Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
An application in account A needs to use an encrypted EBS volume whose snapshots were copied from account B. The EBS volume is encrypted with a customer-managed KMS key in account B. After attaching the volume, the instance fails to mount it and logs show KMS access errors (kms:Decrypt) for the instance role. The instance role in account A already has an IAM policy allowing kms:Decrypt on that key ARN, but the mount still fails. What must be updated in account B to allow the mount to succeed?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Enable KMS automatic key rotation for the customer-managed key in account B.
Key rotation is unrelated to authorization failures. The problem is that the key policy in account B is not allowing the cross-account principal to use kms:Decrypt for the key.
B
Best answer
Update the KMS key policy in account B to allow the instance role’s principal from account A to call kms:Decrypt and kms:CreateGrant.
Customer-managed KMS keys use resource-based key policies to control cross-account usage. Even if the IAM role in account A has kms:Decrypt permissions, the account B key policy must also allow that principal to use the key. Including kms:Decrypt (and often kms:CreateGrant) resolves cross-account mount authorization.
C
Distractor review
Attach the key policy as an IAM permissions policy to the instance role in account A only; key policies are not evaluated cross-account.
KMS key policies are evaluated on the key itself. Without updating the key policy in account B, cross-account calls will still be denied even if IAM permissions exist in account A.
D
Distractor review
Disable encryption on the EBS volume until authorization is fixed, then re-enable encryption after mount.
Disabling encryption violates security requirements and does not address why KMS authorization fails. Encrypted volumes and snapshots require correct KMS policies to be usable.
Common exam trap
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Technical deep dive
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
- Authentication checks who the user is.
- Authorization controls what the user is allowed to do after login.
- Privilege levels affect access to EXEC and configuration commands.
- AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
- Do not assume successful login means full administrative access.
- Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
- Separate login problems from permission problems before choosing the answer.
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More questions from this exam
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Question 2
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Question 3
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Question 4
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Question 5
A team wants to delegate IAM management to developers, but must ensure developers can never grant themselves permissions beyond a specific limit. Which AWS mechanism best matches this requirement?
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Authentication checks who the user is.
What is the correct answer to this question?
The correct answer is: Update the KMS key policy in account B to allow the instance role’s principal from account A to call kms:Decrypt and kms:CreateGrant. — For a customer-managed KMS key, authorization is enforced by the key policy on the key resource itself. In cross-account scenarios, it is common to see failures even when the calling role in account A has an IAM policy permitting kms:Decrypt, because the key policy in account B is still blocking the principal. To fix the mount, update the KMS key policy in account B to allow the specific instance role principal from account A to perform kms:Decrypt and typically kms:CreateGrant. This enables the KMS operations required for EBS to decrypt the data keys during attach/mount. Why others are wrong: A is unrelated to authorization and will not resolve kms:Decrypt access denials. C incorrectly states that key policies aren’t evaluated cross-account; KMS always checks both IAM permissions and the key policy for customer-managed keys. D weakens security and ignores the underlying trust/authorization mechanism needed to use the key for encrypted volume operations.
What should I do if I get this SAA-C03 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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