Is there any way to restrict post requests to my REST API only to requests coming from my own mobile app binary? This app will be distributed on Google Play and the Apple App Store so it should be implied that someone will have access to its binary and try to reverse engineer it.
I was thinking something involving the app signatures, since every published app must be signed somehow, but I can't figure out how to do it in a secure way. Maybe a combination of getting the app signature, plus time-based hashes, plus app-generated key pairs and the good old security though obscurity?
I'm looking for something as fail proof as possible. The reason why is because I need to deliver data to the app based on data gathered by the phone sensors, and if people can pose as my own app and send data to my api that wasn't processed by my own algorithms, it defeats its purpose.
I'm open to any effective solution, no matter how complicated. Tin foil hat solutions are greatly appreciated.
Any credentials that are stored in the app can be exposed by the user. In the case of Android, they can completely decompile your app and easily retrieve them.
If the connection to the server does not utilize SSL, they can be easily sniffed off the network.
Seriously, anybody who wants the credentials will get them, so don't worry about concealing them. In essence, you have a public API.
There are some pitfalls and it takes extra time to manage a public API.
Many public APIs still track by IP address and implement tarpits to simply slow down requests from any IP address that seems to be abusing the system. This way, legitimate users from the same IP address can still carry on, albeit slower.
You have to be willing to shut off an IP address or IP address range despite the fact that you may be blocking innocent and upstanding users at the same time as the abusers. If your application is free, it may give you more freedom since there is no expected level of service and no contract, but you may want to guard yourself with a legal agreement.
In general, if your service is popular enough that someone wants to attack it, that's usually a good sign, so don't worry about it too much early on, but do stay ahead of it. You don't want the reason for your app's failure to be because users got tired of waiting on a slow server.
Your other option is to have the users register, so you can block by credentials rather than IP address when you spot abuse.
Yes, It's public
This app will be distributed on Google Play and the Apple App Store so it should be implied that someone will have access to its binary and try to reverse engineer it.
From the moment its on the stores it's public, therefore anything sensitive on the app binary must be considered as potentially compromised.
The Difference Between WHO and WHAT is Accessing the API Server
Before I dive into your problem I would like to first clear a misconception about who and what is accessing an API server. I wrote a series of articles around API and Mobile security, and in the article Why Does Your Mobile App Need An Api Key? you can read in detail the difference between who and what is accessing your API server, but I will extract here the main takes from it:
The what is the thing making the request to the API server. Is it really a genuine instance of your mobile app, or is it a bot, an automated script or an attacker manually poking around your API server with a tool like Postman?
The who is the user of the mobile app that we can authenticate, authorize and identify in several ways, like using OpenID Connect or OAUTH2 flows.
Think about the who as the user your API server will be able to Authenticate and Authorize access to the data, and think about the what as the software making that request in behalf of the user.
So if you are not using user authentication in the app, then you are left with trying to attest what is doing the request.
Mobile Apps should be as much dumb as possible
The reason why is because I need to deliver data to the app based on data gathered by the phone sensors, and if people can pose as my own app and send data to my api that wasn't processed by my own algorithms, it defeats its purpose.
It sounds to me that you are saying that you have algorithms running on the phone to process data from the device sensors and then send them to the API server. If so then you should reconsider this approach and instead just collect the sensor values and send them to the API server and have it running the algorithm.
As I said anything inside your app binary is public, because as yourself said, it can be reverse engineered:
should be implied that someone will have access to its binary and try to reverse engineer it.
Keeping the algorithms in the backend will allow you to not reveal your business logic, and at same time you may reject requests with sensor readings that do not make sense(if is possible to do). This also brings you the benefit of not having to release a new version of the app each time you tweak the algorithm or fix a bug in it.
Runtime attacks
I was thinking something involving the app signatures, since every published app must be signed somehow, but I can't figure out how to do it in a secure way.
Anything you do at runtime to protect the request you are about to send to your API can be reverse engineered with tools like Frida:
Inject your own scripts into black box processes. Hook any function, spy on crypto APIs or trace private application code, no source code needed. Edit, hit save, and instantly see the results. All without compilation steps or program restarts.
Your Suggested Solutions
Security is all about layers of defense, thus you should add as many as you can afford and required by law(e.g GDPR in Europe), therefore any of your purposed solutions are one more layer the attacker needs to bypass, and depending on is skill-set and time is willing to spent on your mobile app it may prevent them to go any further, but in the end all of them can be bypassed.
Maybe a combination of getting the app signature, plus time-based hashes, plus app-generated key pairs and the good old security though obscurity?
Even when you use key pairs stored in the hardware trusted execution environment, all an attacker needs to do is to use an instrumentation framework to hook in the function of your code that uses the keys in order to extract or manipulate the parameters and return values of the function.
Android Hardware-backed Keystore
The availability of a trusted execution environment in a system on a chip (SoC) offers an opportunity for Android devices to provide hardware-backed, strong security services to the Android OS, to platform services, and even to third-party apps.
