self) -> None:
self.program_headers = []
for idx in range(self.hdr.e_phnum):
offset = self.hdr.e_phoff + idx * self.hdr.e_phentsize
self.program_headers.append(ProgramHeader(self.data, offset, self.hdr))
def _load_dyn_symbols(self) -> None:
# first, load 'verneed' section
verneed = None
for section in self.sections:
if section.sh_type == SHT_GNU_verneed:
strtab = self.sections[section.sh_link].contents() # associated string table
assert verneed is None # only one section of this kind please
verneed = _parse_verneed(section, strtab, self.hdr)
assert verneed is not None
# then, correlate GNU versym sections with dynamic symbol sections
versym = {}
for section in self.sections:
if section.sh_type == SHT_GNU_versym:
versym[section.sh_link] = section
# finally, load dynsym sections
self.dyn_symbols = []
for idx, section in enumerate(self.sections):
if section.sh_type == SHT_DYNSYM: # find dynamic symbol tables
strtab_data = self.sections[section.sh_link].contents() # associated string table
versym_data = versym[idx].contents() # associated symbol version table
self.dyn_symbols += _parse_symbol_table(section, strtab_data, self.hdr, versym_data, verneed)
def _load_dyn_tags(self) -> None:
self.dyn_tags = []
for idx, section in enumerate(self.sections):
if section.sh_type == SHT_DYNAMIC: # find dynamic tag tables
strtab = self.sections[section.sh_link].contents() # associated string table
self.dyn_tags += _parse_dyn_tags(section, strtab, self.hdr)
def _section_to_segment_mapping(self) -> None:
for ph in self.program_headers:
ph.sections = []
for section in self.sections:
if ph.p_vaddr <= section.sh_addr < (ph.p_vaddr + ph.p_memsz):
ph.sections.append(section)
def query_dyn_tags(self, tag_in: int) -> List[Union[int, bytes]]:
'''Return the values of all dyn tags with the specified tag.'''
return [val for (tag, val) in self.dyn_tags if tag == tag_in]
def load(filename: str) -> ELFFile:
with open(filename, 'rb') as f:
data = f.read()
return ELFFile(data)

170
contrib/devtools/security-check.py
View File

@ -6,15 +6,15 @@
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).
Needs `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')
import pixie
OBJDUMP_CMD = os.getenv('OBJDUMP', '/usr/bin/objdump')
OTOOL_CMD = os.getenv('OTOOL', '/usr/bin/otool')
@ -26,75 +26,20 @@ 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
headers = []
for line in stdout.splitlines():
if line.startswith('Program Headers:'):
in_headers = True
count = 0
if line == '':
in_headers = False
if in_headers:
if count == 1: # header line
header = [x.strip() for x in line.split()]
ofs_typ = header.index('Type')
ofs_flags = header.index('Flg')
# assert readelf output is what we expect
if ofs_typ == -1 or ofs_flags == -1:
raise ValueError('Cannot parse elfread -lW output')
elif count > 1:
splitline = [x.strip() for x in line.split()]
typ = splitline[ofs_typ]
if not typ.startswith('[R'): # skip [Requesting ...]
splitline = [x.strip() for x in line.split()]
flags = splitline[ofs_flags]
# check for 'R', ' E'
if splitline[ofs_flags + 1] == 'E':
flags += ' E'
headers.append((typ, flags, []))
count += 1
if line.startswith(' Section to Segment mapping:'):
in_mapping = True
count = 0
if line == '':
in_mapping = False
if in_mapping:
if count == 1: # header line
ofs_segment = line.find('Segment')
ofs_sections = line.find('Sections...')
if ofs_segment == -1 or ofs_sections == -1:
raise ValueError('Cannot parse elfread -lW output')
elif count > 1:
segment = int(line[ofs_segment:ofs_sections].strip())
sections = line[ofs_sections:].strip().split()
headers[segment][2].extend(sections)
count += 1
return headers
elf = pixie.load(executable)
return elf.hdr.e_type == pixie.ET_DYN
def check_ELF_NX(executable) -> bool:
'''
Check that no sections are writable and executable (including the stack)
'''
elf = pixie.load(executable)
have_wx = False
have_gnu_stack = False
for (typ, flags, _) in get_ELF_program_headers(executable):
if typ == 'GNU_STACK':
for ph in elf.program_headers:
if ph.p_type == pixie.PT_GNU_STACK:
have_gnu_stack = True
if 'W' in flags and 'E' in flags: # section is both writable and executable
if (ph.p_flags & pixie.PF_W) != 0 and (ph.p_flags & pixie.PF_X) != 0: # section is both writable and executable
have_wx = True
return have_gnu_stack and not have_wx
@ -104,35 +49,34 @@ def check_ELF_RELRO(executable) -> bool:
GNU_RELRO program header must exist
Dynamic section must have BIND_NOW flag
'''
elf = pixie.load(executable)
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
for ph in elf.program_headers:
# 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 typ == 'GNU_RELRO':
if ph.p_type == pixie.PT_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:]):
for flags in elf.query_dyn_tags(pixie.DT_FLAGS):
assert isinstance(flags, int)
if flags & pixie.DF_BIND_NOW:
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])
elf = pixie.load(executable)
ok = False
for line in stdout.splitlines():
if '__stack_chk_fail' in line:
for symbol in elf.dyn_symbols:
if symbol.name == b'__stack_chk_fail':
ok = True
return ok
@ -142,48 +86,52 @@ def check_ELF_separate_code(executable):
based on their permissions. This checks for missing -Wl,-z,separate-code
and potentially other problems.
