689 lines
24 KiB
Python
689 lines
24 KiB
Python
"""
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Multi-part parsing for file uploads.
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Exposes one class, ``MultiPartParser``, which feeds chunks of uploaded data to
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file upload handlers for processing.
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"""
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import base64
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import binascii
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import cgi
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from urllib.parse import unquote
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from django.conf import settings
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from django.core.exceptions import (
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RequestDataTooBig, SuspiciousMultipartForm, TooManyFieldsSent,
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)
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from django.core.files.uploadhandler import (
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SkipFile, StopFutureHandlers, StopUpload,
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)
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from django.utils.datastructures import MultiValueDict
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from django.utils.encoding import force_text
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from django.utils.text import unescape_entities
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__all__ = ('MultiPartParser', 'MultiPartParserError', 'InputStreamExhausted')
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class MultiPartParserError(Exception):
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pass
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class InputStreamExhausted(Exception):
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"""
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No more reads are allowed from this device.
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"""
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pass
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RAW = "raw"
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FILE = "file"
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FIELD = "field"
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class MultiPartParser:
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"""
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A rfc2388 multipart/form-data parser.
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``MultiValueDict.parse()`` reads the input stream in ``chunk_size`` chunks
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and returns a tuple of ``(MultiValueDict(POST), MultiValueDict(FILES))``.
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"""
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def __init__(self, META, input_data, upload_handlers, encoding=None):
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"""
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Initialize the MultiPartParser object.
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:META:
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The standard ``META`` dictionary in Django request objects.
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:input_data:
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The raw post data, as a file-like object.
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:upload_handlers:
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A list of UploadHandler instances that perform operations on the
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uploaded data.
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:encoding:
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The encoding with which to treat the incoming data.
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"""
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# Content-Type should contain multipart and the boundary information.
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content_type = META.get('CONTENT_TYPE', '')
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if not content_type.startswith('multipart/'):
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raise MultiPartParserError('Invalid Content-Type: %s' % content_type)
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# Parse the header to get the boundary to split the parts.
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ctypes, opts = parse_header(content_type.encode('ascii'))
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boundary = opts.get('boundary')
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if not boundary or not cgi.valid_boundary(boundary):
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raise MultiPartParserError('Invalid boundary in multipart: %s' % boundary.decode())
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# Content-Length should contain the length of the body we are about
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# to receive.
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try:
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content_length = int(META.get('CONTENT_LENGTH', 0))
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except (ValueError, TypeError):
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content_length = 0
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if content_length < 0:
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# This means we shouldn't continue...raise an error.
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raise MultiPartParserError("Invalid content length: %r" % content_length)
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if isinstance(boundary, str):
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boundary = boundary.encode('ascii')
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self._boundary = boundary
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self._input_data = input_data
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# For compatibility with low-level network APIs (with 32-bit integers),
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# the chunk size should be < 2^31, but still divisible by 4.
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possible_sizes = [x.chunk_size for x in upload_handlers if x.chunk_size]
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self._chunk_size = min([2 ** 31 - 4] + possible_sizes)
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self._meta = META
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self._encoding = encoding or settings.DEFAULT_CHARSET
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self._content_length = content_length
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self._upload_handlers = upload_handlers
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def parse(self):
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"""
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Parse the POST data and break it into a FILES MultiValueDict and a POST
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MultiValueDict.
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Return a tuple containing the POST and FILES dictionary, respectively.
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"""
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from django.http import QueryDict
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encoding = self._encoding
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handlers = self._upload_handlers
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# HTTP spec says that Content-Length >= 0 is valid
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# handling content-length == 0 before continuing
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if self._content_length == 0:
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return QueryDict(encoding=self._encoding), MultiValueDict()
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# See if any of the handlers take care of the parsing.
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# This allows overriding everything if need be.
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for handler in handlers:
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result = handler.handle_raw_input(
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self._input_data,
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self._meta,
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self._content_length,
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self._boundary,
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encoding,
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)
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# Check to see if it was handled
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if result is not None:
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return result[0], result[1]
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# Create the data structures to be used later.
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self._post = QueryDict(mutable=True)
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self._files = MultiValueDict()
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# Instantiate the parser and stream:
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stream = LazyStream(ChunkIter(self._input_data, self._chunk_size))
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# Whether or not to signal a file-completion at the beginning of the loop.