While it can be defeated I still recommend you to use it, because not all hackers have the skill set or are willing to spend the time on it, and I would recommend you to read this series of articles about Mobile API Security Techniques to learn about some complementary/similar techniques to the ones you described. This articles will teach you how API Keys, User Access Tokens, HMAC and TLS Pinning can be used to protect the API and how they can be bypassed.
Possible Better Solutions
Nowadays I see developers using Android SafetyNet to attest what is doing the request to the API server, but they fail to understand it's not intended to attest that the mobile app is what is doing the request, instead it's intended to attest the integrity of the device, and I go in more detail on my answer to the question Android equivalent of ios devicecheck. So should I use it? Yes you should, because it is one more layer of defense, that in this case tells you that your mobile app is not installed in a rooted device, unless SafetyNet has been bypassed.
Is there any way to restrict post requests to my REST API only to requests coming from my own mobile app binary?
You can allow the API server to have an high degree of confidence that is indeed accepting requests only from your genuine app binary by implementing the Mobile App Attestation concept, and I describe it in more detail on this answer I gave to the question How to secure an API REST for mobile app?, specially the sections Securing the API Server and A Possible Better Solution.
Do you want to go the Extra Mile?
In any response to a security question I always like to reference the excellent work from the OWASP foundation.
For APIS
OWASP API Security Top 10
The OWASP API Security Project seeks to provide value to software developers and security assessors by underscoring the potential risks in insecure APIs, and illustrating how these risks may be mitigated. In order to facilitate this goal, the OWASP API Security Project will create and maintain a Top 10 API Security Risks document, as well as a documentation portal for best practices when creating or assessing APIs.
For Mobile Apps
OWASP Mobile Security Project - Top 10 risks
The OWASP Mobile Security Project is a centralized resource intended to give developers and security teams the resources they need to build and maintain secure mobile applications. Through the project, our goal is to classify mobile security risks and provide developmental controls to reduce their impact or likelihood of exploitation.
OWASP - Mobile Security Testing Guide:
The Mobile Security Testing Guide (MSTG) is a comprehensive manual for mobile app security development, testing and reverse engineering.
No. You're publishing a service with a public interface and your app will presumably only communicate via this REST API. Anything that your app can send, anyone else can send also. This means that the only way to secure access would be to authenticate in some way, i.e. keep a secret. However, you are also publishing your apps. This means that any secret in your app is essentially being given out also. You can't have it both ways; you can't expect to both give out your secret and keep it secret.
Though this is an old post, I thought I should share the updates from Google in this regard.
You can actually ensure that your Android application is calling the API using the SafetyNet mobile attestation APIs. This adds a little overhead on the network calls and prevents your application from running in a rooted device.
I found nothing similar like SafetyNet for iOS. Hence in my case, I checked the device configuration first in my login API and took different measures for Android and iOS. In case of iOS, I decided to keep a shared secret key between the server and the application. As the iOS applications are a little bit difficult to reversed engineered, I think this extra key checking adds some protection.
Of course, in both cases, you need to communicate over HTTPS.
As the other answers and comments imply, you cant truly restrict API access to only your app but you can take different measures to reduce the attempts. I believe the best solution is to make requests to your API (from native code of course) with a custom header like "App-Version-Key" (this key will be decided at compile time) and make your server check for this key to decide if it should accept or reject. Also when using this method you SHOULD use HTTPS/SSL as this will reduce the risk of people seeing your key by viewing the request on the network.
Regarding Cordova/Phonegap apps, I will be creating a plugin to do the above mentioned method. I will update this comment when its complete.
there is nothing much you can do. cause when you let some one in they can call your APIs. the most you can do is as below:
since you want only and only your application (with a specific package name and signature) calls your APIs, you can get the signature key of your apk pragmatically and send is to sever in every API call and if thats ok you response to the request. (or you can have a token API that your app calls it every beginning of the app and then use that token for other APIs - though token must be invalidated after some hours of not working with)
then you need to proguard your code so no one sees what you are sending and how you encrypt them. if you do a good encrypt decompiling will be so hard to do.
even signature of apk can be mocked in some hard ways but its the best you can do.
Someone have looked at Firebase App Check ?
https://firebase.google.com/docs/app-check
Is there any way to restrict post requests to my REST API only to requests coming from my own mobile app binary?
I'm not sure if there is an absolute solution.
But, you can reduce unwanted requests.
Use an App Check:
The "Firebase App Check" can be used cross-platform (https://firebase.google.com/docs/app-check) - credit to #Xande-Rasta-Moura
iOS: https://developer.apple.com/documentation/devicecheck
Android: https://android-developers.googleblog.com/2013/01/verifying-back-end-calls-from-android.html
Use BasicAuth (for API requests)
Allow a user-agent header for mobile devices only (for API requests)
Use a robots.txt file to reduce bots
User-agent: *
Disallow: /
I'm looking to write a unified email and messaging program. Supporting IMAP, POP, and SMTP are all pretty easy - the protocols are well documented and easy to come by.
Exchange has a SOAP API documented here, whereby you can write an Exchange client which talks with Exchange servers.
