Pivoting Clouds in AWS Organizations – Part 2

As mentioned in part one of this two-part blog series on pentesting AWS Organizations, a singular mindset with regard to AWS account takeovers might result in missed opportunities for larger corporate environments. Specifically, those that leverage AWS Organizations for account management and centralization. Identifying and exploiting a single misconfiguration or credential leak in the context of AWS Organizations could result in a blast radius that encompasses several, if not all, of the remaining AWS company assets.   

To help mitigate this risk, I pulled from my experience in AWS penetration testing to provide an in-depth explanation of key techniques pentesting teams can use to identify weaknesses in AWS Organizations. 

Read part one to explore organizations, trusted access, and delegated administration and dive into various pivoting techniques after showing the initial “easy win” via created (as opposed to invited) member accounts. 

In this section, we will cover additional and newer AWS Organizations security implications and demonstrate a new Pacu module I created for ease of enumeration. 

Table of Contents

Phishing with AWS Account Management

AWS Account Management is an organization-integrated feature that offers a few simple APIs for updating or retrieving an AWS account’s contact information. This presents an interesting phishing vector.

Assuming we have compromised Account A, enable trusted access for Account Management via the CLI. Note Account Management supports delegated administration as well but we are focusing on trusted access for this portion.

With trusted access now enabled, update the contact information for Account B changing items like address or full name to assist in a future social engineering attack. Note: I have not attempted social engineering with AWS by calling the AWS help desk or other contacts, nor am I sanctioning that. This would be more from the perspective of trying to trick an engineer or another representative who manages an AWS account at the company to get access.

Delegated Policies – New Features, New Security Risks

AWS Organizations recently announced a new delegated administrator feature on November 27, 2022.  To summarize this release, AWS Organizations now gives you the ability to grant your delegated administrators more API privileges on top of the read-only access they previously gained by default. Only a subset of the Organization APIs dealing primarily with policy manipulation can be allow-listed for delegated administrators, and the allow-list implementation happens in the management account itself.  

In the image below, we used Account A to attach a Service Control Policy (SCP) to Account C that specifically denies S3 actions. A SCP can be thought of as an Identity and Access Management (IAM) policy filter. SCPs can be attached to accounts (like below) or organization accounts (OUs) and propagate downwards in terms of the overall organization hierarchy. They override any IAM privileges at the user/role level for their associated attached accounts. So even if users or roles in Account C have policies normally granting them S3 actions, they would still be blocked from calling S3 actions as the SCP at the organization-level takes precedence.  

Given this setup and the newly released feature, if a management account grants delegated administrators overly permissive rights in terms of policy access/manipulation, delegated administrators could remove restrictive SCPs from their own account or other accounts they control.

To enable the newer feature, navigate to the Settings tab in Account A and click “Delegate” in the “Delegated administrator for AWS Organizations” panel. In the delegation policy’s “Action” key, add organization APIs from the subset provided in the AWS user guide. 

Note that the actions added include the API calls for attaching and detaching any policy (AttachPolicy/DetachPolicy). Once the actions have been chosen, they are only granted to the member account if the delegation policy lists the member account number as a Principal (Account C in this scenario).

With this setup complete, we can switch to the attacker’s perspective. Assume that we have compromised credentials for Account C and already noted through reconnaissance that the compromised account is a delegated administrator. At this point in our assessment, we want to get access to S3 data but keep getting denied as seen below in Figure 4.

This makes sense as there is an SCP attached to Account C preventing S3 actions. But wait… with the new AWS Organization feature we as delegated admins might have additional privileges related to policy management that are not immediately evident. So, while still in Account C’s AWS Organization service, try to remove the SCP policy created by Account A from Account C.

Since the management account delegated us the rights to detach policy, the operation is successful, and we can now call S3 APIs as seen below in Figure 6. 

Rather than a trial-and-error method, you could also call the “describe-resource-policy” API as Account C and pull down the policy that exists in Account A. Remember that delegated administrators have read-only access by default so this should be possible unless otherwise restricted.

