stream_unzip.py
from functools import partial
from struct import Struct
import asyncio
import bz2
import zlib
from Crypto.Cipher import AES
from Crypto.Hash import HMAC, SHA1
from Crypto.Util import Counter
from Crypto.Protocol.KDF import PBKDF2
from stream_inflate import stream_inflate64
def stream_unzip(zipfile_chunks, password=None, chunk_size=65536, allow_zip64=True):
local_file_header_signature = b'PK\x03\x04'
local_file_header_struct = Struct('<H2sHHHIIIHH')
zip64_compressed_size = 0xFFFFFFFF
zip64_size_signature = b'\x01\x00'
aes_extra_signature = b'\x01\x99'
central_directory_signature = b'PK\x01\x02'
end_of_central_directory_signature = b'PK\x05\x06'
unsigned_short = Struct('<H')
unsigned_long_long = Struct('<Q')
dd_optional_signature = b'PK\x07\x08'
dd_struct_32 = Struct('<0sIII4s')
dd_struct_32_with_sig = Struct('<4sIII4s')
dd_struct_64 = Struct('<0sIQQ4s')
dd_struct_64_with_sig = Struct('<4sIQQ4s')
def next_or_truncated_error(it):
try:
return next(it)
except StopIteration:
raise TruncatedDataError from None
def get_byte_readers(iterable):
# Return functions to return/"replace" bytes from/to the iterable
# - _yield_all: yields chunks as they come up (often for a "body")
# - _get_num: returns a single `bytes` of a given length
# - _return_num_unused: puts a number of "unused" bytes "back", to be retrieved by a yield/get call
# - _return_bytes_unused: return a bytes instance "back" into the stream, to be retrieved later
# - _get_offset_from_start: get the zero-indexed offset from the start of the stream
chunk = b''
offset = 0
offset_from_start = 0
queue = list() # Will typically have at most 1 element, so a list is fine
it = iter(iterable)
def _next():
try:
return queue.pop(0)
except IndexError:
return (next_or_truncated_error(it), 0)
def _yield_num(num):
nonlocal chunk, offset, offset_from_start
while num:
if offset == len(chunk):
chunk, offset = _next()
to_yield = min(num, len(chunk) - offset, chunk_size)
offset = offset + to_yield
num -= to_yield
offset_from_start += to_yield
yield chunk[offset - to_yield:offset]
def _yield_all():
try:
yield from _yield_num(float('inf'))
except TruncatedDataError:
pass
def _get_num(num):
return b''.join(_yield_num(num))
def _return_num_unused(num_unused):
nonlocal offset, offset_from_start
offset -= num_unused
offset_from_start -= num_unused
def _return_bytes_unused(bytes_unused):
nonlocal chunk, offset, offset_from_start
queue.insert(0, (chunk, offset))
chunk = bytes_unused
offset = 0
offset_from_start -= len(bytes_unused)
def _get_offset_from_start():
return offset_from_start
return _yield_all, _get_num, _return_num_unused, _return_bytes_unused, _get_offset_from_start
def get_decompressor_none(num_bytes):
num_decompressed = 0
num_unused = 0
def _decompress(compressed_chunk):
nonlocal num_decompressed, num_unused
to_yield = min(len(compressed_chunk), num_bytes - num_decompressed)
num_decompressed += to_yield
num_unused = len(compressed_chunk) - to_yield
yield compressed_chunk[:to_yield]
def _is_done():
return num_decompressed == num_bytes
def _num_unused():
return num_unused
return _decompress, _is_done, _num_unused
def get_decompressor_deflate():
dobj = zlib.decompressobj(wbits=-zlib.MAX_WBITS)
def _decompress_single(compressed_chunk):
try:
return dobj.decompress(compressed_chunk, chunk_size)
except zlib.error as e:
raise DeflateError() from e
def _decompress(compressed_chunk):
uncompressed_chunk = _decompress_single(compressed_chunk)
