Shared session over several apps (not activities!) - android

I'd like to share data "globally" between applications (not activities). The problem is, I have several applications that need to have only on user session: say you log in to one app and if you open another app it won't ask for you to log in again, but will "remember" your id, and that you are logged in.
I have found this solution using the SQLite.
The apps, I'm talking about won't be on Google Play so theoretically this approach could work, I am however worried that someone could just write a rogue app and set the id in the AndroidManifest.xml and have access to all other apps without authentication (I'm writing enterprise apps, so this could be a serious security breach).
Another possible approach would be to have a separate app only for logging in and storing sessions, that all other apps access with intents... this however seems very messy for several reasons (life-cycle, etc.)
Any thoughts / alternatives?

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How to detect a user after reinstalling the app

I am creating an iOS and Android App and I want to create a screen where the player can start with a guest account or can connect his account with our own accountsystem.
But my question is: Can I detect a user after the app was uninstalled and installed again?
I know that there is something like the vendor. But this will change.
I know that other apps also can do this.
With the user's permission- have them log into an account. Or provide you with their google of facebook account info. So far as hardware ids, those are discouraged and actively being removed to prevent people from the API to prevent this.
Also remember- that unless the user logs in with an account, you don't really know whether it is the same person. You could know its the same phone, but you don't know if he gave it to his kid sister to play on. Or sold it when he got a new one, and now you've given the new owner access to someone else's account. Also, if you rely on hardware ids you won't know its me when I buy a new phone and download it on that.
So yeah- either have him log in with a username and password, or use a 3rd party signon mechanism like Google or Facebook.
For iOS, there is a recommended approach to do that: by using the DeviceCheck framework. The idea here is that it allows you to persist 2 bits of data across app installations on each device. You can set the first bit to 1 if the user has already installed the app or 0 otherwise. And use the second bit, for example, to check if the user has signed in or not.
The official documentation is pretty good, please check it out.
The downside of this approach is that you will also have to do some work on the backend side.
UPDATE:
If you specifically want to detect the account, there is no reliable approach. One of the options is to use identifierForVendor or generate some kind of device fingerprint (for example, by combining the device model, timezone, locale, etc.), but of course, this will not work every time.
Uniquely identifying a device is a security leak, and all platforms are putting serious restrictions on unique persistent identifiers because of privacy concerns.

One Android app to rule them all? (Alternative options to SSO)

I am working with several organizations. They have formed a coalition and have agreed to share apps they have created. The group is trying to implement a set of Android applications that will be used by first responders on shared devices during a high visibility event. The applications are all 3rd party, by various vendors, and since the group does not have time to implement an SSO solution, they are using an app called Keeper to allow the users to store their credentials in a database. This is not an ideal solution, but it’s a time crunch. The biggest issue that they are looking at right now is that, although they can set Keeper to log out of the Keeper app itself after a set amount of time, the applications that the user was logged into will all remain logged in unless the user manually logs out. This means that at shift change, unless the first user manually logs out of all of their apps, the second user will have access to all of their applications.
One of the ideas that they had was to create an external Android script that would allow the user to logout of all applications with a single click. But it seems like this would require access to session ID’s and other information from all of the 3rd party applications. If that were possible, it seems like it would be a scarily large security flaw.
Can anyone shine some light on this for me?

