SAA-C03 Design Secure Architectures Practice Question

Exhibit

Current S3 bucket policy:
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": "*",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::reports-private/*"
    }
  ]
}

CloudFront distribution:
- Origin: s3://reports-private
- Viewer protocol policy: Redirect HTTP to HTTPS
- No origin access identity or origin access control configured

Security requirement:
- Clients must use CloudFront signed URLs or signed cookies
- S3 object URLs must not be directly accessible

Based on the exhibit, users must access private PDF reports only through CloudFront. Direct requests to the S3 object URL must fail, and the bucket should not be publicly readable. Which solution is the best fit?

⚠ Common exam trap

Candidates often assume signed URLs or cookies alone can block direct S3 access, but they only control access at the CloudFront level, not at the S3 bucket level, so the bucket must still be private and explicitly restricted to CloudFront.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Enable CloudFront Origin Access Control for the distribution and update the bucket policy to allow only the CloudFront distribution principal with its SourceArn.

CloudFront Origin Access Control (OAC) allows you to restrict access to an S3 bucket so that only the specific CloudFront distribution can retrieve objects. By updating the bucket policy to allow the CloudFront distribution principal with its SourceArn, you ensure that direct requests to the S3 object URL are denied, while CloudFront-signed URLs or cookies can still control user access. This meets the requirement of blocking direct S3 access while keeping the bucket private.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
Enable CloudFront Origin Access Control for the distribution and update the bucket policy to allow only the CloudFront distribution principal with its SourceArn.
Why this is correct
Origin Access Control is the modern pattern for restricting S3 origins to CloudFront. The bucket policy can then permit only the specific distribution, preventing direct S3 access while keeping the content private. Signed URLs or cookies can still be used at the viewer layer for authorization.
✗
Keep the bucket public and require signed URLs at CloudFront, because signed URLs automatically block all direct S3 requests.
Why it's wrong here
Signed URLs protect access through CloudFront, but they do not make the S3 bucket private. If the bucket policy is public, anyone who knows the S3 URL can still bypass CloudFront. The origin itself must be locked down.
✗
Add an S3 access point and allow the CloudFront distribution to use it without changing the bucket policy.
Why it's wrong here
An access point does not automatically solve the direct-public-access problem. The origin still needs a resource policy that restricts who can read the objects, and the CloudFront distribution must be explicitly authorized to use that origin path.
✗
Attach AWS WAF to the distribution and block requests that do not include a signed cookie.
Why it's wrong here
WAF can help with edge filtering, but it does not prevent direct S3 object URL access. The origin must be private through CloudFront authorization, otherwise the bucket remains reachable outside CloudFront regardless of WAF rules.

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

Go deeper

SAA-C03 Design Secure Architectures Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

Related to this question