I'm currently building a mobile application (iOS at first), which needs a backend web service to communicate with.
Since this service will be exposing data that I only want to be accessed by my mobile clients, I would like to restrict the access to the service.
However I'm in a bit of a doubt as to how this should be implemented. Since my app doesn't require authentication, I can't just authenticate against the service with these credentials. Somehow I need to be able to identify if the request is coming from a trusted client (i.e. my app), and this of course leads to the thought that one could just use certificates. But couldn't this certificate just be extracted from the app and hence misused?
Currently my app is based on iOS, but later on android and WP will come as well.
The web service I'm expecting to develop in nodejs, though this is not a final decision - it will however be a RESTful service.
Any advice on best practice is appreciated!
Simple answer: You cannot prevent just anybody from acecssing your web site from a non-mobile client. You can, however, make it harder.
Easy:
Send a nonstandard HTTP header
Set some unique query parameter
Send an interesting (or subtly non-interesting) User Agent string
(you can probably think of a few more)
Difficult:
Implement a challenge/response protocol to identify your client
(Ab)use HTTP as a transport for your own encrypted content
(you can probably think of a few more)
Of course anybody could extract the data, decompile your code, replay your HTTP requests, and whatnot. But at some point, being able to access a free Web application wouldn't be worth the effort that'd be required to reverse-engineer your app.
There's a more basic question here, however. What would be the harm of accessing your site with some other client? You haven't said; and without that information it's basically impossible to recommend an appropriate solution.
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I have two client applications : Asp.Net MVC Core web app and an Android native mobile app, and an IdentityServer4 Server as an OpenID Server`.
I know that I have to create two client records for both of them (in the IS4's Clients table) :
a Hybrid Flow for the web app
a Hybrid/Authorization Code + PKCE for the native mobile app
But I'm wondering if I can create only one Client info for both of them or not?
I think you should create one client definition for each client, so you better can separate them and better evolve them as needed over time. Also makes it easier to separate them in the logs for example.
A question is however why/if you really need to support the hybrid flow? I think both clients only need to use the authorization code flow.
If you want to follow OAuth 2.1, then there are only two flows to use, either authorization code flow or client credentials flow. All other flows are not recommended due to various security issues. See https://oauth.net/2.1/
Tore's answer gives good reasons to keep those clients separated. If you're still not convinced, I would turn the question around - why do you want to have one logical client data used by two separate clients? This will cause some weird issues in the future. For example, at some point you might want to rate-limit one of those clients, or change client authentication method, or even block one of them completely. You will have to do it for both your apps if you don't create a separate client.
From the security point of view, there is a good reason to keep those two separated: the web client can be a confidential client with a secret assigned. The mobile client will be a public client, without a secret*. This is a solid reason not to mix those two, as you will lower the strength of your security considerably.
*In fact, best practice would be to use DCR and register a new client for each device where your app runs.
Since many website will calling service by Web API. In that case, those methods will be exposed for every one. How can I ensure only my web site can calling my Web API service?
One of the easiest way to secure it as a developer is to get the IT people to do it by limiting access down by IP address from site to site. You could also do this in the app by validating the incoming IP addreseses. Sometimes IP addresses change sometimes they don't. Whenever I have done this have used certificates as there is a trust on both sides of the data divide. Have a look at John Petersens article Making web api's secure it has a section on implementing IP security in your app as well as x509 certificates; complete with code examples that I wont reproduce here. You could try and secure it with SSL and create your own key / trust but its easier to maintain (imo) using x509. Perversely it was much easier in the web service world Microsoft had an API to do this much more simple in WSE extension..
So I'm creating an iOS framework that will be a static library that developers will add to their project, when they create an account on our site I'd like to give them a unique token that they put in their app to use my static library.
For iOS dev's, think TestFlight, you sign up, get an App ID and then run [TestFlight takeOff:<#some-key#>];
I'd like to authenticate the requests that the framework makes to my REST webservice (using https).
Is there anything I can do to prevent people from "breaking into the app code" and stealing the developers api token and using it to make requests? My api endpoints will not be public information, at least for now. and I can't authenticate the user because it's a framework and that would be an awful UX.
The question is, is there anything I can do to prevent this sort of behavior? Should I even care? I will charge the developer per X requests eventually so I was hoping to authenticate this so we don't have spammers racking up a bill for the developer.
