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packet.py
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packet.py
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"""
RADIUS packet
"""
__docformat__ = "epytext en"
#from hashlib import md5
from hashlib import md5
import struct, types, random, UserDict, hmac
import tools
# Packet codes
AccessRequest = 1
AccessAccept = 2
AccessReject = 3
AccountingRequest = 4
AccountingResponse = 5
AccessChallenge = 11
StatusServer = 12
StatusClient = 13
# Current ID
CurrentID = random.randrange(1, 255)
class PacketError(Exception):
pass
class Packet(UserDict.UserDict):
def __init__(self, code=0, id=None, secret="", authenticator=None, **attributes):
"""Constructor
@param dict: RADIUS dictionary
@type dict: pyrad.dictionary.Dictionary class
@param secret: secret needed to communicate with a RADIUS server
@type secret: string
@param id: packet identifaction number
@type id: integer (8 bits)
@param code: packet type code
@type code: integer (8bits)
@param packet: raw packet to decode
@type packet: string
"""
UserDict.UserDict.__init__(self)
self.code=code
if id is not None:
self.id=id
else:
self.id=CreateID()
self.secret=secret
self.authenticator=authenticator
if attributes.has_key("dict"):
self.dict=attributes["dict"]
if attributes.has_key("packet"):
self.DecodePacket(attributes["packet"])
for (key,value) in attributes.items():
if key in [ "dict", "fd", "packet"]:
continue
key=key.replace("_", "-")
self.AddAttribute(key, value)
def CreateReply(self, **attributes):
return Packet(id=self.id, secret=self.secret,
authenticator=self.authenticator, dict=self.dict,
**attributes)
def _EncodeValue(self, attr, value):
if attr.values.HasForward(value):
return attr.values.GetForward(value)
else:
return tools.EncodeAttr(attr.type, value)
def _EncodeKeyValues(self, key, values):
if not isinstance(key, str):
return (key, values)
attr=self.dict.attributes[key]
if attr.vendor:
key=(self.dict.vendors.GetForward(attr.vendor), attr.code)
else:
key=attr.code
return (key, [self._EncodeValue(attr, v) for v in values])
def _DecodeValue(self, attr, value):
if attr.values.HasBackward(value):
return attr.values.GetBackward(value)
else:
return tools.DecodeAttr(attr.type, value)
def _EncodeKey(self, key):
if not isinstance(key, str):
return key
attr=self.dict.attributes[key]
if attr.vendor:
return (self.dict.vendors.GetForward(attr.vendor), attr.code)
else:
return attr.code
def _DecodeKey(self, key):
"Turn a key into a string if possible"
if self.dict.attrindex.HasBackward(key):
return self.dict.attrindex.GetBackward(key)
return key
def AddAttribute(self, key, value):
"""Add an attribute to the packet.
@param key: attribute name or identification
@type key: string, attribute code or (vendor code, attribute code) tuple
@param value: value
@type value: depends on type of attribute
"""
(key,value)=self._EncodeKeyValues(key, [value])
value=value[0]
if self.data.has_key(key):
self.data[key].append(value)
else:
self.data[key]=[value]
def __getitem__(self, key):
if type(key)!=types.StringType:
return self.data[key]
values=self.data[self._EncodeKey(key)]
attr=self.dict.attributes[key]
res=[]
for v in values:
res.append(self._DecodeValue(attr, v))
return res
def __contains__(self, key):
return self.has_key(key)
def has_key(self, key):
try:
return self.data.has_key(self._EncodeKey(key))
except KeyError:
return False
def __delitem__(self, key):
del self.data[self._EncodeKey(key)]
def __setitem__(self, key, item):
if type(key)==types.StringType:
(key,item)=self._EncodeKeyValues(key, [item])
self.data[key]=item
else:
assert isinstance(item, list)
self.data[key]=item
def keys(self):
return [self._DecodeKey(key) for key in self.data.keys()]
def CreateAuthenticator():
"""Create a packet autenticator.
All RADIUS packets contain a sixteen byte authenticator which
is used to authenticate replies from the RADIUS server and in
the password hiding algorithm. This function returns a suitable
random string that can be used as an authenticator.
@return: valid packet authenticator
@rtype: string
"""
data=""
for i in range(16):
data+=chr(random.randrange(0,256))
return data
CreateAuthenticator=staticmethod(CreateAuthenticator)
def CreateID(self):
"""Create a packet ID
All RADIUS requests have a ID which is used to identify
a request. This is used to detect retries and replay
attacks. This function returns a suitable random number
that can be used as ID.
@return: ID number
@rtype: integer
"""
return random.randrange(0,256)
def ReplyPacket(self,attrs=''):
"""Create a ready-to-transmit authentication reply packet
Return a RADIUS packet which can be directly transmitted
to a RADIUS server. This differs with Packet() in how
the authenticator is calculated.