if uncompressed_chunk:
yield uncompressed_chunk
while dobj.unconsumed_tail and not dobj.eof:
uncompressed_chunk = _decompress_single(dobj.unconsumed_tail)
if uncompressed_chunk:
yield uncompressed_chunk
def _is_done():
return dobj.eof
def _num_unused():
return len(dobj.unused_data)
return _decompress, _is_done, _num_unused
def get_decompressor_deflate64():
uncompressed_chunks, is_done, num_bytes_unconsumed = stream_inflate64()
def _decompress(compressed_chunk):
yield from uncompressed_chunks((compressed_chunk,))
return _decompress, is_done, num_bytes_unconsumed
def get_decompressor_bz2():
dobj = bz2.BZ2Decompressor()
def _decompress_single(compressed_chunk):
try:
return dobj.decompress(compressed_chunk, chunk_size)
except OSError as e:
raise BZ2Error() from e
def _decompress(compressed_chunk):
uncompressed_chunk = _decompress_single(compressed_chunk)
if uncompressed_chunk:
yield uncompressed_chunk
while not dobj.eof:
uncompressed_chunk = _decompress_single(b'')
if not uncompressed_chunk:
break
yield uncompressed_chunk
def _is_done():
return dobj.eof
def _num_unused():
return len(dobj.unused_data)
return _decompress, _is_done, _num_unused
def yield_file(yield_all, get_num, return_num_unused, return_bytes_unused, get_offset_from_start):
def get_flag_bits(flags):
for b in flags:
for i in range(8):
yield (b >> i) & 1
def parse_extra(extra):
extra_offset = 0
while extra_offset <= len(extra) - 4:
extra_signature = extra[extra_offset:extra_offset+2]
extra_offset += 2
extra_data_size, = unsigned_short.unpack(extra[extra_offset:extra_offset+2])
extra_offset += 2
extra_data = extra[extra_offset:extra_offset+extra_data_size]
extra_offset += extra_data_size
yield (extra_signature, extra_data)
def get_extra_value(extra, if_true, signature, exception_if_missing, min_length, exception_if_too_short):
value = None
if if_true:
try:
value = extra[signature]
except KeyError:
if exception_if_missing:
raise exception_if_missing()
else:
if len(value) < min_length:
raise exception_if_too_short()
return value
def decrypt_weak_decompress(chunks, decompress, is_done, num_unused):
key_0 = 305419896
key_1 = 591751049
key_2 = 878082192
crc32 = zlib.crc32
bytes_c = bytes
def update_keys(byte):
nonlocal key_0, key_1, key_2
key_0 = ~crc32(bytes_c((byte,)), ~key_0) & 0xFFFFFFFF
key_1 = (key_1 + (key_0 & 0xFF)) & 0xFFFFFFFF
key_1 = ((key_1 * 134775813) + 1) & 0xFFFFFFFF
key_2 = ~crc32(bytes_c((key_1 >> 24,)), ~key_2) & 0xFFFFFFFF
def decrypt(chunk):
chunk = bytearray(chunk)
for i, byte in enumerate(chunk):
temp = key_2 | 2
byte ^= ((temp * (temp ^ 1)) >> 8) & 0xFF
update_keys(byte)
chunk[i] = byte
return bytes(chunk)
for byte in password:
update_keys(byte)
encryption_header = decrypt(get_num(12))
check_password_byte = \
(mod_time >> 8) if has_data_descriptor else \
(crc_32_expected >> 24)
if encryption_header[11] != check_password_byte:
raise IncorrectZipCryptoPasswordError()
while not is_done():
yield from decompress(decrypt(next_or_truncated_error(chunks)))
return_num_unused(num_unused())
def decrypt_aes_decompress(chunks, decompress, is_done, num_unused, key_length_raw):
try:
key_length, salt_length = {1: (16, 8), 2: (24, 12), 3: (32, 16)}[key_length_raw]
except KeyError:
raise InvalidAESKeyLengthError(key_length_raw)
salt = get_num(salt_length)
password_verification_length = 2
keys = PBKDF2(password, salt, 2 * key_length + password_verification_length, 1000)
if keys[-password_verification_length:] != get_num(password_verification_length):
