Envoy CORS Policy Violation

What is Envoy CORS Policy Violation

Understanding Envoy and Its Purpose

Envoy is a high-performance open-source edge and service proxy designed for cloud-native applications. It is widely used for managing microservices traffic, providing observability, and enhancing security. Envoy acts as a communication bus and universal data plane designed for large microservice architectures, making it an essential tool for modern application development.

Identifying the Symptom: CORS Policy Violation

When using Envoy, you might encounter a CORS Policy Violation error. This typically manifests as a failure in the browser when attempting to access resources from a different origin. The error message often indicates that the server's response is not allowing the requested origin, method, or headers.

Explaining the CORS Policy Violation

CORS, or Cross-Origin Resource Sharing, is a security feature implemented by web browsers to prevent malicious websites from accessing resources from a different origin. A CORS Policy Violation occurs when a request made from one origin is blocked by the server because it does not permit the requested origin, method, or headers. This is a common issue when APIs are accessed from web applications hosted on different domains.

Common Causes of CORS Policy Violations

The most common cause of a CORS Policy Violation is a misconfigured CORS policy on the server. This could be due to the server not explicitly allowing the origin of the request, or not permitting the HTTP method or headers used in the request.

Steps to Fix the CORS Policy Violation

To resolve a CORS Policy Violation in Envoy, you need to update the CORS policy in the Envoy configuration. Here are the steps to do so:

Step 1: Access Your Envoy Configuration

Locate your Envoy configuration file, typically named envoy.yaml. This file contains all the settings for your Envoy proxy, including CORS policies.

Step 2: Update the CORS Policy

In the configuration file, locate the section where CORS policies are defined. It usually looks like this:

cors: allow_origin_string_match: - prefix: "https://example.com" allow_methods: "GET, POST, OPTIONS" allow_headers: "Content-Type, Authorization" max_age: "86400"

Modify the allow_origin_string_match to include the origins you want to allow. You can also adjust the allow_methods and allow_headers to match the requirements of your application.

Step 3: Validate and Apply the Configuration

After updating the configuration, validate it to ensure there are no syntax errors. You can use the following command:

envoy --mode validate -c /path/to/envoy.yaml

If the validation is successful, restart Envoy to apply the changes:

systemctl restart envoy

Additional Resources

For more information on configuring CORS in Envoy, you can refer to the official Envoy documentation. Additionally, understanding CORS can be further enhanced by reviewing the Mozilla Developer Network's guide on CORS.