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: /
This question might sound trivial, but even after reading a number of tutorials, I still don't get how the REST security should be implemented.
I have a webpage and soon-to-be-ready mobile app. Both of them will be using the REST API (written in node.js), and the question is - how can I prevent users from modyfing those requests? It's very easy to see the network traffic in the browser, and all the GET/POST requests that are made to the server. It also seems very easy to copy such a request, modify its parameters and/or payload and send it to the server.
How do I make sure that's my webpage or the app who made the request, and not someone else?
Sisyphus is absolutely correct: your focus should be on securing the channel (TLS, SSH, etc) and authentication (e.g. OAuth2).
You should absolutely familiarize yourself with the Open Web Application Security Project (OWASP). In particular, start with:
OWASP Top 10 Cheat Sheet
OWASP REST Security Cheat Sheet
Here is an excellent "hands on" tutorial that gives you a great overview of all the different pieces you need to worry about:
Authenticate a Node.js API with JSON Web Tokens
Once you've gone through the tutorial and scanned the OWASP cheat sheets, you'll have a much better idea of what kinds of things you need to worry about, what options/technologies are available to mitigate those risks, and what might work best for your particular scenario.
Good luck!
Typically, security these days uses a combination of Transport Layer Security and OAuth2. OAuth2 provides authentication and authorisation, ensuring appropriate access to resources, with TLS both securing data over the network and preventing the kind of replay attacks which you're concerned about. Neither are really specific to Restful APIs and you can find them being used in non-Rest contexts also.
Context
I have a Node.js application that has a "complex" set of OAuth flows in order to make the UX simpler.
I have the usual login and registration flow where you may use an OAuth provider to authenticate. I don't require any special scope here, since OAuth is being used purely for authentication and the user has no reason to want to give me elevated access (say to private GitHub repositories), and might even think this is a shady thing to ask, so he goes away and never visits my product again. So, no scope for the pure authentication flow.
The application also has an import functionality where you can import a list of entities from an OAuth provider (say, GitHub repositories). By default, you aren't asked for any scope here either.
Clicking on the "Looking for your private repositories?" button authenticates you against GitHub again, asking for the repo scope. This is all fine and well.
The issue
Is that when the user tries to login again, or otherwise do anything that might authenticate them but doesn't explicitly request the repo scope, GitHub deems this an explicit downgrade request.
The issue is the user wouldn't want to downgrade during logins for no particular reason. Similarly, I don't want to ask for more permissions than I need during logins.
Leaving things in this state would be even worse than asking for repo at login, but that would be an extremely poor choice as well.
Potential Solutions
Besides the two non-solutions, the potential solutions I've come up with are:
Ask GitHub explicitly for unique access tokens based on the requested scope, store the tokens separately, and use them as needed afterwards
That'd be great, except it'd be way too stateful and I haven't found a way to do it anyways; they seem to give you a single token per application user, and I suspect this is how OAuth works, for the most part, but I'm hardly an expert on the matter.
Tell GitHub explicitly not to downgrade a token if it has more priviledge than what it's asking for.
This sounds to me that it should be the default behavior. Anyways, is there any way I can tell GitHub not to downgrade a token?
If not, is there any other way I can fix this without resorting to asking for the same scope across the entire application? This would partially defeat the purpose of scopes in the first place.
Also, is this a GitHub-specific issue? Will I have to deal with this in a provider-by-provider basis? Is there a protocol-level solution that miraculously makes the problem go away? Or is OAuth just not built with UX in mind?
FWIW I'm using iojs and passportjs, but I don't think that has anything to do with the question.
Turns out the issue was in my code, as it usually goes. I was explicitly setting a property (options.scope: [], for those using passport) on the authentication flow, and that resulted in a GitHub authorization URL that contained &scope=&, meaning I was explicitly asking for a downgrade.
Removing the option in case I have no explicit scope to ask for fixed the issue. Woo!
I am trying to figure out what would the best choice be in terms of security for a web application that might (in the future) be used with as well with a dedicated Android app.
Yet, the possibile choices I've been through are OAuth (2-legged) and Basic Http Authentication via TLS.
Please keep in mind that when I refer to OAuth, I am considering both OAuth 1.0a and OAuth 2.0, of course as different alternatives.
Here are my doubts:
1) First, would it make any sense nowadays to set up a security system based on OAuth 1.0a? Should it be considered "too old" and hence a completely wrong pick?
2) I can't figure out a real world scenario where 2-legged OAuth is cleary a better option then Http(S) Auth. What extra bonuses do I get from it?
3) Given that I'm not a veteran security expert, would OAuth be a reasonable choice?
4) Are there support frameworks or other third-party auxiliary tools that one may use in order to obtain a secure-reliable-thrustworty implementation of OAuth in less time and/or with less effort than just trying to figure it out completely by him/herself
It absolutely makes sense. My personal opinion is, that OAuth 1.0a should still be the preferred solution, unless you are absolutely sure that you need OAuth 2. OAuth1 is a strictly defined secure protocol, OAuth2 is a "framework" which is used to create protocols, some of which are less secure.
The main difference is, that when using OAuth you never send password over the wire. Also, your android application doesn't need to know user's password. And if you don't know the password you can't be blamed for leaking it.
OAuth 1.0a is a perfectly reasonable choice. Just make sure to use long (I mean 1K+ long) secrets. Secret is not transmitted with requests, so it won't eat the bandwidth but it is used for generating digital signatures.
There are. But as you're interested in android and I'm not an android specialist I'll leave this to others. You will have better chances for a good answer if you ask this question separately
I'm working on a web site and I plan to use strictly OAuth in for user authentication. I've never implemented session management/user authentication before; and so - naturally - I'm reading up on a lot of how tos to get this done.
The problem I'm running into is that a lot of examples out there for doing things like setting up your realm, authenticator, etc etc seem to rely on the user/password paradigm for authentication. The whole point of going for OAuth is to avoid this in the first place!
That being said; I'm actually not looking for examples of full OAuth implementations right now. I understand that I need to understand that for myself. BUT with a future OAuth implementation in mind; how should I structure my user authentication/session management FOR THE TIME BEING in a way that will allow me to move forward on developing the functionality on my site that I really care about? I suppose I could throw some stuff together for that; but I'm just afraid that down the road I will be shoe horning an OAuth implementation as opposed to do something now which allows me to lay down the basic framework for it and then move on to other things.
So; does anyone know of a good example of laying the groundwork for OAuth on Tomcat 7? For example, which authentication mechanism (Basic, digest, etc) I should use or how I should represent user credentials in my database?
I know that this is kind of a vague question; so I'm not expecting someone to come out and tell me all of the answers I need to know. I'm just looking to get pointed in the right direction here.
Perhaps Spring Security would be useful? Your webapp could leverage Spring Security and use whatever login mechanism you need (i.e., you could do the default form-based authentication or Basic Auth for now, and replace the login/auth piece with an OAuth implementation when you're ready), but still have Spring Security manage authorization to particular resources in your webapp.
Someone has also built OAuth for Spring Security, so it may be a useful addition to your web app all around.