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OAuth2

Build Status License

OAuth2 frameworks for OS X, iOS and tvOS written in Swift 2.2.

Technical documentation is available at p2.github.io/OAuth2. Take a look at the OS X sample app for basic usage of this framework.

The code in this repo requires Xcode 7.3, the built framework can be used on OS X 10.9 or iOS 8 and later. To use on iOS 7 you'll have to include the source files in your main project. Happy to accept pull requests, please see CONTRIBUTING.md

Swift Version

Since the Swift language is constantly evolving I have adopted a versioning scheme mirroring Swift versions: the framework version's first two digits are always the Swift version the library is compatible with, see releases. Code compatible with brand new Swift versions are to be found on a separate feature branch named appropriately.

Usage

To use OAuth2 in your own code, start with import OAuth2 (use p2_OAuth2 if you installed p2.OAuth2 via CocoaPods) in your source files.

For a typical code grant flow you want to perform the following steps. The steps for other flows are mostly the same short of instantiating a different subclass and using different client settings. Most authorize methods take an additional params parameter that allows you to supply custom additional parameters to use during authorization.

1. Create a Settings Dictionary.

let settings = [
    "client_id": "my_swift_app",
    "client_secret": "C7447242-A0CF-47C5-BAC7-B38BA91970A9",
    "authorize_uri": "https://authorize.smarthealthit.org/authorize",
    "token_uri": "https://authorize.smarthealthit.org/token",   // code grant only
    "scope": "profile email",
    "redirect_uris": ["myapp://oauth/callback"],   // register the "myapp" scheme in Info.plist
    "keychain": false,     // if you DON'T want keychain integration
] as OAuth2JSON

2. Instantiate OAuth2

Create an OAuth2CodeGrant Instance. Optionally, set the onAuthorize and onFailure closures or the afterAuthorizeOrFailure closure to keep informed about the status.

let oauth2 = OAuth2CodeGrant(settings: settings)
oauth2.onAuthorize = { parameters in
    print("Did authorize with parameters: \(parameters)")
}
oauth2.onFailure = { error in        // `error` is nil on cancel
    if let error = error {
        print("Authorization went wrong: \(error)")
    }
}

3. Authorize the User

By default the OS browser will be used for authorization if there is no access token present in the keychain. To start authorization call authorize() or, to use embedded authorization, the convenience method authorizeEmbeddedFrom(<# UIViewController or NSWindow #>).

The latter configures authConfig like so:

  • changes authorizeEmbedded to true and
  • sets a root view controller/window, from which to present the login screen, as authorizeContext.

The login screen will only be presented if needed (see Manually Performing Authentication below for details) and will automatically dismiss the login screen on success. See Advanced Settings for other options.

Starting with iOS 9, SFSafariViewController will be used when enabling embedded authorization.

Your oauth2 instance will use an automatically created NSURLSession using an ephemeralSessionConfiguration() configuration for its requests, exposed on oauth2.session. You can set oauth2.sessionConfiguration to your own configuration, for example if you'd like to change timeout values. You can also set oauth2.sessionDelegate to your own session delegate if you like.

oauth2.authConfig.authorizeEmbedded = true
oauth2.authConfig.authorizeContext = <# presenting view controller / window #>
oauth2.authorize()

// for embedded authorization you can just use:
oauth2.authorizeEmbeddedFrom(<# presenting view controller / window #>)

When using the OS browser or the iOS 9 Safari view controller, you will need to intercept the callback in your app delegate. Let the OAuth2 instance handle the full URL:

func application(application: UIApplication,
                 openURL url: NSURL,
           sourceApplication: String?,
                  annotation: AnyObject) -> Bool {
    // you should probably first check if this is your URL being opened
    if <# check #> {
        oauth2.handleRedirectURL(url)
    }
}

See Manually Performing Authentication below for details on how to do this on the Mac.

4. Receive Callback

After everything completes either the onAuthorize or the onFailure closure will be called, and after that the afterAuthorizeOrFailure closure if it has been set. Hence, unless you have a reason to, you don't need to set all three callbacks, you can use any of those.

5. Make Requests

You can now obtain an OAuth2Request, which is an already signed NSMutableURLRequest, to retrieve data from your server. If you use Alamofire there's a class extension below that you can use.

let req = oauth2.request(forURL: <# resource URL #>)
let task = oauth2.session.dataTaskWithRequest(req) { data, response, error in
    if let error = error {
        // something went wrong, check the error
    }
    else {
        // check the response and the data
        // you have just received data with an OAuth2-signed request!
    }
}
task.resume()

Of course you can use your own NSURLSession with these requests, you don't have to use oauth2.session.

6. Cancel Authorization

You can cancel an ongoing authorization any time by calling oauth2.abortAuthorization(). This will cancel ongoing requests (like a code exchange request) or call the callback while you're waiting for a user to login on a webpage. The latter will dismiss embedded login screens or redirect the user back to the app.

