This question is kinda complimentary to "Share credentials between native app and web site", as we aim to share secrets in the opposite direction.
TL;TR: how can we securely share the user's authentication/authorization state from a Web Browser app to a Native Desktop app, so the same user doesn't have to authenticate additionally in the Native app?
TS;WM: We are working on the following architecture: a Web Application (with some HTML front-end UI running inside a Web Browser of user's choice), a Native Desktop Application (implementing a custom protocol handler), a Web API and an OAuth2 service, as on the picture.
Initially, the user is authenticated/authorized in the Web Browser app against the OAuth2 service, using the Authorization Code Grant flow.
Then, the Web Browser content can do one-way talking to the Native app, when the user clicks on our custom protocol-based hyperlinks. Basically, it's done to establish a secure bidirectional back-end communication channel between the two, conducted via the Web API.
We believe that, before acting upon any requests received via a custom protocol link from the Web Browser app, the Native app should first authenticate the user (who is supposed to be the same person using this particular desktop session). We think the Native app should as well use the Authorization Code flow (with PKCE) to obtain an access token for the Web API. Then it should be able to securely verify the origin and integrity of the custom protocol data, using the same Web API.
However, it can be a hindering experience for the user to have to authenticate twice, first in the Web Browser and second in the Native app, both running side-by-side.
Thus, the question: is there a way to pass an OAuth2 access token (or any other authorization bearer) from the Web Browser app to the Native app securely, without compromising the client-side security of this architecture? I.e., so the Native app could call the Web API using the identity from the Web Browser, without having to authenticate the same user first?
Personally, I can't see how we can safely avoid that additional authentication flow. Communication via a custom app protocol is insecure by default, as typically it's just a command line argument the Native app is invoked with. Unlike a TLS channel, it can be intercepted, impersonated etc. We could possibly encrypt the custom protocol data. Still, whatever calls the Native app would have to make to decrypt it (either to a client OS API or some unprotected calls to the Web API), a bad actor/malware might be able to replicate those, too.
Am I missing something? Is there a secure platform-specific solution? The Native Desktop app is an Electron app and is designed to be cross-platform. Most of our users will run this on Windows using any supported browser (including even IE11), but ActiveX or hacking into a running web browser instance is out of question.
The best solution : Single Sign On (SSO) using Custom URL Scheme
When I was checking your question, I remembered the Zoom app that I am using in my office. How it works ?
I have my Gmail account linked to a Zoom account (this is account linkage, which is outside the scope of implementation). When I open Zoom app, I can choose the option to login with Gmail. This opens my browser and take me to Gmail. If I am logged in to Gmail, I am redirected back to a page that asking me to launch Zoom app. How this app launch happen ? The application register a custom URL scheme when app get installed and the final redirect in browser targets this URL. And this URL passes a temporary secret, which Zoom application uses to obtain OAuth tokens. And token obtaining is done independent of the browser, a direct call with SSL to token endpoint of OAuth server.
Well this is Authorization code flow for native applications. And this is how Mobile applications use OAuth. Your main issue, not allowing user to re-login is solved. This is SSO in action.
There is a specification which define best practices around this mechanism. I welcome you to go through RFC8252 - OAuth 2.0 for Native Apps.
Challenge
You need to implement OS specific native code for each application distribution. Windows, Mac and Linux have different implementation support for custom URL scheme.
Advice
PKCE is mandatory (in IETF words SHOULD) for all OAuth grant types. There is this ongoing draft which talks about this. So include PKCE for your implementation too.
With PKCE, the redirect/callback response is protected from stealing. Even some other application intercept the callback, the token request cannot be recreated as the PKCE code_verifer is there.
Also, do not use a custom solution like passing secret through another channel. This will make things complicated when it comes to maintenance. Since this flow already exists in OAuth, you can benefit with libraries and guidance.
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Update : Protecting Token Request
While the custom URL scheme solves the problem of launching the native application, protecting token request can be challenging. There are several options to consider.
- Bind native application launch with a secret shared from browser
When browser based client launch the native client, it can invoke a custom API to generate a secret. This secret acts like a one time password (OTP). User has to enter this value in native app before it obtain tokens. This is a customization on top of Authorization code flow.
- Dynamic client registration & Dynamic client authentication
Embedding secrets into public clients is discouraged by OAuth specification. But as question owner points out, some malicious app may register itself to receive custom URL response and obtain tokens. In such occasion, PKCE can provide an added layer of security.
But still in an extreme case, if malicious app registers the URL plus use PKCE as the original application, then there can be potential threats.
One option is to allow dynamic client registration at the first time of application launch. Here, installer/distribution can include a secret that used along with DCR.