'''
elf = pixie.load(executable)
R = pixie.PF_R
W = pixie.PF_W
E = pixie.PF_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',
b'.init': R | E,
b'.plt': R | E,
b'.plt.got': R | E,
b'.plt.sec': R | E,
b'.text': R | E,
b'.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',
b'.interp': R,
b'.note.gnu.property': R,
b'.note.gnu.build-id': R,
b'.note.ABI-tag': R,
b'.gnu.hash': R,
b'.dynsym': R,
b'.dynstr': R,
b'.gnu.version': R,
b'.gnu.version_r': R,
b'.rela.dyn': R,
b'.rela.plt': R,
b'.rodata': R,
b'.eh_frame_hdr': R,
b'.eh_frame': R,
b'.qtmetadata': R,
b'.gcc_except_table': R,
b'.stapsdt.base': R,
# Writable data
'.init_array': 'RW',
'.fini_array': 'RW',
'.dynamic': 'RW',
'.got': 'RW',
'.data': 'RW',
'.bss': 'RW',
b'.init_array': R | W,
b'.fini_array': R | W,
b'.dynamic': R | W,
b'.got': R | W,
b'.data': R | W,
b'.bss': 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 (typ, flags, sections) in get_ELF_program_headers(executable):
if typ == 'LOAD':
for section in sections:
assert(section not in flags_per_section)
flags_per_section[section] = flags
for ph in elf.program_headers:
if ph.p_type == pixie.PT_LOAD:
for section in ph.sections:
assert(section.name not in flags_per_section)
flags_per_section[section.name] = ph.p_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():
@ -236,7 +184,7 @@ def check_PE_NX(executable) -> bool:
def get_MACHO_executable_flags(executable) -> List[str]:
stdout = run_command([OTOOL_CMD, '-vh', executable])
flags = []
flags: List[str] = []
for line in stdout.splitlines():
tokens = line.split()
# filter first two header lines

81
contrib/devtools/symbol-check.py
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@ -11,10 +11,11 @@ Example usage:
find ../gitian-builder/build -type f -executable | xargs python3 contrib/devtools/symbol-check.py
'''
import subprocess
import re
import sys
import os
from typing import List, Optional, Tuple
from typing import List, Optional
import pixie
# Debian 8 (Jessie) EOL: 2020. https://wiki.debian.org/DebianReleases#Production_Releases
#
@ -50,7 +51,6 @@ IGNORE_EXPORTS = {
'_edata', '_end', '__end__', '_init', '__bss_start', '__bss_start__', '_bss_end__', '__bss_end__', '_fini', '_IO_stdin_used', 'stdin', 'stdout', 'stderr',
'environ', '_environ', '__environ',
}
READELF_CMD = os.getenv('READELF', '/usr/bin/readelf')
CPPFILT_CMD = os.getenv('CPPFILT', '/usr/bin/c++filt')
OBJDUMP_CMD = os.getenv('OBJDUMP', '/usr/bin/objdump')
OTOOL_CMD = os.getenv('OTOOL', '/usr/bin/otool')
@ -76,11 +76,11 @@ ELF_ALLOWED_LIBRARIES = {
'libdl.so.2' # programming interface to dynamic linker
}
ARCH_MIN_GLIBC_VER = {
'80386': (2,1),
'X86-64': (2,2,5),
'ARM': (2,4),
'AArch64':(2,17),
'RISC-V': (2,27)
pixie.EM_386: (2,1),
pixie.EM_X86_64: (2,2,5),
pixie.EM_ARM: (2,4),
pixie.EM_AARCH64:(2,17),
pixie.EM_RISCV: (2,27)
}
MACHO_ALLOWED_LIBRARIES = {
@ -140,29 +140,6 @@ class CPPFilt(object):
self.proc.stdout.close()
self.proc.wait()
def read_symbols(executable, imports=True) -> List[Tuple[str, str, str]]:
'''
Parse an ELF executable and return a list of (symbol,version, arch) tuples
for dynamic, imported symbols.
