Walkthrough of the three-part Try Hack Me (THM) Network Services lab where I will enumerate and exploit a variety of network services and configurations.

NFS

Understanding NFS

What does NFS stand for?

Network File System

What process allows an NFS client to interact with a remote directory as though it was a physical device?

Mounting

What does NFS use to represent files and directories on the server?

file handle

What protocol does NFS use to communicate between the server and client?

RPC

What two pieces of user data does the NFS server take as parameters for controlling user permissions? Format: parameter 1 / parameter 2

user id/group id

Can a Windows NFS server share files with a Linux client? (Y/N)

Can a Linux NFS server share files with a MacOS client? (Y/N)

What is the latest version of NFS? [released in 2016, but is still up to date as of 2020] This will require external research.

4.2

Enumeration NFS

Conduct a thorough port scan scan of your choosing, how many ports are open?

Which port contains the service we’re looking to enumerate?

2049

Now, use /usr/sbin/showmount -e [IP] to list the NFS shares, what is the name of the visible share?

/home

Then, use the mount command we broke down earlier to mount the NFS share to your local machine. Change directory to where you mounted the share- what is the name of the folder inside?

cappucino

Interesting! Let’s do a bit of research now, have a look through the folders. Which of these folders could contain keys that would give us remote access to the server?

.ssh

Which of these keys is most useful to us?

id_rsa

Can we log into the machine using ssh -i <key-file> <username>@<ip> ? (Y/N)

Exploiting NFS

Now, we’re going to add the SUID bit permission to the bash executable we just copied to the share using “sudo chmod +[permission] bash”. What letter do we use to set the SUID bit set using chmod?

wget https://github.com/polo-sec/writing/raw/master/Security%20Challenge%20Walkthroughs/Networks%202/bash

Let’s do a sanity check, let’s check the permissions of the “bash” executable using “ls -la bash”. What does the permission set look like? Make sure that it ends with -sr-x.

-rwsr-sr-x

Great! If all’s gone well you should have a shell as root! What’s the root flag?

THM{nfs_got_pwned}

SMTP

Understanding Telnet

What does SMTP stand for?

Simple Mail Transfer Protocol

What does SMTP handle the sending of? (answer in plural)

emails

What is the first step in the SMTP process?

SMTP handshake

What is the default SMTP port?

25

Where does the SMTP server send the email if the recipient’s server is not available?

smtp queue

On what server does the Email ultimately end up on?

POP/IMAP

Can a Linux machine run an SMTP server? (Y/N)

Can a Windows machine run an SMTP server? (Y/N)

Enumerating SMTP

First, lets run a port scan against the target machine, same as last time. What port is SMTP running on?

25

Okay, now we know what port we should be targeting, let’s start up Metasploit. What command do we use to do this?

msfconsole

Let’s search for the module “smtp_version”, what’s it’s full module name?

auxiliary/scanner/smtp/smtp_version

Great, now- select the module and list the options. How do we do this?

options

Have a look through the options, does everything seem correct? What is the option we need to set?

RHOSTS

Set that to the correct value for your target machine. Then run the exploit. What’s the system mail name?

polosmtp.home

What Mail Transfer Agent (MTA) is running the SMTP server? This will require some external research.

Postfix

Good! We’ve now got a good amount of information on the target system to move onto the next stage. Let’s search for the module “smtp_enum”, what’s it’s full module name?

auxiliary/scanner/smtp/smtp_enum

What option do we need to set to the wordlist’s path?

USER_FILE

Once we’ve set this option, what is the other essential paramater we need to set?

RHOSTS

Okay! Now that’s finished, what username is returned?

administrator

Exploiting SMTP

What is the password of the user we found during our enumeration stage?

alejandro

Great! Now, let’s SSH into the server as the user, what is contents of smtp.txt

THM{who_knew_email_servers_were_c00l?}

MySQL

Understanding MySQL

What type of software is MySQL?

relational database management system

What language is MySQL based on?

SQL

What communication model does MySQL use?

client-server

What is a common application of MySQL?

back end database

What major social network uses MySQL as their back-end database? This will require further research.

Facebook

Enumeration MySQL

As always, let’s start out with a port scan, so we know what port the service we’re trying to attack is running on. What port is MySQL using?

3306

Search for, select and list the options it needs. What three options do we need to set? (in descending order).

PASSWORD/RHOSTS/USERNAME

Run the exploit. By default it will test with the “select version()” command, what result does this give you?

5.7.29-0ubuntu0.18.04.1

Great! We know that our exploit is landing as planned. Let’s try to gain some more ambitious information. Change the “sql” option to “show databases”. how many databases are returned?

Exploiting MySQL

First, let’s search for and select the “mysql_schemadump” module. What’s the module’s full name?

auxiliary/scanner/mysql/mysql_schemadump

Great! Now, you’ve done this a few times by now so I’ll let you take it from here. Set the relevant options, run the exploit. What’s the name of the last table that gets dumped?

x$waits_global_by_latency

Awesome, you have now dumped the tables, and column names of the whole database. But we can do one better… search for and select the “mysql_hashdump” module. What’s the module’s full name?

auxiliary/scanner/mysql/mysql_hashdump

Again, I’ll let you take it from here. Set the relevant options, run the exploit. What non-default user stands out to you?

carl

What is the user/hash combination string?

carl:*EA031893AA21444B170FC2162A56978B8CEECE18

Now, we need to crack the password! Let’s try John the Ripper against it using: “john hash.txt” what is the password of the user we found?

doggie

What’s the contents of MySQL.txt

THM{congratulations_you_got_the_mySQL_flag}

Explorer

Network Services 2

Table of Contents

NFS