SAA-C03 Design Secure Architectures Practice Question
A security requirement states: all uploads to an S3 bucket must (1) use TLS in transit and (2) use server-side encryption with AWS KMS (SSE-KMS) using the CMK key id 'abcd-1234'; otherwise the upload should be rejected. A developer reports that uploads are succeeding even though clients are sometimes using non-encrypted requests. Which bucket policy approach most directly enforces both controls?
⚠ Common exam trap
A common mix-up: candidates confuse S3 default encryption with enforcement—default encryption only applies encryption to objects that lack it, but does not reject non-compliant uploads, so it cannot replace a bucket policy Deny statement for rejecting requests that violate encryption or TLS requirements.
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
✓
Use Deny statements that reject PutObject when aws:SecureTransport is false and reject PutObject when s3:x-amz-server-side-encryption is not 'aws:kms' or when s3:x-amz-server-side-encryption-aws-kms-key-id does not equal 'abcd-1234'.
Bucket policies can use the `aws:SecureTransport` condition key to enforce TLS and the `s3:x-amz-server-side-encryption` and `s3:x-amz-server-side-encryption-aws-kms-key-id` condition keys to enforce SSE-KMS with the specific CMK key ID. By using Deny statements, any request that does not meet both conditions is explicitly rejected, regardless of any Allow statements that might otherwise grant access. This directly enforces the security requirement at the bucket level.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add an Allow statement granting s3:PutObject to the developer role; rely on IAM conditions in the developer role to enforce TLS and SSE-KMS.
Why it's wrong here
A bucket policy Allow does not directly enforce the requirement in a way that rejects noncompliant requests. IAM conditions on the developer role may not apply to every caller (for example, other principals) and are not centrally enforced at the bucket level. The most direct enforcement for a bucket-wide requirement is a policy that explicitly Denies noncompliant PutObject requests based on request attributes.
- ✓
Use Deny statements that reject PutObject when aws:SecureTransport is false and reject PutObject when s3:x-amz-server-side-encryption is not 'aws:kms' or when s3:x-amz-server-side-encryption-aws-kms-key-id does not equal 'abcd-1234'.
Why this is correct
These Deny conditions directly block noncompliant requests regardless of the caller’s IAM permissions because explicit Deny in a resource policy overrides any Allow. aws:SecureTransport identifies whether the request used TLS. The SSE-KMS headers (s3:x-amz-server-side-encryption and s3:x-amz-server-side-encryption-aws-kms-key-id) identify whether SSE-KMS was requested and which CMK key id was used.
- ✗
Enable S3 default encryption to SSE-KMS and remove any bucket policy enforcement, since default encryption automatically rejects all noncompliant uploads.
Why it's wrong here
S3 default encryption applies only when clients omit encryption headers. It does not reliably enforce that the client used a specific CMK key id when encryption headers are provided, and it does not guarantee rejection of explicit noncompliant encryption headers.
- ✗
Attach a WAF rule to the S3 website endpoint to block non-TLS requests, because bucket policies cannot evaluate aws:SecureTransport.
Why it's wrong here
WAF generally applies to supported front-end integrations (such as CloudFront or API Gateway). S3 website endpoints are not the standard S3 API path for PutObject. In contrast, bucket policies can evaluate aws:SecureTransport for S3 API requests, so WAF is not the correct control here.
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
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.