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import random, string
from pysnmp.proto.secmod.rfc3414.priv import base
from pyasn1.type import univ
from pysnmp.proto import error
try:
from Crypto.Cipher import DES
except ImportError:
DES = None
random.seed()
# 8.2.4
class Des(base.AbstractEncryptionService):
serviceID = (1, 3, 6, 1, 6, 3, 10, 1, 2, 2) # usmDESPrivProtocol
_localInt = long(random.random()*0xffffffff)
# 8.1.1.1
def __getEncryptionKey(self, mibInstrumController, privKey):
desKey = privKey[:8]
preIV = privKey[8:16]
snmpEngineBoots, = mibInstrumController.mibBuilder.importSymbols(
'SNMP-FRAMEWORK-MIB', 'snmpEngineBoots'
)
securityEngineBoots = long(snmpEngineBoots.syntax)
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 = self._localInt + 1
return desKey, \
string.join(map(lambda x: chr(x), salt), ''), \
string.join(map(lambda x,y: chr(x^ord(y)), salt, preIV), '')
def __getDecryptionKey(self, mibInstrumController, privKey, salt):
return privKey[:8], string.join(
map(lambda x,y: chr(ord(x)^ord(y)), salt, privKey[8:16]), ''
)
# 8.2.4.1
def encryptData(self, mibInstrumController, encryptKey, dataToEncrypt):
if DES is None:
raise error.StatusInformation(
errorIndication='encryptionError'
)
# 8.3.1.1
desKey, salt, iv = self.__getEncryptionKey(
mibInstrumController, str(encryptKey)
)
# 8.3.1.2
privParameters = univ.OctetString(salt)
# 8.1.1.2
desObj = DES.new(desKey, DES.MODE_CBC, iv) # XXX
plaintext = dataToEncrypt + '\x00' * (8 - len(dataToEncrypt) % 8)
ciphertext = desObj.encrypt(plaintext)
# 8.3.1.3 & 4
return univ.OctetString(ciphertext), privParameters
# 8.2.4.2
def decryptData(self, mibInstrumController, decryptKey,
privParameters, encryptedData):
if DES is None:
raise error.StatusInformation(
errorIndication='decryptionError'
)
# 8.3.2.1
if len(privParameters) != 8:
raise error.StatusInformation(
errorIndication='decryptionError'
)
# 8.3.2.2
salt = str(privParameters)
# 8.3.2.3
desKey, iv = self.__getDecryptionKey(
mibInstrumController, str(decryptKey), salt
)
# 8.3.2.4 -> 8.1.1.3
if len(encryptedData) % 8 != 0:
raise error.StatusInformation(
errorIndication='decryptionError'
)
desObj = DES.new(desKey, DES.MODE_CBC, iv)
# 8.3.2.6
return desObj.decrypt(str(encryptedData))
if __name__ == '__main__':
from pysnmp.smi import builder, instrum
mibInstrumController = instrum.MibInstrumController(
builder.MibBuilder()
)
d = Des()
ct, p = d.encryptData(mibInstrumController, '1234567890123456', 'security? not my problem!')
print d.decryptData(mibInstrumController, '1234567890123456', p, ct)
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