It's been well over a month since I last reported on this, so I think it's fine time I reported about the latest on the subject.
My above comment was mostly correct and slightly wrong. Interestingly, stock Ubuntu 21.10 does not use Wayland (on my setup, at least, with Intel integrated graphics); it uses X11, just like Ubuntu MATE does. But interestingly, Ubiquity on stock Ubuntu starts the *GNOME Shell*, whereas Ubiquity on Ubuntu MATE only starts Marco, a generic Ubiquity top panel (which is supposed to be stocked with indicators, but Ubiquity's panel only works with Unity indicators and not Ayatana indicators), the MATE Settings Daemon, and a handful of other programs. Furthermore, like I suspected, both Ubuntu and Ubuntu MATE start the Ubiquity greeter as root, except their *effective* user IDs are both the respective live session users (`ubuntu` and `ubuntu-mate`, respectively). The latter is done probably to allow communication over D-Bus, because my experiments show that if the process' effective UID is not 999 (the live session user), neither version of Ubiquity will interact with the screen reader. Here's the proof. The first snippet was taken on an Ubuntu 21.10 system (that took me eons to download); the second is from an Ubuntu MATE 21.10 system. Ubuntu: RUSER EUSER PID PPID COMMAND ubuntu ubuntu 1948 1941 /usr/bin/pipewire ubuntu ubuntu 1949 1941 /usr/bin/pipewire-media-session ubuntu ubuntu 1950 1941 /usr/bin/pulseaudio --daemonize=no --log-target=journal ubuntu ubuntu 1953 1941 /usr/bin/dbus-daemon --session --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only ubuntu ubuntu 1966 1941 /usr/libexec/dconf-service ubuntu ubuntu 1983 1703 /usr/libexec/gsd-a11y-settings ubuntu ubuntu 1986 1703 /usr/libexec/gsd-keyboard ubuntu ubuntu 1987 1703 /usr/libexec/gsd-media-keys ubuntu ubuntu 2004 1703 /usr/libexec/gsd-power ubuntu ubuntu 2005 1703 /usr/libexec/gsd-xsettings ubuntu ubuntu 2006 1703 gnome-shell --sm-disable --mode=ubiquity root ubuntu 2028 2009 /usr/bin/python3 /usr/lib/ubiquity/bin/ubiquity --greeter --only ubuntu ubuntu 2151 2146 /usr/bin/dbus-daemon --config-file=/usr/share/defaults/at-spi2/accessibility.conf --nofork --print-address 3 ubuntu ubuntu 2166 1941 /usr/libexec/at-spi2-registryd --use-gnome-session Ubuntu MATE: RUSER EUSER PID PPID COMMAND ubuntu-+ ubuntu-+ 1882 1875 /usr/bin/pulseaudio --daemonize=no --log-target=journal ubuntu-+ ubuntu-+ 1893 1875 /usr/bin/dbus-daemon --session --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only ubuntu-+ ubuntu-+ 1896 1875 /usr/libexec/dconf-service ubuntu-+ ubuntu-+ 1926 1694 /usr/bin/mate-settings-daemon ubuntu-+ ubuntu-+ 1927 1694 marco --sm-disable ubuntu-+ ubuntu-+ 1931 1694 /usr/lib/ubiquity/panel ubuntu-+ ubuntu-+ 1938 1694 nm-applet ubuntu-+ ubuntu-+ 2000 1875 /usr/libexec/at-spi-bus-launcher ubuntu-+ ubuntu-+ 2007 2000 /usr/bin/dbus-daemon --config-file=/usr/share/defaults/at-spi2/accessibility.conf --nofork --print-address 3 root ubuntu-+ 2008 1942 /usr/bin/python3 /usr/lib/ubiquity/bin/ubiquity --greeter --only ubuntu-+ ubuntu-+ 2093 1875 /usr/libexec/at-spi2-registryd --use-gnome-session The output was abbreviated slightly; I remove unrelated processes like the RealtimeKit daemon and UDisks. As you can see, the Ubiquity process (`/usr/bin/python3 /usr/lib/ubiquity/bin/ubiquity` on both of them) runs with a real UID of root, but an effective UID of either `ubuntu` or `ubuntu-mate` (the latter was chopped off by `ps`). So there's no dissimilarity there. ***However...*** With the screen reader enabled, from a command line (Ctrl-Alt-F2) I tried launching a text editor on each of them, first as user 999: DISPLAY=":0" pluma & ...and then as root: sudo env DISPLAY=":0" pluma & ...and then with a real UID of 0 and an effective UID of 999, just like Ubiquity: sudo env DISPLAY=":0" setpriv --ruid 0 --rgid 0 --euid 999 --egid 999 --init-groups pluma & The first command cooperated with the screen reader on both systems (i.e., the screen reader told me stuff like "Edit menu... Select All Ctrl-A"). The last two commands worked fine on Ubuntu but not on Ubuntu MATE. I tried these experiments also on the live desktop, not just at the Ubiquity greeter. The results were the same regardless of whether I tried it on the live desktop or on the Ubiquity greeter. Clearly, Ubuntu and Ubuntu MATE are configured differently, somehow pertaining to user IDs allowed to use accessibility features. But where? I ran the above experiments, but through `strace -s 1048576` to capture all (or most) communications going on between pluma / gedit and D-Bus. The results were stunning: On **both systems**, the first command (running as user ID 999) printed loads of D-Bus interactions involving the accessibility bus; I ran `grep a11y` and that turned up dozens of results. On **only the Ubuntu system** did I find any instance of the word `a11y` from the last two commands. I didn't even find any D-Bus interaction at all from the last two commands on the Ubuntu MATE system! The working theory I have so far is that Ubuntu MATE's D-Bus permissions are somehow more strict than Ubuntu's, so processes like Ubiquity which could "potentially" elevate their privileges above where they are currently can't communicate on the bus. But I have no outright *proof* of that yet. Anyway, I'll keep digging! -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1231091 Title: Screenreader starts, but does not work with installer (ubiquity) in live session To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1231091/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
