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Cross-origin resource sharing (CORS)

Last update: Thu Jan 25 2024 00:00:00 GMT+0000 (Coordinated Universal Time)

CREATED FOR:

  • Intermediate
  • Developer

Adobe Experience Manager as a Cloud Service’s Cross-Origin Resource Sharing (CORS) facilitates non-AEM web properties to make browser-based client-side calls to AEM’s GraphQL APIs, and other AEM Headless resources.

TIP
The following configurations are examples. Ensure you adjust them to align to the requirements of your project.

CORS requirement

CORS is required for browser-based connections to AEM GraphQL APIs, when the client connecting to AEM is NOT served from the same origin (also known as host or domain) as AEM.

Client type
Single-page app (SPA)
Web Component/JS
Mobile
Server-to-server
Requires CORS configuration
✔
✔
✘
✘

AEM Author

Enabling CORS on AEM Author service is different from AEM Publish and AEM Preview services. AEM Author service requires an OSGi configuration to be added to the AEM Author service’s run mode folder, and does not use a Dispatcher configuration.

OSGi configuration

The AEM CORS OSGi configuration factory defines the allow criteria for accepting CORS HTTP requests.

Client connects to
AEM Author
AEM Publish
AEM Preview
Requires CORS OSGi configuration
✔
✘
✘

The example below defines an OSGi configuration for AEM Author (../config.author/..) so it is only active on AEM Author service.

The key configuration properties are:

  • alloworigin and/or alloworiginregexp specifies the origins the client connecting to AEM web runs on.

  • allowedpaths specifies the URL path patterns allowed from the specified origins.

    • To support AEM GraphQL persisted queries, add the following pattern: /graphql/execute.json.*
    • To support Experience Fragments, add the following pattern: /content/experience-fragments/.*

  • supportedmethods specifies the allowed HTTP methods for the CORS requests. To support AEM GraphQL persisted queries (and Experience Fragments), add GET .

  • supportedheaders includes "Authorization" as requests to AEM Author should be authorized.

  • supportscredentials is set to true as request to AEM Author should be authorized.

Learn more about the CORS OSGi configuration.

The following example supports use of AEM GraphQL persisted queries on AEM Author. To use client-defined GraphQL queries, add a GraphQL endpoint URL in allowedpaths and POST to supportedmethods.

  • /ui.config/src/main/content/jcr_root/apps/wknd-examples/osgiconfig/config.author/com.adobe.granite.cors.impl.CORSPolicyImpl~graphql.cfg.json
{
  "alloworigin":[
    "https://spa.external.com/"
  ],
  "alloworiginregexp":[
  ],
  "allowedpaths": [
    "/graphql/execute.json.*",
    "/content/experience-fragments/.*"
  ],
  "supportedheaders": [
    "Origin",
    "Accept",
    "X-Requested-With",
    "Content-Type",
    "Access-Control-Request-Method",
    "Access-Control-Request-Headers",
    "Authorization"
  ],
  "supportedmethods":[
    "GET",
    "HEAD",
    "POST"
  ],
  "maxage:Integer": 1800,
  "supportscredentials": true,
  "exposedheaders":[ "" ]
}

Example OSGi configuration

AEM Publish

Enabling CORS on AEM Publish (and Preview) services are different from the AEM Author service. AEM Publish service requires an AEM Dispatcher configuration to be added to the AEM Publish’s Dispatcher configuration. AEM Publish does not use an OSGi configuration.

When configuring CORS on AEM Publish, ensure:

  • The Origin HTTP request header cannot be sent to AEM Publish service, by removing the Origin header (if previously added) from the AEM Dispatcher project’s clientheaders.any file. Any Access-Control- headers should be removed from the clientheaders.any file and Dispatcher manages them, not AEM Publish service.
  • If you have any CORS OSGi configurations enabled on your AEM Publish service, you have to remove them and migrate their configurations to the Dispatcher vhost configuration outlined below.

Dispatcher configuration

AEM Publish (and Preview) service’s Dispatcher must be configured to support CORS.

