Using AWS WAF with Amazon CloudFront
This section explains how to use AWS WAF with Amazon CloudFront features.
When you create a web ACL, you can specify one or more CloudFront distributions that you want AWS WAF to inspect. AWS WAF starts to inspect and manage web requests for those distributions based on the criteria that you identify in the web ACL. CloudFront provides some features that enhance the AWS WAF functionality. This chapter describes a few ways that you can configure CloudFront to make CloudFront and AWS WAF work better together.
Topics
Using AWS WAF with CloudFront custom error pages
By default, when AWS WAF blocks a web request based on the criteria that you specify, it
returns HTTP status code 403 (Forbidden) to CloudFront, and CloudFront returns that
status code to the viewer. The viewer then displays a brief and sparsely formatted
default message similar to the following:
Forbidden: You don't have permission to access /myfilename.html on this server.
You can override this behavior in your AWS WAF web ACL rules by defining custom responses. For more information about customizing response behavior using AWS WAF rules, see Sending custom responses for Block actions.
Note
Responses that you customize using AWS WAF rules take precedence over any response specifications that you define in CloudFront custom error pages.
If you'd rather display a custom error message through CloudFront, possibly using the same formatting as the rest of your website, you can configure CloudFront to return to the viewer an object (for example, an HTML file) that contains your custom error message.
Note
CloudFront can't distinguish between an HTTP status code 403 that is returned by your origin and one that is returned by AWS WAF when a request is blocked. This means that you can't return different custom error pages based on the different causes of an HTTP status code 403.
For more information about CloudFront custom error pages, see Generating custom error responses in the Amazon CloudFront Developer Guide.
Using AWS WAF with CloudFront for applications running on your own HTTP server
When you use AWS WAF with CloudFront, you can protect your applications running on any HTTP webserver, whether it's a webserver that's running in Amazon Elastic Compute Cloud (Amazon EC2) or a webserver that you manage privately. You can also configure CloudFront to require HTTPS between CloudFront and your own webserver, as well as between viewers and CloudFront.
Requiring HTTPS between CloudFront and your own webserver
To require HTTPS between CloudFront and your own webserver, you can use the CloudFront custom origin feature and configure the Origin Protocol Policy and the Origin Domain Name settings for specific origins. In your CloudFront configuration, you can specify the DNS name of the server along with the port and the protocol that you want CloudFront to use when fetching objects from your origin. You should also ensure that the SSL/TLS certificate on your custom origin server matches the origin domain name you’ve configured. When you use your own HTTP webserver outside of AWS, you must use a certificate that is signed by a trusted third-party certificate authority (CA), for example, Comodo, DigiCert, or Symantec. For more information about requiring HTTPS for communication between CloudFront and your own webserver, see the topic Requiring HTTPS for Communication Between CloudFront and Your Custom Origin in the Amazon CloudFront Developer Guide.
Requiring HTTPS between a viewer and CloudFront
To require HTTPS between viewers and CloudFront, you can change the Viewer Protocol Policy for one or more cache behaviors in your CloudFront distribution. For more information about using HTTPS between viewers and CloudFront, see the topic Requiring HTTPS for Communication Between Viewers and CloudFront in the Amazon CloudFront Developer Guide. You can also bring your own SSL certificate so viewers can connect to your CloudFront distribution over HTTPS using your own domain name, for example https://www.mysite.com. For more information, see the topic Configuring Alternate Domain Names and HTTPS in the Amazon CloudFront Developer Guide.
Choosing the HTTP methods that CloudFront responds to
When you create an Amazon CloudFront web distribution, you choose the HTTP methods that you want CloudFront to process and forward to your origin. You can choose from the following options:
GET,HEAD– You can use CloudFront only to get objects from your origin or to get object headers.GET,HEAD,OPTIONS– You can use CloudFront only to get objects from your origin, get object headers, or retrieve a list of the options that your origin server supports.GET,HEAD,OPTIONS,PUT,POST,PATCH,DELETE– You can use CloudFront to get, add, update, and delete objects, and to get object headers. In addition, you can perform otherPOSToperations such as submitting data from a web form.
You also can use AWS WAF byte match rule statements to allow or block requests based on the HTTP
method, as described in String match rule
statement. If you want to use a combination of
methods that CloudFront supports, such as GET and HEAD, then you
don't need to configure AWS WAF to block requests that use the other methods. If you want
to allow a combination of methods that CloudFront doesn't support, such as GET,
HEAD, and POST, you can configure CloudFront to respond to all
methods, and then use AWS WAF to block requests that use other methods.
For more information about choosing the methods that CloudFront responds to, see Allowed HTTP Methods in the topic Values that You Specify When You Create or Update a Web Distribution in the Amazon CloudFront Developer Guide.
