S3 Bucket Policy Project 3: फक्त VPC Endpoint Access

By Ravindra Bagale, trainer · LinkedIn · Last updated: 28 October 2026

1. Story

Arjun Mehta (बेंगलुरु) व Sophie Martin (Toronto) KYC. फक्त vpce path.

2. VPCe-only का?

हे का लागतं?

Private EC2 असूनही public S3 endpoint शक्य. Condition = फक्त VPCe; stolen key from internet fail.

• Gateway VPCe
• Prefix list route
• SourceVpce
• Endpoint policy

3. Policy

हे काय आहे?

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "DenyUnlessFromMyVpce",
      "Effect": "Deny",
      "Principal": "*",
      "Action": "s3:*",
      "Resource": [
        "arn:aws:s3:::rb-payroll-ap-south-1",
        "arn:aws:s3:::rb-payroll-ap-south-1/*"
      ],
      "Condition": {
        "StringNotEquals": {
          "aws:SourceVpce": "vpce-0a1b2c3d4e5f67890"
        }
      }
    }
  ]
}

Line-by-line

1. Deny unless VPCe.
2. All callers.
3. s3:* lock.
4. Both ARNs.
5. vpce-id.
6. Deny ≠ Allow.

4. CLI

कसं करायचं (step by step)

# Gateway endpoint
aws ec2 create-vpc-endpoint --vpc-id vpc-0123456789abcdef0 \
  --service-name com.amazonaws.ap-south-1.s3 \
  --route-table-ids rtb-aaa rtb-bbb --vpc-endpoint-type Gateway
# { "VpcEndpoint": { "VpcEndpointId": "vpce-0a1b2c3d4e5f67890", ... } }

aws s3api put-bucket-policy --bucket rb-payroll-ap-south-1 --policy file://vpce.json

5. Allow/deny

# ALLOW — EC2 in VPC with endpoint route
aws s3 cp s3://rb-payroll-ap-south-1/payslip.pdf - --region ap-south-1 | wc -c
# >0

# DENY — laptop on internet, same IAM key
aws s3 cp s3://rb-payroll-ap-south-1/payslip.pdf /tmp/x --region ap-south-1
# An error occurred (AccessDenied) when calling the GetObject operation: Access Denied

6. Multi-industry

Payroll, KYC, hospital, govt.

7. AccessDenied debugging आणि Policy Simulator

AccessDenied क्रम: BPA → bucket Deny → IAM Allow → KMS → VPCe → ACL. Simulator BPA/VPC/KMS miss करू शकतो — खऱ्या CLI ने test.

# Decode
aws s3api get-bucket-policy --bucket BUCKET --query Policy --output text | python3 -m json.tool
aws s3api get-public-access-block --bucket BUCKET
aws iam simulate-principal-policy --policy-source-arn ARN \
  --action-names s3:GetObject --resource-arns arn:aws:s3:::BUCKET/key.txt
aws cloudtrail lookup-events --lookup-attributes AttributeKey=EventName,AttributeValue=GetObject --max-items 5

8. Lab: SourceVpce

Org block नसेल तर ap-south-1 (Mumbai). आधी budget alert.

कसं करायचं (step by step)

1. Bucket + VPCe.
2. Policy.
3. Allow inside.
4. Deny outside.

Cleanup (billing थांबवा)

1. Cleanup.
2. Routes.

9. सामान्य errors आणि fixes

प्रत्येक row = खरी चूक. Panic करण्याआधी fix वाचा.

10. Troubleshooting checklist

1. Region + endpoint.
2. Policy + BPA.
3. Lab user.
4. Sid binary search.
5. CloudTrail.
6. KMS test.
7. VPCe path.
8. Lock cleanup.
9. Route check.

11. FAQ

12. Interview Q&A

13. Tips — English, मराठी आणि हिंदी

14. Policy save करण्याआधी checklist

1. Business rule एका वाक्यात.
2. Allow vs Deny-unless; Deny wins.
3. ARN shapes.
4. Condition keys.
5. BPA first.
6. Allow+deny plan.
7. Cleanup plan.
8. json.tool.

15. Policy Simulator walkthrough

Simulator identity/resource typos साठी चांगला; BPA/VPCe/KMS miss होऊ शकतात. नंतर खऱ्या path वरून CLI.

1. Simulator → user/role.
2. Action + ARN.
3. Include bucket policy.
4. CLI confirm.
5. Mismatch → layers.

16. Copy-paste runbook

# 0) Region + names
export AWS_REGION=ap-south-1
export BUCKET=rb-lab-$(date +%s)-ap-south-1

# 1) Create + show BPA
aws s3api create-bucket --bucket $BUCKET --region $AWS_REGION \
  --create-bucket-configuration LocationConstraint=$AWS_REGION
aws s3api get-public-access-block --bucket $BUCKET || true

# 2) Validate + apply policy
python3 -m json.tool policy.json >/dev/null
aws s3api put-bucket-policy --bucket $BUCKET --policy file://policy.json
aws s3api get-bucket-policy --bucket $BUCKET --query Policy --output text | python3 -m json.tool | head

# 3) Allow test + Deny test (fill per project)
# ... project-specific curls / aws s3 cp ...

# 4) Cleanup
aws s3 rm s3://$BUCKET --recursive || true
aws s3api delete-bucket-policy --bucket $BUCKET || true
aws s3api delete-bucket --bucket $BUCKET

17. Industry story bank

वरील प्रत्येक project एक industry story वापरतो. इतर industries मध्ये फक्त bucket/principal/Condition बदला.

• Healthcare: SSE-KMS + OrgID + MFA.
• Fintech: IP + HTTPS + OAC.
• EdTech: OAC only.
• Logistics: VPCe.
• Media: Object Lock.
• Retail: prefix public read.
• SaaS: prefix homes.
• Gov: OrgID + MFA + Lock.

18. AccessDenied debugging flowchart

1. Error code + request id.
2. Bucket + region.
3. BPA.
4. Explicit Deny.
5. Conditions.
6. KMS key policy.
7. OAC id.
8. VPCe path.
9. Simulator + CLI.
10. Support last.

19. PR review checklist

• Valid JSON.
• Required fields.
• No open write.
• Tests.
• Cleanup.

उजळणी, मुलाखत आणि तुलना cards

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अजून cards: Ravi Sir's Cards.