2018-0402 Solution - You're Always Learning

Challenge type: cloud security review

Original code: found here

Description

This week we broke away from pure play application code review and looked at some AWS configuration. Specifically the snippet of configuration provided was for an IAM policy which are codified policies that get attached to users, resources, or just about anything within AWS. IAM policies are there to control what something in AWS can do and under what conditions, it's an extremely important security measure. 

The issue with the originally posted policy was that it was supposed to restrict Pipeline resources to the user that created them. This was even called out in the name of the policy. The effect of the policy was the exact opposite though, instead of denying non-creators access, the policy allowed it. 

This is something that could slip through into real world policies either accidentally or as a possible backdoor. It's very subtle for the human eye to catch because we tend to place more faith in commented code, well named functions, and in this case a well named policy.

Solution

The solution to this is really simple, fortunately. We need to change the effect of the policy from "Allow" to "Deny" as seen in the snippet below.

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