The correct answer is to enable CloudFront Origin Access Control (OAC) for the distribution and update the bucket policy to allow only the CloudFront distribution principal with its SourceArn. This works because OAC replaces the older Origin Access Identity (OAI) by using a fine-grained, condition-based policy that checks the CloudFront distribution’s source ARN, ensuring that only requests routed through that specific distribution are allowed to reach the S3 bucket. On the SAA-C03 exam, this scenario tests your understanding of how to block direct S3 access while allowing only CloudFront, a common pattern for securing private content like PDF reports. A frequent trap is choosing OAI instead of OAC, but remember that OAC is the modern, recommended approach with stronger security and support for features like signed URLs and cookies. Memory tip: think “OAC = Access Control,” where the bucket policy explicitly checks the CloudFront ARN, making direct S3 URLs fail automatically.
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure architectures. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
A
Enable CloudFront Origin Access Control for the distribution and update the bucket policy to allow only the CloudFront distribution principal with its SourceArn.
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.
B
Keep the bucket public and require signed URLs at CloudFront, because signed URLs automatically block all direct S3 requests.
Why wrong: 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.
C
Add an S3 access point and allow the CloudFront distribution to use it without changing the bucket policy.
Why wrong: 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.
D
Attach AWS WAF to the distribution and block requests that do not include a signed cookie.
Why wrong: 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.
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.
Option A is correct because 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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that 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.
Detailed technical explanation
How to think about this question
CloudFront Origin Access Control (OAC) uses a principal (e.g., cloudfront.amazonaws.com) and a condition key (e.g., SourceArn) in the S3 bucket policy to grant access only to a specific distribution. This replaces the older Origin Access Identity (OAI) and supports features like cross-region distributions and KMS encryption. In a real-world scenario, you might combine OAC with CloudFront signed URLs or cookies to enforce user-level authentication, ensuring that even if a user obtains the CloudFront URL, they must have a valid signature to access the PDF.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable CloudFront Origin Access Control for the distribution and update the bucket policy to allow only the CloudFront distribution principal with its SourceArn. — Option A is correct because 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.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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