Mail Server

Introduction

This is the current layout of our department’s mail service. (Source: NASA Document) Our project only focuses on the receiving process. We host a postfix server that communicates with the ldap server. For testing, we send mail directly to postfix , which listens on port 25; we also host a local mailpit service, which we redirect all postfix traffic to. The mimicked layout is as shown in the following graph.

Settings

Postfix

Installation

1. sudo apt install postfix

2. sudo apt install postfix-ldap

3. Configurations:

   • General Mail Configuration Type: Internet site

   • System mail name: csie.ntu.edu.tw

4. Modify /etc/postfix/main.cf Remember to use sudo!

   • add local_recipient_maps =

   • change to relayhost = [127.0.0.1]:1025

   • add ldap:/etc/postfix/ldap-aliases.cf to virtual_alias_maps

   • add local_transport = smtp:[127.0.0.1]:1025

5. Edit ldap-aliases.cf add

   server_host = <ip>:<port>
   search_base = dc=csie,dc=ntu,dc=edu,dc=tw
   version = 3
   
   bind = yes
   bind_dn = uid=mailtest,ou=people,dc=csie,dc=ntu,dc=edu,dc=tw
   bind_pw = <redacted>
   
   query_filter = (cn=%u)
   
   special_result_attribute = uniqueMember
   
   leaf_result_attribute = uid
   
   result_format = %s@csie.ntu.edu.tw
   

   For ldaps, use

   server_host = ldaps://172.16.127.151:636
   search_base = dc=csie,dc=ntu,dc=edu,dc=tw
   version = 3
   
   bind = yes
   bind_dn = uid=mailtest,ou=people,dc=csie,dc=ntu,dc=edu,dc=tw
   bind_pw = <redacted>
   
   tls_ca_cert_file = /etc/postfix/mockldap_ca.crt
   tls_require_cert = yes
   
   query_filter = (cn=%u)
   
   special_result_attribute = uniqueMember
   
   leaf_result_attribute = uid
   
   result_format = %s@csie.ntu.edu.tw
   

   and change ldap:/etc/postfix/ldap-aliases.cf to proxy:ldap:/etc/postfix/ldap-aliases.cf in main.cf.

6. run sudo postfix reload

   needs to be run after every modification to postfix settings

Usage

• Connect to port 25 to send mail.

• • Some scripts:

    need to install pwntools

    send.py:

    from pwn import *
    r = remote("localhost", 25)
    r.recvline()
    sender = input("sender: ")
    r.sendline(b"mail from: " + sender.encode())
    r.recvline()
    receiver = input("receiver: ")
    r.sendline(b"rcpt to: " + receiver.encode())
    r.recvline()
    r.sendline(b"data")
    r.recvline()
    subject = input("subject: ")
    r.sendline(b"Subject: " + subject.encode())
    data = input("data: ")
    r.sendline(data.encode())
    r.sendline(b".")
    r.close()
    

    test_alias.py:

    from pwn import *
    r = remote("localhost", 25)
    r.recvline()
    r.sendline(b"mail from: alias_test@csie.ntu.edu.tw")
    r.recvline()
    receiver = input("receiver: ")
    r.sendline(b"rcpt to: " + receiver.encode())
    r.recvline()
    r.sendline(b"data")
    r.recvline()
    r.sendline(b"Subject: Just a test")
    r.sendline(b"The quick brown fox jumped over the lazy dog.")
    r.sendline(b".")
    r.close()
    

• view mail queue: postqueue -p

• delete from mail queue(in case of wrongly configured mail getting stuck): sudo postsuper -d <mail_id> or sudo postsuper -d all

Mailpit

Installation

sudo sh < <(curl -sL https://raw.githubusercontent.com/axllent/mailpit/develop/install.sh)

Run

mailpit

run with mailpit --webroot /mailpit/ & if use reverse proxy check localhost:8025 with browser for visuals