raise IncorrectAESPasswordError()
decrypter = AES.new(
keys[:key_length], AES.MODE_CTR,
counter=Counter.new(nbits=128, little_endian=True)
)
hmac = HMAC.new(keys[key_length:key_length*2], digestmod=SHA1)
while not is_done():
chunk = next_or_truncated_error(chunks)
yield from decompress(decrypter.decrypt(chunk))
hmac.update(chunk[:len(chunk) - num_unused()])
return_num_unused(num_unused())
if get_num(10) != hmac.digest()[:10]:
raise HMACIntegrityError()
def decrypt_none_decompress(chunks, decompress, is_done, num_unused):
while not is_done():
yield from decompress(next_or_truncated_error(chunks))
return_num_unused(num_unused())
def read_data_and_count_and_crc32(chunks):
offset_1 = None
offset_2 = None
crc_32_actual = zlib.crc32(b'')
l = 0
def _iter():
nonlocal offset_1, offset_2, crc_32_actual, l
offset_1 = get_offset_from_start()
for chunk in chunks:
crc_32_actual = zlib.crc32(chunk, crc_32_actual)
l += len(chunk)
yield chunk
offset_2 = get_offset_from_start()
return _iter(), lambda: offset_2 - offset_1, lambda: crc_32_actual, lambda: l
def checked_from_local_header(chunks, is_aes_2_encrypted, get_crc_32, get_compressed_size, get_uncompressed_size):
yield from chunks
crc_32_data = get_crc_32()
compressed_size_data = get_compressed_size()
uncompressed_size_data = get_uncompressed_size()
if not is_aes_2_encrypted and crc_32_expected != crc_32_data:
raise CRC32IntegrityError()
if compressed_size_data != compressed_size:
raise CompressedSizeIntegrityError()
if uncompressed_size_data != uncompressed_size:
raise UncompressedSizeIntegrityError()
def checked_from_data_descriptor(chunks, is_sure_zip64, is_aes_2_encrypted, get_crc_32, get_compressed_size, get_uncompressed_size):
# The format of the data descriptor is unfortunately not known with absolute certainty in all cases
# so we we use a heuristic to detect it - using the known crc32 value, compressed size, uncompressed
# size of the data, and possible signature of the next section in the stream. There are 4 possible
# formats, and we choose the longest one that matches
#
# Strongly inspired by Mark Adler's unzip - see his reasoning for this at
# https://github.com/madler/unzip/commit/af0d07f95809653b669d88aa0f424c6d5aa48ba0
yield from chunks
crc_32_data = get_crc_32()
compressed_size_data = get_compressed_size()
uncompressed_size_data = get_uncompressed_size()
best_matches = (False, False, False, False, False)
must_treat_as_zip64 = is_sure_zip64 or compressed_size_data > 0xFFFFFFFF or uncompressed_size_data > 0xFFFFFFFF
checks = ((
(dd_struct_64_with_sig, dd_optional_signature),
(dd_struct_64, b''),
) if allow_zip64 else ()) + ((
(dd_struct_32_with_sig, dd_optional_signature),
(dd_struct_32, b''),
) if not must_treat_as_zip64 else ())
dd = get_num(checks[0][0].size)
for dd_struct, expected_signature in checks:
signature_dd, crc_32_dd, compressed_size_dd, uncompressed_size_dd, next_signature = dd_struct.unpack(dd[:dd_struct.size])
matches = (
signature_dd == expected_signature,
is_aes_2_encrypted or crc_32_dd == crc_32_data,
compressed_size_dd == compressed_size_data,
uncompressed_size_dd == uncompressed_size_data,
next_signature in (local_file_header_signature, central_directory_signature),
)
best_matches = max(best_matches, matches, key=lambda t: t.count(True))
if best_matches == (True, True, True, True, True):
break
if not best_matches[0]:
raise UnexpectedSignatureError()
if not best_matches[1]:
