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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2018, Olivier Verriest <verri@x25.pm>
# License: http://snmplabs.com/pysnmp/license.html
#
import sys
import hmac
try:
from hashlib import sha224, sha256, sha384, sha512
except ImportError:
class NotAvailable(object):
def __call__(self, *args, **kwargs):
raise errind.authenticationError
sha224 = sha256 = sha384 = sha512 = NotAvailable()
from pyasn1.type import univ
from pysnmp.proto.secmod.rfc3414.auth import base
from pysnmp.proto.secmod.rfc3414 import localkey
from pysnmp.proto import errind, error
# 7.2.4
class HmacSha2(base.AbstractAuthenticationService):
SHA224_SERVICE_ID = (1, 3, 6, 1, 6, 3, 10, 1, 1, 4) # usmHMAC128SHA224AuthProtocol
SHA256_SERVICE_ID = (1, 3, 6, 1, 6, 3, 10, 1, 1, 5) # usmHMAC192SHA256AuthProtocol
SHA384_SERVICE_ID = (1, 3, 6, 1, 6, 3, 10, 1, 1, 6) # usmHMAC256SHA384AuthProtocol
SHA512_SERVICE_ID = (1, 3, 6, 1, 6, 3, 10, 1, 1, 7) # usmHMAC384SHA512AuthProtocol
KEY_LENGTH = {
SHA224_SERVICE_ID: 28,
SHA256_SERVICE_ID: 32,
SHA384_SERVICE_ID: 48,
SHA512_SERVICE_ID: 64
}
DIGEST_LENGTH = {
SHA224_SERVICE_ID: 16,
SHA256_SERVICE_ID: 24,
SHA384_SERVICE_ID: 32,
SHA512_SERVICE_ID: 48
}
HASH_ALGORITHM = {
SHA224_SERVICE_ID: sha224,
SHA256_SERVICE_ID: sha256,
SHA384_SERVICE_ID: sha384,
SHA512_SERVICE_ID: sha512
}
IPAD = [0x36] * 64
OPAD = [0x5C] * 64
def __init__(self, oid):
if oid not in self.HASH_ALGORITHM:
raise error.ProtocolError('No SHA-2 authentication algorithm %s available' % (oid,))
self.__hashAlgo = self.HASH_ALGORITHM[oid]
self.__digestLength = self.DIGEST_LENGTH[oid]
self.__placeHolder = univ.OctetString((0,) * self.__digestLength).asOctets()
def hashPassphrase(self, authKey):
return localkey.hashPassphrase(authKey, self.__hashAlgo)
def localizeKey(self, authKey, snmpEngineID):
return localkey.localizeKey(authKey, snmpEngineID, self.__hashAlgo)
@property
def digestLength(self):
return self.__digestLength
# 7.3.1
def authenticateOutgoingMsg(self, authKey, wholeMsg):
# 7.3.1.1
location = wholeMsg.find(self.__placeHolder)
if location == -1:
raise error.ProtocolError('Can\'t locate digest placeholder')
wholeHead = wholeMsg[:location]
wholeTail = wholeMsg[location + self.__digestLength:]
# 7.3.1.2, 7.3.1.3
try:
mac = hmac.new(authKey.asOctets(), wholeMsg, self.__hashAlgo)
except errind.ErrorIndication as exc:
raise error.StatusInformation(errorIndication=exc)
# 7.3.1.4
mac = mac.digest()[:self.__digestLength]
# 7.3.1.5 & 6
return wholeHead + mac + wholeTail
# 7.3.2
def authenticateIncomingMsg(self, authKey, authParameters, wholeMsg):
# 7.3.2.1 & 2
if len(authParameters) != self.__digestLength:
raise error.StatusInformation(
errorIndication=errind.authenticationError
)
# 7.3.2.3
location = wholeMsg.find(authParameters.asOctets())
if location == -1:
raise error.ProtocolError('Can\'t locate digest in wholeMsg')
wholeHead = wholeMsg[:location]
wholeTail = wholeMsg[location + self.__digestLength:]
authenticatedWholeMsg = wholeHead + self.__placeHolder + wholeTail
# 7.3.2.4
try:
mac = hmac.new(authKey.asOctets(), authenticatedWholeMsg, self.__hashAlgo)
except errind.ErrorIndication as exc:
raise error.StatusInformation(errorIndication=exc)
# 7.3.2.5
mac = mac.digest()[:self.__digestLength]
# 7.3.2.6
if mac != authParameters:
raise error.StatusInformation(
errorIndication=errind.authenticationFailure
)
return authenticatedWholeMsg
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