check for extra libraries explicitly, fail gracefully

modules/auxiliary/scanner/ssl/bleichenbacher_oracle.py

@@ -9,9 +9,13 @@ import os
 import ssl
 
 # extra modules
-import gmpy2
-from cryptography import x509
-from cryptography.hazmat.backends import default_backend
+dependencies_missing = False
+try:
+    import gmpy2
+    from cryptography import x509
+    from cryptography.hazmat.backends import default_backend
+except ImportError:
+    dependencies_missing = True
 
 from metasploit import module
 
@@ -151,6 +155,10 @@ def oracle(target, pms, cke_2nd_prefix, cipher_handshake=ch_def, messageflow=Fal
 
 
 def run(args):
+    if dependencies_missing:
+        module.log("Module dependencies (gmpy2 and cryptography python libraries) missing, cannot continue", level='error')
+        return
+
     target = (args['rhost'], int(args['rport']))
     timeout = float(args['timeout'])
     cipher_handshake = cipher_handshakes[args['cipher_group']]