Implement a basic SNMP listener

All community strings are logged as they are sent to the server.
This initial implementation only supports SNMPv1 and SNMPv2c.

`pyasn1` is required for this server to function.

Responder.conf

@@ -15,6 +15,7 @@ DNS = On
 LDAP = On
 DCERPC = On
 WINRM = On
+SNMP = Off
 
 ; Custom challenge. 
 ; Use "Random" for generating a random challenge for each requests (Default)

Responder.py

@@ -365,6 +365,10 @@ def main():
 			threads.append(Thread(target=serve_thread_udp, args=('', 53, DNS,)))
 			threads.append(Thread(target=serve_thread_tcp, args=(settings.Config.Bind_To, 53, DNSTCP,)))
 
+		if settings.Config.SNMP_On_Off:
+			from servers.SNMP import SNMP
+			threads.append(Thread(target=serve_thread_udp, args=('', 161, SNMP,)))
+
 		for thread in threads:
 			thread.daemon = True
 			thread.start()

servers/SNMP.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python
+# This file is part of Responder, a network take-over set of tools
+# created and maintained by Laurent Gaffie.
+# email: laurent.gaffie@gmail.com
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+from utils import *
+
+if settings.Config.PY2OR3 == "PY3":
+    from socketserver import BaseRequestHandler
+else:
+    from SocketServer import BaseRequestHandler
+
+from pyasn1.codec.der.decoder import decode
+
+
+class SNMP(BaseRequestHandler):
+    def handle(self):
+        data = self.request[0]
+        received_record, rest_of_substrate = decode(data)
+
+        snmp_version = int(received_record['field-0'])
+
+        if snmp_version > 1:
+            # TODO: Add support for SNMPv3 (which will have a field-0 value of 2)
+            print(text("[SNMP] Unsupported SNMPv3 request received from %s" % self.client_address[0].replace("::ffff:","")))
+            return
+
+        community_string = str(received_record['field-1'])
+
+        SaveToDb(
+            {
+                "module": "SNMP",
+                "type": "Cleartext",
+                "client": self.client_address[0],
+                "user": community_string,
+                "cleartext": community_string,
+                "fullhash": community_string,
+            }
+        )

settings.py

@@ -99,6 +99,7 @@ class Settings:
 		self.DCERPC_On_Off   = self.toBool(config.get('Responder Core', 'DCERPC'))
 		self.WinRM_On_Off    = self.toBool(config.get('Responder Core', 'WINRM'))
 		self.Krb_On_Off      = self.toBool(config.get('Responder Core', 'Kerberos'))
+		self.SNMP_On_Off     = self.toBool(config.get('Responder Core', 'SNMP'))
 
 		# Db File
 		self.DatabaseFile    = os.path.join(self.ResponderPATH, config.get('Responder Core', 'Database'))
@@ -178,6 +179,7 @@ class Settings:
 		self.SMBClearLog     = os.path.join(self.LogDir, 'SMB-Clear-Text-Password-%s.txt')
 		self.SMTPClearLog    = os.path.join(self.LogDir, 'SMTP-Clear-Text-Password-%s.txt')
 		self.MSSQLClearLog   = os.path.join(self.LogDir, 'MSSQL-Clear-Text-Password-%s.txt')
+		self.SNMPLog         = os.path.join(self.LogDir, 'SNMP-Clear-Text-Password-%s.txt')
 
 		self.LDAPNTLMv1Log   = os.path.join(self.LogDir, 'LDAP-NTLMv1-Client-%s.txt')
 		self.HTTPNTLMv1Log   = os.path.join(self.LogDir, 'HTTP-NTLMv1-Client-%s.txt')

utils.py

@@ -509,6 +509,7 @@ def StartupMessage():
 	print('    %-27s' % "RDP server" + (enabled if settings.Config.RDP_On_Off else disabled))
 	print('    %-27s' % "DCE-RPC server" + (enabled if settings.Config.DCERPC_On_Off else disabled))
 	print('    %-27s' % "WinRM server" + (enabled if settings.Config.WinRM_On_Off else disabled))
+	print('    %-27s' % "SNMP server" + (enabled if settings.Config.SNMP_On_Off else disabled))
 	print('')
 
 	print(color("[+] ", 2, 1) + "HTTP Options:")