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https://github.com/p2/OAuth2

OAuth2 framework for macOS and iOS, written in Swift.
https://github.com/p2/OAuth2

ios macos oauth2 oauth2-client oauth2-flow tvos

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OAuth2 framework for macOS and iOS, written in Swift.

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README 

        
OAuth2

======



[![Build Status](https://travis-ci.org/p2/OAuth2.svg?branch=main)](https://travis-ci.org/p2/OAuth2)

[![License](https://img.shields.io/:license-apache-blue.svg)](LICENSE.txt)



OAuth2 frameworks for **macOS**, **iOS** and **tvOS** written in Swift 5.



- [⤵️ Installation](#installation)

- [🛠 Usage](#usage)

- [🖥 Sample macOS app][sample] (with data loader examples)

- [📖 Technical Documentation](https://p2.github.io/OAuth2)



OAuth2 requires Xcode 12.4, the built framework can be used on **OS X 10.15** or **iOS 12** and later.

Happy to accept pull requests, please see [CONTRIBUTING.md](./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](https://github.com/p2/OAuth2/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` in your source files.



In OAuth2 there are [**different kinds of _flows_**](https://tools.ietf.org/html/rfc6749#page-2).

This library supports all of them, make sure you're using the correct one for your use-case and authorization server.

A typical **code grant flow** is used for demo purposes below.

The steps for other flows are mostly the same short of instantiating a different subclass and using different client settings.



Still not working?

See [site-specific peculiarities](#site-specific-peculiarities).



### 1. Instantiate OAuth2 with a Settings Dictionary



In this example you'll be building an iOS client to Github, so the code below will be somewhere in a view controller of yours, _maybe_ the app delegate.



```swift

let oauth2 = OAuth2CodeGrant(settings: [

    "client_id": "my_swift_app",

    "client_secret": "C7447242",

    "authorize_uri": "https://github.com/login/oauth/authorize",

    "token_uri": "https://github.com/login/oauth/access_token",   // code grant only

    "redirect_uris": ["myapp://oauth/callback"],   // register your own "myapp" scheme in Info.plist

    "scope": "user repo:status",

    "secret_in_body": true,    // Github needs this

    "keychain": false,         // if you DON'T want keychain integration

] as OAuth2JSON)

```



See those `redirect_uris`?

You can use the scheme you want, but you must **a)** declare the scheme you use in your `Info.plist` and **b)** register the very same URI on the authorization server you connect to.



Note that **as of iOS 9**, you _should_ use [Universal Links](https://developer.apple.com/library/content/documentation/General/Conceptual/AppSearch/UniversalLinks.html) as your redirect URL, rather than a custom app scheme.

This prevents others from re-using your URI scheme and intercept the authorization flow.  

If you **target iOS 12 and newer** you should be using `ASWebAuthenticationSession`, which makes using your own local redirect scheme secure.



Want to avoid switching to Safari and pop up a SafariViewController or NSPanel?

Set this:



```swift

oauth2.authConfig.authorizeEmbedded = true

oauth2.authConfig.authorizeContext = <# your UIViewController / NSWindow #>

```



Need to specify a separate refresh token URI? You can set the `refresh_uri` in the Settings Dictionary. If specified the library will refresh access tokens using the `refresh_uri` you specified, otherwise it will use the `token_uri`.



Need to debug? Use a `.debug` or even a `.trace` logger:



```swift

oauth2.logger = OAuth2DebugLogger(.trace)

```



For more see [advanced settings](#advanced-settings) below.



### 2. Let the Data Loader or Alamofire Take Over



Starting with version 3.0, there is an `OAuth2DataLoader` class that you can use to retrieve data from an API.

It will automatically start authorization if needed and will ensure that this works even if you have multiple calls going on.

For details on how to configure authorization see step 4 below, in this example we'll use "embedded" authorization, meaning we'll show a SFSafariViewController on iOS if the user needs to log in.



