On 11/27/20 4:17 AM, Peter Bergin wrote:

Hi,

this is a good improvement to the security, thanks for sharing this!

As the global socket now is at /run/wayland-0 users that belongs to group 'wayland' and want to use weston needs to set its XDG_RUNTIME_DIR accordingly. As probably more applications than weston client is using XDG_RUNTIME_DIR it is probably a bad idea to permanently set XDG_RUNTIME_DIR=/run? (Instead of standard /run/user/<uid>) In my setup I created a file /etc/profile.d/wayland.sh that make a symlink to /run/wayland-0 if the user have write permission on it.

     $ cat /etc/profile.d/wayland.sh
     # A global socket is set up that can be used for users belonging to the 
wayland
     # group to connect to weston server. Set up a soft link to that global 
socket.
     WAYLAND_SOCKET=/run/wayland-0
     [ -S $WAYLAND_SOCKET -a -w $WAYLAND_SOCKET ] && ln -s $WAYLAND_SOCKET 
$XDG_RUNTIME_DIR

Ya. I think maybe the problem is that will only work for an interactive shell, and wouldn't work for a service?

Also, you should avoid using the WAYLAND_SOCKET environment variable, as wayland clients will interpret that variable as a file descriptor number where a pre-connected wayland client socket is present when they start up (e.g. when weston launches a client with a pre-connected socket). I suspect the only reason this isn't causing you problems right now is because you aren't exporting it :)

If you want to make something compatible with what I've done here, you could probably get the same effect with:

 if [ -s /run/wayland-0 -a -w /run/wayland-0 ]; then

    export WAYLAND_DISPLAY=/run/wayland-0

 fi



This will make the process a bit more automatic just creating a user and add it to the group wayland. Is this a suitable solution? Is this something that we would like upstream in the weston-init package?

Maybe. I tried really hard to make it so that you make $XDG_RUNTIME_DIR/wayland-0 be populated from /run/wayland-0, but I was unable to make it work (at least with systemd). The problem I found was that the systemd units for dealing with XDG_RUNTIME_DIR only deal with users by their UID, but we only know the user name at compile time (since OE doesn't use fixed UIDs). As such I was unable to get systemd to put things in the correct (UID based) XDG_RUNTIME_DIR.



(Another side note not directly related to openembedded-core but more to HW specific setups (meta-freescale in my case) that I would like to share is that GPU device nodes also need correct permission for the weston user otherwise startup of weston application does not work (if weston using the GPU). In my case on i.Mx8 target I had to change /dev/galcore device node to video group (already prepared in udev-imx-rules package). I hope I can save time for someone else seeing this error message on a i.Mx system:

        $ systemctl status weston
        * weston.service - Weston, a Wayland compositor, as a system service
             Loaded: loaded 
(8;;file://imx8mnevk/lib/systemd/system/weston.service/lib/systemd/system/weston.service8;;;
 enabled; vendor preset: enabled)
             Active: failed (Result: exit-code) since Fri 2020-11-27 10:11:52 
UTC; 13s ago
        TriggeredBy: * weston.socket
               Docs: 8;;man:weston(1)man:weston(1)8;;
                     8;;man:weston.ini(5)man:weston.ini(5)8;;
                     
8;;http://wayland.freedesktop.org/http://wayland.freedesktop.org/8;;
            Process: 276 ExecStart=/usr/bin/weston --modules=systemd-notify.so 
--log=/home/weston/weston.log (code=exited, status=1/FAILURE)
           Main PID: 276 (code=exited, status=1/FAILURE)

        Nov 27 10:11:43 imx8mnevk systemd[1]: Starting Weston, a Wayland 
compositor, as a system service...
        Nov 27 10:11:44 imx8mnevk systemd[276]: 
pam_unix(weston-autologin:session): session opened for user weston by (uid=0)
        Nov 27 10:11:52 imx8mnevk systemd[1]: weston.service: Main process 
exited, code=exited, status=1/FAILURE
        Nov 27 10:11:52 imx8mnevk systemd[1]: weston.service: Failed with 
result 'exit-code'.
        Nov 27 10:11:52 imx8mnevk systemd[1]: Failed to start Weston, a Wayland 
compositor, as a system service.

)


That's pretty common. You could send a patch to the BSP layer to correct the permissions.


Best regards,
/Peter


On 2020-11-19 23:58, Joshua Watt wrote:
Running the weston compositor as the root user is an insecure default
behavior for OE-core. We can do much better, at least when using
systemd. Change the recipe to create a dedicated "weston" user and start
weston as this user. The systemd service and socket units are no longer
template units, as there were several inconsistencies in the templates.
Instead, there is now a global /run/wayland-0 socket that gets created,
and systemd will start weston on demand when a client connects to that
socket or when attempting to reach graphical.target, whichever comes
first. This also allows downstream users to easily change the behavior
so that weston *only* starts on demand by adding a drop file. Access to
the global socket is controlled by a "wayland" group; any user that is a
member of the group can use the socket to talk to the compositor. This
also satisfies another use case where another systemd service might
start a graphical application that needs to display with weston (e.g. a
single function device in kiosk mode). Finally, the udev rules for
starting weston with the existance of a DRM device have been removed.
Being WantedBy= a graphical target should eliminate the need for this
behavior, and having it present makes it difficult for downstream users
to start weston on demand (having to override the udev rules).

