← SOA-C02·Amazon Web Services

Question 1,420 of 1,546

Security and Compliance →mediumMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is the bucket policy that uses a Deny effect with conditions checking both `s3:x-amz-server-side-encryption` equals `aws:kms` and `s3:x-amz-server-side-encryption-aws-kms-key-id` is not null. This works because the first condition ensures the object is encrypted with KMS, while the second condition enforces that a specific KMS key ID is provided, preventing the use of the default AWS-managed KMS key or any other customer key. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how to combine StringNotEquals and Null conditions to enforce a specific KMS key for S3 encryption, a common security requirement for sensitive data. A frequent trap is choosing a policy that only requires SSE-KMS without restricting the key ID, which would allow any KMS key. Remember the mnemonic "Deny the default, demand the specific key" to recall that you must explicitly deny uploads missing both the `aws:kms` value and a non-null key ID.

SOA-C02 Security and Compliance Practice Question

This SOA-C02 practice question tests your understanding of security and compliance. 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 stores sensitive data in an S3 bucket. The security team requires that all objects uploaded to the bucket be encrypted at rest using an AWS KMS customer-managed key. Which S3 bucket policy statement should be added to enforce this requirement?

Question 1mediummultiple choice

Full question →

A
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"}}}
Why wrong: This denies uploads that are not using SSE-KMS, but does not require a specific KMS key, so users could use any KMS key.
B
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"Null":{"s3:x-amz-server-side-encryption":"true"}}}
Why wrong: This only denies uploads without any encryption header, but allows any type of encryption including SSE-S3.
C
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}}
This denies uploads that do not use SSE-KMS and also ensures the KMS key ID is present (though not specific key). However, to enforce a specific key, a condition on the key ID is needed. This statement is a common baseline.
D
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"AES256"}}}
Why wrong: This denies uploads that do not use SSE-S3, which is not the required KMS encryption.

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

✓

{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}}

Option C is correct because the condition 's3:x-amz-server-side-encryption-aws-kms-key-id' checks that the specific KMS key is used, and the condition 's3:x-amz-server-side-encryption' ensures encryption is enforced. Option A is wrong because it allows SSE-S3. Option B is wrong because it allows SSE-KMS but does not restrict to a specific key. Option D is wrong because it denies all uploads without encryption, but does not require the specific KMS key.

Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

Answer analysis

Option-by-option breakdown

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

✗
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"}}}
Why it's wrong here
This denies uploads that are not using SSE-KMS, but does not require a specific KMS key, so users could use any KMS key.
✗
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"Null":{"s3:x-amz-server-side-encryption":"true"}}}
Why it's wrong here
This only denies uploads without any encryption header, but allows any type of encryption including SSE-S3.
✓
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}}
Why this is correct
This denies uploads that do not use SSE-KMS and also ensures the KMS key ID is present (though not specific key). However, to enforce a specific key, a condition on the key ID is needed. This statement is a common baseline.
Related concept
Standard ACLs match source addresses.
✗
{"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"AES256"}}}
Why it's wrong here
This denies uploads that do not use SSE-S3, which is not the required KMS encryption.

Common exam traps

Common exam trap: ACLs stop at the first match

ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.

Detailed technical explanation

How to think about this question

ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.

KKey Concepts to Remember

Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.

TExam Day Tips

Check inbound versus outbound direction.
Read the ACL from top to bottom.
Look for a broader permit or deny above the intended line.

Key takeaway

ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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.

Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SOA-C02 ACL questions on filtering logic and placement.

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FAQ

Questions learners often ask

What does this SOA-C02 question test?

Security and Compliance — This question tests Security and Compliance — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: {"Effect":"Deny","Principal":"*","Action":"s3:PutObject","Resource":"arn:aws:s3:::bucket/*","Condition":{"StringNotEquals":{"s3:x-amz-server-side-encryption":"aws:kms"},"Null":{"s3:x-amz-server-side-encryption-aws-kms-key-id":"true"}}} — Option C is correct because the condition 's3:x-amz-server-side-encryption-aws-kms-key-id' checks that the specific KMS key is used, and the condition 's3:x-amz-server-side-encryption' ensures encryption is enforced. Option A is wrong because it allows SSE-S3. Option B is wrong because it allows SSE-KMS but does not restrict to a specific key. Option D is wrong because it denies all uploads without encryption, but does not require the specific KMS key.

What should I do if I get this SOA-C02 question wrong?

What is the key concept behind this question?

Standard ACLs match source addresses.

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Same concept, more angles

2 more ways this is tested on SOA-C02

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A company has an S3 bucket that stores sensitive customer data. The security team requires that all objects in the bucket be encrypted at rest using AWS KMS. An administrator notices that some objects are not encrypted. What is the MOST efficient way to enforce encryption for future uploads?

hard

A.Use an SCP to require KMS encryption for all S3 actions.
B.Use AWS Config to detect unencrypted objects and automatically encrypt them.
✓ C.Add a bucket policy that denies s3:PutObject unless the request includes the x-amz-server-side-encryption header set to aws:kms.
D.Enable S3 default encryption on the bucket with KMS.

Why C: Option A is correct because a bucket policy that denies PutObject without the correct encryption header will enforce encryption for all uploads. Option B is wrong because S3 default encryption only applies if no encryption header is provided; it can be overridden. Option C is wrong because SCPs affect IAM permissions, not S3 bucket configurations. Option D is wrong because encryption is enforced per object upload, not after upload.

Variation 2. 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?

hard

A."Condition": {"StringEquals": {"s3:x-amz-server-side-encryption": "aws:kms"}}
✓ B."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"}}
C."Condition": {"StringEquals": {"s3:x-amz-server-side-encryption-aws-kms-key-id": "arn:aws:kms:us-east-1:123456789012:key/abc123"}}
D."Condition": {"Null": {"s3:x-amz-server-side-encryption": "false"}}

Why B: The condition 's3:x-amz-server-side-encryption':'aws:kms' ensures KMS encryption is used, and 's3:x-amz-server-side-encryption-aws-kms-key-id' with the specific key ARN ensures only that key is used. Option A enforces KMS encryption but does not specify the key; Option B allows any KMS key; Option C is incorrect because it uses 'Null' condition incorrectly; Option D correctly enforces both encryption and key.

Last reviewed: Jun 20, 2026

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