standard-redirects-for-cloudfront

A Lambda@Edge function that implements standard web server redirects that simplify directory handling.

For example, requests for URI paths that end in "/" are rewritten into "/index.html" before the request is passed on to the CloudFront Origin. You may think of that as an "internal" redirect in webserver terms.

URI paths that end in ".../index.html" are redirected to ".../" with an HTTP status code 301 (Moved Permanently). This is the same as an "external" redirect by a webserver.

URI paths that do not have an extension and do not end with a "/" are redirected to the same path with an appended "/" with an HTTP status code 301 (Moved Permanently). This is again an "external" redirect. (This may hide actual content from the Origin, if you use paths without extensions!).

Examples

/foo/bar/ -> internal redirect -> /foo/bar/index.html
/foo -> external redirect (301) -> /foo/ -> internal redirect -> /foo/index.html
/foo.html -> no redirect
/foo/bar.html -> no redirect
/foo/index.html -> external redirect (301) -> /foo/

Notes

This URL scheme is somewhat opinionated. It tries to balance SEO requirements with server-side tooling. (E.g. S3 tooling tries to infer the content-type from the file extension.)

It allows you to have very nice outward facing URLs like "/cooltopic", that internally use a file with a correct extension: "cooltopic/index.html". To have content other than index.html in a folder, you need to expose the file extension: "/cooltopic/somecontent.html"

Make sure that your CloudFront distribution handles the URL "/" directly by having the property "Default Root Object" set to "index.html".

Updating

1. Install the application "standard-redirects-for-cloudfront".
2. Go to the Cloudformation Console
3. Select the Output Value, this is the ARN (including the version) for the Lambda function.
4. In CloudFront edit a Behaviour and add a Lambda Function Association with the Event Type "Origin Request" and enter the Lambda function ARN from the previous step.
5. Wait for the CloudFront distribution to deploy.

Installation

Installation via the Serverless Application Repository

1. Install the application "standard-redirects-for-cloudfront".
2. Go to the Cloudformation Console
3. Select the created role (which brings you to the IAM console)
4. edit the trust relationship, set the policy to:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": [
          "lambda.amazonaws.com",
          "edgelambda.amazonaws.com"
        ]
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

(This allows CloudFront to execute this function as a Lambda@Edge function.)

5. Select the Output Value, this is the ARN (including the version) for the Lambda function.
6. In CloudFront edit a Behaviour and add a Lambda Function Association with the Event Type "Origin Request" and enter the Lambda function ARN from the previous step.
7. Wait for the CloudFront distribution to deploy.

Contact

For any questions or comments, do contact us!

Email: [email protected]
Web: https://www.digital-sailors.de/

Enjoy!