I'm writing a javascript plugin which will be installed by bloggers/website owners. It will communicate with my remote API.
I'm wondering how to secure the API to ensure that only domains owned by users that have registered an account with the service can access resources from the API. I've read up on OAuth2 and understand the basics, but because the plugin will run from within the browser and not from server to server, i'm not sure how secure this can be.
Tons of services like mixpanel, google analytics, olark use the same concept (i.e. website owner install a line of JS on their site) so it must be a solved problem.
You can insert window.location checks into your script to prevent other people from including it directly off of your servers.
However, it is impossible to prevent people from downloading the scripts locally, removing your protection, then hosting it themselves.
You can require an API key in all server-side requests, but enemies can easily steal API keys from legitimate sites.
Related
I am building an application that has auth system and a lot of post requests,
I want to know how to make my backend endpoints accept only requests that are coming from my application, not from anything else like Postman.
For example, if a user submitted a registration form, a post request is sent to my backend with user info, how can I make sure this post request is coming from my application?
What I was thinking of, is saving a secret on the client’s side that is to be sent with each request to the backend, so that I can make sure the request is coming from my app.
I think SSL pinning is meant for this.
I know that anyone can access my app source code if they extract the APK file.
I want to make sure that no one can alter or steal my source code.
I read that I can make my code unreadable by Obfuscating it ( I still need to figure out how I am going to do that on my EAS build ), is this enough?
And I have to use JailMonkey to detect if the device is rooted.
I am using Expo secure store to save my sensitive info on the client side.
Is this approach good enough, is there anything I am missing?
I have zero information about security, this is just what I learned through searching.
Let me know if you have better suggestions.
Thank you in advance.
The Difference Between WHO and WHAT is Accessing the API Server
I want to know how to make my backend endpoints accept only requests that are coming from my application, not from anything else like Postman.
First, you need to understand the difference between WHO and WHAT is accessing the API Server to be in a better position to look for a solution to your problem.
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.
When you grasp this idea and it's ingrained in your mindset, then you will look into mobile API security with another perspective and be able to see attack surfaces that you never though they existed before.
Certificate Pinning and MitM Atacks
What I was thinking of, is saving a secret on the client’s side that is to be sent with each request to the backend, so that I can make sure the request is coming from my app. I think SSL pinning is meant for this.
Certificate pinning on the mobile app side serves to guarantee that the app is talking only with your API server and not anything else, like when a MitM attack occurs and the app has its requests intercepted, and potentially modified and/or replayed, or simply saved to later extract the secrets from it.
Pinning doesn't guarantee to your API server that the request is coming indeed from what it expects, a genuine and unmodified version of your mobile app, "unless" you implement mutual pinning, that isn't encouraged to do so, because you will need to ship the private key for the API server certificate in the mobile app. Even if you do so, all an attacker needs to do is to extract the private key and will be able to communicate with your API server like if it was your genuine mobile app.
I don't have an article to implement pinning on a react-native mobile app but you can take a look to the one I wrote for Android to understand better all the process. Read my article Securing HTTPS with Certificate Pinning on Android on how you can implement certificate pinning and by the end you will understand how it can prevent a MitM attack.
In this article you have learned that certificate pinning is the act of associating a domain name with their expected X.509 certificate, and that this is necessary to protect trust based assumptions in the certificate chain. Mistakenly issued or compromised certificates are a threat, and it is also necessary to protect the mobile app against their use in hostile environments like public wifis, or against DNS Hijacking attacks.
You also learned that certificate pinning should be used anytime you deal with Personal Identifiable Information or any other sensitive data, otherwise the communication channel between the mobile app and the API server can be inspected, modified or redirected by an attacker.
Finally you learned how to prevent MitM attacks with the implementation of certificate pinning in an Android app that makes use of a network security config file for modern Android devices, and later by using TrustKit package which supports certificate pinning for both modern and old devices.
Bypassing Certificate Pinning
I think SSL pinning is meant for this.
The good news is that you already learned how good pinning is to prevent MitM attacks, now the bad news is that it can be bypassed, and yes I also wrote an article on how to it on Android (sorry to not be specific on react-native). If you want to learn the mechanics of it then read my article How to Bypass Certificate Pinning with Frida on an Android App:
Today I will show how to use the Frida instrumentation framework to hook into the mobile app at runtime and instrument the code in order to perform a successful MitM attack even when the mobile app has implemented certificate pinning.
