The correct answer is to add a condition in the bucket policy using the `aws:PrincipalArn` condition key to restrict S3 bucket access to a specific IAM role. This works because the condition explicitly checks the ARN of the requesting principal, ensuring that only requests from that exact role (e.g., `arn:aws:iam::123456789012:role/EC2AppRole`) are allowed, even if the policy otherwise grants access to an entire AWS account. On the AWS Certified Developer Associate DVA-C02 exam, this tests your understanding of fine-grained IAM policy conditions versus broad account-level permissions—a common trap is assuming that changing the principal to a role ARN in the policy’s `Principal` element is sufficient, but that only works for resource-based policies in the same account; the `aws:PrincipalArn` condition is the cross-account solution. Remember the mnemonic: “PrincipalArn pins the principal”—it locks access to one specific role, blocking all other users, roles, and external accounts.
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of security. 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.
A company uses an S3 bucket to store sensitive customer data. The bucket policy currently allows access to a specific IAM role used by an EC2 instance. A security audit reveals that the bucket is also accessible from an external AWS account. Which action should the security team take to restrict access to only the intended role?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a condition in the bucket policy to allow access only when the request includes the specific IAM role ARN.
Option D is correct because adding a condition in the bucket policy using the `aws:PrincipalArn` condition key allows you to restrict access exclusively to the specific IAM role ARN. This ensures that even if the bucket policy grants access to an external AWS account, only requests made by the designated IAM role (e.g., `arn:aws:iam::123456789012:role/EC2AppRole`) will be allowed, effectively blocking any other principals, including those from external accounts.
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.
✗
Use S3 Object Ownership to disable ACLs.
Why it's wrong here
ACLs are not the issue here.
✗
Enable S3 Block Public Access on the bucket.
Why it's wrong here
This only blocks public access, not cross-account access.
✗
Modify the IAM role trust policy to only allow the EC2 instance.
Why it's wrong here
Trust policy controls who can assume the role, not bucket access.
✓
Add a condition in the bucket policy to allow access only when the request includes the specific IAM role ARN.
Why this is correct
This restricts access to the intended role.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse IAM role trust policies with resource-based policies (like S3 bucket policies), thinking that modifying the trust policy will control access to the bucket, when in fact the bucket policy itself must explicitly restrict the principal.
Detailed technical explanation
How to think about this question
The `aws:PrincipalArn` condition key evaluates the ARN of the principal making the request, which can be an IAM user, role, or federated user. In a bucket policy, you can combine this with `aws:SourceArn` or `aws:SourceAccount` to further restrict cross-account access. For example, a condition like `"StringEquals": {"aws:PrincipalArn": "arn:aws:iam::123456789012:role/EC2AppRole"}` ensures that only requests signed with that role's credentials are allowed, even if the bucket policy grants access to an external account.
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.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a condition in the bucket policy to allow access only when the request includes the specific IAM role ARN. — Option D is correct because adding a condition in the bucket policy using the `aws:PrincipalArn` condition key allows you to restrict access exclusively to the specific IAM role ARN. This ensures that even if the bucket policy grants access to an external AWS account, only requests made by the designated IAM role (e.g., `arn:aws:iam::123456789012:role/EC2AppRole`) will be allowed, effectively blocking any other principals, including those from external accounts.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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