Reeder key localization for AES192/256 encryption implemented

6 files changed, 84 insertions, 4 deletions

diff --git a/CHANGES.txt b/CHANGES.txt
index 7f6977e9..305ba88c 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -9,6 +9,12 @@ Github `repo <https://github.com/etingof/pysnmp>`_
   MIB objects. A side effect of this change is that additional
   var-binds can only be added prior to .resolveMibObjects() is
   run.
+- Non-standard (but apparently used by many vendors) Reeder AES192/256
+  key localization algorithm implemented and set as default for
+  usmAesCfb192Protocol and usmAesCfb256Protocol identifiers.
+  Original and more standard implementation can still be used
+  with the usmAesBlumenthalCfb192Protocol and
+  usmAesBlumenthalCfb192Protocol IDs respectively.
 - Fix to NotificationType to make additional var-binds overriding
   MIB objects implicitly included through NOTIFICATION-TYPE OBJECTS.
 - Fix to SNMP engine boots counter persistence on Python 3.
diff --git a/pysnmp/entity/config.py b/pysnmp/entity/config.py
index 10acd25b..13e284f1 100644
--- a/pysnmp/entity/config.py
+++ b/pysnmp/entity/config.py
@@ -29,8 +29,10 @@ usmNoAuthProtocol = noauth.NoAuth.serviceID
 usmDESPrivProtocol = des.Des.serviceID
 usm3DESEDEPrivProtocol = des3.Des3.serviceID
 usmAesCfb128Protocol = aes.Aes.serviceID
-usmAesCfb192Protocol = aes192.Aes192.serviceID
-usmAesCfb256Protocol = aes256.Aes256.serviceID
+usmAesBlumenthalCfb192Protocol = aes192.Aes192.serviceID  # semi-standard but not widely used
+usmAesBlumenthalCfb256Protocol = aes256.Aes256.serviceID  # semi-standard but not widely used
+usmAesCfb192Protocol = aes192.AesReeder192.serviceID  # non-standard but used by many vendors
+usmAesCfb256Protocol = aes256.AesReeder256.serviceID  # non-standard but used by many vendors
 usmNoPrivProtocol = nopriv.NoPriv.serviceID
 
 # Auth services
@@ -44,6 +46,8 @@ privServices = {des.Des.serviceID: des.Des(),
                 aes.Aes.serviceID: aes.Aes(),
                 aes192.Aes192.serviceID: aes192.Aes192(),
                 aes256.Aes256.serviceID: aes256.Aes256(),
+                aes192.AesReeder192.serviceID: aes192.AesReeder192(),  # non-standard
+                aes256.AesReeder256.serviceID: aes256.AesReeder256(),  # non-standard
                 nopriv.NoPriv.serviceID: nopriv.NoPriv()}
 
 
diff --git a/pysnmp/proto/secmod/eso/priv/aes192.py b/pysnmp/proto/secmod/eso/priv/aes192.py
index 0de69551..7ff2fb25 100644
--- a/pysnmp/proto/secmod/eso/priv/aes192.py
+++ b/pysnmp/proto/secmod/eso/priv/aes192.py
@@ -8,9 +8,26 @@ from pysnmp.proto.secmod.eso.priv import aesbase
 
 
 class Aes192(aesbase.AbstractAes):
-    """AES 192/256 bit encryption (Internet draft)
+    """AES 192 bit encryption (Internet draft)
+
+       Reeder AES encryption:
 
        http://tools.ietf.org/html/draft-blumenthal-aes-usm-04
     """
     serviceID = (1, 3, 6, 1, 4, 1, 9, 12, 6, 1, 1)  # cusmAESCfb192PrivProtocol
     keySize = 24
+
+
+class AesReeder192(aesbase.AbstractAesReeder):
+    """AES 192 bit encryption (Internet draft)
+
+    Reeder AES encryption with non-standard key localization algorithm
+    borrowed from Reeder 3DES draft:
+
+    http://tools.ietf.org/html/draft-blumenthal-aes-usm-04
+    https://tools.ietf.org/html/draft-reeder-snmpv3-usm-3desede-00
+
+    Known to be used by many vendors including Cisco and others.
+    """
+    serviceID = (1, 3, 6, 1, 4, 1, 9, 12, 6, 1, 101)  # cusmAESCfb192PrivProtocol (non-standard)
+    keySize = 24
diff --git a/pysnmp/proto/secmod/eso/priv/aes256.py b/pysnmp/proto/secmod/eso/priv/aes256.py
index c6ec1ab9..6a3885fa 100644
--- a/pysnmp/proto/secmod/eso/priv/aes256.py
+++ b/pysnmp/proto/secmod/eso/priv/aes256.py
@@ -8,9 +8,24 @@ from pysnmp.proto.secmod.eso.priv import aesbase
 
