Re: [android-developers] Why explicit need for Permissions to be specified in Manifest File

Notice that I seemingly contradicted myself in my response to the
question and to Mark. I should point out that Mark's answer is
completely correct: people have a hard time with it, but I don't think
it's impossible (and a number of people have done such things for
similar uses of reflection, not necessarily permissions, however..)
:-)

kris

On Sun, Feb 26, 2012 at 5:10 AM, Kristopher Micinski
<krismicinski@gmail.com> wrote:
> On Thu, Feb 23, 2012 at 6:57 AM, Raja Nagendra Kumar
> <nagendra.raja@tejasoft.com> wrote:
>> Hi,
>>
>> Looking for some inputs why Android explicitly expects all the
>> permissions need to be declared in Android Manifest file..
>>
>> Can Android Run time introspect at run time or during compile time and
>> prepare such info based on the API used by the application...
>>
>> Can it made redundant..through automatic application introspection..
>>
>> Basically looking for why android is designed for explicit permissions
>> declaration.. when it can be automatically discovered at compiler time
>> or at run time..
>>
>
> There are a number of reasons.  The first is just simplicity.
> Integrating a good enough static analysis to make permissions
> inference technically feasible would be possible, but perhaps not that
> useful.  Consider a situation where a programmer uses an API call
> which maps to some permission, but this call is in a piece of code
> which can never be executed.  The fact that it's dead code may be
> highly nontrivial to ascertain.  Another difficulty lies in the fact
> that permissions don't always map onto calls: sometimes they map to
> content providers, guards on intents, etc... So it's not really
> possible without doing some very heavy static analysis to determine
> the possible range of inputs to these intents is.  Unfortunately
> static analysis may be inherently imprecise to the point that you'd
> have to assume that all permissions (which gate content providers)
> were required when someone did a query to a content provider, for
> instance.
>
> In other words, the idea that you can statically determine permissions
> is inherently incorrect: while it's probably technically possible,
> it's a nontrivial area of static analysis and an active topic of
> research..
>
> Kris

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