On 02/26/2015 12:46 AM, Dong Zhou wrote:
> Hi, SE Gurus
> 
> 
> Got a few questions regarding policy update.
> 
> 
> 1) we will have no SEAdmin on the device, so do we still need to
> use buildsebundle ​to create policy update?

Neither SEAdmin nor buildsebundle are part of AOSP, so I guess you are
building one of our branches?

If you want to ship a policy update to a device without performing an
OTA, you need to construct a policy update bundles in the expected
format (that's what buildsebundle does) and you need an app on the
device that can receive such bundles and generate the
android.intent.action.UPDATE_SEPOLICY intent to install the bundle
(that's what SEAdmin demonstrates).  You are free of course to roll your
own tool and app if you wish; buildsebundle and SEAdmin are just
examples.  I don't know what (if anything) Google uses.  IIRC, we had
offered to upload buildsebundle to AOSP but they weren't interested.

> 2) Once we we push the new policy files into /data/security/current, is
> system reboot a mandatory(or recommended) operation? 

The ConfigUpdate SELinuxPolicyInstallReceiver in the system_server will
unpack the bundle under a subdirectory of /data/security, symlink
/data/security/current to it, and then setprop selinux.reload_policy 1
when it receives the intent, causing an immediate reload.  However,
mac_permissions.xml changes do not take effect without a reboot, and
labeling changes in file_contexts are not retroactively applied without
a reboot (and no changes to /system labeling are possible without an OTA
upgrade).

> 3) How to ensure updated sepolicy binary are from the original policy
> issuer and not be tampered with?

The bundle has to be signed by a certificate from otacerts.zip or it
will be rejected by the ConfigUpdate mechanism.

> BTW, we are using Lollipop, with both external/sepolicy and
> device/<device-name>/sepolicy

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