@return: raw packet
@rtype: string
"""
assert(self.authenticator)
assert(self.secret)
#attr=self._PktEncodeAttributes()
#attr=attr+attrs
if self.has_key('Message-Authenticator'):
#self.__delitem__('Message-Authenticator')
self.__setitem__('Message-Authenticator', '\0'*16)
attr=self._PktEncodeAttributes()
header=struct.pack("!BBH", self.code, self.id, (20+len(attr)))
index = attr.find('\0'*16)
#self.__setitem__('Message-Authenticator', hmac.new(self.secret, header + self.authenticator + attr).digest())
attr = attr[:index] + hmac.new(self.secret, header + self.authenticator + attr).digest() + attr[index + 16:]
else:
attr=self._PktEncodeAttributes()
attr=attr+attrs
header=struct.pack("!BBH", self.code, self.id, (20+len(attr)))
authenticator=md5(header[0:4] + self.authenticator
+ attr + self.secret).digest()
return header + authenticator + attr
def VerifyReply(self, reply, rawreply=None):
if reply.id!=self.id:
return False
if rawreply is None:
rawreply=reply.ReplyPacket()
hash=md5(rawreply[0:4] + self.authenticator +
rawreply[20:] + self.secret).digest()
if hash!=rawreply[4:20]:
return False
return True
def _PktEncodeAttribute(self, key, value):
if type(key)==types.TupleType:
value=struct.pack("!L", key[0]) + self._PktEncodeAttribute(key[1], value)
key=26
try:
return "%s%s" % (str(struct.pack("!BB", int(key), len(value)+2)), str(value))
except:
print key, value, type(key), type(value)
return ""
def _PktEncodeAttributes(self):
result=""
for (code, datalst) in self.items():
for data in datalst:
result+=self._PktEncodeAttribute(code, data)
return result
def _PktDecodeVendorAttribute(self, data):
# Check if this packet is long enough to be in the
# RFC2865 recommended form
if len(data)<6:
return (26, data)
try:
(vendor, type, length)=struct.unpack("!LBB", data[:6])[0:3]
except struct.error:
raise PacketError, "Vender attribute header is corrupt"
# Another sanity check
if len(data)!=length+4:
return (26,data)
return ((vendor,type), data[6:])
def DecodePacket(self, packet):
"""Initialize the object from raw packet data.
Decode a packet as received from the network and decode
it.
@param packet: raw packet
@type packet: string"""
try:
(self.code, self.id, length, self.authenticator)=struct.unpack("!BBH16s", packet[0:20])
except struct.error:
raise PacketError, "Packet header is corrupt"
if len(packet)!=length:
raise PacketError, "Packet has invalid length"
if length>8192:
raise PacketError, "Packet length is too long (%d)" % length
self.clear()
packet=packet[20:]
while packet:
try:
(key, attrlen)=struct.unpack("!BB", packet[0:2])
except struct.error:
raise PacketError, "Attribute header is corrupt"
if attrlen<2:
raise PacketError, "Attribute length is too small (%d)" % attrlen
value=packet[2:attrlen]
if key==26:
(key,value)=self._PktDecodeVendorAttribute(value)
if self.data.has_key(key):
self.data[key].append(value)
else:
self.data[key]=[value]
packet=packet[attrlen:]
def __repr__(self):
try:
return '\n '.join((name + str(item) for name, item in (('code: ', self.code), ('id: ', self.id),\
('secret: ', self.secret), ('authenticator: ', self.authenticator.encode("hex")), \
('packet: ', ' \n '.join((str(self._DecodeKey(key))+ ': ' + (str(self[self._DecodeKey(key)][0].encode("hex")) if str(self._DecodeKey(key)).startswith("MS-CHAP")==True else str(self[self._DecodeKey(key)][0])) for key, value in self.iteritems()))))))
except:
return 'Buggy packet %s ' % self.id
class AuthPacket(Packet):
def __init__(self, code=AccessRequest, id=None, secret="", authenticator=None, **attributes):
Packet.__init__(self, code, id, secret, authenticator, **attributes)
def CreateReply(self, **attributes):
return AuthPacket(AccessAccept, self.id,
self.secret, self.authenticator, dict=self.dict,
**attributes)
def RequestPacket(self):
attr=self._PktEncodeAttributes()
if self.authenticator==None:
self.authenticator=self.CreateAuthenticator()
if self.id==None:
self.id=self.CreateID()
header=struct.pack("!BBH16s", self.code, self.id, (20+len(attr)), self.authenticator)
return header+attr
class AcctPacket(Packet):
def __init__(self, code=AccountingRequest, id=None, secret="", authenticator=None, **attributes):
Packet.__init__(self, code, id, secret, authenticator, **attributes)
if attributes.has_key("packet"):
self.raw_packet=attributes["packet"]
def CreateReply(self, **attributes):
return AcctPacket(AccountingResponse, self.id,
self.secret, self.authenticator, dict=self.dict,
**attributes)
def VerifyAcctRequest(self):
assert(self.raw_packet)
hash=md5(self.raw_packet[0:4] + 16*"\x00" +
self.raw_packet[20:] + self.secret).digest()
return hash==self.authenticator
def RequestPacket(self):
"""Create a ready-to-transmit authentication request packet
Return a RADIUS packet which can be directly transmitted
to a RADIUS server.
@return: raw packet
@rtype: string
"""
attr=self._PktEncodeAttributes()
if self.id is None:
self.id=self.CreateID()
header=struct.pack("!BBH", self.code, self.id, (20+len(attr)))
self.authenticator=md5(header[0:4] + 16 * "\x00" + attr
+ self.secret).digest()
return header + self.authenticator + attr
def CreateID():
"""Generate a packet ID.
@return: packet ID
@rtype: 8 bit integer
"""
global CurrentID
CurrentID=(CurrentID+1)%256
return CurrentID