Enumeration Tool for AWS Organizations

A lot of what I covered is based off AWS Organization enumeration. If you compromise an AWS account, you will want to list all organization-related entities to understand the landscape for delegation and the general organization structure (assuming your account is even in an organization).  

To better assist in pentesting AWS Organizations, I added AWS Organizations support to the open-source AWS pentesting tool Pacu. I also wrote an additional Pacu enumeration module for AWS Organizations (organizations__enum). These changes were recently accepted into the Pacu GitHub project and are also available in the traditional pip3 installation procedure detailed in the repository’s README. The two relevant forks are located here:

Note that the GitHub Pacu project contains all APIs discussed thus far, but as you might note in the screenshots below, the pip installation just does not include 1 read-only API (describe-resource-policy) along with 1-2 bug fixes at this time.

I won’t cover how Pacu works as there is plenty of documentation for the tool, but I will run my module from the perspective of a management account and a normal (not a delegated administrator) member account.  

Let’s first run Pacu with respect to Account A. Note that the module collects many associated attributes ranging from a general organization description to delegation data. To see the collected data after running “organizations__enum,” you need to execute “data organizations.” My module also tries to build a visual graph at the end of the enumeration using the account.

At the other extreme, what if the account in question is a member account with no associated delegation? In this case, the module will still pick up the general description of the organization but will not dump all the organization data since your credentials do not have the necessary API permissions. At the very least, this would help tell you at a glance if the account in question is part of an organization. 

Defense

The content discussed above is not any novel zero-days or represents an inherent flaw in AWS itself. The root cause of most of these problems is exposed cleartext credentials and lack of least privilege. The cleartext credentials give an attacker access to the AWS account, with the trusted access and delegated administration allowing for easy pivoting.  

As mentioned in part one, consider a layered defense. Ensure that IAM users/roles adhere to a least privilege methodology, and that organization-integrated features are also monitored and not enabled if not needed. In all cases, protect AWS credentials to avoid access to the AWS environment allowing someone to enumerate the existing resources using a module like the Pacu one above, and subsequently exploit any pivoting vectors. To get a complete picture of the organization’s actions, ensure proper logging is in place as well. 

The following AWS articles provide guidance pertaining to the points discussed above. Or connect with NetSPI to learn how an AWS penetration test can help you uncover areas of misconfiguration or weakness in your AWS environment.  

Final Thoughts & Conclusion

The architecture and considerable number of enabled/delegated service possibilities in AWS Organizations presents a serious vector for lateral movement within corporate environments. This could easily turn a single AWS account takeover into a multiple account takeover that might cross accepted software deployment boundaries (i.e. pre-production & production). More importantly, a lot of examples given above assume you have compromised a single user or role that allowed for complete control over a given AWS account. In reality, you might find yourself in a situation where permissions are more granular so maybe one compromised user/role has the permissions to enable a service, while another user/role has the permissions to call the enabled service on the organization, and so on.  

We covered a lot in this two-part series on pivoting clouds in AWS Organizations. To summarize the key learnings and assist in your own replication, here’s a procedural checklist to follow: 

1. Compromise a set of AWS credentials for a user or role in the compromised AWS Account. 
2. Try to determine if you are the management account, a delegated administrator account, a default member account, or an account not part of an organization. If possible, try to run the Pacu “organizations__enum” module to gather all necessary details in one command.
3. If you are the management account, go through each member account and try to assume the default role. Consider a wordlist with OrganizationAccountAccessRole included. You can also try to leverage any existing enabled services with IAM Identity Center being the desired service. If necessary, you can also check if there are any delegated administrators you have control over that might assist in pivoting. 
4. If you are a delegated administrator, check for associated delegated services to exploit similar to enabled services or try to alter existing SCPs to grant yourself or other accounts more permissions. If necessary, you can also check if there are any other delegated administrators you have control over that might assist in pivoting. 

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