Check in with Apple utilizing Vapor 4

Apple developer portal setup

With the intention to make the Check in with Apple work on your web site you may want a payed developer account. That’ll value you $99 / yr in case you are a person developer. You possibly can evaluate numerous membership choices or simply merely enroll utilizing this hyperlink, however you may want an present Apple ID.

I assume that you just made it up to now and you’ve got a working Apple developer account by now. A typical misbelief about Check in with Apple (SiwA) is that you just want an present iOS utility publised to the App Retailer to make it work, however that is not the case. It really works with no companion app, nevertheless you may want an utility identifier registered within the dev portal.

App identifier

Choose the Identifiers menu merchandise from the record on the left, press the plus (+) button, choose the App IDs choice and press the Proceed button. Fill out the outline discipline and enter a customized bunde indentifier that you just’d like to make use of (e.g. com.mydomain.ios.app). Scroll down the Capabilities record till you discover the Check in With Apple choice, mark the checkbox (the Allow as main App ID ought to seem proper subsequent to an edit button) and press the Proceed button on the highest proper nook. Register the applying identifier utilizing the highest proper button, after you discover all the things all proper.

You must see the newly created AppID within the record, if not there’s a search icon on the proper aspect of the display screen. Choose the AppIDs choice and the applying identifer merchandise ought to seem. 🔍

Service identifier

Subsequent we want a service identifier for SiwA. Press the add button once more and now choose the Companies IDs choice. Enter an outline and fill out the identifier utilizing the identical reverse-domain title model. I desire to make use of my area title with a suffix, that may be one thing like com.instance.siwa.service. Press the Proceed and the Register buttons, we’re virtually prepared with the configuration half.

Filter the record of identifiers by Service IDs and click on on the newly created one. There’s a Configure button, that it’s best to press. Now affiliate the Main App ID to this service identifier by deciding on the applying id that we made beforehand from the choice record. Press the plus button subsequent to the Web site URLs textual content and enter the given area that you just’d like to make use of (e.g. instance.com).

You will even have so as to add at the least one Return URL, which is principally a redirect URL that the service can use after an auth request. You must at all times use HTTPS, however other than this constraint the redirect URL will be something (e.g. https://instance.com/siwa-redirect). #notrailingslash

You possibly can add or take away URLs at any time utilizing this display screen, fortunately there’s a take away choice for each area and redirect URL. Press Subsequent to save lots of the URLs and Completed if you end up prepared with the Check in with Apple service configuration course of.

Keys

The very last thing that we have to create on the dev portal is a personal key for shopper authentication. Choose the Keys menu merchandise on the left and press the add new button. Identify the important thing as you need, choose the Check in with Apple choice from the record. Within the Configure menu choose the Main App ID, it ought to be related with the applying identifier we made earlier. Click on Save to return to the earlier display screen and press Proceed. Evaluate the information and at last press the Register button.

Now that is your solely likelihood to get the registered non-public key, should you pressed the accomplished button with out downloading it, you’ll lose the important thing perpetually, you must make a brand new one, however don’t fret an excessive amount of should you messed it up you’ll be able to click on on the important thing, press the large purple Revoke button to delete it and begin the method once more. This comes helpful if the important thing will get compromised, so do not share it with anyone else in any other case you may must make a brand new one. 🔑

Crew & JWK identifier

I virtually overlook that you’re going to want your group identifier and the JWK identifier for the sign up course of. The JWK id will be discovered beneath the beforehand generated key particulars web page. In the event you click on on the title of the important thing you’ll be able to view the main points. The Key ID is on that web page alongside with the revoke button and the Check in with Apple configuration part the place you will get the group identifier too, for the reason that service bundle identifier is prefixed with that. Alternatively you’ll be able to copy the group id from the very high proper nook of the dev portal, it is proper subsequent to your title.

Implementing Check in With Apple

Earlier than we write a single line of Swift code let me clarify a simplified model of the complete course of.