'''
p = subprocess.Popen([READELF_CMD, '--dyn-syms', '-W', '-h', executable], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Could not read symbols for {}: {}'.format(executable, stderr.strip()))
syms = []
for line in stdout.splitlines():
line = line.split()
if 'Machine:' in line:
arch = line[-1]
if len(line)>7 and re.match('[0-9]+:$', line[0]):
(sym, _, version) = line[7].partition('@')
is_import = line[6] == 'UND'
if version.startswith('@'):
version = version[1:]
if is_import == imports:
syms.append((sym, version, arch))
return syms
def check_version(max_versions, version, arch) -> bool:
if '_' in version:
(lib, _, ver) = version.rpartition('_')
@ -174,36 +151,30 @@ def check_version(max_versions, version, arch) -> bool:
return False
return ver <= max_versions[lib] or lib == 'GLIBC' and ver <= ARCH_MIN_GLIBC_VER[arch]
def elf_read_libraries(filename) -> List[str]:
p = subprocess.Popen([READELF_CMD, '-d', '-W', filename], stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE, universal_newlines=True)
(stdout, stderr) = p.communicate()
if p.returncode:
raise IOError('Error opening file')
libraries = []
for line in stdout.splitlines():
tokens = line.split()
if len(tokens)>2 and tokens[1] == '(NEEDED)':
match = re.match(r'^Shared library: \[(.*)\]$', ' '.join(tokens[2:]))
if match:
libraries.append(match.group(1))
else:
raise ValueError('Unparseable (NEEDED) specification')
return libraries
def check_imported_symbols(filename) -> bool:
elf = pixie.load(filename)
cppfilt = CPPFilt()
ok = True
for sym, version, arch in read_symbols(filename, True):
if version and not check_version(MAX_VERSIONS, version, arch):
for symbol in elf.dyn_symbols:
if not symbol.is_import:
continue
sym = symbol.name.decode()
version = symbol.version.decode() if symbol.version is not None else None
if version and not check_version(MAX_VERSIONS, version, elf.hdr.e_machine):
print('{}: symbol {} from unsupported version {}'.format(filename, cppfilt(sym), version))
ok = False
return ok
def check_exported_symbols(filename) -> bool:
elf = pixie.load(filename)
cppfilt = CPPFilt()
ok = True
for sym,version,arch in read_symbols(filename, False):
if arch == 'RISC-V' or sym in IGNORE_EXPORTS:
for symbol in elf.dyn_symbols:
if not symbol.is_export:
continue
sym = symbol.name.decode()
if elf.hdr.e_machine == pixie.EM_RISCV or sym in IGNORE_EXPORTS:
continue
print('{}: export of symbol {} not allowed'.format(filename, cppfilt(sym)))
ok = False
@ -211,9 +182,11 @@ def check_exported_symbols(filename) -> bool:
def check_ELF_libraries(filename) -> bool:
ok = True
for library_name in elf_read_libraries(filename):
if library_name not in ELF_ALLOWED_LIBRARIES:
print('{}: NEEDED library {} is not allowed'.format(filename, library_name))
elf = pixie.load(filename)
for library_name in elf.query_dyn_tags(pixie.DT_NEEDED):
assert(isinstance(library_name, bytes))
if library_name.decode() not in ELF_ALLOWED_LIBRARIES:
print('{}: NEEDED library {} is not allowed'.format(filename, library_name.decode()))
ok = False
return ok

4
src/Makefile.am
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@ -741,13 +741,13 @@ endif
if GLIBC_BACK_COMPAT
@echo "Checking glibc back compat..."
$(AM_V_at) READELF=$(READELF) CPPFILT=$(CPPFILT) $(PYTHON) $(top_srcdir)/contrib/devtools/symbol-check.py $(bin_PROGRAMS)
$(AM_V_at) CPPFILT=$(CPPFILT) $(PYTHON) $(top_srcdir)/contrib/devtools/symbol-check.py $(bin_PROGRAMS)
endif
check-security: $(bin_PROGRAMS)
if HARDEN
@echo "Checking binary security..."
$(AM_V_at) READELF=$(READELF) OBJDUMP=$(OBJDUMP) OTOOL=$(OTOOL) $(PYTHON) $(top_srcdir)/contrib/devtools/security-check.py $(bin_PROGRAMS)
$(AM_V_at) OBJDUMP=$(OBJDUMP) OTOOL=$(OTOOL) $(PYTHON) $(top_srcdir)/contrib/devtools/security-check.py $(bin_PROGRAMS)
endif
if EMBEDDED_LEVELDB