Related
There are primarily two ways to authenticate using Google's reCAPTCHA Enterprise in a non-Google cloud environment (we use AWS). Google recommends using Service Accounts along with their Java client. However, this approach strikes me as less preferable than the second way Google suggests we can can authenticate, namely, using Api Keys. Authenticating via an Api Key is easy, and it’s similar to how we commonly integrate with other 3rd party services, except rather than a username and password that we must secure, we have an Api Key that we must secure. Authenticating using Service Accounts, however, requires that we store a Json file on each environment in which we run reCAPTCHA, create an environment variable (GOOGLE_APPLICATION_CREDENTIALS) to point to that file, and then use Google's provided Java client (which leverages the environment variable/Json file) to request reCAPTCHA resources.
If we opt to leverage Api Key authentication, we can use Google’s REST Api along with our preferred Http Client (Akka-Http). We merely include the Api Key in a header that is encrypted as part of TLS in transit. However, if we opt for the Service Accounts method, we must use Google’s Java client, which not only adds a new dependency to our service, but also requires its own execution context because it uses blocking i/o.
My view is that unless there is something that I’m overlooking--something that the Service Accounts approach provides that an encrypted Api Key does not--then we should just encrypt an Api Key per environment.
Our Site Key is locked down by our domain, and our Api Key would be encrypted in our source code. Obviously, if someone were to gain access to our unencrypted Api Key, they could perform assessments using our account, but not only would it be exceedingly difficult for an attacker to retrieve our Api Key, the scenario simply doesn't strike me as likely. Performing free reCAPTCHA assessments does not strike me as among the things that a sophisticated attacker would be inclined to do. Am I missing something? I suppose my question is why would we go through the trouble of creating a service account, using the (inferior) Java client, storing a Json file on each pod, create an environment variable, etc. What does that provide us that the Api Key option does not? Does it open up some functionality that I'm overlooking?
I've successfully used Api Keys and it seems to work fine. I have not yet attempted to use Service Accounts as it requires a number of things that I'm disinclined to do. But my worry is that I'm neglecting some security vulnerability of the Api Keys.
After poring a bit more over the documentation, it would seem that there are only two reasons why you'd want to explicitly choose API key-based authentication over an Oauth flow with dedicated service accounts:
Your server's execution environment does not support Oauth flows
You're migrating from reCAPTCHA (non-enterprise) to reCAPTCHA Enterprise and want to ease migration
Beyond that, it seems the choice really comes down to considerations like your organization's security posture and approved authentication patterns. The choice does also materially affect things like how the credentials themselves are provisioned & managed, so if your org happens to already have a robust set of policies in place for the creation and maintenance of service accounts, it'd probably behoove you to go that route.
Google does mention sparingly in the docs that their preferred method for authentication for reCAPTCHA Enterprise is via service accounts, but they also don't give a concrete rationale anywhere I saw.
I recently read a lot of post and article about securing sensitive info into a React Native app. From what I understand, you can't fully protect your sensitive info but only make hacker's life harder to get them.
So, from that point of view, I would like to know if it wouldn't be "safer" to get those sensitive info (i.e. API keys) from an external server (i.e. Rest API).
I explain:
I know about MitM attacks, but would it be safer (and more flexible) to have my mobile app calling my API to get API keys on request thru HTTPS? This way, no sensitive info remains in the app binary files.
And to secure MitM attacks, I could frequently change those API key values so they would remains valid only on a short period of time.
I would like to hear anyone about PROS and CONS of such a system.
APIs Misconceptions
To prepare you for my answer I will first clear out some usual misconceptions around public/private APIs and about who vs what is really accessing your backend.
Public and Private APIs
I often see that developers think that their APIs are private, because they have no docs for it, have not advertise it anywhere, and many other reasons.
The truth is that when you release a mobile app all the APIs it communicates with are now belonging to the public domain and if this APIs don't have an authentication and authorization mechanism in place then all data behind it can be accessed by anyone in the internet that reverse engineers how your mobile app works. Even when APIs have authentication in place they may be vulnerable to bad implementations of it and some have a total lack of authorization mechanisms or buggy ones as per OWASP API Security Top 10 vulnerability list.