Also, it is possible to use dynamic client authentication through a dedicated service. Here, the application's token request contains a temporary token issued by a custom service. Custom service obtain a challenge from native application. This may be done through totp or a cryptographic binding based on an embedded secret. Also it is possible to utilize OTP (as mentioned in first note) issued through browser, which needs to be copy pasted manually by end user. Once validated, this service issue a token which correlate to the secret. In the token request, native client sends this token along with call back values. This way we reduce threat vectors even though we increase implementation complexity.
Summary
Use custom URL scheme to launch the native application
Browser app generate a temporary secret shared with a custom service
At native app launch, user should copy the secret to native app UI
Native app exchange this secret with custom service to obtain a token
This second token combined with call back authorization code (issued through custom url scheme) is used to authenticate to token endpoint
Above can be considered as a dynamic client authentication
Value exposed to user can be a hashed secret, hence original value is never exposed to end user or another client
DCR is also an option but embedded secrets are discouraged in OAuth world
As you mentioned, using a custom protocol handler is not a safe way to pass secrets, since another app may handle your protocol and intercept that secret.
If you are imposing a strict constraint that the communication channel between the native app and the web app is initiated from the web app, and that the native app has not previously established a secure channel (e.g. shared secret which could encrypt other secrets), then it is not possible to safely transmit a secret to the native app.
Imagine if this were possible, then PKCE would be redundant in an OAuth 2.0 Code Flow, since the server could have safely transmitted the access token in response to the authorization request, instead of requiring the code_verifier to be provided with the grant when obtaining the access token.
Just got the following idea. It's simple and while it doesn't allow to fully automate the setup of a secure channel between Web Browser app and the Native app, it may significantly improve the user experience.
We can use Time-based One-Time Password algorithm (TOTP). In a way, it's similar to how we pair a Bluetooth keyboard to a computer or a phone.
The Web Browser app (where the user is already authenticated) could display a time-based code to the user, and the Native app should ask the user to enter that code as a confirmation. It would then use the code to authenticate against the Web API. That should be enough to establish a back-end channel between the two. The life time of the channel should be limited to that of the session within the Web Browser app. This approach might even eliminate the need for a custom protocol communication in the first place.
Still open to other ideas.
You could try driving the synchronization the other way:
Once the user is authenticated into the web app, launch the native app from the web app via the custom URL scheme.
If the native app is not authenticated, connect securely to the backend over HTTPS, create a record for the native app, retrieve a one time token associated with that record and then launch the web app in the user's browser with the token as a URL parameter.
Since the user is authenticated in the browser, when the server sees the token it can bind the native app's record with the user account.
Have the native app poll (or use some other realtime channel like push notifications or a TCP connection) the server to see if the token has been bound to a user account: once that happens you can pass a persistent auth token that the native app can store.
Did you think about using LDAP or Active Directory?
Also OAuth2 could be combined, here are a related question:
- Oauth service for LDAP authentication
- Oauth 2 token for Active Directory accounts
SSO should be easier then too, furthermore access-rights could be managed centralized.
Concerning general security considerations you could work with two servers and redirect form the one for the web-application to the other one after successful access check. That 2nd server can be protected so far that a redirect is required from the 1st server and an access check could be made independent again but without need to login another time, might be important to mention here the proposed usage of Oracle Access Manager in one linked answer for perimeter authentication.
This scenario with two servers could be also hidden by using a proxy-server in the frontend and making the redirects hidden, like that data-transfer between servers would be easier and secure too.
The important point about my proposition is that access to the 2nd server is just not granted if anything is wrong and the data are still protected.
I read here some comments concerning 2FA and some other ideas like tokens, surely those things increase security and it would be good to implement them.
If you like the general idea, I'm willing to spend still some time on the details. Some questions might be helpful for me ;-)
EDIT:
Technically the design in detail might depend on the used external authentication provider like Oracle Access Manager or something else. So if the solution in general sounds reasonable for you it would be useful to elaborate some parameters for the choice of a external authentication provider, i.e. price, open-source, features, etc.
Nevertheless the general procedure then is that the provider issues a token and this token serves for authentication. The token is for unique one-time usage, the second link I posted above has some answers that explain token-usage very well related to security and OAuth.
EDIT2
The Difference between an own OAuth2 / OIDC server and a LDAP/AD server is that you need to program everything by yourself and can't use ready solutions. Nevertheless you're independent and if everything is programmed well perhaps even a bit more secure as your solution is not public available and therefore harder to hack - potential vulnerabilities just can't be known by others. Also you're more independent, never have to wait for updates and are free to change whatever you want at any time. Considering that several software-servers are involved and perhaps even hardware-servers the own solution might be limited scale-able, but that can't be know from outside and depends on your company / team. Your code base probably is slimmer than full-blown solutions as you've only to consider your own solution and requirements.
