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🛡️ AWS S3 Bucket Policy allows public read or write access🟢

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Description​

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Description​

This policy identifies AWS S3 Buckets whose bucket policies grant public read or write access.

A bucket policy is considered public if it contains a statement with "Effect": "Allow" and a "Principal" set to "*" or {"AWS": "*"}. The evaluation focuses on permissions that allow reading (s3:GetObject, s3:GetObjectVersion, s3:ListBucket), writing (s3:PutObject, s3:DeleteObject, s3:DeleteObjectVersion, s3:PutObjectAcl, s3:PutBucketAcl, s3:PutBucketPolicy), or any broader permissions that implicitly include these actions (e.g., "*", s3:*, or s3:Delete*).

Rationale​

Publicly accessible bucket policies pose significant security risks. Granting s3:GetObject to a public principal allows anyone on the internet to read objects stored in the bucket, potentially resulting in data exposure. Similarly, granting write-related permissions, such as s3:PutObject or s3:DeleteObject, allows unauthorized users to upload, modify, or delete objects, jeopardizing data integrity and availability.

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Remediation​

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Remediation​

Disable Public Access for S3 Bucket Policies​

Enable S3 Block Public Access​

Enabling Block Public Access provides a centralized and comprehensive safeguard against unintended public exposure of S3 bucket data. These settings take precedence over any existing ACLs or bucket policies that may otherwise permit public access.

From Command Line​

Use the following command to enable Block Public Access on the bucket:

aws s3api put-public-access-block \
    --bucket {{bucket-name}} \
    --public-access-block-configuration "BlockPublicAcls=true,IgnorePublicAcls=true,BlockPublicPolicy=true,RestrictPublicBuckets=true"
Update the Bucket Policy​

To further restrict public access, review and update the bucket policy to replace broad public access ("Principal": "*") with specific principals as needed.

  1. Retrieve the current bucket policy and save it locally:

    aws s3api get-bucket-policy \
        --bucket {{bucket-name}} \
        --query Policy \
        --output text > policy.json

