CodeSOD: The Secure Cloud API

Melinda's organization has purchased a cloud-based storage system. Like any such system, it has a lovely API which lets you manage quotas and login tokens. It also had a lovely CLI, which was helpful for administrators to modify the cloud environment. Melinda's team built a PHP front-end that could not only manage files, but also allowed administrators to manage those quotas.

Melinda was managing those quotas, and when she clicked the link to view the quotas, she noticed the URL contained ?token=RO-cmV1c2luZyBrZXlzIGlzIFRSV1RG. When she went to modify the quota, the URL parameter became ?token=RW-cmV1c2luZyBrZXlzIGlzIFRSV1RG. That looked like a security key for their cloud API, transmitted in the open. The RW and RO looked like they had something to do with readwrite and readonly, but that wasn't the security model their storage provider used. When Melinda had another co-worker log in, they saw the same tokens. What was going on?

Melinda took a look at the authorization code.

function authorised($token, $verb) { // check if token can do verb // TO DO - turn this in to a database lookup $rights = array( 'RW-cmV1c2luZyBrZXlzIGlzIFRSV1RG' => array('getquota' => 0, 'setquota' => 1), 'RO-cmV1c2luZyBrZXlzIGlzIFRSV1RG' => array('getquota' => 1, 'setquota' => 0) ); return ((isset($rights[$token]) && isset($rights[$token][$verb]) && ($rights[$token][$verb] == 1)));}

The developer behind this wrote their own security model, instead of using the one their storage provider offered. The tokens here were hard-coded secret keys for the API. Essentially this meant no matter who logged in to manage quotas on the application side, the storage system saw them all as a single user- a single user with pretty much unlimited permissions that had root access on every VM in their cloud environment.

"Oh, boy, they released their secret key to essentially a root account, that's bad," you say. It gets worse. The code doesn't, but the logic does.

You see, the culprit here didn't want to learn the API. So they did everything via shell commands. They had one machine set up in the cloud environment with a bunch of machine-based permissions that allowed it to control anything in the cloud. When someone wanted to change quotas, the PHP code would shell out and use SSH to log into that cloud machine as root, and then run the cloud vendor's proprietary CLI tool from within their own environment.

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