warp

README

WARP is an outbound transparent SMTP proxy.

For redirect the port need by iptables rule:

iptables -t nat -A OUTPUT -p tcp --dport 25 -j DNAT --to-destination <proxy-ip>:<proxy-port>

Also, the MTA and Proxy must be on the same host to know the DST Address before NAT.

Usage

To check the operation, use the sandbox environment with the Vagrantfile in the repository.

warp main 🏄 make
env GOOS=linux GOARCH=amd64 go build -o warp ./cmd/warp/main.go
warp main 🏄 vagrant up
...
warp main 🏄 vagrant status
Current machine states:

sender                    running (virtualbox)
receiver                  running (virtualbox)

Start proxy on sender:

warp main 🏄 vagrant ssh sender
vagrant@sender:~$ /vagrant/warp -ip 192.168.30.30 -port 10025
2021/02/06 14:50:44 warp listens to 192.168.30.30:10025

Send mail on sender:

warp main 🏄 vagrant ssh sender
vagrant@sender:~$ smtp-source -m 1 -s 1 -l 10 -S 'Hi, Receiver from Sender' -f root@sender -t root@receiver localhost:25

Output by proxy on sender:

2021/02/06 14:50:48 connected from 192.168.30.40:57493
2021/02/06 14:50:48 connected to 192.168.30.50:25
2021/02/06 14:50:48 <- 220 receiver ESMTP Postfix (Ubuntu)\r\n
2021/02/06 14:50:48 -> EHLO sender\r\n
2021/02/06 14:50:48 |< 250-receiver\r\n250-PIPELINING\r\n250-SIZE 10240000\r\n250-VRFY\r\n250-ETRN\r\n250-STARTTLS\r\n250-ENHANCEDSTATUSCODES\r\n250-8BITMIME\r\n250-DSN\r\n250-SMTPUTF8\r\n250 CHUNKING\r\n
2021/02/06 14:50:48 <- 250-receiver\r\n250-PIPELINING\r\n250-SIZE 10240000\r\n250-VRFY\r\n250-ETRN\r\n250-ENHANCEDSTATUSCODES\r\n250-8BITMIME\r\n250-DSN\r\n250-SMTPUTF8\r\n250 CHUNKING\r\n
2021/02/06 14:50:48 |> STARTTLS\r\n
2021/02/06 14:50:48 >| MAIL FROM:<root@sender> SIZE=327\r\nRCPT TO:<root@receiver> ORCPT=rfc822;root@receiver\r\nDATA\r\n
2021/02/06 14:50:48 |< 220 2.0.0 Ready to start TLS\r\n
2021/02/06 14:50:48 |> EHLO sender\r\n
2021/02/06 14:50:48 pipe locked for tls connection
2021/02/06 14:50:48 |< 250-receiver\r\n250-PIPELINING\r\n250-SIZE 10240000\r\n250-VRFY\r\n250-ETRN\r\n250-ENHANCEDSTATUSCODES\r\n250-8BITMIME\r\n250-DSN\r\n250-SMTPUTF8\r\n250 CHUNKING\r\n
2021/02/06 14:50:48 tls connected, to pipe unlocked
2021/02/06 14:50:48 -> MAIL FROM:<root@sender> SIZE=327\r\nRCPT TO:<root@receiver> ORCPT=rfc822;root@receiver\r\nDATA\r\n
2021/02/06 14:50:48 <- 250 2.1.0 Ok\r\n250 2.1.5 Ok\r\n354 End data with <CR><LF>.<CR><LF>\r\n
2021/02/06 14:50:48 -> Received: from sender (localhost [127.0.0.1])\r\n        by sender (Postfix) with SMTP id 45B113EA9B\r\n for <root@receiver>; Sat,  6 Feb 2021 14:50:48 +0000 (UTC)\r\nFrom: <root@sender>\r\nTo: <root@receiver>\r\nDate: Sat,  6 Feb 2021 14:50:48 +0000 (UTC)\r\nMessage-Id: <a77e.0003.0000@sender>\r\nSubject: Hi, Receiver from Sender\r\n\r\nXXXXXXXXXX\r\n.\r\nQUIT\r\n
2021/02/06 14:50:48 <- 250 2.0.0 Ok: queued as 76DAD4113D\r\n221 2.0.0 Bye\r\n
2021/02/06 14:50:48 connections closed

Received mail on receiver:

warp main 🏄 vagrant ssh receiver
vagrant@receiver:~$ sudo cat /var/spool/mail/root
From root@sender  Fri Feb  5 16:00:41 2021
Return-Path: <root@sender>
X-Original-To: root@receiver
Delivered-To: root@receiver
Received: from receiver (proxy [192.168.30.30])
        by receiver (Postfix) with ESMTPS id 3B9874160A
        for <root@receiver>; Fri,  5 Feb 2021 16:00:41 +0000 (UTC)
Received: from sender (localhost [127.0.0.1])
        by sender (Postfix) with SMTP id C08023E8E0
        for <root@receiver>; Fri,  5 Feb 2021 16:00:01 +0000 (UTC)
From: <root@sender>
To: <root@receiver>
Date: Fri,  5 Feb 2021 16:00:01 +0000 (UTC)
Message-Id: <c2f05.0003.0000@sender>
Subject: Hi, Receiver from Sender

XXXXXXXXXX

Contribution

1. Fork (https://github.com/linyows/warp/fork)
2. Create a feature branch
3. Commit your changes
4. Rebase your local changes against the main branch
5. Run test suite with the go test ./... command and confirm that it passes
6. Run gofmt -s
7. Create a new Pull Request

Author

linyows

Documentation

Index

• Constants
• type Direction
• type Mediator
• type Pipe
  • func (p *Pipe) Do()
• type Server
  • func (s *Server) HandleConnection(conn net.Conn)
  • func (s *Server) OriginalAddrDst(conn net.Conn) (*net.TCPAddr, error)
  • func (s *Server) Start() error

Constants

const SO_ORIGINAL_DST = 80

Types

type Direction

type Direction int

type Mediator

type Mediator func([]byte, int) ([]byte, int)

type Pipe

type Pipe struct {
	// contains filtered or unexported fields
}

func (*Pipe) Do

func (p *Pipe) Do()

type Server

type Server struct {
	Addr string
	Port int
}

func (*Server) HandleConnection

func (s *Server) HandleConnection(conn net.Conn)

func (*Server) OriginalAddrDst

func (s *Server) OriginalAddrDst(conn net.Conn) (*net.TCPAddr, error)

func (*Server) Start

func (s *Server) Start() error