Bug#954135: mate-screensaver: desktop briefly visible after standby/hibernation

["Lorenzo L. Ancora" <lorenzolucio+bugs@live.it>]

Package: mate-screensaver
Version: 1.20.3-3
Severity: minor

Dear maintainer,
when resumed from stand-by or hibernation, mate-screensaver shows the authentication dialog with a delay: in the meantime, all windows not minimized before hibernation are visible, with the risk to reveal confidential information.
Native MATE compositing is enabled and the problem occurs regardless of the amount of open applications.

The expected behavior is that the desktop as a whole is not visible before authentication has been successfully completed, if necessary delaying standby until the desktop has been hidden by an opaque full-screen window.
Regardless of the method, the desktop in its entirety should be considered confidential and kept hidden until authentication is complete.

Thank you,
Lorenzo

-- System Information:
Debian Release: 10.3
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-8-amd64 (SMP w/4 CPU cores)
Locale: LANG=it_IT.UTF-8, LC_CTYPE=it_IT.UTF-8 (charmap=UTF-8), LANGUAGE=it_IT.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages mate-screensaver depends on:
ii  dbus-x11                  1.12.16-1
ii  libatk1.0-0               2.30.0-2
ii  libc6                     2.28-10
ii  libcairo-gobject2         1.16.0-4
ii  libcairo2                 1.16.0-4
ii  libdbus-1-3               1.12.16-1
ii  libdbus-glib-1-2          0.110-4
ii  libgdk-pixbuf2.0-0        2.38.1+dfsg-1
ii  libgl1                    1.1.0-1
ii  libglib2.0-0              2.58.3-2+deb10u2
ii  libgtk-3-0                3.24.5-1
ii  libice6                   2:1.0.9-2
ii  libmate-desktop-2-17      1.20.4-2
ii  libmate-menu2             1.20.2-1
ii  libmatekbd4               1.20.2-1
ii  libnotify4                0.7.7-4
ii  libpam0g                  1.3.1-5
ii  libpango-1.0-0            1.42.4-7~deb10u1
ii  libpangocairo-1.0-0       1.42.4-7~deb10u1
ii  librda0                   0.0.5-1
ii  libsm6                    2:1.2.3-1
ii  libstartup-notification0  0.12-6
ii  libsystemd0               241-7~deb10u3
ii  libx11-6                  2:1.6.7-1
ii  libxext6                  2:1.3.3-1+b2
ii  libxklavier16             5.4-4
ii  libxss1                   1:1.2.3-1
ii  libxxf86vm1               1:1.1.4-1+b2
ii  mate-desktop-common       1.20.4-2
ii  mate-screensaver-common   1.20.3-3
ii  mate-session-manager      1.20.2-1

Versions of packages mate-screensaver recommends:
ii  mate-power-manager  1.20.3-2

Versions of packages mate-screensaver suggests:
pn  rss-glx            <none>
pn  xscreensaver-data  <none>

-- no debconf information