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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2018, Ilya Etingof <etingof@gmail.com>
# License: http://snmplabs.com/pysnmp/license.html
#
import random
from pyasn1.type import univ
from pysnmp.crypto import aes
from pysnmp.proto.secmod.rfc3414.priv import base
from pysnmp.proto.secmod.rfc3414.auth import hmacmd5, hmacsha
from pysnmp.proto.secmod.rfc7860.auth import hmacsha2
from pysnmp.proto.secmod.rfc3414 import localkey
from pysnmp.proto import errind, error
try:
from hashlib import md5, sha1
except ImportError:
import md5
import sha
md5 = md5.new
sha1 = sha.new
random.seed()
# RFC3826
#
class Aes(base.AbstractEncryptionService):
serviceID = (1, 3, 6, 1, 6, 3, 10, 1, 2, 4) # usmAesCfb128Protocol
keySize = 16
_localInt = random.randrange(0, 0xffffffffffffffff)
# 3.1.2.1
def __getEncryptionKey(self, privKey, snmpEngineBoots, snmpEngineTime):
salt = [self._localInt >> 56 & 0xff,
self._localInt >> 48 & 0xff,
self._localInt >> 40 & 0xff,
self._localInt >> 32 & 0xff,
self._localInt >> 24 & 0xff,
self._localInt >> 16 & 0xff,
self._localInt >> 8 & 0xff,
self._localInt & 0xff]
if self._localInt == 0xffffffffffffffff:
self._localInt = 0
else:
self._localInt += 1
return self.__getDecryptionKey(privKey, snmpEngineBoots, snmpEngineTime, salt) + (
univ.OctetString(salt).asOctets(),)
def __getDecryptionKey(self, privKey, snmpEngineBoots,
snmpEngineTime, salt):
snmpEngineBoots, snmpEngineTime, salt = (
int(snmpEngineBoots), int(snmpEngineTime), salt
)
iv = [snmpEngineBoots >> 24 & 0xff,
snmpEngineBoots >> 16 & 0xff,
snmpEngineBoots >> 8 & 0xff,
snmpEngineBoots & 0xff,
snmpEngineTime >> 24 & 0xff,
snmpEngineTime >> 16 & 0xff,
snmpEngineTime >> 8 & 0xff,
snmpEngineTime & 0xff] + salt
return privKey[:self.keySize].asOctets(), univ.OctetString(iv).asOctets()
def hashPassphrase(self, authProtocol, privKey):
if authProtocol == hmacmd5.HmacMd5.serviceID:
hashAlgo = md5
elif authProtocol == hmacsha.HmacSha.serviceID:
hashAlgo = sha1
elif authProtocol in hmacsha2.HmacSha2.hashAlgorithms:
hashAlgo = hmacsha2.HmacSha2.hashAlgorithms[authProtocol]
else:
raise error.ProtocolError(
'Unknown auth protocol %s' % (authProtocol,)
)
return localkey.hashPassphrase(privKey, hashAlgo)
def localizeKey(self, authProtocol, privKey, snmpEngineID):
if authProtocol == hmacmd5.HmacMd5.serviceID:
hashAlgo = md5
elif authProtocol == hmacsha.HmacSha.serviceID:
hashAlgo = sha1
elif authProtocol in hmacsha2.HmacSha2.hashAlgorithms:
hashAlgo = hmacsha2.HmacSha2.hashAlgorithms[authProtocol]
else:
raise error.ProtocolError(
'Unknown auth protocol %s' % (authProtocol,)
)
localPrivKey = localkey.localizeKey(privKey, snmpEngineID, hashAlgo)
return localPrivKey[:self.keySize]
# 3.2.4.1
def encryptData(self, encryptKey, privParameters, dataToEncrypt):
snmpEngineBoots, snmpEngineTime, salt = privParameters
# 3.3.1.1
aesKey, iv, salt = self.__getEncryptionKey(
encryptKey, snmpEngineBoots, snmpEngineTime
)
# 3.3.1.3
# PyCrypto seems to require padding
dataToEncrypt = dataToEncrypt + univ.OctetString((0,) * (16 - len(dataToEncrypt) % 16)).asOctets()
ciphertext = aes.encrypt(dataToEncrypt, aesKey, iv)
# 3.3.1.4
return univ.OctetString(ciphertext), univ.OctetString(salt)
# 3.2.4.2
def decryptData(self, decryptKey, privParameters, encryptedData):
snmpEngineBoots, snmpEngineTime, salt = privParameters
# 3.3.2.1
if len(salt) != 8:
raise error.StatusInformation(
errorIndication=errind.decryptionError
)
# 3.3.2.3
aesKey, iv = self.__getDecryptionKey(
decryptKey, snmpEngineBoots, snmpEngineTime, salt
)
# PyCrypto seems to require padding
encryptedData = encryptedData + univ.OctetString((0,) * (16 - len(encryptedData) % 16)).asOctets()
# 3.3.2.4-6
return aes.decrypt(encryptedData.asOctets(), aesKey, iv)
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