๐Ÿ”’ Authorization

How to use OAuth2 to request access for your application

All Alby API endpoints are secured by OAuth 2.0. Follow these steps in order to allow a user to authorize your application and obtain a token that you can use to access the API on their behalf.

If you want to programmatically access your own Alby account, create an access token and use it as an Authorization header when making API calls: Authorization: Bearer YOUR_ACCESS_TOKEN

Get OAuth client credentials

Login to your account on getalby.com and create a new API client here:

Set Application URL and Callback URL to http://localhost:YOUR_PORT_NUMBER for local development. You can provide a placeholder image if you don't have one for your app yet.

If you are hosting your application, make sure the domain you enter in the callback URL field exactly matches the domain you are hosting your application.

Endpoints

  • Authorization URI https://getalby.com/oauth

  • Token URI https://api.getalby.com/oauth/token

Redirect your users

Redirect your users to the following URL:

https://getalby.com/oauth?client_id=YOUR_CLIENT_ID&response_type=code&redirect_uri=YOUR_CALLBACK_URL&scope=<scope>

To redirect the user to a specific page or endpoint in your app, instead of passing your domain as the callback URL (e.g. http://localhost:8080), include a path such as http://localhost:8080/auth/callback

Parameters

  • client_id The Client ID of your credentials.

  • client_response_type (code is used for this type of authentication)

  • redirect_uri The URI the user should be redirected to after successful authentication. This usually points to your application.

  • scope See here for available options.

  • state (optional) This parameter will be returned to the callback URI.

The redirect should be done using a native browser with a URL bar, not with an embedded webview, so users are able to verify that they are being redirected to the correct URL.

Scopes

Scopes allow you to request fine-grained access permissions for your application. The following scopes are available:

  • account:readRequest the user's Lightning Address and their keysend information.

  • invoices:create: Create invoices on a user's behalf.

  • invoices:read: Read a user's incoming transaction history.

  • transactions:read: Read a user's outgoing transaction history.

  • balance:read: Read a user's balance.

  • payments:send: Send payments on behalf of a user.

You can also request multiple scopes by space-separating and URL encoding them: ...&scope=account:read%20balance:read

If successful, the user will be redirected and your redirect URI will be loaded with a code parameter:

http://localhost:8080/?code=NWRHNWI3OTITOTFHYS0ZZJNJLTK2YJUTMTVLMZIZOGNIODLK

After users have confirmed your request they will be redirected to the redirect_uri you provided. An additional parameter code will be appended which you will need to exchange for an access token.

Using OAuth Libraries

OAuth 2.0 is a well recognized standard for authentication. Chances are high there is a library available for your application stack that allows you to integrate OAuth 2.0 without much hassle.

OAuth 2.0 for Passport.js

passport.use(new OAuth2Strategy({
    authorizationURL: 'https://getalby.com/oauth',
    tokenURL: 'https://api.getalby.com/oauth/token',
    clientID: process.env.ALBY_CLIENT_ID,
    clientSecret: process.env.ALBY_CLIENT_SECRET,
    callbackURL: process.env.ALBY_CALLBACK_URL,
},
    async function (accessToken, refreshToken, profile, cb) {
        // Create a user, save to DB
        return cb(null, user);
    }));

app.get('/auth/callback',
    passport.authenticate('oauth2', { failureRedirect: '/login' }),
    function (req, res) {
        // User has successfully authenticated, redirect
    });

app.get('/login', 
    passport.authenticate('oauth2', { 
        scope: ['account:read', 'invoices:read'], 
        successReturnToOrRedirect: '/' 
    })
);

PKCE

Clients that would need to store their client_secret in a place that is accessible by end-users, for example pure browser-based or mobile apps should use the PKCE extension flow to protect against interception of the authorization code. To do this, before redirecting your users, create a random string between 43-128 characters long, then generate the url-safe base64-encoded SHA256 hash of the string. The original random string is known as the code_verifier, and the hashed version is known as the code_challenge.

In the redirect URL, add 2 extra fields:

  • code_challenge with the hash and

  • code_challenge_method=S256.

Store the code_verifierin local storage, so that you can access it for the 2nd step, after the callback URL has returned. So the request would be:

https://getalby.com/oauth?client_id=YOUR_CLIENT_ID&code_challenge=<CODE_CHALLENGE>&code_challenge_method=S256&response_type=code&redirect_uri=http://localhost:8080&scope=<scope>

In the 2nd request, you should add code_verifieras an extra field. This helps to protect against the authorization code being intercepted and used by malicious software to acquire an access token.

Javascript example with PKCE

Run this in a browser. You are redirected to localhost, so you need to run a server or you need to re-open the static html file and paste the code callback manually after youโ€™ve been redirected.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Public Client Sample</title>
  </head>
  <body>
    <h1>Public Client Sample</h1>
    <button id="startButton">Start OAuth Flow</button>
    <div id="result"></div>
    <script>
        const authorizeEndpoint = "https://getalby.com/oauth";
        const tokenEndpoint = "https://api.getalby.com/oauth/token";
        const clientId = process.env.ALBY_CLIENT_ID;
        const clientSecret = process.env.ALBY_CLIENT_SECRET;
        const callbackUrl = process.env.ALBY_CALLBACK_URL;
	const scopes = "account:read"

        if (window.location.search) {
            var args = new URLSearchParams(window.location.search);
            var code = args.get("code");

            if (code) {
                var xhr = new XMLHttpRequest();

                xhr.onload = function() {
                    var response = xhr.response;
                    var message;

                    if (xhr.status == 200) {
                        message = "Access Token: " + response.access_token;
                    }
                    else {
                        message = "Error: " + response.error_description + " (" + response.error + ")";
                    }

                    document.getElementById("result").innerHTML = message;
                };
                xhr.responseType = 'json';
                xhr.open("POST", tokenEndpoint, true);
                xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
				xhr.setRequestHeader("Authorization", "Basic " + btoa(clientId + ":" + clientSecret));
                xhr.send(new URLSearchParams({
                    code_verifier: window.sessionStorage.getItem("code_verifier"),
                    grant_type: "authorization_code",
                    redirect_uri: callbackUrl,
                    code: code
                }));
            }
        }

        document.getElementById("startButton").onclick = function() {
            var codeVerifier = generateRandomString(64);

            const challengeMethod = crypto.subtle ? "S256" : "plain"

