On Mon, Mar 16, 2009 at 8:28 AM, F H <[email protected]> wrote:

> Is it intended that low level access to Surface Flinger is granted only to
> components that a part of the system and not to applications developed using
> the SDK and signed using an arbitrary certificate?


Yes.


> Is it the intention that an Android platform be signed with a certificate
> unique to an android provider,


Yes.


> who if they wished could enable applications to be signed by the same
> certificate.


No, this would allow you to write third party applications that are either
significant security vulnerabilities and/or break across platform releases.
The platform certificate is intended to be exclusive to the device
manufacturer, and something they keep private.


> When an android system is built - where is the certificate that is used for
> signing the system and does it need to be generated in a particular way
> (e.g. does it need to be generated by some signing authority).


No it can be generated the normal way you general one for an SDK developer.

The development certs are here:

http://android.git.kernel.org/?p=platform/build.git;a=tree;f=target/product/security;h=be33ff699f23419ffd2067daf5489f785551df70;hb=HEAD

I don't know off-hand how you sign with your "real" certs; but a basic rule
is that these are not checked in to any source repository but done as a
separate step as part of making a final release image, and only accessible
to a few select people.


> Presumably applications that connect up to surface flinger are routed
> through something that has the requisite permission. (Or is it that apps in
> general do not use low-level access?).


Applications do not get to use surface flinger.  The window manager uses
surface flinger, and provides the higher-level access that can be kept
stable across releases.

-- 
Dianne Hackborn
Android framework engineer
[email protected]

Note: please don't send private questions to me, as I don't have time to
provide private support.  All such questions should be posted on public
forums, where I and others can see and answer them.

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