Element-Desktop 1.9.7 Windows/Linux login on homeserver not possible

[pprugger]

Steps to reproduce

Download and install Element-Desktop 1.9.7 for Windows
Start Element-Desktop
Click on edit to change the homeserver
Type in your homeserver: https://homeserver-url
Element-Desktop keeps to persist to say it is not e valid homeserver.

Element works on the Webclient, Linux, Android and IOS with this homeserver.
Only the Windows version fails to function.

In my debbuging i found that:
If you just type in the homeserver url the client tries to query .well-known/matrix/client
With the https:// prepended the client does not even query the homeserver
Just says: "Homeserver URL does not seem to be a valid Matrix Homeserver".

Outcome

What did you expect?

Login to my own homeserver

What happened instead?

Just says: "Homeserver URL does not seem to be a valid Matrix Homeserver".

Operating system

Windows 10

Application version

Element-Desktop 1.9.7

How did you install the app?

https://element.io/get-started#download

Homeserver

https://prometheus.umask.eu

Will you send logs?

No

[kittykat]

@pprugger can you please check if there are any errors in the console (you should be able to open it with Ctrl+i, then go to the Console tab)

[pprugger]

Here a screenshot of the errors!

[pprugger]

Additional info:
After many more tests i can confirm, this also occurs on the linux client.
I retestet the 1.9.6 client and this one works.
So it seems this has been introduced in 1.9.7.

Additionally the CORS error in 1.9.7 prevents the client completely from syncing.

[t3chguy]

CORS is entirely outside the hands of Element, it is a handshake between the browser (Chromium) and your Web Server.

If you check the Network tab and try again it'll give you more details about the error.

[pprugger]

Hey @t3chguy !
I am talking about Element-Desktop here.
I just wrote what i observed.
The 1.9.6 desktop client just works.
No CORS errors, login works, sync works.

1.9.7 is broken.
It just keeps syncing forever.

Same server of course.

[t3chguy]

Element Desktop uses Electron which is built on Chromium, hence me saying that.
Again, check the network tab for more details.

[pprugger]

I dont know what that should tell me more than the errors i already have posted.
It shows the same CORS error.
When i set add_header Access-Control-Allow-Origin *;
the client just says that only one origin is allowed.

Also i still have the error, that the server is not a valid homeserver. no idea why.

[t3chguy]

If you click on the request it'll show you response headers, which you can use to figure out why it was flagged as CORS, e.g missing ACAO header.

[pprugger]

As i already stated, i tried setting and changing the ACAO header with no luck.
This though doesn't explain the server_name error.
I guess this are two different things that both came with 1.9.7.

Error processing homeserver config: {state: "FAIL_ERROR", error: "Homeserver URL does not appear to be a valid Matrix homeserver", base_url: "https://prometheus.umask.eu"}

Attempted prometheus.umask.eu as a server_name but it failed Error: Homeserver URL does not appear to be a valid Matrix homeserver
at g (languageHandler.tsx:56)
at Function.buildValidatedConfigFromDiscovery (AutoDiscoveryUtils.tsx:242)
at deriveData (ServerPickerDialog.tsx:95)
at async r.validate (Validation.tsx:95)
at async _.validate (Field.tsx:200)

[t3chguy]

Again, only the info in the Network tab would be helpful as the Javascript Console only contains app logs but with CORS the browser obscures the underlying cause for security reasons.

[pprugger]

This is what Element does:

Sometimes some querky queries

Compared to directly in chrome:

[Melchiorro]

Hello! Exactly the same error on 1.10.* with my homeserver

Linux, android, macos and most windows clients works as before without any problems. Some windows desktop clients lost connection with the server after updating to version 1.10.0. After logging out of the account, it is impossible to log back in - the address of the home server is not accepted. The console shows the following errors

At the same time, in the web version, the same devices connect to the server successfully. There are no errors when running desktop 1.9 too. Update to 1.10.1 not didn't help.

OS: Windows 10.

How else can i help you find the problem?

[Melchiorro]

Okay, we were able to solve this problem. On computers where this problem arose, an alternative dns from Google was registered. For some reason, version 1.10 lost the server until you removed dns from the connection options, but at the same time, 1.9 worked flawlessly on the same device and with dns too.

[Torxed]

CORS is entirely outside the hands of Element, it is a handshake between the browser (Chromium) and your Web Server.

I don't fully agree with this. As the Origin header is all sorts of special when it comes to element/synapse.
For anyone ending up here.. and running nginx as a reverse proxy:

server {
    location / {
        if ($http_origin = 'https://your.frontend.lan') {
                add_header Access-Control-Allow-Origin "https://your.frontend.lan";
        }
        if ($http_origin = 'https://your.backend.lan') {
                add_header Access-Control-Allow-Origin "https://your.backend.lan";
        }
        if ($http_origin = 'vector://vector') {
                add_header Access-Control-Allow-Origin "vector://vector";
        }
    }
}

I don't like adding vector://vector here, but these are the things that have to go in there to avoid the issues above.

[t3chguy]

@Torxed the Matrix spec recommends * https://spec.matrix.org/v1.2/client-server-api/#web-browser-clients - given Matrix is an open protocol and other web clients exist, e.g Hydrogen

[Torxed]

@Torxed the Matrix spec recommends * https://spec.matrix.org/v1.2/client-server-api/#web-browser-clients - given Matrix is an open protocol and other web clients exist, e.g Hydrogen

Correct me if I'm wrong, but that would allow any site to access content on a client running under another domain? Meaning the whole safety that restriction puts in place gets null and void? (Assuming that the browsers honor it in the first place, which all the major ones does)

[t3chguy]

but that would allow any site to access content on a client running under another domain?

No, it merely tells what origins a web browser should allow to make web requests to your API service. It does not control cross-tab or cross-origin access of any data or client state, merely the HTTP request passing or failing.

[turt2live]

From the history it appears as though all cases are configuration errors and not something we can fix ourselves. If you see this, please visit #element-web:matrix.org on Matrix for troubleshooting.