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old_field_name = None
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counters = [0] * len(handlers)
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# Number of bytes that have been read.
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num_bytes_read = 0
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# To count the number of keys in the request.
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num_post_keys = 0
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# To limit the amount of data read from the request.
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read_size = None
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try:
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for item_type, meta_data, field_stream in Parser(stream, self._boundary):
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if old_field_name:
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# We run this at the beginning of the next loop
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# since we cannot be sure a file is complete until
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# we hit the next boundary/part of the multipart content.
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self.handle_file_complete(old_field_name, counters)
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old_field_name = None
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try:
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disposition = meta_data['content-disposition'][1]
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field_name = disposition['name'].strip()
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except (KeyError, IndexError, AttributeError):
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continue
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transfer_encoding = meta_data.get('content-transfer-encoding')
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if transfer_encoding is not None:
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transfer_encoding = transfer_encoding[0].strip()
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field_name = force_text(field_name, encoding, errors='replace')
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if item_type == FIELD:
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# Avoid storing more than DATA_UPLOAD_MAX_NUMBER_FIELDS.
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num_post_keys += 1
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if (settings.DATA_UPLOAD_MAX_NUMBER_FIELDS is not None and
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settings.DATA_UPLOAD_MAX_NUMBER_FIELDS < num_post_keys):
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raise TooManyFieldsSent(
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'The number of GET/POST parameters exceeded '
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'settings.DATA_UPLOAD_MAX_NUMBER_FIELDS.'
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)
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# Avoid reading more than DATA_UPLOAD_MAX_MEMORY_SIZE.
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if settings.DATA_UPLOAD_MAX_MEMORY_SIZE is not None:
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read_size = settings.DATA_UPLOAD_MAX_MEMORY_SIZE - num_bytes_read
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# This is a post field, we can just set it in the post
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if transfer_encoding == 'base64':
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raw_data = field_stream.read(size=read_size)
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num_bytes_read += len(raw_data)
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try:
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data = base64.b64decode(raw_data)
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except binascii.Error:
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data = raw_data
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else:
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data = field_stream.read(size=read_size)
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num_bytes_read += len(data)
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# Add two here to make the check consistent with the
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# x-www-form-urlencoded check that includes '&='.
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num_bytes_read += len(field_name) + 2
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if (settings.DATA_UPLOAD_MAX_MEMORY_SIZE is not None and
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num_bytes_read > settings.DATA_UPLOAD_MAX_MEMORY_SIZE):
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raise RequestDataTooBig('Request body exceeded settings.DATA_UPLOAD_MAX_MEMORY_SIZE.')
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self._post.appendlist(field_name, force_text(data, encoding, errors='replace'))
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elif item_type == FILE:
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# This is a file, use the handler...
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file_name = disposition.get('filename')
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if file_name:
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file_name = force_text(file_name, encoding, errors='replace')
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file_name = self.IE_sanitize(unescape_entities(file_name))
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if not file_name:
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continue
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content_type, content_type_extra = meta_data.get('content-type', ('', {}))
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content_type = content_type.strip()
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charset = content_type_extra.get('charset')
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try:
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content_length = int(meta_data.get('content-length')[0])
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except (IndexError, TypeError, ValueError):
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content_length = None
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counters = [0] * len(handlers)
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try:
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for handler in handlers:
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try:
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handler.new_file(
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field_name, file_name, content_type,
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content_length, charset, content_type_extra,
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)
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except StopFutureHandlers:
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break
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for chunk in field_stream:
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if transfer_encoding == 'base64':
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# We only special-case base64 transfer encoding
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# We should always decode base64 chunks by multiple of 4,
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# ignoring whitespace.
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stripped_chunk = b"".join(chunk.split())
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remaining = len(stripped_chunk) % 4
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while remaining != 0:
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over_chunk = field_stream.read(4 - remaining)
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stripped_chunk += b"".join(over_chunk.split())
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remaining = len(stripped_chunk) % 4
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try:
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chunk = base64.b64decode(stripped_chunk)
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except Exception as exc:
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# Since this is only a chunk, any error is an unfixable error.
