CODEWITHSUNDEEP
phpreference
SecureCloud
SecureCloud

Reputation: 103

PHP Calling a Function from Memory

I'm not sure how to word this so please bear with me.

Here's the scenario:

(Using: PHP 5.4) I created a PHP Function to encrypt / decrypt php files, right now I can read in a php source file & encrypt it. I can also decrypt the file again back to original PHP source code so up until this point everything works perfect.. BUT..

This is my question I need help with: (and a code sample would be nice)

on 'decrypt' $action, I want to decrypt the file into memory and be able to call the function sayHello(), without writing it to a file (I can already do that) by either using memory or a stream, or something I'm not familiar with. not even a tmp file, or no $_SESSION.

The whole purpose of this, I am making a custom compiler for my php code I want to run decrypt($fileName) and be able to call functions or Constants out of it while in memory, and maybe a function to take it outta memory somehow, I will only be using it on files at most like 2kb

If I use a tmp file then there is no sense encrypting it, because they can just use that, defeating the whole purpose, same with $_SESSION. There has to be a way to read a file into memory, include it somehow, and be able to call functions out of it as if it were a regular php file.

example..

fileName: test.php (file to be encrypted)

function sayHello() {
    echo 'hello world';
}

now the file that does the actual encryption / decryption

fileName: compiler.php

function encrypt_decrypt($action, $string) {
    $output = false;
    $encrypt_method = "AES-256-CBC";
    $secret_key = 'faj6mZqjGYlUuj6TA4uQz';
    $secret_iv = 'a6ZcFzXKimxogfo6yHBR';
    $noExt = basename($string, ".php"); <br />
    // hash
    $key = hash('sha256', $secret_key); <br />
    // iv - encrypt method AES-256-CBC expects 16 bytes - else get warning
    $iv = substr(hash('sha256', $secret_iv), 0, 16); <br />
    if ($action == 'encrypt') {
        $fileName = file_get_contents($string);
        $output = openssl_encrypt($fileName, $encrypt_method, $key, 0, $iv);
        $output = base64_encode($output);
        $output = file_put_contents($noExt."_ENC.php", $output);
    }
    else if ($action == 'decrypt') {
        $fileName = file_get_contents($string);
        $output = openssl_decrypt(base64_decode($fileName), $encrypt_method, $key, 0, $iv);

       // Below line works if UnCommented for decrypting to file. (not what i want)
       // $output = file_put_contents("test_ENC_DECRYPTED.php", $output);
       // <== THIS IS WHERE I WANT TO CALL A FUNCTION IN MEMORY, NOT FROM FILE
    }
    return $output;
}

*EDIT: Original Code Located here.. (I modified it to accept files) http://naveensnayak.wordpress.com/2013/03/12/simple-php-encrypt-and-decrypt/

*NOTE: I don't want to use any other dependencies or 3rd party plug-ins or no compilers or extensions. I want this to be portable & work on any PHP 5.3+ version. I realize I said I want to run decrypt($fileName) and I didn't show code for that file, that is because I am going to break this function down and only the decrypter is going to be used after files are encrypted.

Upvotes: 0

Views: 194

Answers (1)

Barmar
Barmar

Reputation: 781059

Use eval:

eval(encrypt_decrypt('decrypt', $filename));

eval executes the code in its argument, just as if it were a file that was loaded.

There are some gotchas, though: if it tries to use variables that reference the script filename, they'll get the script that's doing the decrypting, not the file that contained the encrypted or original decrypted script.

Upvotes: 2

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