I'm looking to find out what protocol IBM (Lotus) Notes uses and how I can go about writing a standalone application which can send and receive mail. (Standalone is a key part of this - I've seen various things about automating the existing client, but I'm looking to write a new client, so I need to know what protocols it uses.)
Language is unimportant to me at this time. I'm leaning towards Python for the project, but I'm still at an exploratory stage where I'm trying to determine what frameworks exist in any language to help me write this.
That's a pretty interesting topic! There are two ways I can think of that provide mail-oriented abstractions, and two that allow you to access mail files as databases directly.
To start out with, and this is very likely the expedient route to take, Domino supports IMAP. It's far from perfect and it's not likely to improve, but it does more or less work for mail access. Not every server has it enabled by default, but it's not terribly difficult or unusual for an administrator to do so.
Recently, the Extension Library has added a JSON-based mail service that purports to provide a pretty friendly API for many operations, but is not complete - for example, it doesn't seem to cover a user's custom views or folders.
Depending on the depth of the project, then there are the routes for accessing the server using Domino's database API, which would be the most flexible but would involve far more hurdles.
The core protocol is NRPC, which, to my knowledge, is only implemented in the core Notes library. As Stan said, it's heavily tied to the presence of an ID file (server or user) and uses that for its encryption. With some setup, you could have that library and ID present and then use the C functions and structs on a platform it supports. This route would give you the most functionality (there are a number of C-level functions to assist with converting between Notes's document representation and MIME).
Alternatively, there is a remote-access protocol called DIIOP that can be used to access a remote Domino server using UN/password credentials via Java objects. This is not enabled for every server, but it's not terribly uncommon, and isn't that hard to enable. You wouldn't have access to all of the C API's functionality for edge cases, but this would cover a lot of ground.
If you want to work in Python, and you are willing to limit yourself to just the most recent versions of the Lotus Domino server, then I think that you should consider using the REST API that is known as the Donmino Data Service. Here's some on-line documentation.
Baas, backend-as-a-service, solutions like Parse.com and StackMob allow application developers to add and use custom code to run server-side business logic. I'm interested in learning how you could add functions to the app server without disruptions to other applications and keep malicious code from accessing the system or data they shouldn't.
I've searched for any posts or disclosures of how Parse or StackMob might have built up their architectures and have come up empty.
Take a look at how Kii Cloud provides custom server side code that you can add to the backend. It basically runs in a sandbox with some access to the server side API (but it's well defined, the user can only access what they are intended to access). An there are also resource limitations such as time constraints (a piece of server code can take do processing forever).
This is not exactly the internals of Kii but I think server side code in most MBaaS providers reflects on what's the correct way to add server side logic on a running system without disrupting the system.
Please head to community.kii.com if you want to discuss internals with the engineers (we're happy to chat with you).
In near future I'll need to start working on a new project that consist of highly loaded TCP/IP servers and clients that communicate to that server. I know the basics of TCP/IP and can make the server and clients talk over the wire.
The problem is that I need to find some ways to protect server against other "clients" that can send bogus data and may crash the server. I'm looking for any ideas or recommendations for an application-level protocol that I can use for my application. Pretty sure there must be some kind of open-source MMORPG game that has already implemented such a protocol.
Any other ideas are very welcome.
P.S. I have checked already the WorldForge project.
Use authentication and write your server so that bogus data doesn't crash it. You can also utilize firewalls where appropriate.
Have a look at http://www.devmaster.net/ for game development. I've read many useful articles there.
Just to be on the safe side, what's the best practice to ensure that only my application has access to my webservice, which is hosted on a public server? Should I implement I shared key or something?
My webservice is hosted on Googles App Engine and my Application runs on iPhones and iPads.
If you need further information, just ask.
Thanks,
Henrik
some sort of challenge/response authentication would be your best bet, but you could use something as simple as a key that's sent with every request. it might be quite easy for someone with a packet sniffer to reverse engineer that security though - i guess the amount of time you spend on it will relate to how much you really care :)
If you require your iphone app users to enter a loginid/password, then it is trivial to achieve what you want. But I assume you don't want that ..
Without that, there is no way to ensure you app has exclusive access to your web-services. People can always sniff HTTP traffic and spoof it. People can decompile/reverse-engineer your app to figure out the key/password.
See other discussions on StackOverflow - How to restrict access to my web service? and How can I create and use a web service in public but still restrict its use to only my app?
You could program your app to only serve requests that include your iPhone's unique identier - see StackOverflow question [Unique identifier for an iPhone app]. The id could still be sniffed, so depending on your needs, you may need methods to counter that.
Well, i had similar problem. What i realized, there is no 100% solution. What i did is, i used different approach. I have implemented OAuth and SSL, of course and than make algorithm for my web service to learn behavior of my app.
I try to put that algorithm in some kind of pattern, template, so it can be used in more scenarios. It's still in developing, so here is code of simple console app that will simulate that algorithm. Hope this can help:
https://github.com/vjeftovic/LearningRESTSimulation