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# Copyright (C) 2013, Red Hat, Inc.
# All rights reserved.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import struct
from kdcproxy import parse_pyasn1 as asn1mod
from kdcproxy.exceptions import ParsingError
class ProxyRequest(object):
TYPE = None
OFFSET = 4
@classmethod
def parse(cls, data):
request, realm, _ = asn1mod.decode_proxymessage(data)
# Check the length of the whole request message.
(length, ) = struct.unpack("!I", request[0:4])
if length + 4 != len(request):
raise ParsingError("Invalid request length.")
for subcls in cls.__subclasses__():
try:
return subcls.parse_request(realm, request)
except ParsingError:
pass
raise ParsingError("Invalid request.")
@classmethod
def parse_request(cls, realm, request):
pretty_name = asn1mod.try_decode(request[cls.OFFSET:], cls.TYPE)
return cls(realm, request, pretty_name)
def __init__(self, realm, request, pretty_name):
self.realm = realm
self.request = request
self.pretty_name = pretty_name
def __str__(self):
return "%s %s (%d bytes)" % (self.realm, self.pretty_name,
len(self.request) - 4)
class TGSProxyRequest(ProxyRequest):
TYPE = asn1mod.TGSREQ
class ASProxyRequest(ProxyRequest):
TYPE = asn1mod.ASREQ
class KPASSWDProxyRequest(ProxyRequest):
TYPE = asn1mod.APREQ
OFFSET = 10
@classmethod
def parse_request(cls, realm, request):
# Check the length count in the password change request, assuming it
# actually is a password change request. It should be the length of
# the rest of the request, including itself.
(length, ) = struct.unpack("!H", request[4:6])
if length != len(request) - 4:
raise ParsingError("Parsing the KPASSWD request length failed.")
# Check the version number in the password change request, assuming it
# actually is a password change request. Officially we support version
# 1, but 0xff80 is used for set-password, so try to accept that, too.
(version, ) = struct.unpack("!H", request[6:8])
if version != 0x0001 and version != 0xff80:
raise ParsingError("The KPASSWD request is an incorrect version.")
# Read the length of the AP-REQ part of the change request. There
# should be at least that may bytes following this length, since the
# rest of the request is the KRB-PRIV message.
(length, ) = struct.unpack("!H", request[8:10])
if length > len(request) - 10:
raise ParsingError("The KPASSWD request appears to be truncated.")
# See if the tag looks like an AP request, which would look like the
# start of a password change request. The rest of it should be a
# KRB-PRIV message.
asn1mod.try_decode(request[10:length + 10], asn1mod.APREQ)
asn1mod.try_decode(request[length + 10:], asn1mod.KRBPriv)
self = cls(realm, request, "KPASSWD-REQ")
self.version = version
return self
def __str__(self):
tmp = super(KPASSWDProxyRequest, self).__str__()
tmp += " (version 0x%04x)" % self.version
return tmp
def decode(data):
return ProxyRequest.parse(data)
def encode(data):
return asn1mod.encode_proxymessage(data)
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