Bypassing certificate pinning is not too hard, just a little laborious, and allows an attacker to understand in detail how a mobile app communicates with its API, and then use that same knowledge to automate attacks or build other services around it.
Code Obfuscation and Modifying Code
I know that anyone can access my app source code if they extract the APK file. I want to make sure that no one can alter or steal my source code.
Sorry, but once you release it to the public is up for grabs for everyone, even if heavily obfuscated its still possible to modify it statically or during runtime.
I read that I can make my code unreadable by Obfuscating it ( I still need to figure out how I am going to do that on my EAS build ), is this enough?
No, you can use the best obfuscation tool, but then an attacker well versed in deobuscation techniques will be able to understand your code and modify it statically or at runtime. Several open-source tools exist to ake this easy, and if you read the article to bypass certificate pinning then you already saw an example of doing it at runtime with 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.
RASP - Runtime Application Self-Protection
And I have to use JailMonkey to detect if the device is rooted.
Using Frida the check can be modified to always return that the device is not rooted. Also JailMonkey may not detect all ways used to hide that a device is rooted, and this a moving target, because hackers and developers are in a constant cat and mouse game.
Sensitive Info Security
I am using Expo secure store to save my sensitive info on the client side.
Even when a secret is securely stored it will need to be used at some point, and the attacker will hook Frida to this point and extract the secret or do it in a MitM attack.
Possible Solutions
Is this approach good enough, is there anything I am missing?
From all I wrote it looks no matter what you are doomed to failure in properly secure your sensitive info and to guarantee that your API server knows that what is making the request is the genuine mobile app it expects, but security its all about of applying as many layers of defences as possible, like done in medieval castles, prisons, etc., because this will increase the level of effort, time and expertise required to succeed in an attack.
You now need to find a solution that allows you to detect MitM attacks, tampered and modified apk binaries, Frida present at runtime and that can deliver a runtime secret to mobile apps that pass a mobile app attestation that guarantees with a very high degree of confidence that such threats are not present. Unfortunately I don't know any open-source project that can deliver all this features, but a commercial solution exists (I work there), and if you want to learn more about you can read the article:
Hands-on Mobile App and API Security - Runtime Secrets Protection
In a previous article we saw how to protect API keys by using Mobile App Attestation and delegating the API requests to a Proxy. This blog post will cover the situation where you can’t delegate the API requests to the Proxy, but where you want to remove the API keys (secrets) from being hard-coded in your mobile app to mitigate against the use of static binary analysis and/or runtime instrumentation techniques to extract those secrets.
We will show how to have your secrets dynamically delivered to genuine and unmodified versions of your mobile app, that are not under attack, by using Mobile App Attestation to secure the just-in-time runtime secret delivery. We will demonstrate how to achieve this with the same Astropiks mobile app from the previous article. The app uses NASA's picture of the day API to retrieve images and descriptions, which requires a registered API key that will be initially hard-coded into the app.
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.
short answer you can't.
I want to know how to make my backend endpoints accept only requests
that are coming from my application, not from anything else like
Postman
the only thing you can do here is cors Cross-Site Request Forgery Prevention. Y to stop other servers from calling your api.
and you can't make only your application communicate with the server
you can hard code(parameters in the request) in the application to send to the server.but hackers can listen to request made from devices
I know that anyone can access my app source code if they extract the
APK file. I want to make sure that no one can alter or steal my source
code.
short answer you also can't
you can use ProGuard(native code) to obfuscate on native android and ios have compiled binary on release but those are not to js
so basically anyone can read your bundle js in plain text editor.
maybe in the future facebook can make something for hermes.
So I'm wondering how I can only make sure that CRUD operations to my restful api is only accepted by my own application and not by outsiders? My application consists of Node js as backend who makes the restful api and android as front-end who communicates with the RESTful api. I've seen JWT tokens but it only works with login system but I have an application without login system.
The reason why is that I don't want to let outsiders read or even write data on my api from for example POSTMAN. How to make sure that people who muse my app can perform CRUD operations to my API?
