This DVA-C02 practice question tests your understanding of security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Refer to the exhibit. An IAM role has the attached policy. A developer is writing an application that will upload objects to the S3 bucket using server-side encryption with AWS KMS (SSE-KMS). The application is failing with an Access Denied error when trying to upload. What is the missing permission?
kms:Decrypt is needed because the S3 API may call Decrypt on the KMS key when the key is not the default or due to regional caching, making this the missing permission.
B
kms:ListKeys on the KMS key
Why wrong: kms:ListKeys is not required for uploading objects with SSE-KMS.
C
kms:Encrypt on the KMS key
Why wrong: kms:Encrypt is not used by S3; the service uses kms:GenerateDataKey instead, which is already permitted.
D
s3:PutObjectAcl on the bucket
Why wrong: s3:PutObjectAcl is not necessary for uploading objects; the policy should include s3:PutObject, but that is not listed as an option.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
kms:Decrypt on the KMS key
The missing permission is kms:Decrypt on the KMS key. Although SSE-KMS requires kms:GenerateDataKey for encryption during upload, certain scenarios (e.g., when the KMS key has already been used in the same region or when the bucket policy includes conditional checks) may require kms:Decrypt to verify key access. The current policy allows kms:GenerateDataKey but lacks kms:Decrypt, causing Access Denied errors for the upload. Option A is correct. Option B (kms:ListKeys) is not required. Option C (kms:Encrypt) is not used by S3 for SSE-KMS. Option D (s3:PutObjectAcl) is not needed for basic uploads.
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.
✓
kms:Decrypt on the KMS key
Why this is correct
kms:Decrypt is needed because the S3 API may call Decrypt on the KMS key when the key is not the default or due to regional caching, making this the missing permission.
Related concept
Standard ACLs match source addresses.
✗
kms:ListKeys on the KMS key
Why it's wrong here
kms:ListKeys is not required for uploading objects with SSE-KMS.
✗
kms:Encrypt on the KMS key
Why it's wrong here
kms:Encrypt is not used by S3; the service uses kms:GenerateDataKey instead, which is already permitted.
✗
s3:PutObjectAcl on the bucket
Why it's wrong here
s3:PutObjectAcl is not necessary for uploading objects; the policy should include s3:PutObject, but that is not listed as an option.
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.
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
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 DVA-C02 ACL questions on filtering logic and placement.
Security — This question tests Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: kms:Decrypt on the KMS key — The missing permission is kms:Decrypt on the KMS key. Although SSE-KMS requires kms:GenerateDataKey for encryption during upload, certain scenarios (e.g., when the KMS key has already been used in the same region or when the bucket policy includes conditional checks) may require kms:Decrypt to verify key access. The current policy allows kms:GenerateDataKey but lacks kms:Decrypt, causing Access Denied errors for the upload. Option A is correct. Option B (kms:ListKeys) is not required. Option C (kms:Encrypt) is not used by S3 for SSE-KMS. Option D (s3:PutObjectAcl) is not needed for basic uploads.
What should I do if I get this DVA-C02 question wrong?
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 DVA-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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