DVA-C02 Security Practice Question
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?
⚠ Common exam trap
Watch out — 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.
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.
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.
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
Granting the production account's root user access to the KMS key and S3 bucket is a severe security anti-pattern and violates the principle of least privilege. The root user possesses unrestricted administrative privileges across the entire account and should only be used for a very limited set of initial account and service management tasks. For routine operational or cross-account access, IAM roles with specific, limited permissions are the secure and auditable method, preventing unnecessary exposure of critical resources.
- ✓
Add a bucket policy allowing the production account's IAM role and a KMS key policy granting the same role.
Why this is correct
To enable secure cross-account access, a bucket policy must explicitly grant the production account's IAM role permissions for S3 actions like `s3:GetObject` on the bucket. Concurrently, a KMS key policy is essential to grant the *same* IAM role `kms:Decrypt` permissions, allowing it to decrypt objects encrypted with that KMS key. This combination of resource-based policies on the S3 bucket and KMS key establishes the necessary trust relationship, ensuring the production account's role can both access the bucket and decrypt its contents.
- ✗
Create an IAM role in the production account with permissions to access the S3 bucket and KMS key.
Why it's wrong here
Creating an IAM role in the production account with permissions to access the S3 bucket and KMS key is a necessary first step, defining the identity's capabilities. However, this identity-based policy alone is insufficient for cross-account access. The S3 bucket and KMS key, residing in a different AWS account, must also have explicit resource-based policies (a bucket policy and a KMS key policy, respectively) that grant permission to the production account's specific IAM role. Without these resource-based policies, the cross-account access will be denied.
- ✗
Enable S3 bucket logging to allow cross-account access.
Why it's wrong here
Enabling S3 bucket logging, such as S3 server access logs or CloudTrail data events, records requests made to the bucket for auditing and monitoring purposes. This feature provides valuable insights into who accessed objects, when, and from where, but it is purely an observability mechanism. S3 logging does not, however, configure or affect the actual access control permissions that determine whether a principal can perform actions on the bucket or its objects.
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
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.