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The systemd System and Service Manager
fc0bb7ccc7
Fixes https://github.com/systemd/systemd/issues/28514. Quoting https://github.com/systemd/systemd/issues/28514#issuecomment-1831781486: > Whenever PAM is enabled for a service, we set up the PAM session and then > fork off a process whose only job is to eventually close the PAM session when > the service dies. That services we run with service privileges, both to > minimize attack surface and because we want to use PR_SET_DEATHSIG to be get > a notification via signal whenever the main process dies. But that only works > if we have the same credentials as that main process. > > Now, if pam_systemd runs inside the PAM stack (which it normally does) it's > session close hook will ask logind to synchronously end the session via a bus > call. Currently that call is not accessible to unprivileged clients. And > that's the part we need to relax: allow users to end their own sessions. The check is implemented in a way that allows the kill if the sender is in the target session. I found 'sudo systemctl --user -M "zbyszek@" is-system-running' to be a convenient reproducer. Before: May 16 16:25:26 x1c systemd[1]: run-u24754.service: Deactivated successfully. May 16 16:25:26 x1c dbus-broker[1489]: A security policy denied :1.24757 to send method call /org/freedesktop/login1:org.freedesktop.login1.Manager.ReleaseSession to org.freedesktop.login1. May 16 16:25:26 x1c (sd-pam)[3036470]: pam_systemd(login:session): Failed to release session: Access denied May 16 16:25:26 x1c systemd[1]: Stopping session-114.scope... May 16 16:25:26 x1c systemd[1]: session-114.scope: Deactivated successfully. May 16 16:25:26 x1c systemd[1]: Stopped session-114.scope. May 16 16:25:26 x1c systemd[1]: session-c151.scope: Deactivated successfully. May 16 16:25:26 x1c systemd-logind[1513]: Session c151 logged out. Waiting for processes to exit. May 16 16:25:26 x1c systemd-logind[1513]: Removed session c151. After: May 16 17:02:15 x1c systemd[1]: run-u24770.service: Deactivated successfully. May 16 17:02:15 x1c systemd[1]: Stopping session-115.scope... May 16 17:02:15 x1c systemd[1]: session-c153.scope: Deactivated successfully. May 16 17:02:15 x1c systemd[1]: session-115.scope: Deactivated successfully. May 16 17:02:15 x1c systemd[1]: Stopped session-115.scope. May 16 17:02:15 x1c systemd-logind[1513]: Session c153 logged out. Waiting for processes to exit. May 16 17:02:15 x1c systemd-logind[1513]: Removed session c153. Edit: this seems to also fix https://github.com/systemd/systemd/issues/8598. It seems that with the call to ReleaseSession, we wait for the pam session close hooks to finish. I inserted a 'sleep(10)' after the call to ReleaseSession in pam_systemd, and things block on that, nothing is killed prematurely. |
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| catalog | ||
| coccinelle | ||
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| factory | ||
| hwdb.d | ||
| LICENSES | ||
| man | ||
| mime | ||
| mkosi.conf.d | ||
| mkosi.images | ||
| mkosi.profiles | ||
| modprobe.d | ||
| network | ||
| pkg | ||
| po | ||
| presets | ||
| rules.d | ||
| shell-completion | ||
| src | ||
| sysctl.d | ||
| sysusers.d | ||
| test | ||
| tmpfiles.d | ||
| tools | ||
| units | ||
| xorg | ||
| .clang-format | ||
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| .editorconfig | ||
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| .mailmap | ||
| .packit.yml | ||
| .pylintrc | ||
| .vimrc | ||
| .ycm_extra_conf.py | ||
| LICENSE.GPL2 | ||
| LICENSE.LGPL2.1 | ||
| meson_options.txt | ||
| meson.build | ||
| meson.version | ||
| mkosi.conf | ||
| NEWS | ||
| README | ||
| README.md | ||
| TODO | ||
System and Service Manager
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