x64 AppImage hangs on launch with blank screen due to QT sandboxing issue

[sysfu]

Environment
PureOS 11 Crimson (debian based)
Kernel 6.1.0-41-amd64
Zano x64 AppImage v2.1.12.443 (hotfix)

Zano AppImage hangs on launch with blank screen. Workaround is to launch AppImage with QTWEBENGINE_DISABLE_SANDBOX=1 variable. This was suggested by Dima (@yadefaults) in Telegram technical support channel.

Dima's response quoted here

How to try to fix it:

Check and enable user namespaces:
sysctl kernel.unprivileged_userns_clone
if 0, then:
sudo sysctl -w kernel.unprivileged_userns_clone=1

Make it permanent:
echo “kernel.unprivileged_userns_clone=1” | sudo tee /etc/sysctl.d/99-userns.conf
sudo sysctl --system

Test that namespaces are actually working:
unshare -Ur true && echo OK

After that, Zano should start without QTWEBENGINE_DISABLE_SANDBOX=1

WARNING⚠️ -> Enabling unprivileged user namespaces is a security compromise (they can make it easier to exploit kernel vulnerabilities). I don't think this is a serious problem - it's just something you need to know.

But if you not lazy you can run it just like this🫠
QTWEBENGINE_DISABLE_SANDBOX=1 ./zano-linux.AppImage

Why this might have happened:
After system updates in PureOS, unprivileged user namespaces are likely disabled/restricted (or security policy is interfering), preventing the Chromium sandbox inside QtWebEngine from initializing. This leaves the GUI blank. Disabling the sandbox confirms the diagnosis.

and my reply

value was already set to 1

$ sysctl kernel.unprivileged_userns_clone
kernel.unprivileged_userns_clone = 1

Namespace test passed too

$ unshare -Ur true && echo OK
OK

Any other troubleshooting suggestions?

[sysfu]

Update; just discovered that now that the wallet is synced up, the AppImage will successfully launch without the QTWEBENGINE_DISABLE_SANDBOX=1 workaround.

[sysfu]

Latest release v2.1.13.445 hangs with blank screen, even with sandbox disabled

QTWEBENGINE_DISABLE_SANDBOX=1 ./zano-linux-x64-release-v2.1.13.445.AppImage

[sysfu]

removed ~/.Zano directory and tried again. segfaulted with message about xinerama extension

$ ./zano-linux-x64-release-v2.1.13.445.AppImage 
Generating icon file: /home/user/.local/share/applications/Zano-release-v2.1.13.445.desktop...
log channels: core currency_protocol tx_pool p2p wallet  enabled
Sandboxing disabled by user.
QObject::connect: No such slot MainWindow::on_menu_show()
QObject::connect: No such slot MainWindow::tray_quit_requested()
qt.network.ssl: QSslSocket: cannot resolve CRYPTO_num_locks
qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_id_callback
qt.network.ssl: QSslSocket: cannot resolve CRYPTO_set_locking_callback
qt.network.ssl: QSslSocket: cannot resolve ERR_free_strings
qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_cleanup
qt.network.ssl: QSslSocket: cannot resolve EVP_CIPHER_CTX_init
qt.network.ssl: QSslSocket: cannot resolve sk_new_null
/tmp/.mount_zano-lq18J1p/AppRun: line 12: 31862 Segmentation fault      usr/bin/Zano "$@"

If Zano fails to launch, it might need to install xinerama extension for the X C Binding with this command:
   sudo apt-get install libxcb-xinerama0

[31912:31912:0100/000000.772953:ERROR:broker_posix.cc(43)] Invalid node channel message
user@mini:~/Downloads$ sudo nala install -y libxcb-xinerama0
[sudo] password for user: 
libxcb-xinerama0 is already at the latest version 1.15-1
Nothing for Nala to do.

[sysfu]

Reproduced this same segfault issue on Void linux. Fresh install of latest release of Zano Linux AppImage v2.1.13.445. Created wallet and started syncing. Application crashed during sync and won't restart. Deleted contents of ~/.Zano directory and tried again. AppImage launch crashes with this error

$ AppImages/zano-linux-x64-release-v2.1.13.445.AppImage &
[1] 11513
[juri@void ~]$ Generating icon file: /home/user/.local/share/applications/Zano-release-v2.1.13.445.desktop...
log channels: core currency_protocol tx_pool p2p wallet  enabled
qt.qpa.screen: QXcbConnection: Could not connect to display 
Could not connect to any X display.
If Zano fails to launch, it might need to install xinerama extension for the X C Binding with this command:
   sudo apt-get install libxcb-xinerama0

On this void system, both the following are installed

[*] libXinerama-1.1.5_1
[*] libxcb-1.17.0_1

Problem is intermittent. Tried again several times, and now Zano wallet is launching.

[sysfu]

I think I've discovered the cause of the xinerama error. Zano app GUI is crashing while downloading the blockchain bootstrap file. If you run ps aux | grep Zano you'll find the zombie process running even though the application gui has vanished. Running pkill Zano and then re-launching the application will resume initial blockchain syncing.

If you don't kill the Zano process first, gui will launch for a second and then disappear. Also throw xinerama errors.

[cryptozoidberg]

hey @sysfu
Sorry for late response to this report.

We never tried to launch Zano on PureOS, unfortunately. But as far as i can see you managed to figure out the problem.
Is there anything we can help you with?

[sysfu]

hey @sysfu Sorry for late response to this report.

We never tried to launch Zano on PureOS, unfortunately. But as far as i can see you managed to figure out the problem. Is there anything we can help you with?

I got the latest version build 2.1.13.445 launching and downloading the blockchain bootstrap for now. I'll re-open this issue if I can reproduce it.

[sysfu]

Reproduced the issue again. It has nothing to do with the contents of the ~/.Zano directory. I think it has something to do with the application not exiting cleanly. I tried launching several times, even logging out and back in. Same issue. The only way I was able to recover the system was by rebooting, after which Zano launched successfully on the first try.

[sysfu]

I think this has something to do with an underlying X11 display or window manager corruption. Maybe something with dbus. Reboots always resolve the hangs with blank white app launch window. Logging out and back into an X session do not.