The weak point in your solution might be that you have to program interfaces to several things that exist ready for business-frameworks. Also it might be hard to consider every single point in a small team, large companies could have more overview and capacity to tackle every potential issue.
I'm using the Expo Facebook login on my React Native app. In my app they can create and join events, which is done via API calls to my Laravel backend. I need these API calls to be authenticated (so some random person can't submit requests on someone else's behalf), but I don't want them to have to login twice. How can I ensure the person making API calls is who they say they are?
When they auth with Facebook they get their unique Facebook user ID, but I'm not sure if that is a secret they would only know after authenticating with FB or if anyone could get it. For my alpha version it's just sending their FB user ID with the request to ensure it's coming from the right person, but that seems really insecure because if anyone gets that ID they can forge requests.
One idea I had was to pass the auth token the React Native app got from Facebook to my API, and then on my server use that auth token to ensure it's really them. That just seems sort of complicated and it's hard to find a package that helps facilitate this, though.
It seems like this has to be a common problem. Any resources on how other apps handle this? Tinder, for example, must have this same problem.
I want to validate a google Authentication Code in my Net Core API with a Google's API or Microsoft.AspNetCore.Authentication.Google. I've seen people usually make a http call to validate the one-time Code following this guide but I think to make the application more robust the validation should be executed with the a proper Google API however I can't find an example code doing it except processing all OAuth flow that's not my case because I already have one-time Code (Authentication Code) gotten by my android application. Is it possible for these Google APIs to validate just the one-time Code? If I can which API should I use and how do I do it?
Btw my android application will be using the back end service a lot so I'm thinking on creating another token for the user not to be prompted with google login every time he uses the service but shouldn't be easier to use the same google's Access Token? I think that they advice to use one-time Code to avoid been caught with man in the middle attack in the future, but if I'm already giving another token for the user access my service shouldn't I use the google's instead already?
We have a webapp that integrates with a number of Google APIs (calendars, contacts, drive). We have an integrations panel where the user can selectively check on each integration. When a new integration is enabled we save the new refresh token Google returns and flag the old one as inactive. Great so far.
The problem is when we request a new scope (incremental), Google seems to correctly add the scope to the User (if we check granted scopes from the frontend it shows the correct list), but if we check scopes from the access token it will only list profile and whatever we just requested.
So if someone enables Calendar, that refresh token will have 'profile' and 'calendar', but if they then enable Drive, the new refresh token will have only 'profile' and 'drive', not 'calendar'. This is especially problematic for our Drive worker, as it will generate a lovely slew of errors as it tries to build out a User's Drive with a valid refresh token but invalid scopes.
On the backend, I'm using the setIncludeGrantedScopes(true) method before I cash in the code, and as far as I know the front end is doing what it should (it does seem to have the expected scopes), but the refresh token is not inclusive.
Tips/tricks/gotchas/etc?
So, it turns out that this was a fairly simple solution, but was documented in only one place: when the front-end requests an additional scope, it must also send up all current scopes.
Failing to do this will cause the returned refresh token to represent only the scopes included in the grant request, while the app will incrementally gain scopes as expected.
I am building a WP7 Twitter client. The normal OAuth 1.0 flow involves obtaining a request token by navigating a web browser to https://api.twitter.com/1/oauth/authenticate with my app's consumer key; this page will show a login prompt and ask the user to authorize my app to perform actions on their behalf. Upon completion, this page will redirect to a callback URL supplied by my app, with the request token supplied as a parameter.
For web apps this makes sense. I don't understand how this is supposed to work for a standalone mobile/desktop app, though. The Twitter API documentation seems to imply that this should be a feasible option. They do offer an alternative xAuth mechanism that allows an app to gather username/password itself and then supply that directly to obtain an access token. The API documentation points out that this is an inferior option (as it requires the user to trust the app, not just Twitter, with their password), but I don't see how I have any reasonable alternative?
(there is also a PIN-based option, but that's a pretty burdensome solution for the user)
I just want to make sure I'm not missing anything obvious.
"For web apps this makes sense. I don't understand how this is
supposed to work for a standalone mobile/desktop app, though."
Just embed a web browser control in your app, and navigate to the twitter authentication page. Then detect the redirection to the callback url (using the Navigating event) and retrieve the parameter. Many twitter apps do that, it's basically the same as asking the user for the login and password, except that instead of your own controls you're displaying twitter's page.
Nope, you're correct. The option for a mobile/desktop application is either a pin-based option or to use xAuth. Once you have an xAuth application has an access token it is indistinguishable from OAuth (it only changes the authorisation workflow). One thing it does change, and this is very specific to Twitter, is that if you do use xAuth then your application will not be allowed to read or write Direct Messages. See Twitter's The Application Permission Model page for more information.