[This wiki page has all you need](https://github.com/p2/OAuth2/wiki/Alamofire-5) to easily use OAuth2 with Alamofire instead.



```swift

let base = URL(string: "https://api.github.com")!

let url = base.appendingPathComponent("user")



var req = oauth2.request(forURL: url)

req.setValue("application/vnd.github.v3+json", forHTTPHeaderField: "Accept")



self.loader = OAuth2DataLoader(oauth2: oauth2)

loader.perform(request: req) { response in

    do {

        let dict = try response.responseJSON()

        DispatchQueue.main.async {

            // you have received `dict` JSON data!

        }

    }

    catch let error {

        DispatchQueue.main.async {

            // an error occurred

        }

    }

}

```



### 3. Make Sure You Intercept the Callback



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



```swift

func application(_ app: UIApplication,

              open url: URL,

               options: [UIApplicationOpenURLOptionsKey: Any] = [:]) -> Bool {

    // you should probably first check if this is the callback being opened

    if <# check #> {

        // if your oauth2 instance lives somewhere else, adapt accordingly

        oauth2.handleRedirectURL(url)

    }

}

```



For iOS 13 make the callback in `SceneDelegate.swift`



```swift

func scene(_ scene: UIScene, openURLContexts URLContexts: Set) {

	if let url = URLContexts.first?.url {

		AppDelegate.shared.oauth2?.handleRedirectURL(url)

	}

}

```



You’re all set!



---



If you want to dig deeper or do authorization yourself, here it goes:



### 4. Manually Authorize the User



By default the OS browser will be used for authorization if there is no access token present or in the keychain.

**Starting with iOS 12**, `ASWebAuthenticationSession` will be used when enabling embedded authorization on iOS (previously, starting with iOS 9, `SFSafariViewController` was used instead).



To start authorization call **`authorize(params:callback:)`** or, to use embedded authorization, the convenience method `authorizeEmbedded(from:callback:)`.



The login screen will only be **presented if needed** (see [_Manually Performing Authorization](#manually-performing-authorization) below for details) and will automatically **dismiss** the login screen on success.

See [_Advanced Settings_](#advanced-settings) for other options.



```swift

oauth2.authorize() { authParameters, error in

    if let params = authParameters {

        print("Authorized! Access token is in `oauth2.accessToken`")

        print("Authorized! Additional parameters: \(params)")

    }

    else {

        print("Authorization was canceled or went wrong: \(error)")   // error will not be nil

    }

}



// for embedded authorization you can simply use:

oauth2.authorizeEmbedded(from: <# presenting view controller / window #>) { ... }



// which is equivalent to:

oauth2.authConfig.authorizeEmbedded = true

oauth2.authConfig.authorizeContext = <# presenting view controller / window #>

oauth2.authorize() { ... }

```



Don't forget, when using the OS browser or the iOS 9+ Safari view controller, you will need to **intercept the callback** in your app delegate.

This is shown under step 2 above.



See [_Manually Performing Authorization_](#manually-performing-authorization) below for details on how to do this on the Mac.



### 5. Receive Callback



After everything completes the callback will be called, **either** with a non-nil _authParameters_ dictionary (which may be empty!), **or** an error.

The access and refresh tokens and its expiration dates will already have been extracted and are available as `oauth2.accessToken` and `oauth2.refreshToken` parameters.

You only need to inspect the _authParameters_ dictionary if you wish to extract additional information.



For advanced use outlined below, there is the `afterAuthorizeOrFail` block that you can use on your OAuth2 instance.

The `internalAfterAuthorizeOrFail` closure is, as its name suggests, provided for internal purposes – it is exposed for subclassing and compilation reasons and you should not mess with it.

As of version 3.0.2, you can no longer use the `onAuthorize` and `onFailure` callback properties, they have been removed entirely.



### 6. Make Requests



You can now obtain an `OAuth2Request`, which is an already signed `MutableURLRequest`, to retrieve data from your server.

This request sets the _Authorization_ header using the access token like so: `Authorization: Bearer {your access token}`.



```swift

let req = oauth2.request(forURL: <# resource URL #>)

// set up your request, e.g. `req.HTTPMethod = "POST"`

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 `URLSession` with these requests, you don't have to use `oauth2.session`; use [OAuth2DataLoader](https://github.com/p2/OAuth2/blob/main/Sources/Base/OAuth2DataLoader.swift), as shown in step 2, or hand it over to _Alamofire_.

[Here's all you need](https://github.com/p2/OAuth2/wiki/Alamofire-4) to easily use OAuth2 with Alamofire.



### 7. 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.



### 8. 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.



### 9. 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.



