# Ensure S3 bucket policies deny insecure (HTTP) uploads

- Source: https://support.icompaas.com/support/solutions/articles/a_1793292222678608-ensure-s3-bucket-policies-deny-insecure-http-uploads
- Section: [Solutions](https://support.icompaas.com/support/solutions) › [AWS_Checks_v5.39.1](https://support.icompaas.com/support/solutions/c_1793285913477877) › [AWS Checks](https://support.icompaas.com/support/solutions/folders/f_1793287194371224)
- Last updated: 2026-10-29
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**Description**

Ensure that every Amazon S3 bucket has a bucket policy that denies uploads made over insecure (HTTP) transport. The policy must contain a Deny statement for the action s3:PutObject, s3:\* or \* that applies when the condition key aws:SecureTransport is false. Using s3:\* or \* is recommended, so that only HTTPS (TLS) requests are accepted for every operation. Buckets without a bucket policy, or whose policy has no such statement, accept plain HTTP requests.

**Rationale**

Requests sent over plain HTTP expose object data and authentication details to eavesdropping and man-in-the-middle attacks. Pre-signed URLs captured in transit can be replayed to read or change data, and traffic can be intercepted or altered. A bucket policy that denies requests when aws:SecureTransport is false forces all clients to use HTTPS and protects the confidentiality and integrity of the data in transit.

**Impact**

-   Ensures all access to the bucket is encrypted in transit with TLS
    
-   Protects pre-signed URLs and request credentials from interception
    
-   Clients or applications that still use plain HTTP (for example, the S3 website endpoint over HTTP) will receive Access Denied errors and must be switched to HTTPS
    

**Default Value**

A new S3 bucket has no bucket policy, so requests over HTTP are not denied.

**Pre-Requisites**

-   IAM permissions: s3:ListAllMyBuckets, s3:GetBucketPolicy and s3:PutBucketPolicy
    
-   Confirmation that all applications and users access the bucket over HTTPS
    
-   A copy of the existing bucket policy, because the new statement must be added to it rather than replace it
    

**Remediation**

**Test Plan**

**Console:**

1.  Sign in to the AWS Management Console at [https://console.aws.amazon.com](https://console.aws.amazon.com/).
    
2.  Open the Amazon S3 console and select **Buckets**.
    
3.  Select a bucket and open the **Permissions** tab.
    
4.  In the **Bucket policy** section, check for a statement that:
    
    -   has "Effect": "Deny",
        
    -   has an Action of s3:\*, \* or s3:PutObject, and
        
    -   has the condition "Bool": { "aws:SecureTransport": "false" }.
        
5.  Repeat for each bucket.
    
6.  If the bucket has no policy, or no such statement exists, follow the implementation steps.
    

**CLI:**

List all buckets:

aws s3api list-buckets --query "Buckets\[\].Name"

Show the bucket policy of a bucket:

aws s3api get-bucket-policy --bucket <BUCKET\_NAME> --query Policy --output text

A bucket fails if the command returns a NoSuchBucketPolicy error, or if the policy has no Deny statement with an Action of s3:\*, \* or s3:PutObject and the condition aws:SecureTransport set to false.

**Implementation Steps**

**Console:**

1.  Sign in to the AWS Management Console at [https://console.aws.amazon.com](https://console.aws.amazon.com/).
    
2.  Open the Amazon S3 console and select the bucket.
    
3.  Open the **Permissions** tab and choose **Edit** in the **Bucket policy** section.
    
4.  Add the following statement to the Statement list, keeping any existing statements (if the bucket has no policy, paste the full policy shown in the CLI step below):
    
    -   {"Sid": "DenyInsecureTransport", "Effect": "Deny", "Principal": "\*", "Action": "s3:\*", "Resource": \["arn:aws:s3:::<BUCKET\_NAME>", "arn:aws:s3:::<BUCKET\_NAME>/\*"\], "Condition": {"Bool": {"aws:SecureTransport": "false"}}}
        
5.  Choose **Save changes**.
    
6.  Repeat for each affected bucket.
    

**CLI:**

The command below replaces the whole bucket policy, so if the bucket already has a policy, first add the DenyInsecureTransport statement to the existing statements from the Test Plan output. The statement also covers the bucket itself, not only its objects. Save the following as policy.json:

{"Version": "2012-10-17", "Statement": \[{"Sid": "DenyInsecureTransport", "Effect": "Deny", "Principal": "\*", "Action": "s3:\*", "Resource": \["arn:aws:s3:::<BUCKET\_NAME>", "arn:aws:s3:::<BUCKET\_NAME>/\*"\], "Condition": {"Bool": {"aws:SecureTransport": "false"}}}\]}

Apply the policy to the bucket:

aws s3api put-bucket-policy --bucket <BUCKET\_NAME> --policy file://policy.json

**Backout Plan**

Before making changes, save the current bucket policy:

aws s3api get-bucket-policy --bucket <BUCKET\_NAME> --query Policy --output text > policy-backup.json

To roll back:

1.  Sign in to the AWS Management Console at [https://console.aws.amazon.com](https://console.aws.amazon.com/).
    
2.  Open the Amazon S3 console, select the bucket and open the **Permissions** tab.
    
3.  Choose **Edit** in the **Bucket policy** section.
    
4.  Remove the DenyInsecureTransport statement, or paste back the saved policy. If the bucket had no policy before, choose **Delete** instead.
    
5.  Choose **Save changes**.
    

**CLI:**

Restore the saved policy:

aws s3api put-bucket-policy --bucket <BUCKET\_NAME> --policy file://policy-backup.json

If the bucket had no policy before, delete the policy instead:

aws s3api delete-bucket-policy --bucket <BUCKET\_NAME>

Note: rolling back allows requests over plain HTTP again.

**Reference**

-   [https://docs.aws.amazon.com/AmazonS3/latest/userguide/security-best-practices.html](https://docs.aws.amazon.com/AmazonS3/latest/userguide/security-best-practices.html)
    
-   [https://docs.aws.amazon.com/config/latest/developerguide/s3-bucket-ssl-requests-only.html](https://docs.aws.amazon.com/config/latest/developerguide/s3-bucket-ssl-requests-only.html)
    
-   [https://docs.aws.amazon.com/cli/latest/reference/s3api/put-bucket-policy.html](https://docs.aws.amazon.com/cli/latest/reference/s3api/put-bucket-policy.html)

## Related compliance guidance

- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them.
- [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.