s3 bucket confused deputy attack

[bcpenta]

Background

This policy ensures that S3 bucket policies with service principals contain conditions to prevent cross-service confused deputy issues. Without these conditions (such as aws:SourceArn, aws:SourceAccount, aws:SourceOrgID, or aws:SourceOrgPaths), attackers may be able to exploit the bucket and upload malicious data or exfiltrate sensitive data from the bucket.
https://docs.aws.amazon.com/IAM/latest/UserGuide/confused-deputy.html

Changes

• Added a new policy AWS.S3.Bucket.PolicyConfusedDeputyProtection to check that S3 bucket policies containing service principals also include at least one condition to limit cross-service permissions.

• This policy examines the conditions associated with service principals to ensure appropriate resource constraints.

Testing

Added test cases to validate the policy:

• S3 bucket policy with a service principal and a compliant condition (expected to pass).
  

• S3 bucket policy with a service principal but without a condition (expected to fail).
  

• S3 bucket policy without a service principal (expected to pass).
  

[arielkr256]

@bcpenta looks like there's a minor linting issue. If you run make fmt it should auto-resolve those for you.