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Created attachment 1439763[details]
Vino dconf key
Description of problem: Bugzilla 1211618 indicated that the way to enable Vino starting with RHEL 7.2 was to populate the dconf key "/org/gnome/settings-daemon/plugins/sharing/vino-server/enabled-connections". However, attempts to disable Vino at the system level by locking down the dconf key fail, and vino-server is still enabled when screen sharing is enabled in GNOME Settings.
Version-Release number of selected component (if applicable):\
vino 3.22.0-3.el7.x86_64
How reproducible: Reproducibility appears to be consistent.
Steps to Reproduce:
1. Populate /etc/dconf/db/local.d with the attached vino.key, renaming as needed.
2. Populate /etc/dconf/db/local.d/lock with the attached vino.lock, renaming as needed.
3. Run "dconf reload" as root to reload the dconf database.
4. As a normal user, enter the Vino settings menu (Applications > System Tools > Settings > Sharing > Screen Sharing) and enable screen sharing.
5. Close the screen sharing window.
Actual results: While GNOME Settings shows screen sharing as disabled after closing the screen sharing window, vino-server is still started and binds to 0.0.0.0:5900 and [::]:5900.
Expected results: vino-server does not start at all, or doesn't bind to any interfaces.
Additional info: A few workarounds exist for this issue, but none that disables Vino in a reliable or verifiable way. Ideally, vino should fail to start if 1) it has been configured as disabled by a clear and checkable key, or 2) it has no interfaces it is configured to bind to. Either way, dconf lockdown should be respected.
I tried to verify the bugfix using a better reproducer:
1. Applications > System Tools > Settings > Sharing > Screen Sharing - disable screen sharing.
2. gsettings set org.gnome.Vino network-interface 'something-wrong'
3. Applications > System Tools > Settings > Sharing > Screen Sharing - enable screen sharing.
4. ss -nlp4 | grep -i vino
Looked OK, i.e. when I used the non-existing 'something-wrong' network interface, vino-3.22.0-6.el7.x86_64 was not listening on any IP (not listed by "ss"), while vino-3.22.0-3.el7.x86_64 listened on "*:5900".
BUT
I had problem to test it on 1 machine, because there was a VM blocking the 5900 port. So I tried to change the default port for vino:
gsettings set org.gnome.Vino alternative-port 5905
gsettings set org.gnome.Vino use-alternative-port true
And ... oops. The fix does not work:
[test@bm-vm-rhel-7 ~]$ rpm -q vino
vino-3.22.0-6.el7.x86_64
[test@bm-vm-rhel-7 ~]$ ss -nlp4
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
...
tcp LISTEN 0 128 *:22 *:*
tcp LISTEN 0 128 127.0.0.1:631 *:*
tcp LISTEN 0 5 *:5905 *:* users:(("vino-server",pid=12573,fd=15))
Conclusion: The fix works with the default port (5900) but NOT with alternative ports. I can not verify.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2018:3140
Created attachment 1439763 [details] Vino dconf key Description of problem: Bugzilla 1211618 indicated that the way to enable Vino starting with RHEL 7.2 was to populate the dconf key "/org/gnome/settings-daemon/plugins/sharing/vino-server/enabled-connections". However, attempts to disable Vino at the system level by locking down the dconf key fail, and vino-server is still enabled when screen sharing is enabled in GNOME Settings. Version-Release number of selected component (if applicable):\ vino 3.22.0-3.el7.x86_64 How reproducible: Reproducibility appears to be consistent. Steps to Reproduce: 1. Populate /etc/dconf/db/local.d with the attached vino.key, renaming as needed. 2. Populate /etc/dconf/db/local.d/lock with the attached vino.lock, renaming as needed. 3. Run "dconf reload" as root to reload the dconf database. 4. As a normal user, enter the Vino settings menu (Applications > System Tools > Settings > Sharing > Screen Sharing) and enable screen sharing. 5. Close the screen sharing window. Actual results: While GNOME Settings shows screen sharing as disabled after closing the screen sharing window, vino-server is still started and binds to 0.0.0.0:5900 and [::]:5900. Expected results: vino-server does not start at all, or doesn't bind to any interfaces. Additional info: A few workarounds exist for this issue, but none that disables Vino in a reliable or verifiable way. Ideally, vino should fail to start if 1) it has been configured as disabled by a clear and checkable key, or 2) it has no interfaces it is configured to bind to. Either way, dconf lockdown should be respected.