Kibana can't recreate proxy location

[w33ble]

When running Kibana behind a proxy, it can no longer reliably recreate it's location. When asking for the details about where it's exposed, the details are invalid:

This is most apparent in dev mode, which spins up a proxy and injects a random basePath value to the config.

• The proxy is running on port 5601, which Kibana knows nothing about
• The server is actually running on port 5603, so that's the only port it can share
• Because basePath is set, all assets are requested with that prefix, meaning requests to 5603 don't work correctly

[w33ble]

A couple possible paths of resolution:

• Ability to tell Kibana the proxy details, so it knows how to craft a URL to it
• Somehow flagging requests as internal and having Kibana drop the basePath entirely

[vidhya03]

+1

[abhijitdeka]

+1

[spalger]

I imagine there is a way to do some of this dynamically with proxy-set headers. We should look into that.

[mike-marcacci]

This is exceedingly frustrating in the default dev setup, as the user-facing server.basePath and dev.basePathProxyTarget are inconsistently trustworthy. For example, I need to redirect to an external OAuth provider:

• if I'm in production and no server.basePath is configured, I can trust request.url.path
• if I'm in production WITH a server.basePath is configured, I can trust request.url.path
• if I'm in development, request.url.path will be missing the randomly generated server.basePath

Similarly, server.port in development is always identical to dev.basePathProxyTarget, with request.info.host using this internal port. As far as I know there's no way to find the correct user-facing port to conduct the redirect without adding dev-specific behavior or assuming the default.