Desktop client gets stuck in loop when trying to authenticate on Linux

[dixhuit]

Expected behaviour

The desktop client authenticates with the remote Nextcloud instance and I progress to whatever the next stage of the wizard is.

Actual behaviour

I get stuck in a loop of being asked to authenticate.

Steps to reproduce

1. Install client via official PPA and launch the client
2. Enter the URL of my remote Nextcloud instance.
3. I took screen grabs to illustrate the next steps:

I then get stuck in a loop of the last 3 screens.

• I've tried authenticating via generated key but it seems to make no difference, I still get the same loop.
• I've successfully connected via webdav.
• I've successfully connected via Android app.
• I've tried the appimage instead of the apt package and I get the same issue.
• I've tried to set up the client on another system (same OS) and I get the same issue.
• My Nextcloud instance is behind a firewall but TCP ports 80 & 443 are open for business.

Client configuration

Client version:
2.5.2git

Operating system:
KDE Neon 5.15

OS language:
?

Qt version used by client package (Linux only, see also Settings dialog):
I don't see this.

Client package (From Nextcloud or distro) (Linux only):
nextcloud-client via ppa:nextcloud-devs/client

Installation path of client:

$ whereis nextcloud
nextcloud: /usr/bin/nextcloud /usr/lib/x86_64-linux-gnu/nextcloud /usr/share/nextcloud

Server configuration

Installed via snap.

Operating system: Ubuntu 18.04

Nextcloud version: 15.0.5

[boot-ini]

I get the same problem on the OSX release (2.5.2 via brew cask, server version is 15.0.6 on Ubuntu 16.04)

Edit edit edit: Disabling E2E encryption fixes it - seems to be the same bug as here: #977

[dixhuit]

Now fixed by setting overwriteprotocol to https on the remote Nextcloud instance:

sudo nextcloud.occ config:system:set overwriteprotocol --value="https"

For anyone following this, I'm prefixing occ with nextcloud. specifically because I installed nextcloud via snap.

In my case, SSL is being handled by Cloudflare so Nextcloud was unaware that it was being used. At least, that's what I've gathered by reading https://help.nextcloud.com/t/stuck-in-a-login-loop-when-logging-in-from-sync-client-on-linux/47549/6

It would be great if the desktop client provided more feedback as to why it's not connecting successfully rather than saying nothing and looping the login procedure.

[boot-ini]

Nice, thanks! I have Nextcloud behind a Caddy reverse proxy so that explains it for me, too. Re-enabled E2E and all is well with the world again.