The Difference Between WHO and WHAT is Accessing the API Server
Before we can understand the options to address your concern I would like to clarify a common misconception among developers regarding the WHO vs the WHAT is accessing an API server.
To better understand the differences between the WHO and the WHAT are accessing an API server, let’s use this picture:
The Intended Communication Channel represents the mobile app being used as you expected, by a legit user without any malicious intentions, using an untampered version of the mobile app, and communicating directly with the API server without being man in the middle attacked.
The actual channel may represent several different scenarios, like a legit user with malicious intentions that may be using a repackaged version of the mobile app, a hacker using the genuine version of the mobile app, while man in the middle attacking it, to understand how the communication between the mobile app and the API server is being done in order to be able to automate attacks against your API. Many other scenarios are possible, but we will not enumerate each one here.
I hope that by now you may already have a clue why the WHO and the WHAT are not the same, but if not it will become clear in a moment.
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.
OAUTH
Generally, OAuth provides to clients a "secure delegated access" to server resources on behalf of a resource owner. It specifies a process for resource owners to authorize third-party access to their server resources without sharing their credentials. Designed specifically to work with Hypertext Transfer Protocol (HTTP), OAuth essentially allows access tokens to be issued to third-party clients by an authorization server, with the approval of the resource owner. The third party then uses the access token to access the protected resources hosted by the resource server.
OpenID Connect
OpenID Connect 1.0 is a simple identity layer on top of the OAuth 2.0 protocol. It allows Clients to verify the identity of the End-User based on the authentication performed by an Authorization Server, as well as to obtain basic profile information about the End-User in an interoperable and REST-like manner.
While user authentication may let the API server know WHO is using the API, it cannot guarantee that the requests have originated from WHAT you expect, the original version of the mobile app.
Now we need a way to identify WHAT is calling the API server, and here things become more tricky than most developers may think. The WHAT is the thing making the request to the API server. Is it really a genuine instance of the mobile app, or is a bot, an automated script or an attacker manually poking around with the API server, using a tool like Postman?
For your surprise you may end up discovering that It can be one of the legit users using a repackaged version of the mobile app or an automated script that is trying to gamify and take advantage of the service provided by the application.
Well, to identify the WHAT, developers tend to resort to an API key that usually they hard-code in the code of their mobile app. Some developers go the extra mile and compute the key at run-time in the mobile app, thus it becomes a runtime secret as opposed to the former approach when a static secret is embedded in the code.
The above write-up was extracted from an article I wrote, entitled WHY DOES YOUR MOBILE APP NEED AN API KEY?, and that you can read in full here, that is the first article in a series of articles about API keys.
Your Question
So I'm wondering how I can only make sure that CRUD operations to my restful api is only accepted by my own application and not by outsiders?
Defending and locking an API server to your own app is not an easy task, because any secrets used to identify the WHO or the WHAT are relatively easy for an attacker to grab. You can read the article How to Extract an API Key from a Mobile App by Static binary analysis where I demonstrate how they can be extracted with the help of several open source tools, like by using the Mobile Security Framework, or you can read this other article Steal that API Key with a Man in the Middle Attack, that uses the open source tool MiTM Proxy to launch a man in the middle attack to extract the API key.
By now you may have already realized that is very hard to defend an API server from being abused by attackers, because after they have extracted the secrets to identify the WHO and the WHAT is making the request, they can use the tool you are concerned about, Postman, or any other one to attack your API server, and pretend to be the legits WHO and WHAT.
You may be asking now... How can I defend my API server?
Defending an API Server
As a best practice a mobile app or a web app should only communicate with an API server that is under your control and any access to third party APIs services must be done by this same API server you control. This way you limit the attack surface to only one place, where you will employ as many layers of defense as what you are protecting is worth.
You can start with reCaptcha V3, followed by Web Application Firewall(WAF) and finally if you can afford it a User Behavior Analytics(UBA) solution.
Google reCAPTCHA V3:
reCAPTCHA is a free service that protects your website from spam and abuse. reCAPTCHA uses an advanced risk analysis engine and adaptive challenges to keep automated software from engaging in abusive activities on your site. It does this while letting your valid users pass through with ease.