7. Re-Authorize

It is safe to always call oauth2.authorize() before performing a request. You can also perform the authorization before the first request after your app became active again. Or you can always intercept 401s in your requests and call authorize again before re-attempting the request.

8. Logout

If you're storing tokens to the keychain, you can call forgetTokens() to throw them away.

However your user is likely still logged in to the website, so on the next authorize() call, the web view may appear and immediately disappear. When using the built-in web view on iOS 8, one can use the following snippet to throw away any cookies the app created. With the newer SFSafariViewController, or logins performed in the browser, it's probably best to directly open the logout page so the user sees the logout happen.

let storage = NSHTTPCookieStorage.sharedHTTPCookieStorage()
storage.cookies?.forEach() { storage.deleteCookie($0) }

Manually Performing Authentication

The authorize() method will:

  1. Check if an access token that has not yet expired is in the keychain, if not
  2. Check if a refresh token is in the keychain, if found
  3. Try to use the refresh token to get a new access token, if it fails
  4. Start the OAuth2 dance by using the authConfig settings to determine how to display an authorize screen to the user

The wiki has the complete call graph of the authorize() method. If you do not wish this kind of automation, the manual steps to show and hide the authorize screens are:

Embedded iOS:

let web = oauth2.authorizeEmbeddedWith(<# presenting view controller #>)
oauth2.authConfig.authorizeEmbeddedAutoDismiss = false
oauth2.afterAuthorizeOrFailure = { wasFailure, error in
    web.dismissViewControllerAnimated(true, completion: nil)
}

Modal Sheet on OS X:

let win = <# window to present from #>
// if `win` is nil, will open a new window
oauth2.authorizeEmbeddedFrom(win)

Present yourself on OS X:

let vc = <# view controller #>
let web = oauth2.presentableAuthorizeViewController()
oauth2.afterAuthorizeOrFailure = { wasFailure, error in
    vc.dismissViewController(web)
}
vc.presentViewController(web, animator: <# animator #>)

iOS/OS X browser:

try! oauth2.openAuthorizeURLInBrowser()

In case you're using the OS browser or the new Safari view controller, you will need to intercept the callback in your app delegate.

iOS

func application(application: UIApplication!,
                 openURL url: NSURL!,
           sourceApplication: String!,
                  annotation: AnyObject!) -> Bool {
    // you should probably first check if this is your URL being opened
    if <# check #> {
        oauth2.handleRedirectURL(url)
    }
}

OS X

See the OAuth2 Sample App's AppDelegate class on how to receive the callback URL in your Mac app. If the authentication displays the code to the user, e.g. with Google's urn:ietf:wg:oauth:2.0:oob callback URL, you can retrieve the code from the user's pasteboard and continue authorization with:

let pboard = NSPasteboard.generalPasteboard()
if let pasted = pboard.stringForType(NSPasteboardTypeString) {
    oauth2.exchangeCodeForToken(pasted)
}

Flows

Based on which OAuth2 flow that you need you will want to use the correct subclass. For a very nice explanation of OAuth's basics: The OAuth Bible.

Code Grant

For a full OAuth 2 code grant flow (response_type=code) you want to use the OAuth2CodeGrant class. This flow is typically used by applications that can guard their secrets, like server-side apps, and not in distributed binaries. In case an application cannot guard its secret, such as a distributed iOS app, you would use the implicit grant or, in some cases, still a code grant but omitting the client secret. It has however become common practice to still use code grants from mobile devices, including a client secret.

This class fully supports those flows, it automatically creates a “Basic” Authorization header if the client has a non-nil client secret. This means that you likely must specify client_secret in your settings; if there is none (like for Reddit) specify the empty string. If the site requires client credentials in the request body, set secretInBody to true, as explained below.

Implicit Grant

An implicit grant (response_type=token) is suitable for apps that are not capable of guarding their secret, such as distributed binaries or client-side web apps. Use the OAuth2ImplicitGrant class to receive a token and perform requests.

Would be nice to add another code example here, but it's pretty much the same as for the code grant.

Client Credentials

A 2-legged flow that lets an app authenticate itself via its client id and secret. Instantiate OAuth2ClientCredentials, as usual supplying client_id but also a client_secret – plus your other configurations – in the settings dict, and you should be good to go.

Username and Password

The Resource Owner Password Credentials Grant is supported with the OAuth2PasswordGrant subclass. Create an instance as shown above, set its username and password properties, then call authorize().

Site-Specific Peculiarities

Some sites might not strictly adhere to the OAuth2 flow. The framework deals with those deviations by creating site-specific subclasses and/or configuration details.