All the login stream has 3 important parts:

• Provoke an online auth request utilizing the SiwA button (begin the OAuth stream)
• Validate the returned person identification token utilizing Apple’s JWK service
• Trade the person identification token for an entry token

A few of the tutorials overcomplicate this, however you may see how simple is to put in writing the complete stream utilizing Vapor 4. We do not even want further scripts that generate tokens we will do all the things in pure Swift, which is sweet. Lets begin a brand new Vapor challenge. You will want the JWT bundle as properly.

import PackageDescription

let bundle = Bundle(
    title: "binarybirds",
    platforms: [
       .macOS(.v10_15)
    ],
    dependencies: [
        .package(url: "https://github.com/vapor/vapor.git", from: "4.4.0"),
        .package(url: "https://github.com/vapor/leaf.git", from: "4.0.0-rc"),
        .package(url: "https://github.com/vapor/jwt.git", from: "4.0.0-rc"),
    ],
    targets: [
        .target(name: "App", dependencies: [
            .product(name: "Vapor", package: "vapor"),
            .product(name: "Leaf", package: "leaf"),
            .product(name: "JWT", package: "jwt"),
        ]),
        .goal(title: "Run", dependencies: ["App"]),
    ]
)

If you do not know find out how to construct the challenge it’s best to learn my novices information about Vapor 4.

The Check in with Apple button

We’ll use the Leaf template engine to render our views, it is fairly easy to make it work, I will present you the configuration file in a second. We’ll use only one easy template this time. We are able to name it index.leaf and save the file into the Sources/Views listing.

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <meta title="viewport" content material="width=device-width, initial-scale=1">
        <model>
            .signin-button {
                width: 240px;
                top: 40px;
            }
            .signin-button > div > div > svg {
                width: 100%;
                top: 100%;
                colour: purple;
            }
            .signin-button:hover {
                cursor: pointer;
            }
            .signin-button > div {
                define: none;
            }
      </model>
    </head>
    <physique>
        <script kind="textual content/javascript" src="https://appleid.cdn-apple.com/appleauth/static/jsapi/appleid/1/en_US/appleid.auth.js"></script>
        <div id="appleid-signin" data-color="black" data-border="false" data-type="sign up" class="signin-button"></div>
        <script kind="textual content/javascript">
            AppleID.auth.init({
                clientId : '#(clientId)',
                scope : '#(scope)',
                redirectURI: '#(redirectUrl)',
                state : '#(state)',
                usePopup : #(popup),
            });
        </script>
    </physique>
</html>

The Check in with Apple JS framework can be utilized to render the login button on the web site. There’s a comparable factor for iOS referred to as AuthenticationServices, however this time we’re solely going to focus on the net. Sadly the sign up button is kind of buggy so we’ve got so as to add some further CSS hack to repair the underlying points. Come on Apple, why do we’ve got to hack these items? 😅

Beginning the AppleID auth course of is actually easy you simply must configure a couple of parameters. The shopper id is service the bundle identifier that we entered on the developer portal. The scope will be both title or e-mail, however you need to use each if you need. The redirect URI is the redirect URL that we registered on the dev portal, and the state ought to be one thing distinctive that you need to use to establish the request. Apple will ship this state again to you within the response.

Noone talks in regards to the usePopup parameter, so we’ll go away it that approach too… 🤔

Alternatively you need to use meta tags to configure the authorization object, you’ll be able to learn extra about this within the Configuring your webpage for Check in with Apple documentation.

Vapor configuration

It is time to configure our Vapor utility so we will render this Leaf template file and use the signing key that we acquired from Apple utilizing the dev portal. We’re coping with some secret information right here, so it’s best to by no means retailer it within the repository, however you need to use Vapor’s setting for this function. I desire to have an extension for the obtainable setting variables.

extension Atmosphere {
    
    static var siwaId = Atmosphere.get("SIWA_ID")!
    
    static let siwaRedirectUrl = Atmosphere.get("SIWA_REDIRECT_URL")!
    
    static var siwaTeamId = Atmosphere.get("SIWA_TEAM_ID")!
    
    static var siwaJWKId = Atmosphere.get("SIWA_JWK_ID")!
    
    static var siwaKey = Atmosphere.get("SIWA_KEY")!
}

In Vapor 4 you’ll be able to setup a customized JWT signer that may signal the payload with the correct keys and different values primarily based on the configuration. This JWT signer can be utilized to confirm the token within the response. It really works like magic. JWT & JWTKit is an official Vapor bundle, there’s undoubtedly no must implement your individual answer. On this first instance we are going to simply put together the signer for later use and render the index web page so we will initalize the OAuth request utilizing the web site.

