# Mail Server
## Introduction
This is the current layout of our department's mail service.
![architecture](https://hackmd.io/_uploads/r1g-RIrs-g.png)
(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.
![simplified_architecture](https://hackmd.io/_uploads/B1aC_PHjWx.png)
## 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`: 
    ```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`:
    ```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