1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
|
#
# 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
from hashlib import md5
from hashlib import sha1
try:
from pysnmpcrypto import des3, PysnmpCryptoError
except ImportError:
PysnmpCryptoError = AttributeError
des3 = None
from pysnmp.proto.secmod.rfc3414.priv import base
from pysnmp.proto.secmod.rfc3414.auth import hmacmd5
from pysnmp.proto.secmod.rfc3414.auth import hmacsha
from pysnmp.proto.secmod.rfc3414 import localkey
from pysnmp.proto.secmod.rfc7860.auth import hmacsha2
from pysnmp.proto import errind
from pysnmp.proto import error
from pyasn1.type import univ
random.seed()
# 5.1.1
class Des3(base.AbstractEncryptionService):
"""Reeder 3DES-EDE for USM (Internet draft).
https://tools.ietf.org/html/draft-reeder-snmpv3-usm-3desede-00
"""
SERVICE_ID = (1, 3, 6, 1, 6, 3, 10, 1, 2, 3) # usm3DESEDEPrivProtocol
KEY_SIZE = 32
local_int = random.randrange(0, 0xffffffff)
def hashPassphrase(self, authProtocol, privKey):
if authProtocol == hmacmd5.HmacMd5.SERVICE_ID:
hashAlgo = md5
elif authProtocol == hmacsha.HmacSha.SERVICE_ID:
hashAlgo = sha1
elif authProtocol in hmacsha2.HmacSha2.HASH_ALGORITHM:
hashAlgo = hmacsha2.HmacSha2.HASH_ALGORITHM[authProtocol]
else:
raise error.ProtocolError(
'Unknown auth protocol %s' % (authProtocol,)
)
return localkey.hashPassphrase(privKey, hashAlgo)
# 2.1
def localizeKey(self, authProtocol, privKey, snmpEngineID):
if authProtocol == hmacmd5.HmacMd5.SERVICE_ID:
hashAlgo = md5
elif authProtocol == hmacsha.HmacSha.SERVICE_ID:
hashAlgo = sha1
elif authProtocol in hmacsha2.HmacSha2.HASH_ALGORITHM:
hashAlgo = hmacsha2.HmacSha2.HASH_ALGORITHM[authProtocol]
else:
raise error.ProtocolError(
'Unknown auth protocol %s' % (authProtocol,)
)
localPrivKey = localkey.localizeKey(privKey, snmpEngineID, hashAlgo)
# now extend this key if too short by repeating steps that includes the hashPassphrase step
while len(localPrivKey) < self.KEY_SIZE:
# this is the difference between reeder and bluementhal
newKey = localkey.hashPassphrase(localPrivKey, hashAlgo)
localPrivKey += localkey.localizeKey(newKey, snmpEngineID, hashAlgo)
return localPrivKey[:self.KEY_SIZE]
# 5.1.1.1
def __getEncryptionKey(self, privKey, snmpEngineBoots):
# 5.1.1.1.1
des3Key = privKey[:24]
preIV = privKey[24:32]
securityEngineBoots = int(snmpEngineBoots)
salt = [
securityEngineBoots >> 24 & 0xff,
securityEngineBoots >> 16 & 0xff,
securityEngineBoots >> 8 & 0xff,
securityEngineBoots & 0xff,
self.local_int >> 24 & 0xff,
self.local_int >> 16 & 0xff,
self.local_int >> 8 & 0xff,
self.local_int & 0xff
]
if self.local_int == 0xffffffff:
self.local_int = 0
else:
self.local_int += 1
# salt not yet hashed XXX
return (des3Key.asOctets(),
univ.OctetString(salt).asOctets(),
univ.OctetString(map(lambda x, y: x ^ y, salt, preIV.asNumbers())).asOctets())
@staticmethod
def __getDecryptionKey(privKey, salt):
return (privKey[:24].asOctets(),
univ.OctetString(map(lambda x, y: x ^ y, salt.asNumbers(), privKey[24:32].asNumbers())).asOctets())
# 5.1.1.2
def encryptData(self, encryptKey, privParameters, dataToEncrypt):
snmpEngineBoots, snmpEngineTime, salt = privParameters
des3Key, salt, iv = self.__getEncryptionKey(
encryptKey, snmpEngineBoots
)
privParameters = univ.OctetString(salt)
plaintext = dataToEncrypt + univ.OctetString((0,) * (8 - len(dataToEncrypt) % 8)).asOctets()
try:
ciphertext = des3.encrypt(plaintext, des3Key, iv)
except PysnmpCryptoError:
raise error.StatusInformation(
errorIndication=errind.unsupportedPrivProtocol
)
return univ.OctetString(ciphertext), privParameters
# 5.1.1.3
def decryptData(self, decryptKey, privParameters, encryptedData):
snmpEngineBoots, snmpEngineTime, salt = privParameters
if len(salt) != 8:
raise error.StatusInformation(
errorIndication=errind.decryptionError
)
des3Key, iv = self.__getDecryptionKey(decryptKey, salt)
if len(encryptedData) % 8 != 0:
raise error.StatusInformation(
errorIndication=errind.decryptionError
)
ciphertext = encryptedData.asOctets()
try:
plaintext = des3.decrypt(ciphertext, des3Key, iv)
except PysnmpCryptoError:
raise error.StatusInformation(
errorIndication=errind.unsupportedPrivProtocol
)
return plaintext
|