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raise MultiPartParserError("Could not decode base64 data.") from exc
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for i, handler in enumerate(handlers):
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chunk_length = len(chunk)
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chunk = handler.receive_data_chunk(chunk, counters[i])
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counters[i] += chunk_length
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if chunk is None:
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# Don't continue if the chunk received by
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# the handler is None.
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break
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except SkipFile:
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self._close_files()
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# Just use up the rest of this file...
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exhaust(field_stream)
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else:
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# Handle file upload completions on next iteration.
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old_field_name = field_name
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else:
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# If this is neither a FIELD or a FILE, just exhaust the stream.
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exhaust(stream)
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except StopUpload as e:
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self._close_files()
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if not e.connection_reset:
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exhaust(self._input_data)
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else:
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# Make sure that the request data is all fed
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exhaust(self._input_data)
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# Signal that the upload has completed.
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# any() shortcircuits if a handler's upload_complete() returns a value.
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any(handler.upload_complete() for handler in handlers)
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self._post._mutable = False
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return self._post, self._files
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def handle_file_complete(self, old_field_name, counters):
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"""
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Handle all the signaling that takes place when a file is complete.
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"""
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for i, handler in enumerate(self._upload_handlers):
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file_obj = handler.file_complete(counters[i])
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if file_obj:
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# If it returns a file object, then set the files dict.
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self._files.appendlist(force_text(old_field_name, self._encoding, errors='replace'), file_obj)
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break
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def IE_sanitize(self, filename):
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"""Cleanup filename from Internet Explorer full paths."""
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return filename and filename[filename.rfind("\\") + 1:].strip()
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def _close_files(self):
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# Free up all file handles.
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# FIXME: this currently assumes that upload handlers store the file as 'file'
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# We should document that... (Maybe add handler.free_file to complement new_file)
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for handler in self._upload_handlers:
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if hasattr(handler, 'file'):
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handler.file.close()
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class LazyStream:
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"""
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The LazyStream wrapper allows one to get and "unget" bytes from a stream.
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Given a producer object (an iterator that yields bytestrings), the
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LazyStream object will support iteration, reading, and keeping a "look-back"
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variable in case you need to "unget" some bytes.
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"""
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def __init__(self, producer, length=None):
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"""
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Every LazyStream must have a producer when instantiated.
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A producer is an iterable that returns a string each time it
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is called.
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"""
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self._producer = producer
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self._empty = False
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self._leftover = b''
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self.length = length
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self.position = 0
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self._remaining = length
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self._unget_history = []
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def tell(self):
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return self.position
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def read(self, size=None):
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def parts():
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remaining = self._remaining if size is None else size
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# do the whole thing in one shot if no limit was provided.
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if remaining is None:
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yield b''.join(self)
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return
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# otherwise do some bookkeeping to return exactly enough
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# of the stream and stashing any extra content we get from
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# the producer
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while remaining != 0:
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assert remaining > 0, 'remaining bytes to read should never go negative'
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try:
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chunk = next(self)
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except StopIteration:
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return
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else:
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emitting = chunk[:remaining]
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self.unget(chunk[remaining:])
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remaining -= len(emitting)
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yield emitting
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out = b''.join(parts())
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return out
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def __next__(self):
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"""
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Used when the exact number of bytes to read is unimportant.
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Return whatever chunk is conveniently returned from the iterator.
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Useful to avoid unnecessary bookkeeping if performance is an issue.
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"""
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if self._leftover:
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output = self._leftover
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self._leftover = b''
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else:
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output = next(self._producer)
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self._unget_history = []
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self.position += len(output)
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return output
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def close(self):
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"""
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Used to invalidate/disable this lazy stream.
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Replace the producer with an empty list. Any leftover bytes that have
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already been read will still be reported upon read() and/or next().
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"""
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self._producer = []
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def __iter__(self):
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return self
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def unget(self, bytes):
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"""
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Place bytes back onto the front of the lazy stream.
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Future calls to read() will return those bytes first. The
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stream position and thus tell() will be rewound.
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"""
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if not bytes:
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return
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self._update_unget_history(len(bytes))
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self.position -= len(bytes)
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self._leftover = bytes + self._leftover
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def _update_unget_history(self, num_bytes):
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"""
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Update the unget history as a sanity check to see if we've pushed
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back the same number of bytes in one chunk. If we keep ungetting the
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same number of bytes many times (here, 50), we're mostly likely in an
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infinite loop of some sort. This is usually caused by a
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maliciously-malformed MIME request.
