emailrelay-edit-envelope.js

//
// SPDX-FileCopyrightText: 2026 Graeme Walker <graeme_walker@users.sourceforge.net>
// SPDX-License-Identifier: FSFAP
//
// Copyright (c) 2026 Graeme Walker <graeme_walker@users.sourceforge.net>
//
// Copying and distribution of this file, with or without modification,
// are permitted in any medium without royalty provided the copyright
// notice and this notice are preserved.  This file is offered as-is,
// without any warranty.
// ===
//
// emailrelay-edit-envelope.js
//
// An example E-MailRelay filter script for Windows that
// edits the message's envelope file.
//
// In this example the "MailFromAuthOut" field in the
// envelope file is modified; this is used as the MAIL FROM
// AUTH parameter when the emailrelay server forwards the
// message to the downstream server. In principle (RFC-2554)
// when relaying the outgoing MAIL FROM AUTH value should
// be the same as the incoming value iff the submitting
// client was authenticated and trusted; or it can be the
// submitting client's authentication id if there was no
// incoming value; or it can be "<>".
//
try
{
    // parse the command-line to get the envelope filename
    var content = WScript.Arguments(0) ;
    var envelope = WScript.Arguments(1) ;

    // open the envelope file
    var fs = WScript.CreateObject( "Scripting.FileSystemObject" ) ;
    var ts = fs.OpenTextFile( envelope , 1 , false ) ;

    // read the contents of the envelope file
    var txt = ts.ReadAll() ;
    ts.Close() ;

    // read the incoming values
    var re_auth_in = new RegExp( "^X-MailRelay-MailFromAuthIn: *(\\S*)" , "m" ) ;
    txt.match( re_auth_in ) ;
    var auth_in = RegExp.lastParen ;
    var re_authentication = new RegExp( "^X-MailRelay-Authentication: *(\\S*)" , "m" ) ;
    txt.match( re_authentication ) ;
    var authentication = RegExp.lastParen ;

    // choose the auth-out value
    var auth_out = "<>" ;
    if( authentication )
    {
            function xtext( x ) { return x } // todo
            auth_out = auth_in ? auth_in : xtext(authentication) ;
    }

    // set the auth-out
    var re = new RegExp( "X-MailRelay-MailFromAuthOut: *\\S*" ) ;
    txt = txt.replace( re , "X-MailRelay-MailFromAuthOut: " + auth_out ) ;

    // write the envelope file back out
    ts = fs.OpenTextFile( envelope , 2 , false ) ;
    ts.Write( txt ) ;
    ts.Close() ;

    // successful exit
    WScript.Quit( 0 ) ;
}
catch( e )
{
    // report errors using the special <<...>> markers
    WScript.StdOut.WriteLine( "<<edit failed>>" ) ;
    WScript.StdOut.WriteLine( "<<" + e + ">>" ) ;
    WScript.Quit( 1 ) ;
}