... see more

policy.yaml​

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Linked Framework Sections​

SectionSub SectionsInternal RulesPoliciesFlagsCompliance
💼 AWS Foundational Security Best Practices v1.0.0 → 💼 [S3.2] S3 general purpose buckets should block public read access2no data
💼 AWS Foundational Security Best Practices v1.0.0 → 💼 [S3.3] S3 general purpose buckets should block public write access2no data
💼 AWS Well-Architected → 💼 SEC08-BP04 Enforce access control8no data
💼 Cloudaware Framework → 💼 Public Data Access13no data
💼 FedRAMP High Security Controls → 💼 AC-3 Access Enforcement (L)(M)(H)49103no data
💼 FedRAMP High Security Controls → 💼 AC-4 Information Flow Enforcement (M)(H)248188no data
💼 FedRAMP High Security Controls → 💼 AC-4(21) Physical or Logical Separation of Information Flows (M)(H)18141no data
💼 FedRAMP High Security Controls → 💼 AC-6 Least Privilege (M)(H)81287no data
💼 FedRAMP High Security Controls → 💼 AC-21 Information Sharing (M)(H)19no data
💼 FedRAMP High Security Controls → 💼 SC-7 Boundary Protection (L)(M)(H)10999no data
💼 FedRAMP High Security Controls → 💼 SC-7(3) Access Points (M)(H)19no data
💼 FedRAMP High Security Controls → 💼 SC-7(4) External Telecommunications Services (M)(H)49no data
💼 FedRAMP High Security Controls → 💼 SC-7(20) Dynamic Isolation and Segregation (H)20no data
💼 FedRAMP High Security Controls → 💼 SC-7(21) Isolation of System Components (H)37no data
💼 FedRAMP Low Security Controls → 💼 AC-3 Access Enforcement (L)(M)(H)103no data
💼 FedRAMP Low Security Controls → 💼 SC-7 Boundary Protection (L)(M)(H)50no data
💼 FedRAMP Moderate Security Controls → 💼 AC-3 Access Enforcement (L)(M)(H)103no data
💼 FedRAMP Moderate Security Controls → 💼 AC-4 Information Flow Enforcement (M)(H)1169no data
💼 FedRAMP Moderate Security Controls → 💼 AC-4(21) Physical or Logical Separation of Information Flows (M)(H)141no data
💼 FedRAMP Moderate Security Controls → 💼 AC-6 Least Privilege (M)(H)687no data
💼 FedRAMP Moderate Security Controls → 💼 AC-21 Information Sharing (M)(H)19no data
💼 FedRAMP Moderate Security Controls → 💼 SC-7 Boundary Protection (L)(M)(H)783no data
💼 FedRAMP Moderate Security Controls → 💼 SC-7(3) Access Points (M)(H)19no data
💼 FedRAMP Moderate Security Controls → 💼 SC-7(4) External Telecommunications Services (M)(H)49no data
💼 NIST CSF v2.0 → 💼 DE.CM-01: Networks and network services are monitored to find potentially adverse events187no data
💼 NIST CSF v2.0 → 💼 DE.CM-09: Computing hardware and software, runtime environments, and their data are monitored to find potentially adverse events185no data
💼 NIST CSF v2.0 → 💼 ID.AM-03: Representations of the organization's authorized network communication and internal and external network data flows are maintained128no data
💼 NIST CSF v2.0 → 💼 PR.AA-05: Access permissions, entitlements, and authorizations are defined in a policy, managed, enforced, and reviewed, and incorporate the principles of least privilege and separation of duties199no data
💼 NIST CSF v2.0 → 💼 PR.DS-01: The confidentiality, integrity, and availability of data-at-rest are protected248no data
💼 NIST CSF v2.0 → 💼 PR.DS-02: The confidentiality, integrity, and availability of data-in-transit are protected219no data
💼 NIST CSF v2.0 → 💼 PR.DS-10: The confidentiality, integrity, and availability of data-in-use are protected249no data
💼 NIST CSF v2.0 → 💼 PR.IR-01: Networks and environments are protected from unauthorized logical access and usage165no data
💼 NIST SP 800-53 Revision 5 → 💼 AC-3 Access Enforcement15866no data
💼 NIST SP 800-53 Revision 5 → 💼 AC-3(7) Access Enforcement _ Role-based Access Control36no data
💼 NIST SP 800-53 Revision 5 → 💼 AC-4 Information Flow Enforcement32120207no data
💼 NIST SP 800-53 Revision 5 → 💼 AC-4(21) Information Flow Enforcement _ Physical or Logical Separation of Information Flows83141no data
💼 NIST SP 800-53 Revision 5 → 💼 AC-6 Least Privilege102580no data
💼 NIST SP 800-53 Revision 5 → 💼 AC-21 Information Sharing219no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7 Boundary Protection2911108no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7(3) Boundary Protection _ Access Points19no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7(4) Boundary Protection _ External Telecommunications Services49no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7(9) Boundary Protection _ Restrict Threatening Outgoing Communications Traffic35no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7(11) Boundary Protection _ Restrict Incoming Communications Traffic37no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7(16) Boundary Protection _ Prevent Discovery of System Components37no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7(20) Boundary Protection _ Dynamic Isolation and Segregation20no data
💼 NIST SP 800-53 Revision 5 → 💼 SC-7(21) Boundary Protection _ Isolation of System Components37no data
💼 PCI DSS v3.2.1 → 💼 1.2.1 Restrict inbound and outbound traffic to that which is necessary for the cardholder data environment, and specifically deny all other traffic.16111no data
💼 PCI DSS v3.2.1 → 💼 1.3.1 Implement a DMZ to limit inbound traffic to only system components that provide authorized publicly accessible services, protocols, and ports.10100no data
💼 PCI DSS v3.2.1 → 💼 1.3.2 Limit inbound Internet traffic to IP addresses within the DMZ.100no data
💼 PCI DSS v3.2.1 → 💼 1.3.4 Do not allow unauthorized outbound traffic from the cardholder data environment to the Internet.15no data
💼 PCI DSS v3.2.1 → 💼 1.3.5 Permit only “established” connections into the network.100no data
💼 PCI DSS v3.2.1 → 💼 1.3.6 Place system components that store cardholder data in an internal network zone, segregated from the DMZ and other untrusted networks.15no data
💼 PCI DSS v3.2.1 → 💼 7.2.1 Coverage of all system components.11no data
💼 PCI DSS v4.0.1 → 💼 1.3.1 Inbound traffic to the CDE is restricted.111no data
💼 PCI DSS v4.0.1 → 💼 1.3.2 Outbound traffic from the CDE is restricted.111no data
💼 PCI DSS v4.0.1 → 💼 1.4.2 Inbound traffic from untrusted networks to trusted networks is restricted.100no data
💼 PCI DSS v4.0.1 → 💼 1.4.4 System components that store cardholder data are not directly accessible from untrusted networks.15no data
💼 PCI DSS v4.0.1 → 💼 7.3.1 An access control system(s) is in place that restricts access based on a user's need to know and covers all system components.11no data
💼 PCI DSS v4.0 → 💼 1.3.1 Inbound traffic to the CDE is restricted.31111no data
💼 PCI DSS v4.0 → 💼 1.3.2 Outbound traffic from the CDE is restricted.111no data
💼 PCI DSS v4.0 → 💼 1.4.2 Inbound traffic from untrusted networks to trusted networks is restricted.31100no data
💼 PCI DSS v4.0 → 💼 1.4.4 System components that store cardholder data are not directly accessible from untrusted networks.15no data
💼 PCI DSS v4.0 → 💼 7.3.1 An access control system(s) is in place that restricts access based on a user's need to know and covers all system components.11no data