add Date header support to SMTP deliver

the SMTP mixin now supports the Date header.
The user can supply a a value for the Date Header
or else it will automatically use the current local
DateTime. This will help alleviate certain issues
caused by servers setting this field for the cliebnt incorrectly

MSP-9390

lib/msf/core/exploit/smtp_deliver.rb

@@ -26,6 +26,7 @@ module Exploit::Remote::SMTPDeliver
       [
         OptAddress.new("RHOST", [ true, "The SMTP server to send through" ]),
         OptPort.new("RPORT", [ true, "The SMTP server port (e.g. 25, 465, 587, 2525)", 25 ]),
+        OptString.new('DATE', [false, 'Override the DATE: field with this value', '']),
         OptString.new('MAILFROM', [ true, 'The FROM address of the e-mail', 'random@example.com' ]),
         OptString.new('MAILTO', [ true, 'The TO address of the email' ]),
         OptString.new('SUBJECT', [ true, 'Subject line of the email' ]),
@@ -140,6 +141,14 @@ module Exploit::Remote::SMTPDeliver
     raw_send_recv("MAIL FROM: <#{datastore['MAILFROM']}>\r\n", nsock)
     raw_send_recv("RCPT TO: <#{datastore['MAILTO']}>\r\n", nsock)
 
+    # If the user supplied a Date field, use that, else use the current
+    # DateTime in the propper RFC2822 format.
+    if datastore['DATE'].present?
+      raw_send_recv("Date: #{datastore['DATE']}\r\n", nsock)
+    else
+      raw_send_recv("Date: #{DateTime.now.rfc2822}\r\n", nsock)
+    end
+
     resp = raw_send_recv("DATA\r\n", nsock)
 
     # Avoid sending tons of data and killing the connection if the server