import Vapor
import Leaf
import JWT

extension JWKIdentifier {
    static let apple = JWKIdentifier(string: Atmosphere.siwaJWKId)
}

extension String {
    var bytes: [UInt8] {
        return .init(self.utf8)
    }
}

public func configure(_ app: Software) throws {
    
    app.views.use(.leaf)
    

    app.middleware.use(SessionsMiddleware(session: app.classes.driver))

    app.jwt.apple.applicationIdentifier = Atmosphere.siwaId
    
    let signer = strive JWTSigner.es256(key: .non-public(pem: Atmosphere.siwaKey.bytes))
    app.jwt.signers.use(signer, child: .apple, isDefault: false)

    app.get { req -> EventLoopFuture<View> in
        struct ViewContext: Encodable {
            var clientId: String
            var scope: String = "title e-mail"
            var redirectUrl: String
            var state: String
            var popup: Bool = false
        }

        let state = [UInt8].random(rely: 16).base64
        req.session.information["state"] = state
        let context = ViewContext(clientId: Atmosphere.siwaId,
                                  redirectUrl: Atmosphere.siwaRedirectUrl,
                                  state: state)
        return req.view.render("index", context)
    }
}

The session middleware is used to switch a random generated code between the index web page and the redirect handler. Now should you run the app and click on on the Check in with Apple button you may see that the stream begins, however it’ll fail after you recognized your self. That is okay, the 1st step is accomplished. ✅

The redirect handler

Apple will attempt to ship a POST request with an object that incorporates the Apple ID token to the registered redirect URI after you have recognized your self utilizing their login field. We are able to mannequin this response object as an AppleAuthResponse struct within the following approach:

import Basis

struct AppleAuthResponse: Decodable {

    enum CodingKeys: String, CodingKey {
        case code
        case state
        case idToken = "id_token"
        case person
    }

    let code: String
    let state: String
    let idToken: String
    let person: String
}

The authorization code is the primary parameter, the state shuld be equal along with your state worth that you just ship as a parameter whenever you press the login button, if they do not match do not belief the response any person is attempting to hack you. The idToken is the Apple ID token, we’ve got to validate that utilizing the JWKS validation endpoint. The person string is the e-mail tackle of the person.

app.submit("siwa-redirect") { req in
    let state = req.session.information["state"] ?? ""
    let auth = strive req.content material.decode(AppleAuthResponse.self)
    guard !state.isEmpty, state == auth.state else {
        return req.eventLoop.future("Invalid state")
    }

    return req.jwt.apple.confirm(auth.idToken, applicationIdentifier: Atmosphere.siwaId)
    .flatMap { token in
        
    }
}

The code above will deal with the incoming response. First it will attempt to decode the AppleAuthResponse object from the physique, subsequent it will name the Apple verification service utilizing your non-public key and the idToken worth from the response. This validation service returns an AppleIdentityToken object. That is a part of the JWTKit bundle. We have simply accomplished Step 2. ☺️

Exchanging the entry token

The AppleIdentityToken solely lives for a brief time frame so we’ve got to alternate it for an entry token that can be utilized for for much longer. We now have to assemble a request, we’re going to use the next request physique to alternate tokens:

struct AppleTokenRequestBody: Encodable {
    
    enum CodingKeys: String, CodingKey {
        case clientId = "client_id"
        case clientSecret = "client_secret"
        case code
        case grantType = "grant_type"
        case redirectUri = "redirect_uri"
    }
    
    
    let clientId: String

    
    let clientSecret: String

    
    let code: String
    
    
    let redirectUri: String
    
    
    let grantType: String = "authorization_code"
}

We’ll additionally must generate the shopper secret, primarily based on the response we’re going to make a brand new AppleAuthToken object for this that may be signed utilizing the already configured JWT service.

struct AppleAuthToken: JWTPayload {
    let iss: String
    let iat = Int(Date().timeIntervalSince1970)
    let exp: Int
    let aud = "https://appleid.apple.com"
    let sub: String

    init(clientId: String, teamId: String, expirationSeconds: Int = 86400 * 180) {
        sub = clientId
        iss = teamId
        exp = self.iat + expirationSeconds
    }

    func confirm(utilizing signer: JWTSigner) throws {
        guard iss.rely == 10 else {
            throw JWTError.claimVerificationFailure(title: "iss", motive: "TeamId have to be your 10-character Crew ID from the developer portal")
        }

        let lifetime = exp - iat
        guard 0...15777000 ~= lifetime else {
            throw JWTError.claimVerificationFailure(title: "exp", motive: "Expiration have to be between 0 and 15777000")
        }
    }
}

