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Message #25438
[Bug 1306781] Re: Kernel to userspace communication is needed to notify trusted helpers of profile changes
** Changed in: apparmor (Ubuntu)
Importance: Medium => Low
** Changed in: apparmor
Importance: Medium => Low
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https://bugs.launchpad.net/bugs/1306781
Title:
Kernel to userspace communication is needed to notify trusted helpers
of profile changes
Status in AppArmor Linux application security framework:
Triaged
Status in “apparmor” package in Ubuntu:
Triaged
Status in “dbus” package in Ubuntu:
New
Bug description:
It is common for trusted helpers to cache information about a profile,
such as the profile name and enforcement mode, when they're making
AppArmor policy decisions. However, there's currently no way for the
trusted helper to receive notification when changes are made to the
profile.
For example, dbus-daemon caches the profile name and enforcement mode
when an application connects to the bus. If the profile is in enforce
mode when the application connects but the system administrator moves
the profile to complain mode, dbus-daemon does not find out about the
change and continues to enforce the profile.
The opposite is true, as well. If a profile is in complain mode when
an application connects to the bus and is then moved to enforce mode,
dbus-daemon continues to treat the profile as if it were in complain
mode until the application reconnects to the bus.
To solve this, there are two options that immediately come to mind:
1. dbus-daemon checks with the kernel before every permission query.
It would get the latest profile information and then decide what to do
(query and enforce if the profile is in enforce mode, query and allow
if in complain mode, don't query if unconfined). This results in an
extra round trip per query and would hurt performance.
2. The kernel could notify trusted helpers when profile changes are
made, such as when an enforcement mode changes, a new profile is
loaded, a profile is removed, a profile is renamed, etc. Userspace
would need to be able to receive the notification and invalidate its
cached information for that profile. This could become complicated in
some trusted helper implementations.
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