CORS plugin

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

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

Terminology

plugin: a plugin executing actions inside IAM before or after a request has been proxied to the upstream API.
Service: the IAM entity representing an external upstream API or microservice.
Route: the IAM entity representing a way to map downstream requests to upstream services.
upstream service: this refers to your own API/service sitting behind IAM, to which client requests are forwarded.

Configuration

This plugin is compatible with requests with the following protocols:

http
https

This plugin is compatible with DB-less mode.

Enabling the plugin on a Service

With a database

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

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

Without a database

Configure this plugin on a Service by adding this section do your declarative configuration file:

plugins:
- name: cors
  service: {service}
  config:
    origins: http://mockbin.com
    methods:
    - GET
    - POST
    headers:
    - Accept
    - Accept-Version
    - Content-Length
    - Content-MD5
    - Content-Type
    - Date
    - X-Auth-Token
    exposed_headers: X-Auth-Token
    credentials: true
    max_age: 3600

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

Enabling the plugin on a Route

With a database

Configure this plugin on a Route with:

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

Without a database

Configure this plugin on a Route by adding this section do your declarative configuration file:

plugins:
- name: cors
  route: {route}
  config:
    origins: http://mockbin.com
    methods:
    - GET
    - POST
    headers:
    - Accept
    - Accept-Version
    - Content-Length
    - Content-MD5
    - Content-Type
    - Date
    - X-Auth-Token
    exposed_headers: X-Auth-Token
    credentials: true
    max_age: 3600

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

Global plugins

Using a database, all plugins can be configured using the http://localhost:8001/plugins/ endpoint.
Without a database, all plugins can be configured via the plugins: entry on the declarative configuration file.

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

Parameters

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

form parameter	description
`name`	The name of the plugin to use, in this case `cors`
`service_id`	The id of the Service which this plugin will target.
`route_id`	The id of the Route which this plugin will target.
`enabled` default value: `true`	Whether this plugin will be applied.
`config.origins` optional	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 IAM 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
`config.headers` optional default value: Value of the `Access-Control-Request-Headers` request header	Value for the `Access-Control-Allow-Headers` header
`config.exposed_headers` optional	Value for the `Access-Control-Expose-Headers` header. 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 Routes that have been configured with a paths setting, and it will not work for Routes that are being resolved using a custom DNS (the hosts property).

To learn how to configure paths for a Route, please read the Proxy Reference.