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.
API Keys Service
I know about MitM attacks, but would it be safer (and more flexible) to have my mobile app calling my API to get API keys on request thru HTTPS? This way, no sensitive info remains in the app binary files.
While you indeed don't have any sensitive info in the app binary files you haven't solved the problem. In my opinion you are more exposed, because you are now getting the API keys from an public and open API endpoint.
I say it's open because you don't have any safeguard that what is making the request to it are indeed a genuine and untampered version of your mobile app.
So, now all an attacker needs to do is to MitM attack your mobile app or decompile it to see from which API endpoint you grab the API keys to make the requests, and then replicate the procedure from their automated scripts/bots, therefore doesn't really matter that you don't have them hardcoded in the app binary any more.
API Keys Rotation
And to secure MitM attacks, I could frequently change those API key values so they would remains valid only on a short period of time.
In light of the above explanation , on the API Keys Service section, you can even make the API keys restricted to be used only for one single request that the attacker will still succeed, because the attacker will be able to query the API endpoint to obtain API keys as if he was what the backend expects, a genuine and untampered version of your mobile app.
So, to be clear I am in favour of API keys rotation but only if you can get them into your mobile app from a secured external source, but your approach is open to be accessed by anyone on the internet.
I would like to hear anyone about PROS and CONS of such a system.
The system you are describing is not advisable to implement, because without being secured it's just a security disaster asking to occur. Securing it with an API key it's just going back to the initial problem with the disadvantage that your giving back to the mobile the sensitive info you want to keep away from hackers.
The best approach for you is to use a Reverse Proxy to keep the API keys private and secured from prying eyes.
The Reverse Proxy Approach
So, from that point of view, I would like to know if it wouldn't be "safer" to get those sensitive info (i.e. API keys) from an external server (i.e. Rest API).
What you are looking for is to implement a Reverse Proxy, that is usually used to protect access to third party APIs and your own APIs, by having the mobile app delegating the API requests to the Reverse Proxy, instead of asking for the API keys to make them from inside the mobile app.
The Reverse Proxy approach will avoid to have several API keys harcoded in the mobile app, but you still need one API key to protect access to the Reverse Proxy, therefore you are still vulnerable to the MitM attacks and to static reverse engineering of your mobile app.
The advantage now is that all your sensitive API keys are private and in an environment you can control and employ as many security measures you need to ensure that the request are indeed from what your backend expects, a genuine and untampered version of your mobile app.
Learn more about using a Reverse Proxy by reading the article I wrote Using a Reverse Proxy to Protect Third Party APIs:
In this article you will start by learning what Third Party APIs are, and why you shouldn’t access them directly from within your mobile app. Next you will learn what a Reverse Proxy is, followed by when and why you should use it to protect the access to the Third Party APIs used in your mobile app.
While the article focus on third party APIs the principle also applies to use with your own APIs.
Preventing MitM Attacks
When certificate pinning is implemented in a mobile app to secure the https channel then the sensitive data on the API requests is more safeguarded from being extracted.
I recommend you to read the section Preventing MitM Attacks in this answer I gave to another question where you will learn how to implement static certificate pinning and how to bypass it.
Despite being possible to bypass certificate pinning I still strongly recommend it to be implemented, because it reduces the attack surface on your mobile app.
A Possible Better Solution
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 solution will be the use of a Mobile App Attestation solution that will allow your backend to have an high degree of confidence that the request is from what it expects, a genuine and untampered version of your mobile 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.
Consider an API that a client accesses directly (machine to machine) and that doesn't require user-specific authentication. The way I understand it, in client_credentials, the client must store a client_id and client_secret that it uses to acquire and refresh tokens. With an API key, the client just stores the key. What makes OAuth more secure in this case? It would appear to me that if the API key is never compromised, no attacker could pose as the intended client. And if the API key is compromised, it is effectively the same as compromising the client_id and client_secret, which an attacker would be able to use to obtain tokens and access the data in the API, posing as the client.
edit: clarified this is a machine-to-machine call
TLDR;
The difference comes down to direct access vs. delegated access.
