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# AES 192/256 bit encryption (Internet draft)
# http://tools.ietf.org/html/draft-blumenthal-aes-usm-04
from pysnmp.proto.secmod.rfc3826.priv import aes
from pysnmp.proto.secmod.rfc3414.auth import hmacmd5, hmacsha
from pysnmp.proto.secmod.rfc3414 import localkey
from pysnmp.proto import error
from math import ceil
try:
from hashlib import md5, sha1
except ImportError:
import md5, sha
md5 = md5.new
sha1 = sha.new
class AbstractAes(aes.Aes):
serviceID = ()
keySize = 0
# 3.1.2.1
def localizeKey(self, authProtocol, privKey, snmpEngineID):
if authProtocol == hmacmd5.HmacMd5.serviceID:
localPrivKey = localkey.localizeKeyMD5(privKey, snmpEngineID)
while ceil(self.keySize/len(localPrivKey)):
localPrivKey = localPrivKey + md5(localPrivKey).digest()
elif authProtocol == hmacsha.HmacSha.serviceID:
localPrivKey = localkey.localizeKeySHA(privKey, snmpEngineID)
while ceil(self.keySize/len(localPrivKey)):
localPrivKey = localPrivKey + sha1(localPrivKey).digest()
else:
raise error.ProtocolError(
'Unknown auth protocol %s' % (authProtocol,)
)
return localPrivKey[:self.keySize]
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