Hi Andrew, On Fri, Apr 18, 2025 at 5:12 AM Andrew Sayers <andrew+antispam-20250418@xxxxxxxxxxxxxxx> wrote: > > On 16/04/2025 16:19, Andrew Sayers wrote: > > Obex is a device-oriented protocol, so only one instance can run per device. > > But Linux file security is user-oriented, so obexd should be a user service. > > Tell systemd to only run this service for the first non-system user to log in. > > > > Without this patch, errors like the following will occur if you > > use the "switch account" feature of your desktop environment, > > then log in with another account: > > > > Mar 26 15:20:38 andrews-2024-laptop bluetoothd[873]: src/profile.c:register_profile() :1.2016 tried to register 00001133-0000-1000-8000-00805f9b34fb which is already registered > > Mar 26 15:20:38 andrews-2024-laptop bluetoothd[873]: src/profile.c:register_profile() :1.2016 tried to register 00001132-0000-1000-8000-00805f9b34fb which is already registered > > Mar 26 15:20:38 andrews-2024-laptop bluetoothd[873]: src/profile.c:register_profile() :1.2016 tried to register 0000112f-0000-1000-8000-00805f9b34fb which is already registered > > Mar 26 15:20:38 andrews-2024-laptop bluetoothd[873]: src/profile.c:register_profile() :1.2016 tried to register 00001104-0000-1000-8000-00805f9b34fb which is already registered > > Mar 26 15:20:38 andrews-2024-laptop bluetoothd[873]: src/profile.c:register_profile() :1.2016 tried to register 00001106-0000-1000-8000-00805f9b34fb which is already registered > > Mar 26 15:20:38 andrews-2024-laptop bluetoothd[873]: src/profile.c:register_profile() :1.2016 tried to register 00001105-0000-1000-8000-00805f9b34fb which is already registered > > Mar 26 15:20:38 andrews-2024-laptop bluetoothd[873]: src/profile.c:register_profile() :1.2016 tried to register 00005005-0000-1000-8000-0002ee000001 which is already registered > > Mar 26 15:20:38 andrews-2024-laptop obexd[1795560]: bluetooth: RequestProfile error: org.bluez.Error.NotPermitted, UUID already registered > > Mar 26 15:20:38 andrews-2024-laptop obexd[1795560]: bluetooth: RequestProfile error: org.bluez.Error.NotPermitted, UUID already registered > > Mar 26 15:20:38 andrews-2024-laptop obexd[1795560]: bluetooth: RequestProfile error: org.bluez.Error.NotPermitted, UUID already registered > > Mar 26 15:20:38 andrews-2024-laptop obexd[1795560]: bluetooth: RequestProfile error: org.bluez.Error.NotPermitted, UUID already registered > > Mar 26 15:20:38 andrews-2024-laptop obexd[1795560]: bluetooth: RequestProfile error: org.bluez.Error.NotPermitted, UUID already registered > > Mar 26 15:20:38 andrews-2024-laptop obexd[1795560]: bluetooth: RequestProfile error: org.bluez.Error.NotPermitted, UUID already registered > > Mar 26 15:20:38 andrews-2024-laptop obexd[1795560]: bluetooth: RequestProfile error: org.bluez.Error.NotPermitted, UUID already registered > > > > The above errors indicate the service completely failed to register, so this > > does not change the user experience beyond removing the above messages. > > Specifically, the first user who logs in to a multi-user system still retains > > obex access to devices paired by users who log in later. > > > > This is based on a pair of recent changes to the FluidSynth daemon: > > > > https://github.com/FluidSynth/fluidsynth/pull/1491 > > https://github.com/FluidSynth/fluidsynth/pull/1528 > > > > This was discussed in the comments for a GitHub advisory available at > > https://github.com/bluez/bluez/security/advisories/GHSA-fpgq-25xf-jcwv > > but comments are not shown in the published version of the advisory. > > To summarise the useful conversation with Luiz Augusto von Dentz: > > > > Obex requires access to the user's home directory, so an attacker can only > > transfer files between locations the user controls. That may be a problem > > if the user who runs obexd is different to the user who paired the device, > > but solving that would involve pairing per-user, which causes other problems. > > Bluetooth connections can be initiated by peripherals, so switching user could > > trigger re-pairing and cause the original user to lose access to the device. > > This may seem reasonable for file access, but for example users would likely > > object to constantly re-pairing their Bluetooth keyboard. > > > > Signed-off-by: Andrew Sayers <kernel.org@xxxxxxxxxxxxxxx> > > --- > > obexd/src/obex.service.in | 6 ++++++ > > tools/bluez.tmpfiles.in | 1 + > > 2 files changed, 7 insertions(+) > > > > diff --git a/obexd/src/obex.service.in b/obexd/src/obex.service.in > > index cf4d8c985..42d2185fb 100644 > > --- a/obexd/src/obex.service.in > > +++ b/obexd/src/obex.service.in > > @@ -1,10 +1,16 @@ > > [Unit] > > Description=Bluetooth OBEX service > > +# This is a user-specific service, but bluetooth is a device-specific protocol. > > +# Only run one instance at a time, even if multiple users log in at once: > > +ConditionPathExists=!/run/lock/bluez/obexd.lock > > +ConditionUser=!@system > > > > [Service] > > Type=dbus > > BusName=org.bluez.obex > > ExecStart=@PKGLIBEXECDIR@/obexd > > +ExecStartPre=touch /run/lock/bluez/obexd.lock > > +ExecStopPost=rm -f /run/lock/bluez/obexd.lock > > Recent experience with the equivalent FluidSynth patch shows that, > if a package maintainer upgrades without adding the tmpfile, > the above causes the service to fail in ways that users find confusing. > > One solution would be to prefix a '-' to make systemd ignore errors: > > +-ExecStartPre=touch /run/lock/bluez/obexd.lock > +-ExecStopPost=rm -f /run/lock/bluez/obexd.lock > > That would reduce a missing tmpfile from a crash to just log spam. > But if the tmpfile gains a more important use case in future, > you might uncover bugs in distro's that never installed the tmpfile. > > An alternative would be to add a comment like: > > +# If the service fails on the following line, please ensure > +# the bluez tmpfile has been installed in /usr/lib/tmpfiles.d/ > +ExecStartPre=touch /run/lock/bluez/obexd.lock > +ExecStopPost=rm -f /run/lock/bluez/obexd.lock > > That wouldn't fix the problem, but would make it easier to debug, > and hopefully nudge users to file a useful report with their distro. Yeah, let's do that, can you send an update to the series? > > > > [Install] > > Alias=dbus-org.bluez.obex.service > > diff --git a/tools/bluez.tmpfiles.in b/tools/bluez.tmpfiles.in > > index e69de29bb..05b8ad65c 100644 > > --- a/tools/bluez.tmpfiles.in > > +++ b/tools/bluez.tmpfiles.in > > @@ -0,0 +1 @@ > > +d /run/lock/bluez 0777 root root -- Luiz Augusto von Dentz
