basic subscriptions system

1 files changed, 157 insertions, 0 deletions

diff --git a/python/defusedxml/xmlrpc.py b/python/defusedxml/xmlrpc.py
new file mode 100644
index 0000000..2a456e6
--- /dev/null
+++ b/python/defusedxml/xmlrpc.py
@@ -0,0 +1,157 @@
+# defusedxml
+#
+# Copyright (c) 2013 by Christian Heimes <christian@python.org>
+# Licensed to PSF under a Contributor Agreement.
+# See http://www.python.org/psf/license for licensing details.
+"""Defused xmlrpclib
+
+Also defuses gzip bomb
+"""
+from __future__ import print_function, absolute_import
+
+import io
+
+from .common import (
+    DTDForbidden, EntitiesForbidden, ExternalReferenceForbidden, PY3)
+
+if PY3:
+    __origin__ = "xmlrpc.client"
+    from xmlrpc.client import ExpatParser
+    from xmlrpc import client as xmlrpc_client
+    from xmlrpc import server as xmlrpc_server
+    from xmlrpc.client import gzip_decode as _orig_gzip_decode
+    from xmlrpc.client import GzipDecodedResponse as _OrigGzipDecodedResponse
+else:
+    __origin__ = "xmlrpclib"
+    from xmlrpclib import ExpatParser
+    import xmlrpclib as xmlrpc_client
+    xmlrpc_server = None
+    from xmlrpclib import gzip_decode as _orig_gzip_decode
+    from xmlrpclib import GzipDecodedResponse as _OrigGzipDecodedResponse
+
+try:
+    import gzip
+except ImportError:
+    gzip = None
+
+
+# Limit maximum request size to prevent resource exhaustion DoS
+# Also used to limit maximum amount of gzip decoded data in order to prevent
+# decompression bombs
+# A value of -1 or smaller disables the limit
+MAX_DATA = 30 * 1024 * 1024  # 30 MB
+
+
+def defused_gzip_decode(data, limit=None):
+    """gzip encoded data -> unencoded data
+
+    Decode data using the gzip content encoding as described in RFC 1952
+    """
+    if not gzip:
+        raise NotImplementedError
+    if limit is None:
+        limit = MAX_DATA
+    f = io.BytesIO(data)
+    gzf = gzip.GzipFile(mode="rb", fileobj=f)
+    try:
+        if limit < 0:  # no limit
+            decoded = gzf.read()
+        else:
+            decoded = gzf.read(limit + 1)
+    except IOError:
+        raise ValueError("invalid data")
+    f.close()
+    gzf.close()
+    if limit >= 0 and len(decoded) > limit:
+        raise ValueError("max gzipped payload length exceeded")
+    return decoded
+
+
+class DefusedGzipDecodedResponse(gzip.GzipFile if gzip else object):
+    """a file-like object to decode a response encoded with the gzip
+    method, as described in RFC 1952.
+    """
+
+    def __init__(self, response, limit=None):
+        # response doesn't support tell() and read(), required by
+        # GzipFile
+        if not gzip:
+            raise NotImplementedError
+        self.limit = limit = limit if limit is not None else MAX_DATA
+        if limit < 0:  # no limit
+            data = response.read()
+            self.readlength = None
+        else:
+            data = response.read(limit + 1)
+            self.readlength = 0
+        if limit >= 0 and len(data) > limit:
+            raise ValueError("max payload length exceeded")
+        self.stringio = io.BytesIO(data)
+        gzip.GzipFile.__init__(self, mode="rb", fileobj=self.stringio)
+
+    def read(self, n):
+        if self.limit >= 0:
+            left = self.limit - self.readlength
+            n = min(n, left + 1)
+            data = gzip.GzipFile.read(self, n)
+            self.readlength += len(data)
+            if self.readlength > self.limit:
+                raise ValueError("max payload length exceeded")
+            return data
+        else:
+            return gzip.GzipFile.read(self, n)
+
+    def close(self):
+        gzip.GzipFile.close(self)
+        self.stringio.close()
+
+
+class DefusedExpatParser(ExpatParser):
+
+    def __init__(self, target, forbid_dtd=False, forbid_entities=True,
+                 forbid_external=True):
+        ExpatParser.__init__(self, target)
+        self.forbid_dtd = forbid_dtd
+        self.forbid_entities = forbid_entities
+        self.forbid_external = forbid_external
+        parser = self._parser
+        if self.forbid_dtd:
+            parser.StartDoctypeDeclHandler = self.defused_start_doctype_decl
+        if self.forbid_entities:
+            parser.EntityDeclHandler = self.defused_entity_decl
+            parser.UnparsedEntityDeclHandler = self.defused_unparsed_entity_decl
+        if self.forbid_external:
+            parser.ExternalEntityRefHandler = self.defused_external_entity_ref_handler
+
+    def defused_start_doctype_decl(self, name, sysid, pubid,
+                                   has_internal_subset):
+        raise DTDForbidden(name, sysid, pubid)
+
+    def defused_entity_decl(self, name, is_parameter_entity, value, base,
+                            sysid, pubid, notation_name):
+        raise EntitiesForbidden(name, value, base, sysid, pubid, notation_name)
+
+    def defused_unparsed_entity_decl(self, name, base, sysid, pubid,
+                                     notation_name):
+        # expat 1.2
+        raise EntitiesForbidden(name, None, base, sysid, pubid, notation_name)
+
+    def defused_external_entity_ref_handler(self, context, base, sysid,
+                                            pubid):
+        raise ExternalReferenceForbidden(context, base, sysid, pubid)
+
+
+def monkey_patch():
+    xmlrpc_client.FastParser = DefusedExpatParser
+    xmlrpc_client.GzipDecodedResponse = DefusedGzipDecodedResponse
+    xmlrpc_client.gzip_decode = defused_gzip_decode
+    if xmlrpc_server:
+        xmlrpc_server.gzip_decode = defused_gzip_decode
+
+
+def unmonkey_patch():
+    xmlrpc_client.FastParser = None
+    xmlrpc_client.GzipDecodedResponse = _OrigGzipDecodedResponse
+    xmlrpc_client.gzip_decode = _orig_gzip_decode
+    if xmlrpc_server:
+        xmlrpc_server.gzip_decode = _orig_gzip_decode