OSM tiles response error when loaded with Cesium

[giohappy]

On the contrary of MapStore itself, the GeoNode client receives a response error (418 I'm a teapot) for OSM tiles loaded by the Cesium viewer.

After investigating a few combinations of headers, it looks like the two problematic ones are:

• accept: */* -> apparently this is accepted if the Referrer is also set (don't know why!)
• missing referrer -> it's ok only if accept: image/avif,image/webp,image/apng,image/svg+xml,image/*,*/*;q=0.8' is set

3D viewer in GeoNode:

• the referrer is not sent and accept is set to */* -> we get the error

2D viewer in GeoNode:

• the referrer is not sent BUT accept is set to image/avif,image/webp,image/apng,image/svg+xml,image/*,*/*;q=0.8 -> we get the tiles

2D and 3D in MapStore behave the same as GeoNode for the accept header but the referrer in MapStore is set for both cases.
So the problem is the missing Referrer inside the requests from GeoNode + Cesium.

The reason the referrer is not sent is due to different values for the Referrer Policy header set by MapStore and GeoNode:

• MapStore: strict-origin-when-cross-origin
• GeoNode: same-origin

The quick solutions is to add SECURE_REFERRER_POLICY = 'strict-origin-when-cross-origin' to GeoNode settings.

[ridoo]

An evergreen of nerd history 🫖 ..

Weird behavior, though. Perhaps, the tiles serving backend has HTCPCP enabled, or what?

I see that python's request lib is implementing '418' response code and some SO posts indicate, that such status can be returned even when scheme is not 'coffee://'.

In your tests, the user-agent was set?

[giohappy]

@ridoo I think OSM simply uses that nerdy return code when either the referrer is missing or that accept header is not fully specified.
We should ask OSM maintainers the reason for this odd combination. The agent is set by the browser's HTTP client libs underlying MS and Cesium.
In my tests this is what is set: user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

[ridoo]

Hey @giohappy it seems that the missing Referer conflicts with OSM's technical usage-policy:

• Valid HTTP User-Agent identifying application. Faking another app’s User-Agent WILL get you blocked. Using a library’s default User-Agent is NOT recommended as they may be blocked if another user of the library is misusing it. If a device automatically sends an X-Requested-With header with an application specific Application ID, this will be considered an acceptable substitute for the HTTP User-Agent, although we still recommend setting a valid HTTP User-Agent for the application.
• When coming from a web page, a valid HTTP Referer. Apps generally do not have a HTTP referer.
• DO NOT send no-cache headers. (“Cache-Control: no-cache”, “Pragma: no-cache” etc.)
• Cache Tile downloads locally according to HTTP Expiry Header, alternatively a minimum of 7 days.
• Recommended: HTTP/2 or HTTP/3 support to allow multiplexed downloads

[giohappy]

Yes @ridoo that's why I changed the settings. Now the Referrer is sent as requested.