The answer is a KMS key policy. This is correct because a KMS key policy is the primary access control mechanism for a customer managed key, and it can explicitly grant or deny permissions like kms:Encrypt and kms:Decrypt to specific IAM roles within the same account using the `aws:PrincipalArn` condition key, which directly enforces the restriction. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this tests your understanding that IAM policies alone are insufficient for KMS unless the key policy explicitly allows IAM access—a common trap is assuming an IAM role’s permissions automatically apply to a key without a matching key policy statement. For a short, focused answer, remember that the key policy is the gatekeeper; without it, even an admin role cannot use the key. Memory tip: “Key policy first, IAM policy second—the key policy is the lock, the IAM policy is the key.”
SOA-C02 Security and Compliance Practice Question
This SOA-C02 practice question tests your understanding of security and compliance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 wants to ensure that only specific IAM roles within the same AWS account can encrypt and decrypt data using an AWS KMS customer managed key. Which type of policy must be configured to achieve this restriction?
Why wrong: An IAM policy alone cannot grant KMS key permissions unless the key policy also allows IAM policies. The key policy must explicitly allow the roles.
B
KMS key policy
KMS key policies are resource-based policies that define who can use the key. They are required to grant access to IAM roles.
C
Service control policy (SCP)
Why wrong: SCPs are used in AWS Organizations to control permissions at the account level, not for individual KMS keys.
D
Resource policy attached to the KMS key
Why wrong: KMS uses key policies, not resource policies. The term resource policy is generally used for S3 or SNS; KMS has key policies.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
KMS key policy
A KMS key policy is the primary mechanism to control access to a customer managed key. By default, a KMS key policy must explicitly grant the necessary permissions (kms:Encrypt, kms:Decrypt) to IAM roles, and it can restrict those permissions to specific roles within the same account using the `aws:PrincipalArn` condition key. This ensures that only the designated IAM roles can encrypt and decrypt data with that key.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
IAM policy attached to the roles
Why it's wrong here
An IAM policy alone cannot grant KMS key permissions unless the key policy also allows IAM policies. The key policy must explicitly allow the roles.
✓
KMS key policy
Why this is correct
KMS key policies are resource-based policies that define who can use the key. They are required to grant access to IAM roles.
Related concept
Read the scenario before looking for a memorised answer.
✗
Service control policy (SCP)
Why it's wrong here
SCPs are used in AWS Organizations to control permissions at the account level, not for individual KMS keys.
✗
Resource policy attached to the KMS key
Why it's wrong here
KMS uses key policies, not resource policies. The term resource policy is generally used for S3 or SNS; KMS has key policies.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think an IAM policy alone is sufficient to grant KMS key access, but they forget that KMS key policies act as a resource-based policy that must explicitly allow the IAM principal, otherwise the IAM policy is ignored.
Detailed technical explanation
How to think about this question
Under the hood, KMS key policies are JSON documents that define who can use the key and under what conditions. They can use the `Principal` element to specify IAM roles by ARN, and the `Condition` element with `aws:SourceAccount` or `aws:PrincipalArn` to restrict access to the same account. A common real-world scenario is when you need to enforce that only a specific application role (e.g., an EC2 instance role) can decrypt data, while preventing any other role or user in the account from doing so, which is achieved by combining a key policy with IAM policies and optionally using grants for fine-grained control.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: KMS key policy — A KMS key policy is the primary mechanism to control access to a customer managed key. By default, a KMS key policy must explicitly grant the necessary permissions (kms:Encrypt, kms:Decrypt) to IAM roles, and it can restrict those permissions to specific roles within the same account using the `aws:PrincipalArn` condition key. This ensures that only the designated IAM roles can encrypt and decrypt data with that key.
What should I do if I get this SOA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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