Question 97301 in Nginx Question posted in
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What is the modern approach to secure communication between backend and mobile application? – Nginx

I’ve read a lot of articles on this subject and they all suggest completely different things that I can’t yet structure in my head.

I have one backend app (spring-boot + kotlin). I have nginx and one android (kotlin) mobile app uses backend api and of course Postgres. By the way backend app and postgres are packages in docker containers via docker-compose.

My task is to make the API of my backend service can only be used by this mobile application and no one else. But I also want it to be able to use the API if I have a Web application in the future.

I would be fantastically grateful if you could describe, in a few words, modern technology that could be used to accomplish my task.
For example:

  • Spring-security: a huge thing that you don’t know what to do with, most likely you can use it to solve your problems, but it’s overkill. But if you decide to use spring-security, this will help you {…}

…

By the way, I’m not against spring-security, I just really think it’s too much for my task. But I’d be happy to hear your opinion.

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Answers


  1. 0

    The easiest way probably is to define a shared secret on the phone and the backend service.

    On the mobile phone, with each request, you send the secret, e.g., as an HTTP header.

    On the backend, you need to implement a Filter (e.g., OncePerRequestFilter) that checks the request for the secret and compares it to the value stored in the backend.

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  2. 0

    Your Problem

    My task is to make the API of my backend service can only be used by this mobile application and no one else. But I also want it to be able to use the API if I have a Web application in the future.

    You have in hands a very hard task to complete. While not impossible it’s very hard to accomplish with code written on your own or by trying to leverage security features on your framework of choice.

    To understand why it’s so hard you first need to understand the difference between who is in the request versus what is doing the request.

    The Difference Between WHO and WHAT is Accessing the 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.

    So 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.

    After you understand this idea and it’s ingrained in your mindset, you will look into mobile API security with another perspective, and you will be able to see attack surfaces that you never though they could exist.

    Possible Solution

    I would be fantastically grateful if you could describe, in a few words, modern technology that could be used to accomplish my task.

    I recommend you to read this answer I gave to the question How to secure an API REST for mobile app?, especially the sections Hardening and Shielding the Mobile App, Securing the API Server and A Possible Better Solution.

    The best approach to solve your problem is to go with a Mobile App Attestation solution suggested in the answer I linked. A Mobile App Attestation needs to be able to work in tandem with your mobile app and backend in order for the backend to have a very high degree of confidence that what is making the request is indeed a genuine version of your mobile app, that hasn’t been tampered with statically or at runtime, and it’s not under a
    MitM Attack

    The Manipulator-in-the middle attack (MITM) intercepts a communication between two systems. For example, in an http transaction the target is the TCP connection between client and server. Using different techniques, the attacker splits the original TCP connection into 2 new connections, one between the client and the attacker and the other between the attacker and the server, as shown in figure 1. Once the TCP connection is intercepted, the attacker acts as a proxy, being able to read, insert and modify the data in the intercepted communication.

    The MITM attack is very effective because of the nature of the http protocol and data transfer which are all ASCII based. In this way, it’s possible to view and interview within the http protocol and also in the data transferred. So, for example, it’s possible to capture a session cookie reading the http header, but it’s also possible to change an amount of money transaction inside the application context

    Be aware that solutions to solve your problem that are specific to the backend or to the mobile app will not be able to achieve a very high degree of confidence in securing your API backend from serving requests not originated from your genuine mobile app, but it’s better to have them then nothing.

    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.

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