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Enabling Cross Origin Resource Sharing (CORS)

When KrakenD endpoints are consumed from a browser, you might need to enable the Cross-Origin Resource Sharing (CORS) module as browsers restrict cross-origin HTTP requests initiated from scripts.

When the Cross-Origin Resource Sharing (CORS) configuration is enabled, KrakenD uses additional HTTP headers to tell browsers that they can use resources from a different origin (domain, protocol, or port). For instance, you will need this configuration if your web page is hosted at https://domain-a.com and the Javascript references the KrakenD API at https://domain-b.com.

Configuration

CORS configuration lives in the root of the file, as it’s a service component. Add the namespace github_com/devopsfaith/krakend-cors under the global extra_config, as follows:

{
  "version": 2,
  "extra_config": {
    "github_com/devopsfaith/krakend-cors": {
      "allow_origins": [
        "*"
      ],
      "allow_methods": [
        "GET",
        "HEAD",
        "POST"
      ],
      "expose_headers": [
        "Content-Length",
        "Content-Type"
      ],
      "max_age": "12h",
      "allow_headers": [
        "Accept-Language"
      ],
      "allow_credentials": false
    }
  }

The configuration options of this component are as follows:

  • allow_methods (list): The array of all HTTP methods accepted, in uppercase.
  • allow_origins (list): An array with all the origins allowed, examples of values are https://example.com, or * (any origin).
  • expose_headers (list): Headers that are safe to expose to the API of a CORS API specification
  • max_age (string): For how long the response can be cached. The value needs to specify units. Valid time units are: ns, us, (or ┬Ás), ms, s, m, h E.g., 12h for 12 hours.
  • allow_credentials (boolean): When requests can include user credentials like cookies, HTTP authentication or client side SSL certificates

Allow credentials and wildcards

According to the CORS specification, you are not allowed to use wildcards and credentials at the same time. If you need to do this, check this workaround
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