```swift

let storage = HTTPCookieStorage.shared

storage.cookies?.forEach() { storage.deleteCookie($0) }

```



Manually Performing Authorization

---------------------------------



The `authorize(params:callback:)` method will:



1. Check if an authorize call is already running, if yes it will abort with an `OAuth2Error.alreadyAuthorizing` error

2. Check if an access token that has not yet expired is already present (or in the keychain), if not

3. Check if a refresh token is available, if found

4. Try to use the refresh token to get a new access token, if it fails

5. Start the OAuth2 dance by using the `authConfig` settings to determine how to display an authorize screen to the user



Your `oauth2` instance will use an automatically created `URLSession` 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.



The wiki has [the complete call graph](https://github.com/p2/OAuth2/wiki/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**:



```swift

let url = try oauth2.authorizeURL(params: <# custom parameters or nil #>)

oauth2.authConfig.authorizeEmbeddedAutoDismiss = false

let web = try oauth2.authorizer.authorizeSafariEmbedded(from: <# view controller #>, at: url)

oauth2.afterAuthorizeOrFail = { authParameters, error in

    // inspect error or oauth2.accessToken / authParameters or do something else

    web.dismissViewControllerAnimated(true, completion: nil)

}

```



**Modal Sheet on macOS**:



```swift

let window = <# window to present from #>

let url = try oauth2.authorizeURL(params: <# custom parameters or nil #>)

let sheet = try oauth2.authorizer.authorizeEmbedded(from: window, at: url)

oauth2.afterAuthorizeOrFail = { authParameters, error in

    // inspect error or oauth2.accessToken / authParameters or do something else

    window.endSheet(sheet)

}

```



**New window on macOS**:



```swift

let url = try oauth2.authorizeURL(params: <# custom parameters or nil #>)

let windowController = try oauth2.authorizer.authorizeInNewWindow(at: url)

oauth2.afterAuthorizeOrFail = { authParameters, error in

    // inspect error or oauth2.accessToken / authParameters or do something else

    windowController.window?.close()

}

```



**iOS/macOS browser**:



```swift

let url = try oauth2.authorizeURL(params: <# custom parameters or nil #>)

try oauth2.authorizer.openAuthorizeURLInBrowser(url)

oauth2.afterAuthorizeOrFail = { authParameters, error in

    // inspect error or oauth2.accessToken / authParameters or do something else

}

```



**macOS**



See the [OAuth2 Sample App][sample]'s AppDelegate class on how to receive the callback URL in your Mac app.

If the authorization 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:



```swift

let pboard = NSPasteboard.general()

if let pasted = pboard.string(forType: 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](http://oauthbible.com/#oauth-2-three-legged).



#### 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](https://github.com/reddit/reddit/wiki/OAuth2#token-retrieval-code-flow)) specify the empty string.

If the site requires client credentials in the request body, set `clientConfig.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 authorize 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()`.



### Device Grant



The [OAuth 2.0 Device Authorization Grant](https://datatracker.ietf.org/doc/html/rfc8628) flow is implemented in the `OAuth2DeviceGrant` subclass.

Although this flow is designed for devices that either lack a browser to perform a user-agent-based authorization or are input constrained, it is also very useful for applications not allowed to [start their own webserver (loopback URL) or register a custom URL scheme](https://www.oauth.com/oauth2-servers/redirect-uris/redirect-uris-native-apps/) to finish the authorization code grant flow.

To initiate the device grant flow, the `deviceAuthorizeURL` needs to be correctly configured to point towards the device authorization endpoint. By calling the `OAuth2DeviceGrant.start(useNonTextualTransmission:params:completion:)` method, the client obtains [all necessary details](https://datatracker.ietf.org/doc/html/rfc8628#section-3.2) to complete the authorization on a secondary device or in the system browser.



Site-Specific Peculiarities

---------------------------



Some sites might not strictly adhere to the OAuth2 flow, from returning data differently like Facebook to omitting mandatory return parameters like Instagram & co.

The framework deals with those deviations by creating site-specific subclasses and/or configuration details.

If you need to pass additional **headers** or **parameters**, you can supply these in the settings dict like so:



```swift

let oauth2 = OAuth2CodeGrant(settings: [

    "client_id": "...",

    ...

    "headers": ["Accept": "application/vnd.github.v3+json"],

    "parameters": ["duration": "permanent"],

] as OAuth2JSON)

```



- [GitHub](https://github.com/p2/OAuth2/wiki/GitHub)

- [Facebook](https://github.com/p2/OAuth2/wiki/Facebook)

- [Reddit](https://github.com/p2/OAuth2/wiki/Reddit)

- [Google](https://github.com/p2/OAuth2/wiki/Google)

- [LinkedIn](https://github.com/p2/OAuth2/wiki/LinkedIn)

- [Instagram, Bitly, Pinterest, ...](https://github.com/p2/OAuth2/wiki/Instagram,-Bitly,-Pinterest-and-others)

- [Uber](https://github.com/p2/OAuth2/wiki/Uber)

- [BitBucket](https://github.com/p2/OAuth2/wiki/BitBucket)



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 (not possible with the newer authorization sessions mentioned below):



    oauth2.authConfig.authorizeEmbeddedAutoDismiss = false



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



    oauth2.clientConfig.secretInBody = true

    // or in your settings:

    "secret_in_body": true



Sometimes you also need to provide additional authorization parameters.