How do other iOS frameworks handle this?
Any design ideas and criticism welcome.
I'm not sure what you're trying to do is ever possible. If the text is in the client code, it can be pulled out. SSL-pinning won't really help you here either because the cert is in the client binary as well.
One way you might be able to get close is to use the developer's authentication system. Say a user logs in into the developer's auth system, then server side you generate a short-lived key for that user. Then the client code can be passed (over SSL-pinning) that short-lived key and use that to make your API calls. However, this requires the developer to actually have a secure auth system, and without SSL-pinning, they're vulnerable to a simple man-in-the-middle attack which will reveal the short-lived key.
You can try to minimize the damage by throttling API calls on your end, or trying using per-app heuristics to approximate what normal API usage would look like. Anything out of the norm will get flagged as potentially hacker based. That might be enough to flush out most of the wanna-be-hackers. The true hackers will learn of the throttling and be clever about circumventing it...
Your safest bet is to make it a server-side library instead of a client-side library. However, that's certainly not a super-sexy solution either. Not all apps have a server side component... and even if they do, once the developer's server is compromised (ie. gets spammed or hacked, etc) it's game over once again. But, in the end, the nice thing about a server-side solution is that you're at least less vulnerable to an attack and you put the responsibility of securing the system on the developer.
What's really lacking here is some form of Apple-based verification for network calls originating from Apple devices.... but that probably won't ever happen. :)
I'm coding a desktop application for our university . Users need to signup before using this software and registration request is sent to a server written by me, too. So I'm struggling with kind of network application. ( Suppose that the request format is as simple as a HTTP request sent to an arbitrary port number )
But now I'm wondering whether it's necessary to protect registration process using CAPTCHA or not? Do I need to ensure that the signup request is not generated by a computer?
As your application is for a limited user group (your university only), I think you do not need a captcha, because the risk is very low that someone is in this group how wants to annoy you.
Also scripting for a desktop application is (a bit) more complicated than for web applications, this will decrease the risk, too. IF you are struggling with bot-registrations you could still ship the captcha as an update and only accept registrations from the updated version, don't you?
I think that would irritate the human users, who, I believe, would make all your users. Please note that on the net, only a small portion of users are bots. What about a campus? How many computers are on a campus to be worry about? Besides, all those computers are supervised by people you know, and even if a program is installed on one of them (or even all of them) to joke with you, you can call the authorities of the university. So if I were you, I would put my time on betterment of other things, instead.
No you don't need CAPTCHA. CAPTCHA was made because of the limitations imposed by a web browser while still wanting the wide availability that a website provides. Your application doesn't have either of these limitations. Your desktop application can implement whatever security methods it wants and it only needs to be distributed to a specific set of clients.
That doesn't mean you shouldn't have some security policies set up to prevent anyone on the school campus (or internet) from telneting to the port and creating an account. This can most easily be done by using PKI and distributing a unique private key and open public key with the desktop application. The server can then verify that the client has the private key before accepting registrations (plus you could encrypt any communications between the client/server). Of course anyone with access to the desktop application could get the private key, but it's at least more secure than not doing anything at all to prove they can register accounts.
I have had experienced with iOS development but no Client Server type applications.
I have heard about HTTPS, REST, JSON, etc. I am confused on the differences.
My app that I want to build is getting a list of data to output to the user and also sending a form to the server to be processed. E.g. A Membership Application to the Server with personal information and other pertaining information to be stored in the server. I also need the connection to be secure and the user must logon to the server with a username and password.
How does my app communicate with the server? Is it using NSURLRequest?
What is the best method or protocol to accomplish this?
Thanks!
HTTPS, REST, and JSON are different tools you can use when performing networked operations (more specifically, a secure protocol, a web service architecture, and a method of object serialization, respectively). If you don't know what these mean, I would do a little reading before attempting to build an iOS app that functions as a client. The link johnathon posted in the comments is a little low-level for what you're wanting to do, but searching around for "consuming a web service with iOS" might be good.
Also, does the service already exist? If so, your task is essentially to understand how to communicate with the server.
Once you're a little more up-to-speed on the fundamentals, however, the AFNetworking library is phenomenal.