SOA-C02 Security and Compliance Practice Question

A company has an S3 bucket that stores sensitive customer data. The security team requires that all objects uploaded to the bucket must be encrypted at rest using AWS KMS with a specific customer managed key. Which bucket policy condition should be used to enforce 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

✓

"Condition": {"StringEquals": {"s3:x-amz-server-side-encryption": "aws:kms", "s3:x-amz-server-side-encryption-aws-kms-key-id": "arn:aws:kms:us-east-1:123456789012:key/abc123"}}

It uses both conditions: 's3:x-amz-server-side-encryption' set to 'aws:kms' ensures that objects are encrypted with SSE-KMS, and 's3:x-amz-server-side-encryption-aws-kms-key-id' set to the specific key ARN ensures that only the designated customer managed key is used. Option A enforces KMS encryption but does not restrict which KMS key, allowing any managed key. Option C enforces a specific key ARN but does not require the encryption header to be present, which could allow objects without encryption if the key ID header is omitted (though in practice, the key ID is only valid with SSE-KMS, the condition alone is not sufficient to guarantee encryption). Option D uses a 'Null' condition incorrectly and would not properly enforce encryption.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

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"Condition": {"StringEquals": {"s3:x-amz-server-side-encryption": "aws:kms"}}
Why it's wrong here
This only enforces KMS encryption but does not restrict which KMS key can be used; any KMS key would be accepted.
✓
"Condition": {"StringEquals": {"s3:x-amz-server-side-encryption": "aws:kms", "s3:x-amz-server-side-encryption-aws-kms-key-id": "arn:aws:kms:us-east-1:123456789012:key/abc123"}}
Why this is correct
Combines both conditions to enforce KMS encryption and the specific customer managed key, meeting the requirement.
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"Condition": {"StringEquals": {"s3:x-amz-server-side-encryption-aws-kms-key-id": "arn:aws:kms:us-east-1:123456789012:key/abc123"}}
Why it's wrong here
This requires the specific key but does not enforce that the encryption is KMS; a request without encryption header would fail, but the condition alone is insufficient.
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"Condition": {"Null": {"s3:x-amz-server-side-encryption": "false"}}
Why it's wrong here
The Null condition checks if the header is absent; 'false' means the header must be present, but it doesn't enforce KMS specifically.

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

SOA-C02 Security and Compliance Practice Question

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

Related to this question