OAuth allows you to make delegated access. The benefits of delegated access don't change if there is a user involved or not. The same arguments that make the OAuth Authorization code flow attractive for user-to-machine access, apply to the OAuth Client credentials flow for machine-to-machine access.
Ask yourself, do you want the resource server to handle client credentials or not?
On confidential clients for machine-to-machine access, the cost of delegated access vs. direct access may very well outweigh the benefits. That's why so many APIs still use API keys. You'll have to decide that for your individual use case.
Differences
In the OAuth client credentials flow, the client sends an access token to the resource server, which it got beforehand by the authorization server after presenting its client ID and secret. The resource server never sees the client secret. With an API key, the client sends the key with every request.
OAuth adds an additional layer of indirection with the authorization server, such that the credentials themselves never get transmitted to the resource server. This allows the authorization server to give the client only access for a limited amount of time or with limited permissions, without ever needing to change the actual client credentials. It also allows to revoke access tokens without revoking the credentials themselves. For multiple instances of a client this allows you to revoke access for some but not all.
Of course this all comes at the cost of a more complex implementation, and an additional roundtrip from the client to the authorization server.
I won't touch on transmission (URL, header, body, etc.) or format (random string, signed JWT, etc.), since these can be the same for access tokens just as for API keys.
Another, maybe not so obvious, advantage of OAuth is having a clear spec that libraries, documentation and discussions can be based on. With direct access there is no single best practice and different people may understand different things when referring to direct access methods like API keys.
With client credential flow your Client Id and Client Secret are sent to the authorization server to get back an access token. For all subsequent request to the API/resource servers, you pass the access token and not the client credentials themselves. The access token is usually a JWT, which is a set of encoded claims including the token expiry (exp), not before (nbf), token issuer (iss), authorized party (azp), roles, permissions, etc.
This has a number of advantages over a simple API Key approach. e.g.
If the access token (which is included in requests to the API/resource server) is compromised, it's only valid until it expires (which is typically ~1 day for M2M tokens). If an API Key is compromised, it can be used indefinitely or until it's explicitly blocked by the API/resource server.
JWT access tokens are encoded JSON objects that contains a number of fields (a.k.a. claims) that can be used for fine grained authorization e.g. roles, permissions, grant type, authorized party etc. An API Key is generally opaque and is all or nothing when it comes to auth.
You machine tokens can get validated and authorized on the API/resource servers the same way as your user tokens, so you don't end up with multiple auth implementations on the back-end.
OAuth Client Credentials Flow
What is the security difference between API Keys and the client credentials flow of OAuth?
OAuth client credentials flow is not meant to be used by public clients, just between machines.
From auth0.com/docs:
Client Credentials Flow
With machine-to-machine (M2M) applications, such as CLIs, daemons, or services running on your back-end, the system authenticates and authorizes the app rather than a user. For this scenario, typical authentication schemes like username + password or social logins don't make sense. Instead, M2M apps use the Client Credentials Flow (defined in OAuth 2.0 RFC 6749, section 4.4), in which they pass along their Client ID and Client Secret to authenticate themselves and get a token.
So, I am not sure what is your scenario, but I will assume in my reply that you are referring to public clients.
If it is in the public client code, then it is public
The way I understand it, in client_credentials, the client must store a client_id and client_secret that it uses to acquire and refresh tokens.
Yes, it needs to be stored in the client code for the client to be able to obtain the OAuth token.
If you use the client_secret from a web app or mobile app you are making it public, therefore not a secret anymore.
Extracting secrets from public clients
For example, in a web app all it takes to extract the client_secret is to hit F12 in the browser and search for it, thus how much time can this take?
