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CORS

Easily add Cross-origin resource sharing (CORS) to a Service, a Route (or the deprecated API entity) by enabling this plugin.

Note: The functionality of this plugin as bundled with versions of Kong prior to 0.10.3 differs from what is documented herein. Refer to the CHANGELOG for details.

Terminology

  • plugin: a plugin executing actions inside Kong before or after a request has been proxied to the upstream API.
  • Service: the Kong entity representing an external upstream API or microservice.
  • Route: the Kong entity representing a way to map downstream requests to upstream services.
  • Upstream service: this refers to your own API/service sitting behind Kong, to which client requests are forwarded.
  • API: a legacy entity used to represent your upstream services. Deprecated in favor of Services since CE 0.13.0 and EE 0.32.

Configuration

Enabling the plugin on a Service

Configure this plugin on a Service by making the following request:

$ curl -X POST http://kong:8001/services/{service}/plugins \
    --data "name=cors"  \
    --data "config.origins=http://mockbin.com" \
    --data "config.methods=GET, POST" \
    --data "config.headers=Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Auth-Token" \
    --data "config.exposed_headers=X-Auth-Token" \
    --data "config.credentials=true" \
    --data "config.max_age=3600"

{service} is the id or name of the Service that this plugin configuration will target.

Enabling the plugin on a Route

Configure this plugin on a Route with:

$ curl -X POST http://kong:8001/routes/{route}/plugins \
    --data "name=cors"  \
    --data "config.origins=http://mockbin.com" \
    --data "config.methods=GET, POST" \
    --data "config.headers=Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Auth-Token" \
    --data "config.exposed_headers=X-Auth-Token" \
    --data "config.credentials=true" \
    --data "config.max_age=3600"

{route} is the id or name of the Route that this plugin configuration will target.

Enabling the plugin on an API

If you are using an older version of Kong with the legacy API entity (deprecated in favor of Services since CE 0.13.0 and EE 0.32.), you can configure this plugin on top of such an API by making the following request:

$ curl -X POST http://kong:8001/apis/{api}/plugins \
    --data "name=cors"  \
    --data "config.origins=http://mockbin.com" \
    --data "config.methods=GET, POST" \
    --data "config.headers=Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Auth-Token" \
    --data "config.exposed_headers=X-Auth-Token" \
    --data "config.credentials=true" \
    --data "config.max_age=3600"
  • api: either id or name of the API that this plugin configuration will target.

Global plugins

A plugin which is not associated to any Service, Route, or Consumer (or API, if you are using an older version of Kong) is considered "global", and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

Plugins can be configured using the http://kong:8001/plugins/ endpoint.

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

Form ParameterDescription
nameThe name of the plugin to use, in this case cors
service.idThe ID of the Service the plugin targets.
route.idThe ID of the Route the plugin targets.
enabled

default value: true		Whether this plugin will be applied.
api_idThe ID of the API the plugin targets.

Note: The API Entity is deprecated in favor of Services since CE 0.13.0 and EE 0.32.
config.origins
optional

A comma-separated list of allowed domains for the Access-Control-Allow-Origin header. If you wish to allow all origins, add * as a single value to this configuration field. The accepted values can either be flat strings or PCRE regexes. NOTE: Prior to Kong 0.10.x, this parameter was config.origin (note the change in trailing s), and only accepted a single value, or the * special value.
config.methods
optional

default value:

GET, HEAD, PUT, PATCH, POST

Value for the Access-Control-Allow-Methods header, expects a comma delimited string (e.g. GET,POST).
config.headers
optional

default value:

Value of the Access-Control-Request-Headers request header

Value for the Access-Control-Allow-Headers header, expects a comma delimited string (e.g. Origin, Authorization).
config.exposed_headers
optional

Value for the Access-Control-Expose-Headers header, expects a comma delimited string (e.g. Origin, Authorization). If not specified, no custom headers are exposed.
config.credentials
optional

default value:

false

Flag to determine whether the Access-Control-Allow-Credentials header should be sent with true as the value.
config.max_age
optional

Indicated how long the results of the preflight request can be cached, in seconds.
config.preflight_continue
optional

default value:

false

A boolean value that instructs the plugin to proxy the OPTIONS preflight request to the upstream service.

Known issues

Below is a list of known issues or limitations for this plugin.

CORS Limitations

If the client is a browser, there is a known issue with this plugin caused by a limitation of the CORS specification that doesn’t allow to specify a custom Host header in a preflight OPTIONS request.

Because of this limitation, this plugin will only work for APIs that have been configured with a uris setting, and it will not work for APIs that are being resolved using a custom DNS (the hosts property).

To learn how to configure uris for an API, please read the Proxy Reference.