...helps you detect abusive traffic on your website without any user friction. It returns a score based on the interactions with your website and provides you more flexibility to take appropriate actions.
WAF - Web Application Firewall:
A web application firewall (or WAF) filters, monitors, and blocks HTTP traffic to and from a web application. A WAF is differentiated from a regular firewall in that a WAF is able to filter the content of specific web applications while regular firewalls serve as a safety gate between servers. By inspecting HTTP traffic, it can prevent attacks stemming from web application security flaws, such as SQL injection, cross-site scripting (XSS), file inclusion, and security misconfigurations.
UBA - User Behavior Analytics:
User behavior analytics (UBA) as defined by Gartner is a cybersecurity process about detection of insider threats, targeted attacks, and financial fraud. UBA solutions look at patterns of human behavior, and then apply algorithms and statistical analysis to detect meaningful anomalies from those patterns—anomalies that indicate potential threats. Instead of tracking devices or security events, UBA tracks a system's users. Big data platforms like Apache Hadoop are increasing UBA functionality by allowing them to analyze petabytes worth of data to detect insider threats and advanced persistent threats.
All this solutions work based on a negative identification model, by other words they try their best to differentiate the bad from the good by identifying what is bad, not what is good, thus they are prone to false positives, despite of the advanced technology used by some of them, like machine learning and artificial intelligence.
So you may find yourself more often than not in having to relax how you block the access to the API server in order to not affect the good users. This also means that this solutions require constant monitoring to validate that the false positives are not blocking your legit users and that at same time they are properly keeping at bay the unauthorized ones.
Regarding APIs serving mobile apps a positive identification model can be used by using a Mobile App Attestation solution that guarantees to the API server that the requests can be trusted without the possibility of false positives.
Mobile App Attestation
The role of a Mobile App Attestation service is to guarantee at run-time that your mobile app was not tampered or is not running in a rooted device by running a SDK in the background that will communicate with a service running in the cloud to attest the integrity of the mobile app and device is running on.
On successful attestation of the mobile app integrity a short time lived JWT token is issued and signed with a secret that only the API server and the Mobile App Attestation service in the cloud are aware. In the case of failure on the mobile app attestation the JWT token is signed with a secret that the API server does not know.
Now the App must sent with every API call the JWT token in the headers of the request. This will allow the API server to only serve requests when it can verify the signature and expiration time in the JWT token and refuse them when it fails the verification.
Once the secret used by the Mobile App Attestation service is not known by the mobile app, is not possible to reverse engineer it at run-time even when the App is tampered, running in a rooted device or communicating over a connection that is being the target of a Man in the Middle Attack.
The Mobile App Attestation service already exists as a SAAS solution at Approov(I work here) that provides SDKs for several platforms, including iOS, Android, React Native and others. The integration will also need a small check in the API server code to verify the JWT token issued by the cloud service. This check is necessary for the API server to be able to decide what requests to serve and what ones to deny.
In Conclusion
The reason why is that I don't want to let outsiders read or even write data on my api from for example POSTMAN.
Well Postman uses a custom http header by default, thus is easy to block requests from it, but this will only works if the user doesn't disable this feature of Postamn, and attackers always disable them, therefore this measure will not be very effective, and once Postman is not the only tool out there, you need to be more sophisticated in your defenses than this.
How to make sure that people who muse my app can perform CRUD operations to my API?
I think you want to mean that only people using your app can perform the CRUD operations.
In the end, the solution to use in order to protect your API server must be chosen in accordance with the value of what you are trying to protect and the legal requirements for that type of data, like the GDPR regulations in Europe.
So my recommendation is that you implement a Mobile App Attestation solution, because its a positive model that can address your concerns.
I am building a website analytics solution based on Azure Event Hubs. I have Javascript code embedded in each web page that publishes events directly to an Event Hub via the Azure Event Hubs REST API.
The REST API requires that each call be authenticated via a SAS token. My questions is - Do I have to code up a server side endpoint that will provide my publishers with temporary tokens before they can start publishing?
Are there alternative approaches?
Does the REST API provide this "authenticate" end point out of the box? (couldn't find it here)
Or, how terrible, security wise would it be to have a token hard coded into the client-side code?