Now, in a mobile app, some may think it's secure because they are compiled into a binary but is almost as easy as it is in the browser, because we have several open-source tools that can help us with this task, like the MobSF framework, and on Linux, you can even achieve this with the strings command. Using the MobSF to perform static binary analysis on the mobile app binary allows for anyone without hacking knowledge to easily extract the client_secret in minutes, just like I show in my article How to Extract an API key from a Mobile App with Static Binary Analysis:
The range of open source tools available for reverse engineering is huge, and we really can't scratch the surface of this topic in this article, but instead, we will focus in using the Mobile Security Framework(MobSF) to demonstrate how to reverse engineer the APK of our mobile app. MobSF is a collection of open-source tools that present their results in an attractive dashboard, but the same tools used under the hood within MobSF and elsewhere can be used individually to achieve the same results.
So, the process of extracting the api-key in my article is the same you will use to extract the client_secret or any other string of your interest in the mobile app binary.
OAuth or API Key?
What makes OAuth more secure in this case? It would appear to me that if the API key is never compromised, no attacker could pose as the intended client. And if the API key is compromised, it is effectively the same as compromising the client_id and client_secret, which an attacker would be able to use to obtain tokens and access the data in the API, posing as the client.
If used from a public client neither are secure, because if read my linked article, you understand by now how easy is to bypass an API Key or extract the client_secret and client_id.
So, if your client is public you should not use the OAuth client credential flow, thus you need to go with the insecure API key approach or you can be more diligent and try to apply defence-in-depth approaches, but this will depend if the API clients are only web apps or mobile apps or both.
If your API clients are only web apps I invite you to read my answer to the question Secure API data from calls out of the app, especially the section dedicated to Defending the API Server.
In the case the API clients are only mobile apps then I recommend you to read this answer I gave to the question How to secure an API REST for mobile app?, especially the sections Securing the API Server and A Possible Better Solution.
On the other hand, if your API clients are both a web app and a mobile app I recommend you to apply the security measures more relevant to you from both answers linked above.
Remember that security is always about adding as many layers of defences as you can afford or it's required by law. Even in the past century, the castles were built with a lot of different security defence layers, thus this is nothing new to the digital era.
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.
For Web Apps
The Web Security Testing Guide:
The OWASP Web Security Testing Guide includes a "best practice" penetration testing framework which users can implement in their own organizations and a "low level" penetration testing guide that describes techniques for testing most common web application and web service security issues.
I am using HERE api in both frontend and backend. If I try to put my app_id and app_code into the frontend code, it will be available to anyone seeing my site.
I can try to create a domain whitelist and put my domain in this. But still, if I set the HTTP header "Referer" to my domain, I am able to access the API from any IP.
So, what do I do?
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.
To better understand the differences between the WHO and the WHAT are accessing an API server, let’s use this picture:
So replace the mobile app by web app, and keep following my analogy around this picture.
The Intended Communication Channel represents the web app being used as you expected, by a legit user without any malicious intentions, communicating with the API server from the browser, not using Postman or using any other tool to perform a man in the middle(MitM) attack.
The actual channel may represent several different scenarios, like a legit user with malicious intentions that may be using Curl or a tool like Postman to perform the requests, a hacker using a MitM attack tool, like MitmProxy, to understand how the communication between the web app and the API server is being done in order to be able to replay the requests or even automate attacks against the API server. 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 web 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 browser were your web app should be running from, with a real user.
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 web 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 manipulating manually the requests or an automated script that is trying to gamify and take advantage of the service provided by the web app.
Well, to identify the WHAT, developers tend to resort to an API key that usually is sent in the headers of the web app. Some developers go the extra mile and compute the key at run-time in the web app, inside obfuscated javascript, thus it becomes a runtime secret, that can be reverse engineered by deobusfaction tools, and by inspecting the traffic between the web app and API server with the F12 or MitM tools.
The above write-up was extracted from an article I wrote, entitled WHY DOES YOUR MOBILE APP NEED AN API KEY?. While in the context of a Mobile App, the overall idea is still valid in the context of a web app. You wish you can read the article in full here, that is the first article in a series of articles about API keys.
