php-eval-hook

A PHP extension for hooking eval(). Useful for dumping eval-obfuscated code. The extension is expected to work with PHP 7.x in general. May work with PHP 5.x but is untested.

Why fancyhooker over evalhook?

Changing the name of the extension from evalhook to fancyhooker can bypass the protection because many obfuscators check for the presence of the evalhook extension specifically. By using a different name, the obfuscator's check will not trigger and the extension will be able to run. The name fancyhooker is arbitrary and can be any other name that is not being checked for by the obfuscator.

Compiling steps

Install php and php-dev packages. Here we are using the packages available on the official Ubuntu 18.04 repos.
```
$ sudo apt install php7.2 php7.2-dev
```

Clone the repository

$ git clone https://github.com/RKursatV/php-eval-hook-altered

Run phpize. This will generate the Makefile and other files needed for buidling the extension.
```
$ cd php-eval-hook
$ phpize
```

Build the extension. make install copies the .so to the appropriate location.

$ ./configure --enable-fancyhooker

$ make

$ make install
Installing shared extensions:     /usr/lib/php/20170718/

Registering the extension with PHP

Find the location of php.ini.

$ php -r 'phpinfo();' | grep php.ini
Configuration File (php.ini) Path => /etc/php/7.2/cli
Loaded Configuration File => /etc/php/7.2/cli/php.ini

Edit php.ini and add the line extension=fancyhooker.so at the end.

$ echo "extension=fancyhooker.so" >> /etc/php/7.2/cli/php.ini

Ensure that the extension is properly loaded.

$ php -r 'print_r(get_loaded_extensions());' | grep fancyhooker
    [14] => fancyhooker

$ php -r 'phpinfo();' | grep eval
fancyhooker
eval() hooking => enabled
callback function => __eval

Usage

You must define a callback function named __eval in your PHP code. The extension will call this function whenever it encounters an eval. Inside your callback you can print the code to stdout or dump to a file or whatever you want.

Example

Original Code

<?php
function test_obfuscated()
{
	echo("This is an obfuscated function\n");
}

test_obfuscated();
?>

obfuscated.php [Generated from Simple online PHP obfuscator]

<?php
eval(str_rot13(gzinflate(str_rot13(base64_decode('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')))));
?>

harness.php

<?php
function __eval($code, $file) {
  echo "eval() @ {$file}:\n{$code}\n\n";

  // return FALSE if you want to prevent the eval()
  // return false;

  // return a string if you want to replace the eval-d code
  // return 'echo 2;';

  // return nothing to continue execution normally
}

include("obfuscated.php");
?>

$ php obfuscated.php
This is an obfuscated function

$ php harness.php | tail

eval() @ /workspace/php7/obfuscated.php(2) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'
d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : ev
al()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code:
function test_obfuscated()
{
        echo("This is an obfuscated function\n");
}

test_obfuscated();

This is an obfuscated function

Credits

The extension is based on php-eval.

License

MIT

RKursatV / php-eval-hook-altered