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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2019, Ilya Etingof <etingof@gmail.com>
# License: http://snmplabs.com/pysnmp/license.html
#
import random
try:
from hashlib import md5, sha1
except ImportError:
import md5
import sha
md5 = md5.new
sha1 = sha.new
from sys import version_info
try:
from pysnmpcrypto import des, PysnmpCryptoError
except ImportError:
PysnmpCryptoError = AttributeError
des = None
from pysnmp.proto.secmod.rfc3414.priv import base
from pysnmp.proto.secmod.rfc3414.auth import hmacmd5, hmacsha
from pysnmp.proto.secmod.rfc3414 import localkey
from pysnmp.proto.secmod.rfc7860.auth import hmacsha2
from pysnmp.proto import errind, error
from pyasn1.type import univ
random.seed()
# 8.2.4
class Des(base.AbstractEncryptionService):
serviceID = (1, 3, 6, 1, 6, 3, 10, 1, 2, 2) # usmDESPrivProtocol
keySize = 16
if version_info < (2, 3):
_localInt = int(random.random() * 0xffffffff)
else:
_localInt = random.randrange(0, 0xffffffff)
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]
# 8.1.1.1
def __getEncryptionKey(self, privKey, snmpEngineBoots):
desKey = privKey[:8]
preIV = privKey[8:16]
securityEngineBoots = int(snmpEngineBoots)
salt = [securityEngineBoots >> 24 & 0xff,
securityEngineBoots >> 16 & 0xff,
securityEngineBoots >> 8 & 0xff,
securityEngineBoots & 0xff,
self._localInt >> 24 & 0xff,
self._localInt >> 16 & 0xff,
self._localInt >> 8 & 0xff,
self._localInt & 0xff]
if self._localInt == 0xffffffff:
self._localInt = 0
else:
self._localInt += 1
return (desKey.asOctets(),
univ.OctetString(salt).asOctets(),
univ.OctetString(map(lambda x, y: x ^ y, salt, preIV.asNumbers())).asOctets())
@staticmethod
def __getDecryptionKey(privKey, salt):
return (privKey[:8].asOctets(),
univ.OctetString(map(lambda x, y: x ^ y, salt.asNumbers(), privKey[8:16].asNumbers())).asOctets())
# 8.2.4.1
def encryptData(self, encryptKey, privParameters, dataToEncrypt):
snmpEngineBoots, snmpEngineTime, salt = privParameters
# 8.3.1.1
desKey, salt, iv = self.__getEncryptionKey(
encryptKey, snmpEngineBoots
)
# 8.3.1.2
privParameters = univ.OctetString(salt)
# 8.1.1.2
plaintext = dataToEncrypt + univ.OctetString((0,) * (8 - len(dataToEncrypt) % 8)).asOctets()
try:
ciphertext = des.encrypt(plaintext, desKey, iv)
except PysnmpCryptoError:
raise error.StatusInformation(
errorIndication=errind.unsupportedPrivProtocol
)
# 8.3.1.3 & 4
return univ.OctetString(ciphertext), privParameters
# 8.2.4.2
def decryptData(self, decryptKey, privParameters, encryptedData):
snmpEngineBoots, snmpEngineTime, salt = privParameters
# 8.3.2.1
if len(salt) != 8:
raise error.StatusInformation(
errorIndication=errind.decryptionError
)
# 8.3.2.2 no-op
# 8.3.2.3
desKey, iv = self.__getDecryptionKey(decryptKey, salt)
# 8.3.2.4 -> 8.1.1.3
if len(encryptedData) % 8 != 0:
raise error.StatusInformation(
errorIndication=errind.decryptionError
)
try:
# 8.3.2.6
return des.decrypt(encryptedData.asOctets(), desKey, iv)
except PysnmpCryptoError:
raise error.StatusInformation(
errorIndication=errind.unsupportedPrivProtocol
)
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