raise CRC32IntegrityError()
if not best_matches[2]:
raise CompressedSizeIntegrityError()
if not best_matches[3]:
raise UncompressedSizeIntegrityError()
if not best_matches[4]:
raise UnexpectedSignatureError(next_signature)
return_bytes_unused(dd[dd_struct.size - 4:]) # 4 is the length of next signature we have already taken
version, flags, compression_raw, mod_time, mod_date, crc_32_expected, compressed_size_raw, uncompressed_size_raw, file_name_len, extra_field_len = \
local_file_header_struct.unpack(get_num(local_file_header_struct.size))
flag_bits = tuple(get_flag_bits(flags))
if (
flag_bits[4] # Enhanced deflating
or flag_bits[5] # Compressed patched
or flag_bits[6] # Strong encrypted
or flag_bits[13] # Masked header values
):
raise UnsupportedFlagsError(flag_bits)
file_name = get_num(file_name_len)
extra = dict(parse_extra(get_num(extra_field_len)))
is_weak_encrypted = flag_bits[0] and compression_raw != 99
is_aes_encrypted = flag_bits[0] and compression_raw == 99
aes_extra = get_extra_value(extra, is_aes_encrypted, aes_extra_signature, MissingAESExtraError, 7, TruncatedAESExtraError)
is_aes_2_encrypted = is_aes_encrypted and aes_extra[0:2] == b'\x02\x00'
if is_weak_encrypted and password is None:
raise MissingZipCryptoPasswordError()
if is_aes_encrypted and password is None:
raise MissingAESPasswordError()
compression = \
unsigned_short.unpack(aes_extra[5:7])[0] if is_aes_encrypted else \
compression_raw
if compression not in (0, 8, 9, 12):
raise UnsupportedCompressionTypeError(compression)
has_data_descriptor = flag_bits[3]
might_be_zip64 = compressed_size_raw == zip64_compressed_size and uncompressed_size_raw == zip64_compressed_size
zip64_extra = get_extra_value(extra, might_be_zip64, zip64_size_signature, False, 16, TruncatedZip64ExtraError)
is_sure_zip64 = bool(zip64_extra)
if not allow_zip64 and is_sure_zip64:
raise UnsupportedZip64Error()
compressed_size = \
None if has_data_descriptor and compression in (8, 9, 12) else \
unsigned_long_long.unpack(zip64_extra[8:16])[0] if is_sure_zip64 else \
compressed_size_raw
uncompressed_size = \
None if has_data_descriptor and compression in (8, 9, 12) else \
unsigned_long_long.unpack(zip64_extra[:8])[0] if is_sure_zip64 else \
uncompressed_size_raw
decompressor = \
get_decompressor_none(uncompressed_size) if compression == 0 else \
get_decompressor_deflate() if compression == 8 else \
get_decompressor_deflate64() if compression == 9 else \
get_decompressor_bz2()
decompressed_bytes = \
decrypt_weak_decompress(yield_all(), *decompressor) if is_weak_encrypted else \
decrypt_aes_decompress(yield_all(), *decompressor, key_length_raw=aes_extra[4]) if is_aes_encrypted else \
decrypt_none_decompress(yield_all(), *decompressor)
counted_decompressed_bytes, get_compressed_size, get_crc_32_actual, get_uncompressed_size = read_data_and_count_and_crc32(decompressed_bytes)
checked_bytes = \
checked_from_data_descriptor(counted_decompressed_bytes, is_sure_zip64, is_aes_2_encrypted, get_crc_32_actual, get_compressed_size, get_uncompressed_size) if has_data_descriptor else \
checked_from_local_header(counted_decompressed_bytes, is_aes_2_encrypted, get_crc_32_actual, get_compressed_size, get_uncompressed_size)
return file_name, uncompressed_size, checked_bytes
def all():
yield_all, get_num, return_num_unused, return_bytes_unused, get_offset_from_start = get_byte_readers(zipfile_chunks)
while True:
signature = get_num(len(local_file_header_signature))