Signed-off-by: Joshua Watt<[email protected]>
---
  meta/recipes-graphics/wayland/weston-init.bb  | 33 ++++++++++++-------
  .../wayland/weston-init/71-weston-drm.rules   |  2 --
  .../{[email protected]  => weston.service}       | 14 +++++---
  .../wayland/weston-init/weston.socket         | 14 ++++++++
  .../wayland/weston-init/[email protected]        | 10 ------
  5 files changed, 45 insertions(+), 28 deletions(-)
  delete mode 100644 
meta/recipes-graphics/wayland/weston-init/71-weston-drm.rules
  rename meta/recipes-graphics/wayland/weston-init/{[email protected]  => 
weston.service} (83%)
  create mode 100644 meta/recipes-graphics/wayland/weston-init/weston.socket
  delete mode 100644meta/recipes-graphics/wayland/weston-init/[email protected]

diff --git a/meta/recipes-graphics/wayland/weston-init.bb 
b/meta/recipes-graphics/wayland/weston-init.bb
index a616c473ec..65d7b81dc5 100644
--- a/meta/recipes-graphics/wayland/weston-init.bb
+++ b/meta/recipes-graphics/wayland/weston-init.bb
@@ -7,9 +7,8 @@ PACKAGE_ARCH = "${MACHINE_ARCH}"
SRC_URI ="file://init \ file://weston.env \ file://weston.ini \ - file://[email protected] \ - file://[email protected] \ - file://71-weston-drm.rules \ + file://weston.service \ + file://weston.socket \ file://weston-autologin \ file://weston-start" @@ -36,17 +35,15 @@ do_install() {
        install -Dm644 ${WORKDIR}/weston.env ${D}${sysconfdir}/default/weston
# Install Weston systemd service and accompanying udev rule
-       install -D -p -m0644 ${WORKDIR}/[email protected]  
${D}${systemd_system_unitdir}/[email protected]
-       install -D -p -m0644 ${WORKDIR}/[email protected]  
${D}${systemd_system_unitdir}/[email protected]
+       install -D -p -m0644 ${WORKDIR}/weston.service 
${D}${systemd_system_unitdir}/weston.service
+       install -D -p -m0644 ${WORKDIR}/weston.socket 
${D}${systemd_system_unitdir}/weston.socket
          if ["${@bb.utils.filter('DISTRO_FEATURES', 'pam', d)}"  ]; then
                install -D -p -m0644 ${WORKDIR}/weston-autologin 
${D}${sysconfdir}/pam.d/weston-autologin
          fi
        sed -i -e s:/etc:${sysconfdir}:g \
                -e s:/usr/bin:${bindir}:g \
                -e s:/var:${localstatedir}:g \
-               ${D}${systemd_unitdir}/system/[email protected]
-       install -D -p -m0644 ${WORKDIR}/71-weston-drm.rules \
-               ${D}${sysconfdir}/udev/rules.d/71-weston-drm.rules
+               ${D}${systemd_unitdir}/system/weston.service
        # Install weston-start script
        install -Dm755 ${WORKDIR}/weston-start ${D}${bindir}/weston-start
        sed -i 's,@DATADIR@,${datadir},g' ${D}${bindir}/weston-start
@@ -58,11 +55,15 @@ do_install() {
if ["${@bb.utils.contains('PACKAGECONFIG', 'no-idle-timeout', 'yes', 'no', d)}" = "yes" ]; then
                sed -i -e "/^\[core\]/a idle-time=0" 
${D}${sysconfdir}/xdg/weston/weston.ini
        fi
+
+       install -dm 755 -o weston -g weston ${D}/home/weston
  }
INHIBIT_UPDATERCD_BBCLASS ="${@oe.utils.conditional('VIRTUAL-RUNTIME_init_manager', 'systemd', '1', '', d)}" -inherit update-rc.d features_check systemd
+inherit update-rc.d features_check systemd useradd
+
+USERADD_PACKAGES = "${PN}"
# rdepends on weston which depends on virtual/egl
  # requires pam enabled if started via systemd
@@ -73,10 +74,18 @@ RDEPENDS_${PN} = "weston kbd"
  INITSCRIPT_NAME = "weston"
  INITSCRIPT_PARAMS = "start 9 5 2 . stop 20 0 1 6 ."
-FILES_${PN} += "${sysconfdir}/xdg/weston/weston.ini ${systemd_system_unitdir}/[email protected] ${systemd_system_unitdir}/[email protected] ${sysconfdir}/default/weston ${sysconfdir}/pam.d/"
+FILES_${PN} += "\
+    ${sysconfdir}/xdg/weston/weston.ini \
