opensmtpd-filter-replace-from_reply.go

package main

import (
	"bufio"
	"flag"
	"fmt"
	"log"
	"os"
	"strings"
	"net/mail"
)

var mailFrom string
var fromToReply bool
var needReplace bool = true

func init() {
	flag.StringVar(&mailFrom, "mailFrom", "", "Email for rewrite")
	flag.BoolVar(&fromToReply, "fromToReply", true, "Move mail from address to Reply-To field")
	flag.Parse()
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	if (mailFrom == ""){
		log.Println("Not set email address for rewrite")
		return
	}

	for scanner.Scan() {
		line := scanner.Text()

		if strings.HasPrefix(line, "config|ready") {
			fmt.Println("register|filter|smtp-in|data-line")
			fmt.Println("register|filter|smtp-in|mail-from")
			fmt.Println("register|ready")
		}else{
			dataSplit := strings.Split(line, "|")
			if len(dataSplit) >= 8 {
				switch dataSplit[4] {
					case "mail-from" :
						fmt.Printf("filter-result|%s|rewrite|%s\n", strings.Join(dataSplit[5:7], "|"), "<"+mailFrom+">")
						needReplace = true
					break;
					case "data-line":
						if needReplace && strings.HasPrefix(strings.ToUpper(dataSplit[7]), "FROM:"){
							var from = strings.TrimSpace(dataSplit[7][5:]);
							dataSplit[7] = "From: <"+mailFrom+">"
							fmt.Printf("filter-dataline|%s\n", strings.Join(dataSplit[5:], "|"))
							if (fromToReply && from != "" && valid(from)){
								dataSplit[7] = "Reply-To: "+from
								fmt.Printf("filter-dataline|%s\n", strings.Join(dataSplit[5:], "|"))
							}
							needReplace = false
						}else{
							fmt.Printf("filter-dataline|%s\n", strings.Join(dataSplit[5:], "|"))
						}
					break;
				}
			}
		}
	}

	if err := scanner.Err(); err != nil {
		log.Println(err)
	}
}

func valid(email string) bool {
    _, err := mail.ParseAddress(email)
    return err == nil
}