The http.cors.allow-headers setting in Elasticsearch controls which HTTP headers are allowed in cross-origin resource sharing (CORS) requests. It is part of Elasticsearch's CORS configuration and helps define which headers can be used when a web application from a different origin makes requests to your Elasticsearch cluster.
Description
- Default value:
X-Requested-With, Content-Type, Content-Length, Authorization - Possible values: A comma-separated list of HTTP header names
- Recommendations: Include only the headers necessary for your application to function properly while maintaining security
This setting is used in conjunction with other CORS-related settings to configure how Elasticsearch responds to cross-origin requests. It's particularly important when you have web applications hosted on different domains that need to interact with your Elasticsearch cluster directly from the browser.
Example
To add a custom header to the allowed list, you can use the cluster settings API:
PUT /_cluster/settings
{
"persistent": {
"http.cors.allow-headers": "X-Requested-With, Content-Type, Content-Length, Authorization, My-Custom-Header"
}
}
In this example, we've added My-Custom-Header to the list of allowed headers. This change might be necessary if your application uses a custom header for authentication or to pass specific information to Elasticsearch.
Common Issues or Misuses
- Overly permissive configuration: Allowing too many headers can potentially expose your cluster to security risks.
- Forgetting to enable CORS: The
http.cors.allow-headerssetting has no effect ifhttp.cors.enabledis not set totrue. - Misconfiguration leading to CORS errors: If required headers are not included, browser requests may fail due to CORS restrictions.
Do's and Don'ts
- Do carefully consider which headers are necessary for your application.
- Do use this setting in conjunction with other CORS settings for a complete CORS configuration.
- Don't include sensitive headers that could expose security information.
- Don't set this to
*(wildcard) as it allows any header and may pose security risks. - Do test your CORS configuration thoroughly after making changes.
Frequently Asked Questions
Q: How does http.cors.allow-headers relate to the Access-Control-Allow-Headers response header?
A: The http.cors.allow-headers setting determines the content of the Access-Control-Allow-Headers response header sent by Elasticsearch in response to CORS preflight requests.
Q: Can I use wildcards in the http.cors.allow-headers setting?
A: No, wildcards are not supported for this setting. You must explicitly list each allowed header.
Q: How do I allow all headers without specifying them individually?
A: While not recommended for security reasons, you can set http.cors.allow-headers to * to allow all headers. However, this should be done with caution and only in controlled environments.
Q: Will changing http.cors.allow-headers affect existing connections?
A: Changes to this setting take effect immediately for new requests, but existing connections may continue to use the previous configuration until they are closed.
Q: Is http.cors.allow-headers case-sensitive?
A: Header names in HTTP are case-insensitive, so the values in http.cors.allow-headers are also treated as case-insensitive. However, it's a good practice to use the canonical capitalization for clarity.