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"""
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self._unget_history = [num_bytes] + self._unget_history[:49]
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number_equal = len([
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current_number for current_number in self._unget_history
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if current_number == num_bytes
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])
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if number_equal > 40:
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raise SuspiciousMultipartForm(
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"The multipart parser got stuck, which shouldn't happen with"
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" normal uploaded files. Check for malicious upload activity;"
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" if there is none, report this to the Django developers."
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)
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class ChunkIter:
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"""
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An iterable that will yield chunks of data. Given a file-like object as the
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constructor, yield chunks of read operations from that object.
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"""
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def __init__(self, flo, chunk_size=64 * 1024):
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self.flo = flo
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self.chunk_size = chunk_size
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def __next__(self):
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try:
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data = self.flo.read(self.chunk_size)
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except InputStreamExhausted:
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raise StopIteration()
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if data:
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return data
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else:
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raise StopIteration()
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def __iter__(self):
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return self
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class InterBoundaryIter:
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"""
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A Producer that will iterate over boundaries.
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"""
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def __init__(self, stream, boundary):
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self._stream = stream
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self._boundary = boundary
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def __iter__(self):
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return self
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def __next__(self):
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try:
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return LazyStream(BoundaryIter(self._stream, self._boundary))
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except InputStreamExhausted:
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raise StopIteration()
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class BoundaryIter:
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"""
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A Producer that is sensitive to boundaries.
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Will happily yield bytes until a boundary is found. Will yield the bytes
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before the boundary, throw away the boundary bytes themselves, and push the
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post-boundary bytes back on the stream.
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The future calls to next() after locating the boundary will raise a
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StopIteration exception.
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"""
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def __init__(self, stream, boundary):
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self._stream = stream
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self._boundary = boundary
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self._done = False
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# rollback an additional six bytes because the format is like
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# this: CRLF<boundary>[--CRLF]
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self._rollback = len(boundary) + 6
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# Try to use mx fast string search if available. Otherwise
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# use Python find. Wrap the latter for consistency.
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unused_char = self._stream.read(1)
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if not unused_char:
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raise InputStreamExhausted()
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self._stream.unget(unused_char)
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def __iter__(self):
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return self
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def __next__(self):
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if self._done:
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raise StopIteration()
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stream = self._stream
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rollback = self._rollback
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bytes_read = 0
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chunks = []
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for bytes in stream:
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bytes_read += len(bytes)
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chunks.append(bytes)
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if bytes_read > rollback:
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break
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if not bytes:
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break
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else:
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self._done = True
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if not chunks:
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raise StopIteration()
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chunk = b''.join(chunks)
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boundary = self._find_boundary(chunk)
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if boundary:
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end, next = boundary
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stream.unget(chunk[next:])
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self._done = True
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return chunk[:end]
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else:
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# make sure we don't treat a partial boundary (and
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# its separators) as data
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if not chunk[:-rollback]: # and len(chunk) >= (len(self._boundary) + 6):
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# There's nothing left, we should just return and mark as done.
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self._done = True
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return chunk
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else:
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stream.unget(chunk[-rollback:])
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return chunk[:-rollback]
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def _find_boundary(self, data):
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"""
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Find a multipart boundary in data.
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Should no boundary exist in the data, return None. Otherwise, return
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a tuple containing the indices of the following:
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* the end of current encapsulation
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* the start of the next encapsulation
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"""
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index = data.find(self._boundary)
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|
if index < 0:
|
|
return None
|
|
else:
|
|
end = index
|
|
next = index + len(self._boundary)
|
|
# backup over CRLF
|
|
last = max(0, end - 1)
|
|
if data[last:last + 1] == b'\n':
|
|
end -= 1
|
|
last = max(0, end - 1)
|
|
if data[last:last + 1] == b'\r':
|
|
end -= 1
|
|
return end, next
|
|
|
|
|
|
def exhaust(stream_or_iterable):
|
|
"""Exhaust an iterator or stream."""
|
|
try:
|
|
iterator = iter(stream_or_iterable)
|
|
except TypeError:
|
|
iterator = ChunkIter(stream_or_iterable, 16384)
|
|
|
|
for __ in iterator:
|
|
pass
|
|
|
|
|
|
def parse_boundary_stream(stream, max_header_size):
|
|
"""
|
|
Parse one and exactly one stream that encapsulates a boundary.