+    ${systemd_system_unitdir}/weston.service \
+    ${systemd_system_unitdir}/weston.socket \
+    ${sysconfdir}/default/weston \
+    ${sysconfdir}/pam.d/ \
+    /home/weston \
+    "
CONFFILES_${PN} += "${sysconfdir}/xdg/weston/weston.ini ${sysconfdir}/default/weston" -SYSTEMD_SERVICE_${PN} ="weston@%i.service"
-SYSTEMD_AUTO_ENABLE = "disable"
+SYSTEMD_SERVICE_${PN} = "weston.service weston.socket"
+USERADD_PARAM_${PN} = "--home /home/weston --shell /bin/sh --user-group -G 
video,input weston"
+GROUPADD_PARAM_${PN} = "-r wayland"
diff --git a/meta/recipes-graphics/wayland/weston-init/71-weston-drm.rules b/meta/recipes-graphics/wayland/weston-init/71-weston-drm.rules
deleted file mode 100644
index 1a1b8bbda4..0000000000
--- a/meta/recipes-graphics/wayland/weston-init/71-weston-drm.rules
+++ /dev/null
@@ -1,2 +0,0 @@
-ACTION=="add", SUBSYSTEM=="graphics", KERNEL=="fb0", TAG+="systemd", 
ENV{SYSTEMD_WANTS}+="[email protected]"
-ACTION=="add", SUBSYSTEM=="drm", KERNEL=="card0", TAG+="systemd", 
ENV{SYSTEMD_WANTS}+="[email protected]"
diff --gita/meta/recipes-graphics/wayland/weston-init/[email protected]  
b/meta/recipes-graphics/wayland/weston-init/weston.service
similarity index 83%
rename frommeta/recipes-graphics/wayland/weston-init/[email protected]
rename to meta/recipes-graphics/wayland/weston-init/weston.service
index ce8f4fb71a..e09625b31c 100644
---a/meta/recipes-graphics/wayland/weston-init/[email protected]
+++ b/meta/recipes-graphics/wayland/weston-init/weston.service
@@ -9,6 +9,7 @@ Documentation=man:weston(1)  man:weston.ini(5)
  Documentation=http://wayland.freedesktop.org/
# Make sure we are started after logins are permitted.
+Requires=systemd-user-sessions.service
  After=systemd-user-sessions.service
# If Plymouth is used, we want to start when it is on its way out.
@@ -18,6 +19,9 @@ After=plymouth-quit-wait.service
  Wants=dbus.socket
  After=dbus.socket
+# Ensure the socket is present
+Requires=weston.socket
+
  # Since we are part of the graphical session, make sure we are started before
  # it is complete.
  Before=graphical.target
@@ -37,10 +41,11 @@ TimeoutStartSec=60
  WatchdogSec=20
# The user to run Weston as.
-User=%I
+User=weston
+Group=weston
-# Make sure working directory is users home directory
-WorkingDirectory=/home/%i
+# Make sure the working directory is the users home directory
+WorkingDirectory=/home/weston
# Set up a full user session for the user, required by Weston.
  PAMName=weston-autologin
@@ -61,5 +66,6 @@ UtmpIdentifier=tty7
  UtmpMode=user
[Install]
+# Note: If you only want weston to start on-demand, remove this line with a
+# service drop file
  WantedBy=graphical.target
-DefaultInstance=tty7
diff --git a/meta/recipes-graphics/wayland/weston-init/weston.socket 
b/meta/recipes-graphics/wayland/weston-init/weston.socket
new file mode 100644
index 0000000000..c1bdc83c05
--- /dev/null
+++ b/meta/recipes-graphics/wayland/weston-init/weston.socket
@@ -0,0 +1,14 @@
+[Unit]
+Description=Weston socket
+RequiresMountsFor=/run
+
+[Socket]
+ListenStream=/run/wayland-0
+SocketMode=0775
+SocketUser=weston
+SocketGroup=wayland
+RemoveOnStop=yes
+
+[Install]
+WantedBy=sockets.target
+
diff --gita/meta/recipes-graphics/wayland/weston-init/[email protected]  
b/meta/recipes-graphics/wayland/weston-init/[email protected]
deleted file mode 100644
index f1790d74a8..0000000000
---a/meta/recipes-graphics/wayland/weston-init/[email protected]
+++ /dev/null
@@ -1,10 +0,0 @@
-[Unit]
-Description=Weston Wayland socket
[email protected]
-
-[Socket]
-ListenStream=/run/user/1000/wayland-%I
-
-[Install]
-WantedBy=sockets.target
-



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