hardMultiple ChoiceObjective-mapped
S3 Bucket Policy vs ACL Evaluation Order
Exhibit
Refer to the exhibit.
---
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:PutObject",
"Resource": "arn:aws:s3:::data-bucket/*",
"Condition": {
"Bool": {
"aws:SecureTransport": "true"
}
}
},
{
"Effect": "Deny",
"Action": "s3:*",
"Resource": "arn:aws:s3:::data-bucket/*",
"Condition": {
"Bool": {
"aws:SecureTransport": "false"
}
}
}
]
}
---An administrator applies the above S3 bucket policy to a bucket named 'data-bucket' that contains sensitive logs. The policy is intended to allow uploads only over HTTPS. After applying, the administrator finds that uploads using the AWS CLI without HTTPS still succeed. What is the most likely reason?
Quick Answer
The answer is that the bucket’s ACLs grant PutObject permission to the authenticated user, which takes effect before the bucket policy is evaluated. This occurs because S3 bucket policy vs ACL evaluation order is not a strict sequential hierarchy; instead, S3 evaluates all access control mechanisms independently and grants access if any applicable policy allows it, unless an explicit Deny exists from the same source. In this case, the ACL’s Allow for PutObject is evaluated first and permits the upload, so the bucket policy’s Deny based on the aws:SecureTransport condition never overrides it. For the CCSP exam, this tests your understanding of S3’s authorization model, where ACLs, bucket policies, and user policies are all considered, and a single Allow from any source can bypass a Deny from a different source. A common trap is assuming a bucket policy Deny always wins, but remember: ACLs are evaluated independently and can grant access before the policy’s Deny is even checked. Memory tip: “ACLs allow first, policies deny later—if any source says yes, the request goes through.”
⚠ Common exam trap
ISC2 often tests the misconception that Allow statements can override Deny statements due to evaluation order. In reality, an explicit Deny always takes precedence over any Allow. However, if a Deny statement's conditions are not met, the Deny does not apply, and an Allow may grant access. Candidates should understand that a correctly written Deny condition is essential to enforce security constraints.
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
✓
The Deny statement's condition is incorrectly specified, preventing it from matching non-HTTPS requests.
The bucket policy likely contains an Allow statement granting PutObject and a Deny statement intended to block non-HTTPS requests using the aws:SecureTransport condition key. However, if the Deny statement uses an incorrect condition operator (e.g., StringEquals instead of Bool), the condition never evaluates to true for non-HTTPS requests. As a result, the Deny statement does not apply, and the Allow statement permits the upload regardless of transport. This is a common syntax configuration error. In AWS IAM policy evaluation, an explicit Deny always overrides an Allow, but only if the Deny statement's conditions match the request. Therefore, a misconfigured condition effectively bypasses the Deny.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The 'aws:SecureTransport' condition key is not supported for S3 bucket policies.
Why it's wrong here
The 'aws:SecureTransport' condition key is fully supported for S3 bucket policies and is commonly used to enforce HTTPS.
- ✗
The policy does not apply to requests made by the AWS root account user.
Why it's wrong here
AWS root account users are not exempt from bucket policies; an explicit Deny in a bucket policy applies to all principals, including the root user.
- ✗
The bucket's ACLs grant PutObject permission to the authenticated user, which takes effect before the bucket policy is evaluated.
Why it's wrong here
In Amazon S3, an explicit Deny in a bucket policy overrides any Allow granted by ACLs. ACL permissions are evaluated before bucket policies, but a Deny in the bucket policy will still supersede the ACL Allow.
- ✓
The Deny statement's condition is incorrectly specified, preventing it from matching non-HTTPS requests.
Why this is correct
If the Deny statement's condition is incorrectly specified (e.g., wrong operator), the condition will not match non-HTTPS requests, and the Deny will not be applied, allowing the Allow statement to grant access.
Visual reference
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
Related to this question
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Same concept, more angles
1 more way this is tested on CCSP
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. Refer to the exhibit. A security engineer discovers that the S3 bucket policy allows public read access from the entire corporate network (10.0.0.0/16). However, the company wants to restrict access only to the security team's subnet (10.0.1.0/24). What modification should be made to the policy?
hard- A.Add a Deny statement for the 10.0.0.0/16 range.
- B.Add a Deny statement for IP addresses outside 10.0.1.0/24.
- C.Remove the Condition element to allow access from any IP.
- ✓ D.Change the Condition value to "aws:SourceIp": "10.0.1.0/24".
Why D: Modifying the Condition value to "aws:SourceIp": "10.0.1.0/24" directly restricts the S3 bucket policy to allow read access only from the security team's subnet. The original policy uses the aws:SourceIp condition key with the broader 10.0.0.0/16 range, so narrowing it to 10.0.1.0/24 precisely enforces the required access control. This approach leverages AWS IAM policy evaluation logic where an explicit Allow with a condition must be satisfied for access to be granted.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CCSP practice question is part of Courseiva's free ISC2 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 CCSP exam.