Make trunk encryption optional

.travis.yml

@@ -8,13 +8,12 @@ matrix:
   - os: linux
     dist: trusty
     python: '2.7'
-# pycryptodomex seems to fail on AES import
-#  - os: linux
-#    dist: trusty
-#    python: '3.2'
-#  - os: linux
-#    dist: trusty
-#    python: '3.3'
+  - os: linux
+    dist: trusty
+    python: '3.2'
+  - os: linux
+    dist: trusty
+    python: '3.3'
   - os: linux
     dist: trusty
     python: '3.4'

CHANGES.txt

@@ -2,7 +2,7 @@
 Revision 0.4.5, released XX-01-2019
 -----------------------------------
 
-No changes so far
+- Trunk encryption (and therefore `pycryptodomex` package) made optional
 
 Revision 0.4.4, released 30-12-2018
 -----------------------------------

optional-requirements.txt

@@ -0,0 +1 @@
+pycryptodomex

requirements.txt

@@ -1,2 +1 @@
-pycryptodomex
 pysnmp>=4.4.3,<5.0.0

snmpfwd/trunking/crypto.py

@@ -4,30 +4,53 @@
 # Copyright (c) 2014-2019, Ilya Etingof <etingof@gmail.com>
 # License: http://snmplabs.com/snmpfwd/license.html
 #
-from Cryptodome import Random
-from Cryptodome.Cipher import AES
-from pyasn1.compat.octets import int2oct, oct2int, str2octs
+try:
+    from Cryptodome import Random
+    from Cryptodome.Cipher import AES
 
+    from pyasn1.compat.octets import int2oct, oct2int, str2octs
 
-class AESCipher(object):
-    @staticmethod
-    def pad(s, BS=16):
-        return s + (BS - len(s) % BS) * int2oct(BS - len(s) % BS)
+except ImportError:
 
-    @staticmethod
-    def unpad(s):
-        return s[0:-oct2int(s[-1])]
+    from snmpfwd.error import SnmpfwdError
 
-    def encrypt(self, key, raw):
-        raw = self.pad(raw)
-        iv = Random.new().read(AES.block_size)
-        cipher = AES.new(str2octs(key), AES.MODE_CBC, iv)
-        return iv + cipher.encrypt(raw) 
 
-    def decrypt(self, key, enc):
-        iv = enc[:16]
-        cipher = AES.new(str2octs(key), AES.MODE_CBC, iv)
-        return self.unpad(cipher.decrypt(enc[16:]))
+    class NoCipher(object):
+        msg = ('Trunk encryption is not available. Make sure '
+               'to install the `pycryptodomex` package')
 
-encrypt = AESCipher().encrypt
-decrypt = AESCipher().decrypt
+        def encrypt(self, key, raw):
+            raise SnmpfwdError(self.msg)
+
+        def decrypt(self, key, raw):
+            raise SnmpfwdError(self.msg)
+
+    Cipher = NoCipher
+
+else:
+
+    class AESCipher(object):
+        @staticmethod
+        def pad(s, BS=16):
+            return s + (BS - len(s) % BS) * int2oct(BS - len(s) % BS)
+
+        @staticmethod
+        def unpad(s):
+            return s[0:-oct2int(s[-1])]
+
+        def encrypt(self, key, raw):
+            raw = self.pad(raw)
+            iv = Random.new().read(AES.block_size)
+            cipher = AES.new(str2octs(key), AES.MODE_CBC, iv)
+            return iv + cipher.encrypt(raw)
+
+        def decrypt(self, key, enc):
+            iv = enc[:16]
+            cipher = AES.new(str2octs(key), AES.MODE_CBC, iv)
+            return self.unpad(cipher.decrypt(enc[16:]))
+
+    Cipher = AESCipher
+
+
+encrypt = Cipher().encrypt
+decrypt = Cipher().decrypt