Understand Cross-Origin Resource Sharing (CORS)

Adobe Experience Manager’s Cross-Origin Resource Sharing (CORS) facilitates non-AEM web properties to make client-side calls to AEM, both authenticated and unauthenticated, to fetch content or directly interact with AEM.

The OSGI configuration outlined in this document is sufficient for:

If multi-origin CORS access is required on AEM Publish, refer to this documentation.

Adobe Granite Cross-Origin Resource Sharing Policy OSGi configuration

CORS configurations are managed as OSGi configuration factories in AEM, with each policy being represented as one instance of the factory.

Adobe Granite Cross-Origin Resource Sharing Policy (com.adobe.granite.cors.impl.CORSPolicyImpl)

Policy selection

A policy is selected by comparing the

The first policy matching these values are used. If none is found, any CORS request is denied.

If no policy is configured at all, CORS requests will also not be answered as the handler is disabled and thus effectively denied - as long as no other module of the server responds to CORS.

Policy properties

Allowed Origins

Allowed Origins (Regexp)

Allowed Paths

Exposed Headers

Maximum Age

Supported Headers

Allowed Methods

Supports Credentials

Example configurations

Site 1 is a basic, anonymously accessible, read-only scenario where content is consumed via GET requests:

{
  "supportscredentials":false,
  "exposedheaders":[
    ""
  ],
  "supportedmethods":[
    "GET",
    "HEAD"
  ],
  "alloworigin":[
    "http://127.0.0.1:3000",
    "https://site1.com"

  ],
  "maxage:Integer": 1800,
  "alloworiginregexp":[
    "http://localhost:.*"
    "https://.*\.site1\.com"
  ],
  "allowedpaths":[
    "/content/_cq_graphql/site1/endpoint.json",
    "/graphql/execute.json.*",
    "/content/site1/.*"
  ],
  "supportedheaders":[
    "Origin",
    "Accept",
    "X-Requested-With",
    "Content-Type",
    "Access-Control-Request-Method",
    "Access-Control-Request-Headers"
  ]
}

Site 2 is more complex and requires authorized and mutating (POST, PUT, DELETE) requests:

{
  "supportscredentials":true,
  "exposedheaders":[
    ""
  ],
  "supportedmethods":[
    "GET",
    "HEAD"
    "POST",
    "DELETE",
    "PUT"
  ],
  "alloworigin":[
    "http://127.0.0.1:3000",
    "https://site2.com"

  ],
  "maxage:Integer": 1800,
  "alloworiginregexp":[
    "http://localhost:.*"
    "https://.*\.site2\.com"
  ],
  "allowedpaths":[
    "/content/site2/.*",
    "/libs/granite/csrf/token.json",
  ],
  "supportedheaders":[
    "Origin",
    "Accept",
    "X-Requested-With",
    "Content-Type",
    "Access-Control-Request-Method",
    "Access-Control-Request-Headers",
    "Authorization",
    "CSRF-Token"
  ]
}

Dispatcher caching concerns and configuration dispatcher-caching-concerns-and-configuration

Starting with Dispatcher 4.1.1+ response headers can be cached. This makes it possible to cache CORS headers along w the CORS-requested resources, as long as the request is anonymous.

Generally, the same considerations for caching content at Dispatcher can be applied to caching CORS response headers at dispatcher. The following table defines when CORS headers (and thus CORS requests) can be cached.

Allowing CORS request headers

To allow the required HTTP request headers to passthrough to AEM for processing, they must be allowed in the Disaptcher’s /clientheaders configuration.

/clientheaders {
   ...
   "Origin"
   "Access-Control-Request-Method"
   "Access-Control-Request-Headers"
}

Caching CORS resposne headers

To allow the caching and serving of CORS headers on cached content, add following /cache /headers configuration to the AEM Publish dispatcher.any file.

/publishfarm {
    ...
    /cache {
        ...
        # CORS HTTP response headers
        # https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#the_http_response_headers
        /headers {
            ...
            "Access-Control-Allow-Origin"
            "Access-Control-Expose-Headers"
            "Access-Control-Max-Age"
            "Access-Control-Allow-Credentials"
            "Access-Control-Allow-Methods"
            "Access-Control-Allow-Headers"
        }
    ...
    }
...
}

Remember to restart the web server application after making changes to the dispatcher.any file.

It is likely clearing the cache entirely is required to ensure the headers are appropriately cached on the next request after a /cache/headers configuration update.

Troubleshooting CORS

Logging is available under com.adobe.granite.cors:

Tips:

Supporting materials