This can be done in 3 ways:



    oauth2.authParameters = ["duration": "permanent"]

    // or in your settings:

    "parameters": ["duration": "permanent"]

    // or when you authorize manually:

    oauth2.authorize(params: ["duration": "permanent"]) { ... }



Similar is how you specify custom HTTP headers:



    oauth2.clientConfig.authHeaders = ["Accept": "application/json, text/plain"]

    // or in your settings:

    "headers": ["Accept": "application/json, text/plain"]



Some sites (e.g. Slack) validate the User-Agent string against supported browser versions, which may not match WebKit's default in embedded mode. The embedded mode User-Agent may be overriden with:



    oauth2.customUserAgent = "Version/15.6.1 Safari"

    // or in your settings:

    "custom_user_agent": "Your string of choice"



Starting with version 2.0.1 on iOS 9, `SFSafariViewController` will be used for embedded authorization.

Starting after version 4.2, on iOS 11 (`SFAuthenticationSession`) and iOS 12 (`ASWebAuthenticationSession`), you can opt-in to these newer authorization session view controllers:



    oauth2.authConfig.ui.useAuthenticationSession = true



To revert to the old custom `OAuth2WebViewController`, which you _should not do_ because `ASWebAuthenticationSession` is way more secure:



    oauth2.authConfig.ui.useSafariView = false



To customize the _go back_ button when using `OAuth2WebViewController` on iOS 8 and older:



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



See below for settings about [the keychain](#keychain) and [PKCE](#pkce).



Usage with Alamofire

--------------------



You'll get the best experience when using Alamofire v4 or newer and OAuth2 v3 and newer:



- How to use Alamofire [version 4 and newer](https://github.com/p2/OAuth2/wiki/Alamofire-4)

- How to use [version 3 and older](https://github.com/p2/OAuth2/wiki/Alamofire-3)



Dynamic Client Registration

---------------------------



There is support for [dynamic client registration](https://tools.ietf.org/html/rfc7591).

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 `register(client:callback:)` method manually if you need to.

Registration parameters are taken from the client's configuration.



```swift

let oauth2 = OAuth2...()

oauth2.registerClientIfNeeded() { error in

    if let error = error {

        // registration failed

    }

    else {

        // client was registered

    }

}

```



```swift

let oauth2 = OAuth2...()

let dynreg = OAuth2DynReg()

dynreg.register(client: oauth2) { params, error in

    if let error = error {

        // registration failed

    }

    else {

        // client was registered with `params`

    }

}

```



PKCE

----



PKCE support is controlled by the `useProofKeyForCodeExchange` property, and the `use_pkce` key in the settings dictionary.

It is disabled by default. When enabled, a new code verifier string is generated for every authorization request. 



Keychain

--------



This framework can transparently use the iOS and macOS keychain.

It is controlled by the `useKeychain` property, which can be disabled during initialization with the `keychain` settings dictionary key.

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-authorize 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.



These are the settings dictionary keys you can use for more control:



- `keychain`: a bool on whether to use keychain or not, true by default

- `keychain_access_mode`: a string value for keychain kSecAttrAccessible attribute, "kSecAttrAccessibleWhenUnlocked" by default, you can change this to e.g. "kSecAttrAccessibleAfterFirstUnlock" if you need the tokens to be available when the phone is locked.

- `keychain_access_group`: a string value for keychain kSecAttrAccessGroup attribute, nil by default

- `keychain_account_for_client_credentials`: the name to use to identify client credentials in the keychain, "clientCredentials" by default

- `keychain_account_for_tokens`: the name to use to identify the tokens in the keychain, "currentTokens" by default



Installation

------------



You can use the _Swift Package Manager_, _git_ or _Carthage_.

The preferred way is to use the _Swift Package Manager_.



#### Swift Package Manager



In Xcode 11 and newer, choose "File" from the Xcode Menu, then "Swift Packages" » "Add Package Dependency..." and paste the URL of this repo: `https://github.com/p2/OAuth2.git`. Pick a version and Xcode should do the rest.



#### Carthage



Installation via Carthage is easy enough:



```ruby

github "p2/OAuth2" ~> 4.2

```



#### 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](assets/step-adding.png)



Now link the framework to your app:



![Linking](assets/step-linking.png)



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



License

-------



This code is released under the [_Apache 2.0 license_](LICENSE.txt), 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.



[sample]: https://github.com/p2/OAuth2App