Client connects to
AEM Author
AEM Publish
AEM Preview
Requires Dispatcher CORS configuration
✘
✔
✔

Set CORS headers in vhost

  1. Open the vhost configuration file for the AEM Publish service, in your Dispatcher configuration project, typically at dispatcher/src/conf.d/available_vhosts/<example>.vhost

  2. Copy the contents of the <IfDefine ENABLE_CORS>...</IfDefine> block below, into your enabled vhost configuration file.

    code language-none h-17 
        <VirtualHost *:80>
   ...
   <IfModule mod_headers.c>
       ################## Start of CORS configuration ##################

       SetEnvIfExpr "req_novary('Origin') == ''" CORSType=none CORSProcessing=false
       SetEnvIfExpr "req_novary('Origin') != ''" CORSType=cors CORSProcessing=true CORSTrusted=false

       SetEnvIfExpr "req_novary('Access-Control-Request-Method') == '' && %{REQUEST_METHOD} == 'OPTIONS' && req_novary('Origin') != ''" CORSType=invalidpreflight CORSProcessing=false
       SetEnvIfExpr "req_novary('Access-Control-Request-Method') != '' && %{REQUEST_METHOD} == 'OPTIONS' && req_novary('Origin') != ''" CORSType=preflight CORSProcessing=true CORSTrusted=false
       SetEnvIfExpr "req_novary('Origin') -strcmatch '%{REQUEST_SCHEME}://%{HTTP_HOST}*'" CORSType=samedomain CORSProcessing=false

       # For requests that require CORS processing, check if the Origin can be trusted
       SetEnvIfExpr "%{HTTP_HOST} =~ /(.*)/ " ParsedHost=$1

       ################## Adapt regex to match CORS origin(s) for your environment
       SetEnvIfExpr "env('CORSProcessing') == 'true' && req_novary('Origin') =~ m#(https://.*\.your-domain\.tld(d+?lang=en)?$)#" CORSTrusted=true

       # Extract the Origin header
       SetEnvIfNoCase ^Origin$ ^(.*)$ CORSTrustedOrigin=$1

       # Flush If already set
       Header unset Access-Control-Allow-Origin
       Header unset Access-Control-Allow-Credentials

       # Trusted
       Header always set Access-Control-Allow-Credentials "true" "expr=reqenv('CORSTrusted') == 'true'"
       Header always set Access-Control-Allow-Origin "%{CORSTrustedOrigin}e" "expr=reqenv('CORSTrusted') == 'true'"
       Header always set Access-Control-Allow-Methods "GET" "expr=reqenv('CORSTrusted') == 'true'"
       Header always set Access-Control-Max-Age 1800 "expr=reqenv('CORSTrusted') == 'true'"
       Header always set Access-Control-Allow-Headers "Origin, Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-Headers" "expr=reqenv('CORSTrusted') == 'true'"

       # Non-CORS or Not Trusted
       Header unset Access-Control-Allow-Credentials "expr=reqenv('CORSProcessing') == 'false' || reqenv('CORSTrusted') == 'false'"
       Header unset Access-Control-Allow-Origin "expr=reqenv('CORSProcessing') == 'false' || reqenv('CORSTrusted') == 'false'"
       Header unset Access-Control-Allow-Methods "expr=reqenv('CORSProcessing') == 'false' || reqenv('CORSTrusted') == 'false'"
       Header unset Access-Control-Max-Age "expr=reqenv('CORSProcessing') == 'false' || reqenv('CORSTrusted') == 'false'"

       # Always vary on origin, even if its not there.
       Header merge Vary Origin

       # CORS - send 204 for CORS requests which are not trusted
       RewriteCond expr "reqenv('CORSProcessing') == 'true' && reqenv('CORSTrusted') == 'false'"
       RewriteRule "^(.*)" - [R=204,L]

       # Remove Origin before sending to AEM Publish if this configuration handles the CORS
       RequestHeader unset Origin "expr=reqenv('CORSTrusted') == 'true'"

       ################## End of CORS configuration ##################
   </IfModule>
   ...
 </VirtualHost>

  3. Match the desired Origins accessing your AEM Publish service by updating the regular expression in the line below. If multiple origins are required, duplicate this line and update for each origin/origin pattern.

    code language-none 
    SetEnvIfExpr "env('CORSProcessing') == 'true' && req_novary('Origin') =~ m#(https://.*.your-domain.tld(:\d+)?$)#" CORSTrusted=true

    • For example, to enable CORS access from origins:

      • Any subdomain on https://example.com
      • Any port on http://localhost

      Replace the line with the following two lines:

      code language-none 
      SetEnvIfExpr "env('CORSProcessing') == 'true' && req_novary('Origin') =~ m#(https://.*\.example\.com$)#" CORSTrusted=true
SetEnvIfExpr "env('CORSProcessing') == 'true' && req_novary('Origin') =~ m#(http://localhost(:\d+)?$)#" CORSTrusted=true

Example Dispatcher configuration

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