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# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
import bz2
import io
import lzma
import os
import struct
import zlib
from xml.etree.ElementTree import XML
class ZlibFile(object):
def __init__(self, fileobj):
self.fileobj = fileobj
self.decompressor = zlib.decompressobj()
self.buf = b""
def read(self, length):
cutoff = min(length, len(self.buf))
result = self.buf[:cutoff]
self.buf = self.buf[cutoff:]
while len(result) < length:
buf = self.fileobj.read(io.DEFAULT_BUFFER_SIZE)
if not buf:
break
buf = self.decompressor.decompress(buf)
cutoff = min(length - len(result), len(buf))
result += buf[:cutoff]
self.buf += buf[cutoff:]
return result
def unxar(fileobj):
magic = fileobj.read(4)
if magic != b"xar!":
raise Exception("Not a XAR?")
header_size = fileobj.read(2)
header_size = struct.unpack(">H", header_size)[0]
if header_size > 64:
raise Exception(
f"Don't know how to handle a {header_size} bytes XAR header size"
)
header_size -= 6 # what we've read so far.
header = fileobj.read(header_size)
if len(header) != header_size:
raise Exception("Failed to read XAR header")
(
version,
compressed_toc_len,
uncompressed_toc_len,
checksum_type,
) = struct.unpack(">HQQL", header[:22])
if version != 1:
raise Exception(f"XAR version {version} not supported")
toc = fileobj.read(compressed_toc_len)
base = fileobj.tell()
if len(toc) != compressed_toc_len:
raise Exception("Failed to read XAR TOC")
toc = zlib.decompress(toc)
if len(toc) != uncompressed_toc_len:
raise Exception("Corrupted XAR?")
toc = XML(toc).find("toc")
for f in toc.findall("file"):
if f.find("type").text != "file":
continue
filename = f.find("name").text
data = f.find("data")
length = int(data.find("length").text)
size = int(data.find("size").text)
offset = int(data.find("offset").text)
encoding = data.find("encoding").get("style")
fileobj.seek(base + offset, os.SEEK_SET)
content = Take(fileobj, length)
if encoding == "application/octet-stream":
if length != size:
raise Exception(f"{length} != {size}")
elif encoding == "application/x-bzip2":
content = bz2.BZ2File(content)
elif encoding == "application/x-gzip":
# Despite the encoding saying gzip, it is in fact, a raw zlib stream.
content = ZlibFile(content)
else:
raise Exception(f"XAR encoding {encoding} not supported")
yield filename, content
class Pbzx(object):
def __init__(self, fileobj):
magic = fileobj.read(4)
if magic != b"pbzx":
raise Exception("Not a PBZX payload?")
# The first thing in the file looks like the size of each
# decompressed chunk except the last one. It should match
# decompressed_size in all cases except last, but we don't
# check.
chunk_size = fileobj.read(8)
chunk_size = struct.unpack(">Q", chunk_size)[0]
self.fileobj = fileobj
self._init_one_chunk()
def _init_one_chunk(self):
self.offset = 0
header = self.fileobj.read(16)
if header == b"":
self.chunk = ""
return
if len(header) != 16:
raise Exception("Corrupted PBZX payload?")
decompressed_size, compressed_size = struct.unpack(">QQ", header)
chunk = self.fileobj.read(compressed_size)
if compressed_size == decompressed_size:
self.chunk = chunk
else:
self.chunk = lzma.decompress(chunk)
if len(self.chunk) != decompressed_size:
raise Exception("Corrupted PBZX payload?")
def read(self, length=None):
if length == 0:
return b""
if length and len(self.chunk) >= self.offset + length:
start = self.offset
self.offset += length
return self.chunk[start : self.offset]
else:
result = self.chunk[self.offset :]
self._init_one_chunk()
if self.chunk:
# XXX: suboptimal if length is larger than the chunk size
result += self.read(None if length is None else length - len(result))
return result
class Take(object):
"""
File object wrapper that allows to read at most a certain length.
"""
def __init__(self, fileobj, limit):
self.fileobj = fileobj
self.limit = limit
def read(self, length=None):
if length is None:
length = self.limit
else:
length = min(length, self.limit)
result = self.fileobj.read(length)
self.limit -= len(result)
return result
def uncpio(fileobj):
while True:
magic = fileobj.read(6)
# CPIO payloads in mac pkg files are using the portable ASCII format.
if magic != b"070707":
if magic.startswith(b"0707"):
raise Exception("Unsupported CPIO format")
raise Exception("Not a CPIO header")
header = fileobj.read(70)
(
dev,
ino,
mode,
uid,
gid,
nlink,
rdev,
mtime,
namesize,
filesize,
) = struct.unpack(">6s6s6s6s6s6s6s11s6s11s", header)
mode = int(mode, 8)
nlink = int(nlink, 8)
namesize = int(namesize, 8)
filesize = int(filesize, 8)
name = fileobj.read(namesize)
if name[-1] != 0:
raise Exception("File name is not NUL terminated")
name = name[:-1]
if name == b"TRAILER!!!":
break
if b"/../" in name or name.startswith(b"../") or name == b"..":
raise Exception(".. is forbidden in file name")
if name.startswith(b"."):
name = name[1:]
if name.startswith(b"/"):
name = name[1:]
content = Take(fileobj, filesize)
yield name, mode, content
# Ensure the content is totally consumed
while content.read(4096):
pass
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