Your Problem
I can try to create a domain whitelist and put my domain in this. But still, if I set the HTTP header "Referer" to my domain, I am able to access the API from any IP.
So this seems to be related with using the HERE admin interface, and I cannot help you here...
So, what do I do?
I am using HERE API in both frontend and backend.
The frontend MUST always delegate access to third part APIs into a backend that is under the control of the owner of the frontend, this way you don't expose access credentials to access this third part services in your frontend.
So the difference is that now is under your direct control how you will protect against abuse of HERE API access, because you are no longer exposing to the public the HERE api_id and api_code, and access to it must be processed through your backend, where your access secrets are hidden from public pry eyes, and where you can easily monitor and throttle usage, before your bill skyrockets in the HERE API.
If I try to put my app_id and app_code into the frontend code, it will be available to anyone seeing my site.
So to recap, the only credentials you SHOULD expose in your frontend is the ones to access your backend, the usual api-key and Authorization tokens, or whatsoever you want to name them, not the api_id or api_code to access the HERE API. This approach leaves you only with one access to protect, instead of multiple ones.
Defending an API Server
As I already said, but want to reinforce a web app should only communicate with an API server that is under your control and any access to third part 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 defence as what you are protecting is worth.
For an API serving a web app, you can employ several layers of dense, starting 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 the 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 these 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 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 these solutions require constant monitoring to validate that the false positives are not blocking your legit users and that at the same time they are properly keeping at bay the unauthorized ones.
Summary
Anything that runs on the client side and needs some secret to access an API can be abused in different ways and you must delegate the access to all third part APIs to a backend under your control, so that you reduce the attack surface, and at the same time protect their secrets from public pry eyes.
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 using API keys may sound like locking the door of your home and leave the key under the mat, but not using them is liking leaving your car parked with the door closed, but the key in the ignition.
Going the Extra Mile
OWASP Web Top 10 Risks
The OWASP Top 10 is a powerful awareness document for web application security. It represents a broad consensus about the most critical security risks to web applications. Project members include a variety of security experts from around the world who have shared their expertise to produce this list.
I have developed API in dot net. This API is consumed by different application. I have to generate a different key for each application which is consumed by this API. Can anyone please share their Ideas. This is first time i am doing such tasks.
Your Problem
I have developed API in dot net. This API is consumed by different application. I have to generate a different key for each application which is consumed by this API.
When creating an API, no matter if consumed by one or more applications you need to deal with the fact of WHAT is accessing the API and sometimes you also need to care about WHO is accessing it.
With this in mind lets clear a common misconception among developers about WHO and WHAT is accessing an API server.
The Difference Between WHO and WHAT is Accessing the API Server
I don't know if the applications consuming the API are mobile or web based, but I will do my analogy using a mobile application, and for a web application the difference between WHO and WHAT will make no difference.
To better understand the differences between the WHO and the WHAT are accessing a mobile app, 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.
Defending an API Server
Can anyone please share their Ideas.
A mobile app or a web app should only communicate with a API server that is under your control and any access to third part 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.
For an API serving a web app you can employ several layers of dense, starting 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.
The 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.
Summary
I think it should be pretty clear by now that you will need to use an API key for each application to identify the WHAT, and if you care about the WHO you should employ an OAUTH solution to, and then choose what defense layers you want to put in place on the API server to guarantee that you really know that the WHAT and the WHO is accessing the API server are really the ones you expect.
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 using API keys may sound like locking the door of your home and leave the key under the mat, but not using them is liking leaving your car parked with the door closed, but the key in the ignition.
Going the Extra Mile
This is first time i am doing such tasks.
So I real recommend you to read some links...
Web Apps
OWASP Web Top 10 Risks
The OWASP Top 10 is a powerful awareness document for web application security. It represents a broad consensus about the most critical security risks to web applications. Project members include a variety of security experts from around the world who have shared their expertise to produce this list.
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.