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157 lines
5.3 KiB
157 lines
5.3 KiB
# defusedxml
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#
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# Copyright (c) 2013 by Christian Heimes <christian@python.org>
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# Licensed to PSF under a Contributor Agreement.
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# See http://www.python.org/psf/license for licensing details.
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"""Defused xmlrpclib
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Also defuses gzip bomb
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"""
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from __future__ import print_function, absolute_import
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import io
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from .common import (
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DTDForbidden, EntitiesForbidden, ExternalReferenceForbidden, PY3)
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if PY3:
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__origin__ = "xmlrpc.client"
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from xmlrpc.client import ExpatParser
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from xmlrpc import client as xmlrpc_client
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from xmlrpc import server as xmlrpc_server
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from xmlrpc.client import gzip_decode as _orig_gzip_decode
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from xmlrpc.client import GzipDecodedResponse as _OrigGzipDecodedResponse
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else:
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__origin__ = "xmlrpclib"
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from xmlrpclib import ExpatParser
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import xmlrpclib as xmlrpc_client
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xmlrpc_server = None
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from xmlrpclib import gzip_decode as _orig_gzip_decode
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from xmlrpclib import GzipDecodedResponse as _OrigGzipDecodedResponse
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try:
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import gzip
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except ImportError:
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gzip = None
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# Limit maximum request size to prevent resource exhaustion DoS
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# Also used to limit maximum amount of gzip decoded data in order to prevent
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# decompression bombs
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# A value of -1 or smaller disables the limit
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MAX_DATA = 30 * 1024 * 1024 # 30 MB
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def defused_gzip_decode(data, limit=None):
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"""gzip encoded data -> unencoded data
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Decode data using the gzip content encoding as described in RFC 1952
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"""
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if not gzip:
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raise NotImplementedError
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if limit is None:
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limit = MAX_DATA
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f = io.BytesIO(data)
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gzf = gzip.GzipFile(mode="rb", fileobj=f)
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try:
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if limit < 0: # no limit
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decoded = gzf.read()
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else:
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decoded = gzf.read(limit + 1)
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except IOError:
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raise ValueError("invalid data")
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f.close()
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gzf.close()
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if limit >= 0 and len(decoded) > limit:
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raise ValueError("max gzipped payload length exceeded")
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return decoded
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class DefusedGzipDecodedResponse(gzip.GzipFile if gzip else object):
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"""a file-like object to decode a response encoded with the gzip
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method, as described in RFC 1952.
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"""
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def __init__(self, response, limit=None):
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# response doesn't support tell() and read(), required by
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# GzipFile
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if not gzip:
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raise NotImplementedError
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self.limit = limit = limit if limit is not None else MAX_DATA
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if limit < 0: # no limit
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data = response.read()
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self.readlength = None
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else:
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data = response.read(limit + 1)
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self.readlength = 0
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if limit >= 0 and len(data) > limit:
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raise ValueError("max payload length exceeded")
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self.stringio = io.BytesIO(data)
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gzip.GzipFile.__init__(self, mode="rb", fileobj=self.stringio)
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def read(self, n):
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if self.limit >= 0:
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left = self.limit - self.readlength
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n = min(n, left + 1)
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data = gzip.GzipFile.read(self, n)
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self.readlength += len(data)
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if self.readlength > self.limit:
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raise ValueError("max payload length exceeded")
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return data
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else:
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return gzip.GzipFile.read(self, n)
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def close(self):
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gzip.GzipFile.close(self)
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self.stringio.close()
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class DefusedExpatParser(ExpatParser):
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def __init__(self, target, forbid_dtd=False, forbid_entities=True,
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forbid_external=True):
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ExpatParser.__init__(self, target)
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self.forbid_dtd = forbid_dtd
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self.forbid_entities = forbid_entities
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self.forbid_external = forbid_external
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parser = self._parser
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if self.forbid_dtd:
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parser.StartDoctypeDeclHandler = self.defused_start_doctype_decl
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if self.forbid_entities:
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parser.EntityDeclHandler = self.defused_entity_decl
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parser.UnparsedEntityDeclHandler = self.defused_unparsed_entity_decl
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if self.forbid_external:
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parser.ExternalEntityRefHandler = self.defused_external_entity_ref_handler
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def defused_start_doctype_decl(self, name, sysid, pubid,
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has_internal_subset):
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raise DTDForbidden(name, sysid, pubid)
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def defused_entity_decl(self, name, is_parameter_entity, value, base,
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sysid, pubid, notation_name):
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raise EntitiesForbidden(name, value, base, sysid, pubid, notation_name)
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def defused_unparsed_entity_decl(self, name, base, sysid, pubid,
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notation_name):
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# expat 1.2
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raise EntitiesForbidden(name, None, base, sysid, pubid, notation_name)
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def defused_external_entity_ref_handler(self, context, base, sysid,
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pubid):
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raise ExternalReferenceForbidden(context, base, sysid, pubid)
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def monkey_patch():
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xmlrpc_client.FastParser = DefusedExpatParser
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xmlrpc_client.GzipDecodedResponse = DefusedGzipDecodedResponse
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xmlrpc_client.gzip_decode = defused_gzip_decode
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if xmlrpc_server:
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xmlrpc_server.gzip_decode = defused_gzip_decode
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def unmonkey_patch():
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xmlrpc_client.FastParser = None
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xmlrpc_client.GzipDecodedResponse = _OrigGzipDecodedResponse
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xmlrpc_client.gzip_decode = _orig_gzip_decode
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if xmlrpc_server:
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xmlrpc_server.gzip_decode = _orig_gzip_decode
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