Skip to main content

LFI to DB and backdoor

I am decribing a high level, theortical way of converting LFI to DB compromise and creating a backdoor.
A long time ago, came across an application which was vulnerable to LFI (Local File Inclusion).

The LFI found was different from traditional one, since the filenmames were not being passed in any parameter, so was hard to detect also. A file called default.cgi contained code that which looks for a file in the directory and include it for some sort of processing, that was a business requirement, if not found, displayed 'File not found' error. So in order to exploit it one need to append a file name just after default.cgi?.  This way, could view any file from app server to OS level. Many sensitive files are easily accessible even from other folders too. /etc/passwd was accessible but /etc/shadow was not present, unfortunately. 

After browsing through almost all the files present at the server, came across a few interesting files (conn.cgi) which contained the logic of connecting to DB. 

The file also mentioned name of other files which needs to be downloaded in order to connect the file. It describes  about an encrypted db-password file which has to be decrypted. In order to decrypt the file, we needed to download a binary file from the server. The file also describes what command to be run in order to get the un-encrypted password file.

We accessed both the files, and saved the responses locally. Now we had to run the command mentioned. After a few hours of efforts we finally got the decrypted db password file, which contained passwords and other necessary details required for connecting the DB. Finally, using a client we were able to connect to the DB. 

Next steps were to insert a backdoor code in the table and write to a file using OUTFILE command, and save to one of the paths on the server so that we can fetch the files from the internet and run the command. Unfortunately, it didn't work for us. Were facing issue with using the OUTFILE command on the clients we had. But theoretically, it's possible, maybe with some other DB type. 

Comments

Post a Comment

Popular posts from this blog

Ardilla- New tool for finding SQL Injection and XSS

Three Researchers -- MIT's Adam Kiezun , Stanford's Philip Guo , and Syracuse University's Karthick Jayaraman -- has developed a new tool ' Ardilla ' that automatically finds and exploits SQL injection and cross-site scripting vulnerabilities in Web applications. It creates inputs that pinpoint bugs in Web applications and then generates SQL injection and XSS attacks. But for now Ardilla is for PHP -based Web app only. The researchers say Ardilla found 68 never-before found vulnerabilities in five different PHP applications using the tool -- 23 SQL injection and 45 XSS flaws. More information is awaited. For their attack generation techniques refer to their document at: http://www.cs.washington.edu/homes/mernst/pubs/create-attacks-tr054.pdf
Post a Comment
Read more

File Upload through Null Byte Injection

Sometimes, during file upload we come across situation wherein there would be check on the file extension at the client side as well as server side too. If the application does allow only .jpeg extension to be uploaded, the client side java script checks for the extension of the file before passing the request. We all know that how easily this can be defeated. Some applications, checks for the extension at the server side also. That's not easy to bypass. However there are some ways with which it still can be bypassed. Most of server side scripts are written in high level languages such as Php, Java etc who still use some C/C++ libraries to read the file name and contents. That leads to the problem. In C/C++ a line ends with /00 or which is called Null Byte. So whenever the interpreter sees a null byte at the end of the a string, it stops reading thinking it has reached at the end of the string. This can be used for the bypass. It works for many servers, specially php servers. T
1 comment
Read more

jtool - an alternative to otool

jtool comes with a capability of running on Linux environment. Some ipa scanning tools are created to run on Linux environment where mac environment is not available. In such cases tools such as otool and class-dump-z will not work. So jtool can be an alternative to otool. For more information on jtool please refer to http://www.newosxbook.com/tools/jtool.html . It lists down various commands which have same output as otool or a equivalent. There are several commands mentioned in link. But for our customized requirements and basis checks I have listed down the below ones after running on many binaries. The outputs are similar or equivalent to otool and class-dump-z: Commands for checking PIE flag (ASLR) in jTool jtool -d -v -arch | grep stack ·           Automatic Reference Counting (ARC) protection: jtool -d -v -arch | grep _objc_release ·           To check if the device is jailbroken: jtool -d -v -arch | grep jail ·           Dyldinfo compatible options
1 comment
Read more