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Question 710 of 1,040

Design Secure Architectures →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is to add a bucket policy that allows s3:GetObject only when the principal is cloudfront.amazonaws.com and the aws:SourceArn matches your CloudFront distribution ARN, while also blocking public access. This works because Origin Access Control (OAC) uses a service principal and the SourceArn condition to cryptographically tie the permission to your specific distribution, so even if someone guesses the S3 URL, CloudFront is the only entity authorized to fetch objects. On the SAA-C03 exam, this scenario tests your understanding of how OAC replaces the older Origin Access Identity (OAI) and enforces a more secure, conditional trust between CloudFront and S3. A common trap is choosing a bucket policy that only checks the principal without the SourceArn condition, which would allow any CloudFront distribution to access your bucket. Remember the mnemonic: “Principal plus SourceArn locks the barn door.”

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.

You serve private reports stored in an S3 bucket through CloudFront. After a recent change, users report that they can access the S3 object URLs directly (bypassing CloudFront), which violates your design. You want to ensure S3 objects are readable only through CloudFront using Origin Access Control (OAC), even if someone guesses the S3 URL. Which update best enforces this at the S3 bucket level?

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.

Question 1mediummultiple choice

Full question →

A
Add a bucket policy Allow for s3:GetObject only when the principal is cloudfront.amazonaws.com and aws:SourceArn matches your CloudFront distribution ARN, while blocking public access.
CloudFront OAC requests are authorized via a CloudFront principal plus a SourceArn restriction. Coupled with public access blocking, this prevents direct S3 URL reads.
B
Enable an S3 bucket lifecycle policy to transition objects to Glacier, so public S3 URLs become inaccessible.
Why wrong: Lifecycle transitions do not prevent public access. Users could still access objects while they exist in a readable storage class.
C
Rely only on CloudFront signed URLs validation; do not change the S3 bucket policy.
Why wrong: Signed URLs control CloudFront access but do not restrict direct S3 access. If the bucket allows it, S3 URLs will still work.
D
Add a WAF rule on CloudFront to block requests that contain "amazonaws.com" in the URL path.
Why wrong: WAF rules apply at CloudFront, not S3. Direct S3 requests would bypass CloudFront, so WAF cannot protect the bucket.

Full breakdown with real-world context →

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

✓

Add a bucket policy Allow for s3:GetObject only when the principal is cloudfront.amazonaws.com and aws:SourceArn matches your CloudFront distribution ARN, while blocking public access.

Option A is correct because it uses an S3 bucket policy that grants s3:GetObject access only when the principal is cloudfront.amazonaws.com and the aws:SourceArn matches the CloudFront distribution ARN. This ensures that only CloudFront, using Origin Access Control (OAC), can retrieve objects, blocking direct S3 URL access even if the URL is guessed. Blocking public access at the bucket level further prevents any anonymous or public reads.

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.

✓
Add a bucket policy Allow for s3:GetObject only when the principal is cloudfront.amazonaws.com and aws:SourceArn matches your CloudFront distribution ARN, while blocking public access.
Why this is correct
CloudFront OAC requests are authorized via a CloudFront principal plus a SourceArn restriction. Coupled with public access blocking, this prevents direct S3 URL reads.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable an S3 bucket lifecycle policy to transition objects to Glacier, so public S3 URLs become inaccessible.
Why it's wrong here
Lifecycle transitions do not prevent public access. Users could still access objects while they exist in a readable storage class.
✗
Rely only on CloudFront signed URLs validation; do not change the S3 bucket policy.
Why it's wrong here
Signed URLs control CloudFront access but do not restrict direct S3 access. If the bucket allows it, S3 URLs will still work.
✗
Add a WAF rule on CloudFront to block requests that contain "amazonaws.com" in the URL path.
Why it's wrong here
WAF rules apply at CloudFront, not S3. Direct S3 requests would bypass CloudFront, so WAF cannot protect the bucket.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates may think CloudFront signed URLs alone are sufficient for security, but without a restrictive bucket policy, the S3 bucket remains publicly accessible, allowing direct URL access to bypass CloudFront.

Detailed technical explanation

How to think about this question

Origin Access Control (OAC) replaces the older Origin Access Identity (OAI) and uses a bucket policy with the aws:SourceArn condition to restrict access to a specific CloudFront distribution. The aws:SourceArn condition is evaluated against the distribution's ARN, preventing other AWS accounts or services from using the same principal. This policy works even if the S3 bucket is configured to block all public access, as the CloudFront service principal is an AWS service, not a public entity.

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.

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FAQ

Questions learners often ask

What does this SAA-C03 question test?

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: Add a bucket policy Allow for s3:GetObject only when the principal is cloudfront.amazonaws.com and aws:SourceArn matches your CloudFront distribution ARN, while blocking public access. — Option A is correct because it uses an S3 bucket policy that grants s3:GetObject access only when the principal is cloudfront.amazonaws.com and the aws:SourceArn matches the CloudFront distribution ARN. This ensures that only CloudFront, using Origin Access Control (OAC), can retrieve objects, blocking direct S3 URL access even if the URL is guessed. Blocking public access at the bucket level further prevents any anonymous or public reads.

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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Same concept, more angles

1 more ways this is tested on SAA-C03

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A static website uses an Amazon S3 bucket as the origin for an Amazon CloudFront distribution. The team accidentally configured the S3 bucket policy to allow s3:GetObject to Principal "*", so objects are accessible via direct S3 URLs. They want to ensure objects are retrievable only through CloudFront. What is the best corrective action?

medium

✓ A.Remove public access from the bucket and update the bucket policy to allow GetObject only from CloudFront using the distribution’s SourceArn (and use CloudFront origin access control or origin access identity).
B.Enable S3 static website hosting and disable CloudFront, because website hosting blocks direct object URL access.
C.Add a WAF rule that rate-limits requests to the S3 bucket domain to make direct access impractical.
D.Turn on S3 object versioning so that attackers cannot read previous objects.

Why A: Option A is correct because the S3 bucket policy currently allows s3:GetObject from any principal, making objects publicly accessible via direct S3 URLs. By removing public access and updating the policy to restrict GetObject to only requests that originate from the CloudFront distribution (using either Origin Access Control or Origin Access Identity), objects become retrievable exclusively through CloudFront, preventing direct S3 access.

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This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.