DBS-C01 Database Security Practice Question
A company has an Amazon S3 bucket that stores database backup files. The backups are encrypted using server-side encryption with AWS KMS (SSE-KMS). The security team wants to ensure that only a specific IAM role can decrypt the backups when restoring the database. Which policy should be attached to the KMS key to achieve this?
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
✓
A KMS key policy that grants kms:Decrypt to the IAM role.
A KMS key policy can grant the kms:Decrypt permission to a specific IAM role, ensuring only that role can decrypt the backups. Option A is incorrect because an S3 bucket policy cannot grant kms:Decrypt; KMS permissions are controlled via KMS key policies or IAM policies. Option B is incorrect because s3:GetObject alone does not enable decryption of SSE-KMS encrypted objects; decryption also requires kms:Decrypt. Option C is incorrect because an IAM policy attached to the role that grants kms:Decrypt is not sufficient unless the KMS key policy also allows the role to use the key; the key policy must explicitly grant permission to the role or the root account.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
An S3 bucket policy that grants kms:Decrypt to the IAM role.
Why it's wrong here
S3 bucket policies cannot grant KMS permissions.
- ✗
An S3 bucket policy that grants s3:GetObject to the IAM role.
Why it's wrong here
The S3 bucket policy controls access to the object, not decryption of the key.
- ✗
An IAM policy attached to the role that grants kms:Decrypt.
Why it's wrong here
The KMS key policy must also allow the role; otherwise, the IAM policy alone is insufficient if the key policy denies.
- ✓
A KMS key policy that grants kms:Decrypt to the IAM role.
Why this is correct
The KMS key policy controls who can use the key for decryption.
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 DBS-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 DBS-C01 exam.