|
|
"""
|
|
# Stream at beginning of header, look for end of header
|
|
# and parse it if found. The header must fit within one
|
|
# chunk.
|
|
chunk = stream.read(max_header_size)
|
|
|
|
# 'find' returns the top of these four bytes, so we'll
|
|
# need to munch them later to prevent them from polluting
|
|
# the payload.
|
|
header_end = chunk.find(b'\r\n\r\n')
|
|
|
|
def _parse_header(line):
|
|
main_value_pair, params = parse_header(line)
|
|
try:
|
|
name, value = main_value_pair.split(':', 1)
|
|
except ValueError:
|
|
raise ValueError("Invalid header: %r" % line)
|
|
return name, (value, params)
|
|
|
|
if header_end == -1:
|
|
# we find no header, so we just mark this fact and pass on
|
|
# the stream verbatim
|
|
stream.unget(chunk)
|
|
return (RAW, {}, stream)
|
|
|
|
header = chunk[:header_end]
|
|
|
|
# here we place any excess chunk back onto the stream, as
|
|
# well as throwing away the CRLFCRLF bytes from above.
|
|
stream.unget(chunk[header_end + 4:])
|
|
|
|
TYPE = RAW
|
|
outdict = {}
|
|
|
|
# Eliminate blank lines
|
|
for line in header.split(b'\r\n'):
|
|
# This terminology ("main value" and "dictionary of
|
|
# parameters") is from the Python docs.
|
|
try:
|
|
name, (value, params) = _parse_header(line)
|
|
except ValueError:
|
|
continue
|
|
|
|
if name == 'content-disposition':
|
|
TYPE = FIELD
|
|
if params.get('filename'):
|
|
TYPE = FILE
|
|
|
|
outdict[name] = value, params
|
|
|
|
if TYPE == RAW:
|
|
stream.unget(chunk)
|
|
|
|
return (TYPE, outdict, stream)
|
|
|
|
|
|
class Parser:
|
|
def __init__(self, stream, boundary):
|
|
self._stream = stream
|
|
self._separator = b'--' + boundary
|
|
|
|
def __iter__(self):
|
|
boundarystream = InterBoundaryIter(self._stream, self._separator)
|
|
for sub_stream in boundarystream:
|
|
# Iterate over each part
|
|
yield parse_boundary_stream(sub_stream, 1024)
|
|
|
|
|
|
def parse_header(line):
|
|
"""
|
|
Parse the header into a key-value.
|
|
|
|
Input (line): bytes, output: str for key/name, bytes for values which
|
|
will be decoded later.
|
|
"""
|
|
plist = _parse_header_params(b';' + line)
|
|
key = plist.pop(0).lower().decode('ascii')
|
|
pdict = {}
|
|
for p in plist:
|
|
i = p.find(b'=')
|
|
if i >= 0:
|
|
has_encoding = False
|
|
name = p[:i].strip().lower().decode('ascii')
|
|
if name.endswith('*'):
|
|
# Lang/encoding embedded in the value (like "filename*=UTF-8''file.ext")
|
|
# http://tools.ietf.org/html/rfc2231#section-4
|
|
name = name[:-1]
|
|
if p.count(b"'") == 2:
|
|
has_encoding = True
|
|
value = p[i + 1:].strip()
|
|
if has_encoding:
|
|
encoding, lang, value = value.split(b"'")
|
|
value = unquote(value.decode(), encoding=encoding.decode())
|
|
if len(value) >= 2 and value[:1] == value[-1:] == b'"':
|
|
value = value[1:-1]
|
|
value = value.replace(b'\\\\', b'\\').replace(b'\\"', b'"')
|
|
pdict[name] = value
|
|
return key, pdict
|
|
|
|
|
|
def _parse_header_params(s):
|
|
plist = []
|
|
while s[:1] == b';':
|
|
s = s[1:]
|
|
end = s.find(b';')
|
|
while end > 0 and s.count(b'"', 0, end) % 2:
|
|
end = s.find(b';', end + 1)
|
|
if end < 0:
|
|
end = len(s)
|
|
f = s[:end]
|
|
plist.append(f.strip())
|
|
s = s[end:]
|
|
return plist
|