            Promise.resolve()
                .then(() => {
                    if (challengeMethod === 'S256') {
                        return generateCodeChallenge(codeVerifier)
                    } else {
                        return codeVerifier
                    }
                })
                .then(function(codeChallenge) {
                    window.sessionStorage.setItem("code_verifier", codeVerifier);

                    var redirectUri ="http://localhost:8080/";
                    var args = new URLSearchParams({
                        response_type: "code",
                        client_id: clientId,
						scope: scopes,
                        code_challenge_method: challengeMethod,
                        code_challenge: codeChallenge,
                        redirect_uri: redirectUri
                    });
                window.location = authorizeEndpoint + "/?" + args;
            });
        }

        async function generateCodeChallenge(codeVerifier) {
            var digest = await crypto.subtle.digest("SHA-256",
                new TextEncoder().encode(codeVerifier));

            return btoa(String.fromCharCode(...new Uint8Array(digest)))
                .replace(/=/g, '').replace(/\+/g, '-').replace(/\//g, '_')
        }

        function generateRandomString(length) {
            var text = "";
            var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

            for (var i = 0; i < length; i++) {
                text += possible.charAt(Math.floor(Math.random() * possible.length));
            }

            return text;
        }

        if (!crypto.subtle) {
            document.writeln('<p>' +
                    '<b>WARNING:</b> The script will fall back to using plain code challenge as crypto is not available.</p>' +
                    '<p>Javascript crypto services require that this site is served in a <a href="https://developer.mozilla.org/en-US/docs/Web/Security/Secure_Contexts">secure context</a>; ' +
                    'either from <b>(*.)localhost</b> or via <b>https</b>. </p>' +
                    '<p> You can add an entry to /etc/hosts like "127.0.0.1 public-test-client.localhost" and reload the site from there, enable SSL using something like <a href="https://letsencrypt.org/">letsencypt</a>, or refer to this <a href="https://stackoverflow.com/questions/46468104/how-to-use-subtlecrypto-in-chrome-window-crypto-subtle-is-undefined">stackoverflow article</a> for more alternatives.</p>' +
                    '<p>If Javascript crypto is available this message will disappear.</p>')
        }
    </script>
  </body>
</html>

Requesting an access token

Make a HTTP POST using form-data (Content-Type: application/x-www-form-urlencoded), including the previously obtained code and use the client credentials as basic authentication. In case of a client that cannot use the client secret, use the empty string instead.

It is also possible to send the client credentials in the http form parameters, instead of using basic authentication. Use client_idand client_secret as the field names. Replace redirect_uri with your app callback url.

 curl \
 -u YOUR_CLIENT_ID:YOUR_CLIENT_SECRET \
 -X POST https://api.getalby.com/oauth/token \
 -F 'code=<code>' \
 -F 'grant_type=authorization_code' \
 -F 'redirect_uri=YOUR_CALLBACK_URL'
 -F 'code_verifier=<code_verifier (optional, in case of PKCE)>

The response will be:

 {
 "access_token": "your_access_token",
 "expires_in": 7200,
 "refresh_token": "your_refresh_token",
 "scope": "<scope>",
 "token_type": "Bearer"
 }

You can then use this access_token to make API requests.

The access token should be used as an Authorization header when making subsequent API calls Authorization: Bearer $access_token

Refreshing a token

A refresh token can only be refreshed once (returning a new request token and access token). Make sure to avoid race conditions (e.g. two requests to refresh a token in parallel) as subsequent requests will return an invalid_grant error. The Alby JS SDK handles this automatically for you. If you're having trouble with a custom implementation, don't hesitate to reach out.

Use the refresh token to obtain a new access token / refresh token.

curl \
 -u YOUR_CLIENT_ID:YOUR_CLIENT_SECRET \
 -X POST https://api.getalby.com/oauth/token \
 -F 'refresh_token=<refresh_token>' \
 -F 'grant_type=refresh_token'h

โœ… Successful response

HTTP/1.1 200 OK
Content-Type: application/json

{
  access_token: '...',
  expires_in: 7200,
  refresh_token: '...',
  scope: 'account:read invoices:read',
  token_type: 'Bearer'
}

โŒ Error

Requests using expired or invalid access tokens will result in an error like:

HTTP/1.1 401 Unauthorized
Content-Type: application/json

{
    "error": "expired access token",
    "status": 401
}

Debugging with token introspection

You can use an OAuth token to query information about its client id, its redirect uri and its scopes:

curl https://api.getalby.com/oauth/token/introspect
-H Authorization:<TOKEN>

Response:

{
    "client_id": "F1kfpr0vi4",
    "redirect_uri": "http://localhost:8080",
    "scopes": {
        "invoices:read": "Read your invoice history, get realtime updates on invoices."
    }
}

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