Q: To secure an S3 bucket powering a static website, you put CloudFront in front of it. How do you strictly guarantee that users can never bypass CloudFront and access the S3 bucket directly via its public URL?
You must implement Origin Access Control (OAC) (the modern replacement for Origin Access Identity, OAI).
#AWS #Cost & Architecture #L2 #Cloud #Infrastructure #S3
🎙️ Candidate Opening & Architectural Context
""When an interviewer asks how I troubleshoot this in AWS, I frame it through my hands-on production experience. The interviewer is testing: Origin Access Control (OAC), S3 Bucket Policies.. I structure my answer around systematic triage first, root cause analysis second, and permanent remediation third.""
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🛠️ Production Runbook & Step-by-Step Resolution
1️⃣
Initial Diagnostics & Root Cause Analysis
You must implement Origin Access Control (OAC) (the modern replacement for Origin Access Identity, OAI).
- Block all Public Access directly on the S3 bucket.
- In CloudFront, configure the S3 Origin to strictly use an OAC.
- Update the S3 Bucket Policy to explicitly grant
s3:GetObjectpermission strictly to the Principalcloudfront.amazonaws.com, utilizing aConditionblock that enforcesStringEquals: AWS:SourceArnmatching the specific ARN of your CloudFront distribution.
2️⃣
Remediation & Permanent Safeguards
This mathematically guarantees that the bucket will aggressively reject any request that didn't natively originate from your precise CloudFront distribution.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: Block all Public Access directly on the S3 bucket.."
⚡ 60-Second Elevator Pitch Talking Points
- Block all Public Access directly on the S3 bucket.
- In CloudFront, configure the S3 Origin to strictly use an OAC.
- Update the S3 Bucket Policy to explicitly grant s3:GetObject permission strictly to the Principal...
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