Since we’ve got to make a brand new request we will use the built-in AysncHTTPClient service. I’ve made a little bit extension across the HTTPClient object to simplify the request creation course of.

extension HTTPClient {
    static func appleAuthTokenRequest(_ physique: AppleTokenRequestBody) throws -> HTTPClient.Request {
        var request = strive HTTPClient.Request(url: "https://appleid.apple.com/auth/token", methodology: .POST)
        request.headers.add(title: "Consumer-Agent", worth: "Mozilla/5.0 (Home windows NT 6.2) AppleWebKit/536.6 (KHTML, like Gecko) Chrome/20.0.1090.0 Safari/536.6'")
        request.headers.add(title: "Settle for", worth: "utility/json")
        request.headers.add(title: "Content material-Sort", worth: "utility/x-www-form-urlencoded")
        request.physique = .string(strive URLEncodedFormEncoder().encode(physique))
        return request
    }
}

The humorous factor right here is should you do not add the Consumer-Agent header the SiwA service will return with an error, the issue was talked about in this text additionally mentioned on the Apple Developer Fourms.

Anyway, let me present you the entire redirect handler. 🤓

app.submit("siwa-redirect") { req -> EventLoopFuture<String> in
    let state = req.session.information["state"] ?? ""
    let auth = strive req.content material.decode(AppleAuthResponse.self)
    guard !state.isEmpty, state == auth.state else {
        return req.eventLoop.future("Invalid state")
    }

    return req.jwt.apple.confirm(auth.idToken, applicationIdentifier: Atmosphere.siwaId)
    .flatMap { token -> EventLoopFuture<HTTPClient.Response> in
        do {
            let secret = AppleAuthToken(clientId: Atmosphere.siwaId, teamId: Atmosphere.siwaTeamId)
            let secretJwtToken = strive app.jwt.signers.signal(secret, child: .apple)

            let physique = AppleTokenRequestBody(clientId: Atmosphere.siwaId,
                                             clientSecret: secretJwtToken,
                                             code: auth.code,
                                             redirectUri: Atmosphere.siwaRedirectUrl)

            let request = strive HTTPClient.appleAuthTokenRequest(physique)
            return app.http.shopper.shared.execute(request: request)
        }
        catch {
            return req.eventLoop.future(error: error)
        }
    }
    .map { response -> String in
        guard var physique = response.physique else {
            return "n/a"
        }
        return physique.readString(size: physique.readableBytes) ?? "n/a"
    }
}

As you’ll be able to see I am simply sending the alternate request and map the ultimate response to a string. From this level it’s very easy to implement a decoder, the response is one thing like this:

struct AppleAccessToken: Decodable {

    enum CodingKeys: String, CodingKey {
        case accessToken = "access_token"
        case tokenType = "token_type"
        case expiresIn = "expires_in"
        case refreshToken = "refresh_token"
        case idToken = "id_token"
    }

    let accessToken: String
    let tokenType: String
    let expiresIn: Int
    let refreshToken: String
    let idToken: String
}

You should utilize this response to authenticate your customers, however that is up-to-you primarily based by yourself enterprise logic & necessities. You should utilize the identical authTokenRequest methodology to refresh the token, you simply must set the grant kind to refresh_token as an alternative of authorization_code

I do know that there’s nonetheless room for enhancements, the code is way from excellent, however it’s a working proof of idea. The article is getting actually lengthy, so possibly that is the proper time cease. 😅

If you’re on the lookout for a superb place to be taught extra about SiwA, it’s best to verify this hyperlink.

Conclusion

You possibly can have a working Check in with Apple implementation inside an hour in case you are utilizing Vapor 4. The toughest half right here is that you must determine each single little element by your self, different folks’s supply code. I am attempting to elucidate issues as simple as potential however hey, I am nonetheless placing collectively the items for myself too.

That is a particularly enjoyable journey for me. Transferring again to the server aspect after virtually a decade of iOS growth is a refreshing expertise. I can solely hope you may take pleasure in my upcoming e-book referred to as Sensible Server Facet Swift, as a lot as I take pleasure in studying and writing in regards to the Vapor. ❤️