if signature == local_file_header_signature:
yield yield_file(yield_all, get_num, return_num_unused, return_bytes_unused, get_offset_from_start)
elif signature in (central_directory_signature, end_of_central_directory_signature):
for _ in yield_all():
pass
break
else:
raise UnexpectedSignatureError(signature)
for file_name, file_size, unzipped_chunks in all():
yield file_name, file_size, unzipped_chunks
for _ in unzipped_chunks:
raise UnfinishedIterationError()
async def async_stream_unzip(chunks, *args, **kwargs):
async def to_async_iterable(sync_iterable):
# asyncio.to_thread is not available until Python 3.9, and StopIteration doesn't get
# propagated by run_in_executor, so we use a sentinel to detect the end of the iterable
done = object()
it = iter(sync_iterable)
# contextvars are not available until Python 3.7
try:
import contextvars
except ImportError:
get_args = lambda: (next, it, done)
else:
get_args = lambda: (contextvars.copy_context().run, next, it, done)
while True:
value = await loop.run_in_executor(None, *get_args())
if value is done:
break
yield value
def to_sync_iterable(async_iterable):
# The built-in aiter and anext functions are not available until Python 3.10
async_it = async_iterable.__aiter__()
while True:
try:
value = asyncio.run_coroutine_threadsafe(async_it.__anext__(), loop).result()
except StopAsyncIteration:
break
yield value
# get_running_loop is preferred, but isn't available until Python 3.7
try:
loop = asyncio.get_running_loop()
except:
loop = asyncio.get_event_loop()
unzipped_chunks = stream_unzip(to_sync_iterable(chunks), *args, **kwargs)
async for name, size, chunks in to_async_iterable(unzipped_chunks):
yield name, size, to_async_iterable(chunks)
class UnzipError(Exception):
pass
class InvalidOperationError(UnzipError):
pass
class UnfinishedIterationError(InvalidOperationError):
pass
class UnzipValueError(UnzipError, ValueError):
pass
class DataError(UnzipValueError):
pass
class UncompressError(UnzipValueError):
pass
class DeflateError(UncompressError):
pass
class BZ2Error(UncompressError):
pass
class UnsupportedFeatureError(DataError):
pass
class UnsupportedFlagsError(UnsupportedFeatureError):
pass
class UnsupportedCompressionTypeError(UnsupportedFeatureError):
pass
class UnsupportedZip64Error(UnsupportedFeatureError):
pass
class TruncatedDataError(DataError):
pass
class UnexpectedSignatureError(DataError):
pass
class MissingExtraError(DataError):
pass
class MissingAESExtraError(MissingExtraError):
pass
class TruncatedExtraError(DataError):
pass
class TruncatedZip64ExtraError(TruncatedExtraError):
pass
class TruncatedAESExtraError(TruncatedExtraError):
pass
class InvalidExtraError(TruncatedExtraError):
pass
class InvalidAESKeyLengthError(TruncatedExtraError):
pass
class IntegrityError(DataError):
pass
class HMACIntegrityError(IntegrityError):
pass
class CRC32IntegrityError(IntegrityError):
pass
class SizeIntegrityError(IntegrityError):
pass
class UncompressedSizeIntegrityError(SizeIntegrityError):
pass
class CompressedSizeIntegrityError(SizeIntegrityError):
pass
class PasswordError(UnzipValueError):
pass
class MissingPasswordError(UnzipValueError):
pass
class MissingZipCryptoPasswordError(MissingPasswordError):
pass
class MissingAESPasswordError(MissingPasswordError):
pass
class IncorrectPasswordError(PasswordError):
pass
class IncorrectZipCryptoPasswordError(IncorrectPasswordError):
pass
class IncorrectAESPasswordError(IncorrectPasswordError):
pass