Adds SilverStripe support for using the S3 adapter for Flysystem

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3.0.0 2023-11-30 21:01 UTC

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Last update: 2024-03-19 01:40:07 UTC


SilverStripe module to store assets in S3 rather than on the local filesystem.

Note: This module does not currently implement any kind of bucket policy for protected assets. It is up to you to implement this yourself using AWS bucket policy.

Environment setup

The module requires a few environment variables to be set. Full details can be seen in the SilverStripeS3AdapterTrait trait. These are mandatory.

  • AWS_REGION: The AWS region your S3 bucket is hosted in (e.g. eu-central-1)
  • AWS_BUCKET_NAME: The name of the S3 bucket to store assets in.

If running outside of an EC2 instance it will be necessary to specify an API key and secret.

  • AWS_ACCESS_KEY_ID: Your AWS access key that has access to the bucket you want to access
  • AWS_SECRET_ACCESS_KEY: Your AWS secret corresponding to the access key

Example YML Config when running outside of EC2:

  envvarset: AWS_BUCKET_NAME
  - "#assetsflysystem"
        region: "`AWS_REGION`"
        version: latest
          key: "`AWS_ACCESS_KEY_ID`"
          secret: "`AWS_SECRET_ACCESS_KEY`"

(Optional) CDN Implementation

If you're serving assets from S3, it's recommended that you utilise CloudFront. This improves performance and security over exposing from S3 directly.

Once you've set up your CloudFront distribution, ensure that assets are reachable within the assets directory of the cdn (for example; and set the following environment variable:

  • AWS_PUBLIC_CDN_PREFIX: Your CloudFront distribution domain that has access to the bucket you want to access

For example, adding this to your .env:


will change your URLs from something like:

to something like:

You can override the default /assets/ path by redeclaring the PublicCDNAdapter constructor, with the paramater for the cdnAssetsDir set to a string of your folder name:

Name: silverstripes3-cdn
  - "#assetsflysystem"
  - "#silverstripes3-flysystem"
    class: SilverStripe\S3\Adapter\PublicCDNAdapter
      s3Client: '%$Aws\S3\S3Client'
      bucket: '`AWS_BUCKET_NAME`'
      prefix: '`AWS_PUBLIC_BUCKET_PREFIX`'
      visibility: null
      mimeTypeDetector: null
      cdnPrefix: '`AWS_PUBLIC_CDN_PREFIX`'
      options: []
      cdnAssetsDir: "cms-assets" # example of a custom assets folder name, which will produce


This will install the most recent applicable version of the module given your other Composer requirements.

Note: This currently immediately replaces the built-in local asset store that comes with SilverStripe with one based on S3. Any files that had previously been uploaded to an existing asset store will be unavailable (though they won't be lost - just run composer remove silverstripe/s3 to remove the module and restore access).


Assets are classed as either 'public' or 'protected' by SilverStripe. Public assets can be freely downloaded, whereas protected assets (e.g. assets not yet published) shouldn't be directly accessed.

The module supports this by streaming the contents of protected files down to the browser via the web server (as opposed to linking to S3 directly) by default. To ensure that protected assets can't be accessed, ensure you setup an appropriate bucket policy (see below for an untested example).

Configuring S3

The 'protected' S3 asset store should be protected using standard AWS IAM policies that disallow all access to anonymous users, but still allow the action s3:GetObject for both public and protected files. Protected files will be streamed from AWS, so they do not need to be accessed by users directly. Therefore, something similar to the following bucket policy may be useful.

Make sure you replace <bucket-name> below with the appropriate values.

Note: The below policy has not been extensively tested - feedback welcome.

  "Policy": {
    "Version": "2012-10-17",
    "Statement": [
        "Sid": "AddPerm",
        "Effect": "Allow",
        "Principal": "*",
        "Action": "s3:GetObject",
        "Resource": "arn:aws:s3:::<bucket-name>/public/*"

If you are utilising a CloudFront distribution for your public assets, you will have the option of securing your S3 bucket against all public access while still allowing access to your public files via your CloudFront distribution and access to your protected files via signed URLs.

For developers

Read Setting up a local sandbox for developing the Silverstripe S3 module if you wish to do some local development.


  • Run composer remove silverstripe/s3 to remove the module.