DEA-C01 Data Security and Governance Practice Question
A data engineer is setting up cross-account access to an encrypted S3 bucket. The bucket uses a customer-managed KMS key. The engineer has configured the bucket policy and the IAM role in the source account. The target account still gets access denied errors when trying to read objects. What is the most likely cause?
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
✓
The KMS key policy does not grant the target account's IAM role the kms:Decrypt permission.
For cross-account access to an S3 bucket encrypted with a customer-managed KMS key, the KMS key policy must explicitly grant the target account's IAM role the kms:Decrypt permission. Without this, the target account will get access denied errors even if the bucket policy and IAM role are correctly configured. Option B is incorrect because Object Ownership does not affect cross-account read access. Option C is incorrect because the bucket policy only needs to allow the target account's IAM role, not the root user. Option D is incorrect because VPC Endpoint policies are not relevant to this cross-account access issue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The KMS key policy does not grant the target account's IAM role the kms:Decrypt permission.
Why this is correct
Correct. The KMS key policy must grant the target account's IAM role kms:Decrypt permission to allow decryption of objects encrypted with that key.
- ✗
The S3 bucket has Object Ownership set to BucketOwnerPreferred.
Why it's wrong here
Incorrect. Object Ownership settings like BucketOwnerPreferred do not affect cross-account read permissions; they control ownership of objects written by other accounts.
- ✗
The bucket policy does not allow the target account's root user.
Why it's wrong here
Incorrect. The bucket policy should allow the specific IAM role in the target account, not the root user. The root user is not used for direct access; IAM roles are used.
- ✗
The VPC Endpoint policy blocks access from the target account.
Why it's wrong here
Incorrect. VPC Endpoint policies control access from within a VPC, but cross-account access errors are not typically caused by VPC endpoint configurations unless the request originates from a VPC endpoint.
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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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 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 DEA-C01 exam.