Or, technically feasible but security-wise much worse than option 2, Hard-code the Event Hub's Shared Access Key in the client-side code and use something like the (unofficial) Azure ServiceBus JavaScript SDK to generate the SAS token on the fly?
Event Hub REST api does not provide an authentication end point. You will have to code up the generation of SAS tokens per client (browser or device) on your server side (may be as part of your AuthN/Z routines?). Refer to RedDog.ServiceBus nuget package to generate SAS tokens for your Event Hub, per client. Also this article on IoT, explains authenticating against Event Hubs using the aforementioned package.
In my opinion, I would much rather do the above and rule out #2 and #3. They (2 & 3) leave the solution vulnerable and violate best practices.
Considering the example set by Google Analytics and other browser analytics providers, the second alternative in my question is quite acceptable.
That is, a SAS token can be generated on a "per site" (or "per analytics customer") basis and be shared by all browsers that this site is tracked on. The generation of the keys can be done via a tool like Sandrino Di Mattia's Event Hubs Signature Generator based on his RedDog Azure library.
This way tokens can be generated once when a publisher is onboarded and there is no need for an online Web API endpoint to be constantly available.
As an alternative approach, you could consider Application Insights for event ingestion. Depending on the type of event collection you're doing, you could be using it and exporting data using built in archiving mechanisms or querying endpoints for specific events from time to time. App Insights was designed for JS in-browser scenarios, can handle a large number of RPS + you get some reports, analytics, querying endpoints and some other interesting features. It provides an SDK and JS lib you can use, and implemnts batching for you using browser's local storage.
As a side note, consider that browsers (and any other JS code running on it) as an insecure client. That means, even if you write a mechanism to do a request to a server-side app written by you to get the SAS key, any developer will be able to intercept in memory. So, the most secure thing you could do is a) have a server-side code that generates a short-lived SAS key and b) let your clients authenticate before calling this server-side code. Or, ignore the problem and filter invalid events you receive.
Both GA and App Insights work by exposing a common key. As far as I know, Google Analytics uses heuristics to filter invalid requests. I suppose App Insights do the same.
I would like to develop a client side javascript widget that may be included on authorized partner web sites only. The javascript widget will make REST calls back to the main website. Partner web sites should be able to use the javascript widget without installing any server side components. Any attempt by an unauthorized site to use a given key should fail. Obviously, any API keys that are delivered to a web browser would ultimately be vulnerable to exposure even if they were obscured somehow.
One real world example I looked to for ideas is the Google Maps Javascript API v3, which imposes quota limits and optionally allows API clients to restrict access for a given key to specified domains. But it looks like this restriction is based on referers, which seems too easy to forge. It seems like websites using this system are vulnerable to an attacker using their keys (which are visible in plain text in the HTML) and running enough API calls to exceed the quota. Also worth noting, is that Google distinguishes between “Browser keys” and “Server keys”.
Here are some related questions I found, none with encouraging answers:
How can PHP driven API authenticate genuine client (referer) cross-domain (knowing that headers can be spoofed)?
Securing an API for use with Javascript widget
Javascript API - Restrict Domain by providing whitelisting option to user
Is there an existing design pattern, standard or cryptographic scheme that addresses this issue? Or is there no way to accomplish this without some server side component?
Consider the usecase in which a website uses a paid analytics package to track user behavior on said site.
In that case the website needs to securely communicate with an API of the analytics provider (all clientside through javascript).
How can this be done securely? To my understanding of the various authentication protocols a secret token is always needed to setup a secret-handshake between client and server. Using oAuth1a this is all packed in HMAC, etc. but still the secret must be available.
Given that:
the secret code must be available to the client in javascript to do authenticated calls
javascript on the client can obviously be inspected by anyone
How would you keep the secret safe? It seems you can't, but how then do all these paid 3rd party services which communicate through clientside JS keep things secure?
As stipulated by the referenced answer below, it seems Google Maps API is doing this with the HOST header which apparently (?) can't be spoofed.
How does Google Maps secure their API Key? How to make something similar?.
Thus, having a sever-side map which uses a map of <apikey -> allowed HOST headers> would do the trick.