Usage with Alamofire

Here's an extension that can be used with Alamofire:

import Alamofire

extension OAuth2 {
    public func request(
        method: Alamofire.Method,
        _ URLString: URLStringConvertible,
        parameters: [String: AnyObject]? = nil,
        encoding: Alamofire.ParameterEncoding = .URL,
        headers: [String: String]? = nil)
        -> Alamofire.Request
    {
        
        var hdrs = headers ?? [:]
        if let token = accessToken {
            hdrs["Authorization"] = "Bearer \(token)"
        }
        return Alamofire.request(
            method,
            URLString,
            parameters: parameters,
            encoding: encoding,
            headers: hdrs)
    }
}

You can now use the handle to your OAuth2 instance instead of using Alamofire directly to make requests that are signed. Of course this will only work once you have an access token. You can use hasUnexpiredAccessToken() to check for one or just always call authorize() first; it will call your callback immediately if you have a token.

oauth2.request(.GET, "http://httpbin.org/get")

Dynamic Client Registration

There is support for dynamic client registration. If during setup registration_url is set but client_id is not, the authorize() call automatically attempts to register the client before continuing to the actual authorization. Client credentials returned from registration are stored to the keychain.

The OAuth2DynReg class is responsible for handling client registration. You can use its registerClient(client:callback:) method manually if you need to. Registration parameters are taken from the client's configuration.

let oauth2 = OAuth2...()
oauth2.registerClientIfNeeded() { error in
    if let error = error {
        // registration failed
    }
    else {
        // client was registered
    }
}
let oauth2 = OAuth2...()
let dynreg = OAuth2DynReg()
dynreg.registerClient(oauth2) { params, error in
    if let error = error {
        // registration failed
    }
    else {
        // client was registered with `params`
    }
}

Keychain

This framework can transparently use the iOS and OS X keychain. It is controlled by the useKeychain property, which can be disabled during initialization with the "keychain" setting. Since this is enabled by default, if you do not turn it off during initialization, the keychain will be queried for tokens and client credentials related to the authorization URL. If you turn it off after initialization, the keychain will be queried for existing tokens, but new tokens will not be written to the keychain.

If you want to delete the tokens from keychain, i.e. log the user out completely, call forgetTokens(). If you have dynamically registered your client and want to start anew, you can call forgetClient().

Ideally, access tokens get delivered with an "expires_in" parameter that tells you how long the token is valid. If it is missing the framework will still use those tokens if one is found in the keychain and not re-perform the OAuth dance. You will need to intercept 401s and re-authenticate if an access token has expired but the framework has still pulled it from the keychain. This behavior can be turned off by supplying "token_assume_unexpired": false in settings or setting clientConfig.accessTokenAssumeUnexpired to false.

Advanced Settings

The main configuration you'll use with oauth2.authConfig is whether or not to use an embedded login:

oauth2.authConfig.authorizeEmbedded = true

Similarly, if you want to take care of dismissing the login screen yourself:

oauth2.authConfig.authorizeEmbeddedAutoDismiss = false

Some sites also want the client-id/secret combination in the request body, not in the Authorization header:

oauth2.authConfig.secretInBody = true

Starting with version 2.0.1 on iOS 9, SFSafariViewController will be used for embedded authorization. To revert to the old custom OAuth2WebViewController:

oauth2.authConfig.ui.useSafariView = false

To customize the go back button when using OAuth2WebViewController:

oauth2.authConfig.ui.backButton = <# UIBarButtonItem(...) #>

Installation

You can use git, CocoaPods and possibly Carthage to install the framework.

CocoaPods

Add a Podfile that contains at least the following information to the root of your app project, then do pod install. If you're unfamiliar with CocoaPods, read using CocoaPods.

platform :ios, '8.0'      # or platform :osx, '10.9'
pod 'p2.OAuth2'
use_frameworks!

Carthage

Install via Carthage is possibly working with this Cartfile:

github "p2/OAuth2" ~> 2.2

git

Using Terminal.app, clone the OAuth2 repository, best into a subdirectory of your app project:

$ cd path/to/your/app
$ git clone --recursive https://github.com/p2/OAuth2.git

If you're using git you'll want to add it as a submodule. Once cloning completes, open your app project in Xcode and add OAuth2.xcodeproj to your app:

Adding to Xcode

Now link the framework to your app:

Linking

These three steps are needed to:

  1. Make your App also build the framework
  2. Link the framework into your app
  3. Embed the framework in your app when distributing

NOTE that as of Xcode 6.2, the "embed" step happens in the "General" tab. You may want to perform step 2 and 3 from the "General" tab. Also make sure you select the framework for the platform, as of Xcode 7 this is visible behind OAuth2.framework.

License

This code is released under the Apache 2.0 license, which means that you can use it in open as well as closed source projects. Since there is no NOTICE file there is nothing that you have to include in your product.