Android policy update
mark at livecode.com
Thu May 18 08:51:21 CEST 2017
On 2017-05-18 00:25, J. Landman Gay via use-livecode wrote:
> I just got a developer email about a revision to Google's policies for
> apps on Google Play. Google will not allow apps that download
> executable code, similar to Apple's policy. It sounds like that
> includes stack content downloaded via a "launcher" app.
I would agree with Richard's analysis - albeit with one caveat discussed
Is it just me or is the wording of that page is atrocious? I hope there
is a more detailed normative document in which these restrictions are
placed (like the Apple SDK/Store Agreement). After all in the
(presumably non-normative preamble) it says:
"An app distributed via Google Play may not modify, replace, or update
itself using any method other than Google Play’s update mechanism.
Likewise, an app may not download executable code (e.g. dex, JAR, .so
files) from a source other than Google Play. This restriction does not
apply to code that runs in a virtual machine and has limited access to
Then in what appears to be the normative section, it says:
"The following are explicitly prohibited:
- Apps or SDKs that download executable code, such as dex files or
native code, from a source other than Google Play."
This is somewhat contradictory without an explicit definition of what
they mean by 'executable code'. However, reading between the lines I
would infer that what they mean is this:
"It is explicitly prohibited to allow an app to download code from
outside of Google Play which is able to call more Android APIs than the
host app was originally able to do."
Anyway, reading between the lines, the reasoning behind this is simple -
google can check all dex, JAR and .SO files which flow through Google
Play for malicious code. They cannot check any code which is downloaded
outside of Google Play - so if code is downloaded outside of Google Play
then it must not create any more 'routes in' to the OS in order to
trigger vulnerabilities and the only 'routes in' to the OS are Android
API calls, whether they be Java or C.
Anyway, I think you are fine as right now the range of APIs which the
Android engine uses is fixed at the point of building an Android
standalone and we are definitely a VM (LiveCode Script runs using an
Abstract Syntax Tree, LiveCode Builder a ByteCode Machine) - thus we can
Okay so the caveat. I really want the above paragraph to be true,
however it actually isn't if one casts a critical eye over the whole
We potentially have an issue with LiveCode Builder... Well, not LiveCode
Builder, but its FFI capabilities.
It's very presence and the way it works means that in actual fact, we
cannot say that 'code that runs in a virtual machine has limited access
to Android APIs' - even the existing C FFI mechanism allows you to hook
up to arbitrary C APIs; the upcoming Java FFI mechanism makes this even
easier (as connecting to Java APIs is a fair bit easily than C - from
the point of view of the developer, at least).
Indeed, LCB modules are loadable at runtime, so you could download an
LCB module which hooks into APIs the existing app does not; and then
call them. Further than that, it is possible to write an LCB module
which allows arbitrary machine code to be executed directly.
This will require some thought - I'd rather LiveCode didn't get
Mark Waddingham ~ mark at livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
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