Vsftpd Backdoor - Ekoparty Prectf - Amn3S1A Team

It's a 32bits elf binary of some version of vsftpd, where it have been added a backdoor, they don't specify is an authentication backdoor, a special command or other stuff.

I started looking for something weird on the authentication routines, but I didn't found anything significant in a brief period of time, so I decided to do a bindiff, that was the key for locating the backdoor quickly. I do a quick diff of the strings with the command "strings bin | sort -u" and "vimdiff" and noticed that the backdoored binary has the symbol "execl" which is weird because is a call for executing elfs, don't needed for a ftp service, and weird that the compiled binary doesn't has that symbol.

Looking the xrefs of "execl" on IDA I found that code that is a clear backdoor, it create a socket, bind a port and duplicate the stdin, stdout and stderr to the socket and use the execl:

There are one xrefs to this function, the function that decides when trigger that is that kind of systems equations decision:

The backdoor was not on the authentication, it was a special command to trigger the backdoor, which is obfuscated on that systems equation, it was no needed to use a z3 equation solver because is a simple one and I did it by hand.

The equation:

cmd[0] = 69

cmd[1] = 78

cmd[1] + cmd[2] = 154

cmd[2] + cmd[3] = 202

cmd[3] + cmd[4] = 241

cmd[4] + cmd[5] = 233

cmd[5] + cmd[6] = 217

cmd[6] + cmd[7] = 218

cmd[7] + cmd[8] = 228

cmd[8] + cmd[9] = 212

cmd[9] + cmd[10] = 195

cmd[10] + cmd[11] = 195

cmd[11] + cmd[12] = 201

cmd[12] + cmd[13] = 207

cmd[13] + cmd[14] = 203

cmd[14] + cmd[15] = 215

cmd[15] + cmd[16] = 235

cmd[16] + cmd[17] = 242

The solution:

cmd[0] = 69

cmd[1] = 75

cmd[2] = 79

cmd[3] = 123

cmd[4] = 118

cmd[5] = 115

cmd[6] = 102

cmd[7] = 116

cmd[8] = 112

cmd[9] = 100

cmd[10] = 95

cmd[11] = 100

cmd[12] = 101

cmd[13] = 106

cmd[14] = 97                    

cmd[15] = 118

cmd[16] = 117

cmd[17] = 125

The flag:

EKO{vsftpd_dejavu}

The binary:
https://ctf.ekoparty.org/static/pre-ekoparty/backdoor

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"OpenVAS stands for Open Vulnerability Assessment System and is a network security scanner with associated tools like a graphical user front-end. The core is a server component with a set of network vulnerability tests (NVTs) to detect security problems in remote systems and applications." read more...

Website: http://www.openvas.org

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How To Start PHP And MYSQL | The Best Server For PHP And MYSQL | Tutorial 1

Many of people want to start PHP programming embedded with MYSQL databases concepts. So i thought that I should start a series about PHP and MYSQL. So in this series of video tutorials you exactly got the content about PHP and MYSQL.

As PHP is server side scripting language. So it requires a server to get execute over the web browser. First of all you have to download and install a server that may be XAMPP, WAMPP or LAMPP. I'm using XAMPP server in the tutorials. So if you wanna follow me then download a XAMPP server. I'm using this because it has a good interface to work  and it's really simple. XAMPP is compatible with windows, MAC and Linux operating as well. WAMPP is only for windows and LAMPP is used for MAC and Linux operating system. So i prefer XAMPP for this series.

How to create Database

Step 1:

Open Your XAMPP control panel and start Apache and Mysql services.

Step 2:

Go to your Web browser and type "localhost/phpmyadmin". It will open your databases area. If you have an error then your services are not in running state. If you have any error then comment below.

Step 3:

Click over the "new" to create a new database.

Step 4:

Write Database_Name and click over the Create button. For example Facebook, Students etc.

Step 5:

Write Table_Name like admin, users etc. your can increase and decrease the size of rows. Click over Save/Create button.

Step 6:

Write your Attribute_Names in first column like Username, Email, Passwords etc. In the next data type column you have to select the data type whether it is integer or string type etc. In the next column you have to set the length of string/words.

Step 7:

If you wanna go through with a Primary_Key. Then just you have to checked the Auto_Increment box as you will shown in the video. For further watch the video for better understanding.