Best approach to identify if user paid for an app on google play

I seem to have reached dead-end as to how may i create a proper model which plays well under a scenario that i have in mind.
The scenario is as follows; User purchases an application from Google play. At run-time i request user credentials (Google account associated with current device) which i then transfer to a web-service. At that point the back-end service tries to Auth user and identify if they have actually purchased the application in question and only then return any data relative to the request. (keep in mind that any request in general, as we are talking about a content based application, to the web-service at any point of the run-time life-cycle must always pass through the above pipe).
Now the reason for the above scenario being so specific is for the following reason;
-I would like everything to be managed by the end service rather than having any Auth process running natively as it may easily get bypassed. What i mean is that as long as anyone can decompile the application on their device, inspect the code, recompile it to their needs, have full access to any file if the device is rooted or even be allowed to clear any data related to the application by simply pressing the "clear data" option from android's application settings..... i do not see any other viable scenario other than the one i described above.
Now having said all of the above my problem is that it seems that Google does not like this specific scenario with both Google play developer api and Google+ api.
So i would really appreciate your comments, thoughts and any related materials you may have to offer in regards to the scenario i mentioned and ways to tackle down this problem.
I don't know of any such API that you can use. Why not try LVL, which would make sure that it's actually downloaded from the Android market? And if it's a paid app, the user must have definitely paid for it.
As far as decompiling is concerned, try Proguard. It's not 100% perfect solution, but it's pretty hard to break it.
Now, coming to the content. If you don't want anyone else to steal your content, then encrypt and save it. You can have a pretty good encryption mechanism that works with your web services, which would ensure that it's very very difficult to break.
What's wrong with using LVL and ProGuard? These tools were designed specifically to address your concerns with license verification and reverse engineering, respectively.
And, really don't worry too much about the one in a thousand people who might try to get your paid app for free. If your app is any good, then you'll be making plenty of sales anyway.
If I've read your proposal correctly, that sounds like a gross violation of your users' privacy and would definitely be a violation of Google's ToS. Why would your users give you their private credentials? They aren't supposed to be given to anyone, so why should they trust you or your systems with them? You would also be liable if you got hacked and credentials were stolen.

How to implement trialware model on Android?

Any tips on how to implement a trialware model for Android apps? I plan to release my app as a free app that expires after 30 days unless the user buys the license via an in-app purchase.
I can use the Android Market API to tell if they bought the license, so my main question is how to prevent the user from un-installing and re-installing my app every 30 days? Can I save something to their phone in a permanent and reliable way that will remain on the phone even if they uninstall? I know nothing will stop a determined hacker, I just want to stop the average user.
I am also open to different approaches to going trialware on Android.
Thanks in advance,
Barry
Have you read the documentation on Application Licensing? Specifically, have a look at Implementing a Policy
I also have found this resource very helpful in determining the best way to get a unique ID for any one device. Android - Identifying App Installations -- They discuss pros/cons to the different approaches -- Straight from the developer's mouths!
I would avoid leaving unwanted remains of the application on their phone.
Instead, you can take some unique identifier of the device, and send it to your server, if this ID was not registered before, send it activation code, if it was, don't send it.
Store this activation code in some shared preferences etc. and when the application starts, check if the activation code is there and if it is valid.
They don't even have to uninstall, just clean app data. You can save something to an obscure location on the SD card, but that's also fairly easy to circumvent, even easier if they read this forum :) Your best bet is to have the app call home to your server and check if licensed periodically. That of course comes with it's own problems: do you allow it to run if network connection is never available, etc.

How to restrict an application to only one user

I'm creating an Android application for a fantasy league as part of a college project. It's a paid application, and requires each download to be associated with only one team.
I'm confused as to how best go about it. If a user goes to settings and clears the data from there, all files, settings and databases would be deleted rendering a locally stored indicator for "The app has already run before and hence user is registered" as pointless.
Another option that had come to my mind was to store the IMEI no on a remote database (with SHA1 encryption to protect the data) but the problem with this is that, if a user loses or changes his phone, his further participation would be impossible. Additionally, users understandably don't like to share IMEI numbers and it's acceptable.
The best solution in my mind was to restrict usage of the app to the Google account that was used to download the application. With this, even a change of handsets would allow further participation of the user. However, I've not been able to find a way to obtain the Android Market account (only require E-mail) which resulted in the download.
So, my question is, how do I best go about with the problem that I face? Is there a way to get the Android Market username? Or is there a worthy alternative?
The server-side option is what you want, you can get a unique id from each phone and use that as your identifier.

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