[New Rule] AWS STS Role Chaining

[imays11]

Pull Request

Issue link(s): https://github.com/elastic/ia-trade-team/issues/458

Summary - What I changed

Identifies role chaining activity. Role chaining is when you use one assumed role to assume a second role through the AWS CLI or API. While this a recognized functionality in AWS, role chaining can be abused for privilege escalation if the subsequent assumed role provides additional privileges. Role chaining can also be used as a persistence mechanism as each AssumeRole action results in a refreshed session token with a 1 hour maximum duration. This rule looks for role chaining activity happening within a single account, to eliminate false positives produced by common cross-account behavior.

How To Test

• I have a terraform script to create the necessary role resources and a python script to emulate the role-chaining behavior. I can share for testing upon request.

Screenshot of ES|QL query

## Checklist

• Added a label for the type of pr: bug, enhancement, schema, Rule: New, Rule: Deprecation, Rule: Tuning, Hunt: New, or Hunt: Tuning so guidelines can be generated
• Secret and sensitive material has been managed correctly

[protectionsmachine]

Rule: New - Guidelines

These guidelines serve as a reminder set of considerations when proposing a new rule.

Documentation and Context

• Detailed description of the rule.
• List any new fields required in ECS/data sources.
• Link related issues or PRs.
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Testing and Validation

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[Aegrah]

This rule looks for role chaining activity happening within a single account

How is this done? By using the aws.cloudtrail.resources.account_id == aws.cloudtrail.recipient_account_id statement?

[imays11]

Yes that's correct