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Question 579 of 1,616

Security →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that both a bucket policy and a KMS key policy are required. This is because cross-account S3 access with KMS encryption involves two separate authorization layers: the S3 bucket policy controls who can perform the s3:GetObject action on the bucket, while the KMS key policy controls who can call kms:Decrypt to unlock the encrypted object. Without the key policy explicitly granting the production account’s IAM role, the bucket policy alone is insufficient—the KMS service will deny decryption for any principal not listed in the key policy. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of how resource-based policies interact across services; a common trap is assuming an IAM role in the target account can bypass the key policy. Remember the two-policy rule: bucket for S3, key for KMS—both must name the cross-account role.

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 manages multiple AWS accounts using AWS Organizations. A developer needs to allow an IAM role in the production account to read objects from an S3 bucket in the development account. The bucket is encrypted with an AWS KMS customer managed key (CMK) in the development account. Which of the following is required to enable this cross-account access?

Question 1mediummultiple choice

Full question →

A
Grant the production account's root user access to the KMS key and the S3 bucket.
Why wrong: Root user access is not necessary; IAM roles are used for cross-account access.
B
Add a bucket policy allowing the production account's IAM role and a KMS key policy granting the same role.
The bucket policy grants access to the bucket, and the KMS key policy allows decryption of encrypted objects.
C
Create an IAM role in the production account with permissions to access the S3 bucket and KMS key.
Why wrong: The IAM role in the production account is necessary, but it alone does not grant cross-account access; the resource-based policies (bucket policy and key policy) are also required.
D
Enable S3 bucket logging to allow cross-account access.
Why wrong: Bucket logging does not affect access permissions.

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 allowing the production account's IAM role and a KMS key policy granting the same role.

Option B is correct because cross-account access to an S3 bucket encrypted with a KMS customer managed key requires both a bucket policy that grants the production account's IAM role s3:GetObject permission and a KMS key policy that grants the same role kms:Decrypt permission. The bucket policy authorizes the S3 operation, while the key policy authorizes decryption of the object; both policies must explicitly allow the cross-account principal.

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.

✗
Grant the production account's root user access to the KMS key and the S3 bucket.
Why it's wrong here
Root user access is not necessary; IAM roles are used for cross-account access.
✓
Add a bucket policy allowing the production account's IAM role and a KMS key policy granting the same role.
Why this is correct
The bucket policy grants access to the bucket, and the KMS key policy allows decryption of encrypted objects.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create an IAM role in the production account with permissions to access the S3 bucket and KMS key.
Why it's wrong here
The IAM role in the production account is necessary, but it alone does not grant cross-account access; the resource-based policies (bucket policy and key policy) are also required.
✗
Enable S3 bucket logging to allow cross-account access.
Why it's wrong here
Bucket logging does not affect access permissions.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume a bucket policy alone is sufficient for cross-account access, forgetting that KMS-encrypted objects require a separate key policy grant for the decrypt permission.

Detailed technical explanation

How to think about this question

Under the hood, when a principal in the production account makes a GetObject request, S3 evaluates the bucket policy for the s3:GetObject action, and if the object is KMS-encrypted, S3 calls KMS to decrypt the envelope key. KMS evaluates the key policy for kms:Decrypt; if the key policy does not explicitly allow the production account's role, the request fails with an access denied error, even if the bucket policy allows it. A real-world scenario is when a data analytics pipeline in a production account needs to read encrypted data from a development account's S3 bucket; both policies must be configured correctly to avoid silent failures.

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 DVA-C02 question test?

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 bucket policy allowing the production account's IAM role and a KMS key policy granting the same role. — Option B is correct because cross-account access to an S3 bucket encrypted with a KMS customer managed key requires both a bucket policy that grants the production account's IAM role s3:GetObject permission and a KMS key policy that grants the same role kms:Decrypt permission. The bucket policy authorizes the S3 operation, while the key policy authorizes decryption of the object; both policies must explicitly allow the cross-account principal.

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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This DVA-C02 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 DVA-C02 exam.