95058a435e
This is trivially exploitable (in the sense of causing a crash from SEGV) e.g.
by 'shutdown now "Message %s %s %n"'. The message is settable through polkit,
but is limited to auth_admin:
<action id="org.freedesktop.login1.set-wall-message">
<description gettext-domain="systemd">Set a wall message</description>
<message gettext-domain="systemd">Authentication is required to set a wall message</message>
<defaults>
<allow_any>auth_admin_keep</allow_any>
<allow_inactive>auth_admin_keep</allow_inactive>
<allow_active>auth_admin_keep</allow_active>
</defaults>
</action>
Bug introduced in 9ef15026c0e7e6600372056c43442c99ec53746e
('logind/systemctl: introduce SetWallMessage and --message', 2015-09-15).
Based on 0cb09bcb825ab86ba4ca70be4e6322eaf9baee95.
System and Service Manager
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