 
 class Aes256(aesbase.AbstractAes):
-    """AES 192/256 bit encryption (Internet draft)
+    """AES 256 bit encryption (Internet draft)
 
        http://tools.ietf.org/html/draft-blumenthal-aes-usm-04
     """
     serviceID = (1, 3, 6, 1, 4, 1, 9, 12, 6, 1, 2)  # cusmAESCfb256PrivProtocol
     keySize = 32
+
+
+class AesReeder256(aesbase.AbstractAesReeder):
+    """AES 256 bit encryption (Internet draft)
+
+    Reeder AES encryption with non-standard key localization algorithm
+    borrowed from Reeder 3DES draft:
+
+    http://tools.ietf.org/html/draft-blumenthal-aes-usm-04
+    https://tools.ietf.org/html/draft-reeder-snmpv3-usm-3desede-00
+
+    Known to be used by many vendors including Cisco and others.
+    """
+    serviceID = (1, 3, 6, 1, 4, 1, 9, 12, 6, 1, 102)  # cusmAESCfb256PrivProtocol (non-standard)
+    keySize = 32
diff --git a/pysnmp/proto/secmod/eso/priv/aesbase.py b/pysnmp/proto/secmod/eso/priv/aesbase.py
index bd0a19ec..fd484265 100644
--- a/pysnmp/proto/secmod/eso/priv/aesbase.py
+++ b/pysnmp/proto/secmod/eso/priv/aesbase.py
@@ -41,3 +41,39 @@ class AbstractAes(aes.Aes):
                 'Unknown auth protocol %s' % (authProtocol,)
             )
         return localPrivKey[:self.keySize]
+
+
+class AbstractAesReeder(AbstractAes):
+    """AES encryption with non-standard key localization.
+
+    Cisco devices do not use:
+
+    https://tools.itef.org/pdf/draft_bluementhal-aes-usm-04.txt
+
+    for key localization instead, they use the procedure for 3DES key localization
+    specified in:
+
+    https://tools.itef.org/pdf/draft_reeder_snmpv3-usm-3desede-00.pdf
+
+    The difference between the two is that the Reeder draft does key extension by repeating
+    the steps in the password to key algorithm (hash phrase, then localize with SNMPEngine ID).
+    """
+
+    # 2.1 of https://tools.itef.org/pdf/draft_bluementhal-aes-usm-04.txt
+    def localizeKey(self, authProtocol, privKey, snmpEngineID):
+        if authProtocol == hmacmd5.HmacMd5.serviceID:
+            localPrivKey = localkey.localizeKeyMD5(privKey, snmpEngineID)
+            # now extend this key if too short by repeating steps that includes the hashPassphrase step
+            while len(localPrivKey) < self.keySize:
+                newKey = hashPassphraseMD5(localPrivKey)  # this is the difference between reeder and bluementhal
+                localPrivKey += localizeKeyMD5(newKey, snmpEngineID)
+        elif authProtocol == hmacsha.HmacSha.serviceID:
+            localPrivKey = localkey.localizeKeySHA(privKey, snmpEngineID)
+            while len(localPrivKey < self.keySize):
+                newKey = hashPassphraseSHA(localPrivKey)
+                localPrivKey += localizeKeySHA(newKey, snmpEngineID)
+        else:
+            raise error.ProtocolError(
+                'Unknown auth protocol %s' % (authProtocol,)
+            )
+        return localPrivKey[:self.keySize]
diff --git a/pysnmp/proto/secmod/rfc3414/service.py b/pysnmp/proto/secmod/rfc3414/service.py
index 415ee827..401558f5 100644
--- a/pysnmp/proto/secmod/rfc3414/service.py
+++ b/pysnmp/proto/secmod/rfc3414/service.py
@@ -46,6 +46,8 @@ class SnmpUSMSecurityModel(AbstractSecurityModel):
                     aes.Aes.serviceID: aes.Aes(),
                     aes192.Aes192.serviceID: aes192.Aes192(),
                     aes256.Aes256.serviceID: aes256.Aes256(),
+                    aes192.AesReeder192.serviceID: aes192.AesReeder192(),  # non-standard
+                    aes256.AesReeder256.serviceID: aes256.AesReeder256(),  # non-standard
                     nopriv.NoPriv.serviceID: nopriv.NoPriv()}
 
     def __init__(self):