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--- |
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layout: learn |
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permalink: /:collection/:path.html |
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--- |
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# Add Auth to your DApp |
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{:.no_toc} |
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|
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The way you can add Blockstack Auth to your DApp depends on whether your |
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app is a modern decentralized Blockstack App where code runs client-side without |
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trusted servers or a legacy client-server app where a server is trusted. |
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|
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* TOC |
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{:toc} |
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|
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## Authentication in Client-side apps |
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|
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This method is appropriate for decentralized client-side apps where the user's |
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zone of trust — the parts of the app that the user is trusting — begins and ends |
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with the code running on their own computer. In apps like these, any code the |
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app interacts with that's not on their own computer such as external servers |
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does not need to know who they are. |
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|
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[Blockstack.js](https://blockstack.github.io/blockstack.js/) provides API |
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methods that help you to implement Blockstack Authentication in your client-side |
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app. |
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|
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### Default flow |
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|
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The preferred way to implement authentication in these apps is to use the |
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default flow. This flow encapsulates authentication behind a few function |
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calls and makes it very fast to get up and running. |
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|
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The default process use these four functions: |
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|
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- <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#redirecttosignin" target="_blank">UserSession.redirectToSignIn</a> |
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- <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#issigninpending" target="_blank">UserSession.isSignInPending</a> |
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- <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#handlependingsignin" target="_blank">UserSession.handlePendingSignIn</a> |
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- <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#loaduserdata" target="_blank">UserSession.loadUserData</a> |
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|
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When your app wants to start the sign in process, typically when the user clicks |
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a **Sign in with Blockstack** button, your app will call the `UserSession.redirectToSignIn`. |
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This creates an ephemeral transit key, stores it in the web browser's |
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`localStorage`. Then, the function is used to create an authentication request token. The Blockstack Browser |
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redirects the user to the Blockstack Browser to approve the sign in request. |
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|
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|
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When a user approves a sign in request, the Blockstack Browser returns a signed `authResponse` token to the `redirectURI` specified in `UserSession.redirectToSignIn`. |
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|
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To check for the presence of this token, your app should call `UserSession.isSignInPending`. If this returns `true`, the app should then call `UserSession.handlePendingSignIn`. This decodes the token, returns the signed-in-user's data, and simultaneously storing it to `localStorage` so that it can be retrieved later with `loadUserData`. |
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|
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```js |
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import * as blockstack from 'blockstack' |
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|
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var userSession = new UserSession() |
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if (userSession.isSignInPending()) { |
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userSession.handlePendingSignIn() |
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.then(userData => { |
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const profile = userData.profile |
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}) |
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} |
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|
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``` |
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|
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By default, these method use the `store_write` scope which allows the DApp to read the user profile and read/write user data for the DApp. To specify a different scope, use a <a href="https://blockstack.github.io/blockstack.js/classes/appconfig.html" target="\_blank">AppConfig</a> object. |
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|
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### Custom flows |
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|
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Alternatively, you can generate your own transit private key and/or |
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authentication request token using the <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#makeauthrequest" target="_blank">UserSession.makeAuthRequest</a> function. This function gives you more control over the authentication experience. For example, you can change the sign in experience so that it prompts users who have not yet created a Blockstack identity, to choose a hub URL. |
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|
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The `makeAuthRequest()` method takes the following parameters: |
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|
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<dl class="uk-description-list"> |
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<dt class="uk-text-lowercase"> |
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<code>transitPrivateKey(String = generateAndStoreTransitKey())</code> |
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</dt> |
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<dd>A HEX encoded transit private key.</dd> |
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<dt class="uk-text-lowercase"> |
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<code>redirectURI(String = `${window.location.origin}/`)</code> |
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</dt> |
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<dd>Location to redirect the user to after sign in approval.</dd> |
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<dt class="uk-text-lowercase"> |
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<code>manifestURI(String = `${window.location.origin}/manifest.json`)</code> |
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</dt> |
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<dd> |
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Location of this app's manifest file. |
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</dd> |
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<dt class="uk-text-lowercase"> |
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<code>scopes (Array = DEFAULT_SCOPE)</code> |
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</dt> |
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<dd>The permissions this app is requesting.</dd> |
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<dt class="uk-text-lowercase"> |
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<code>appDomain(String = window.location.origin)</code> |
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</dt> |
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<dd>The origin of this app.</dd> |
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<dt class="uk-text-lowercase"> |
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<code>expiresAt(Number = nextHour().getTime())</code> |
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</dt> |
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<dd>The time at which this request is no longer valid.</dd> |
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<dt class="uk-text-lowercase"> |
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<code>extraParams(Object = {})</code> |
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</dt> |
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<dd>Any extra parameters to pass to the authenticator. Use this to pass options that aren't part of the Blockstack authentication specification, but might be supported by special authenticators.</dd> |
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</dl> |
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|
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|
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For example, you could use the following code to generate an authentication |
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request on `https://alice.example.com` or `https://bob.example.com` for an app |
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running on origin `https://example.com`. |
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|
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```js |
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|
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const transitPrivateKey = generateAndStoreTransitKey() |
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const redirectURI = 'https://example.com/authLandingPage' |
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const manifestURI = 'https://example.com/manifest.json' |
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const scopes = ['scope_write', 'publish_data'] |
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const appDomain = 'https://example.com' |
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|
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const authRequest = makeAuthRequest(transitPrivateKey, redirectURI, manifestURI, scopes, appDomain) |
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|
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redirectToSignInWithAuthRequest(authRequest) |
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``` |
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|
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## Authentication in client-server apps |
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|
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{% include note.html content="Client-server authentication requires using a library written in the |
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language of your server app. There are private methods in blockstack.js that can |
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be accomplish this on node.js server apps, but they are not currently part of |
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our public, supported API." %} |
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|
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Using Blockstack Authentication in client-server apps is very similar to |
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client-side apps. You generate the authentication request using the same code in |
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the client as described above. |
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|
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The main difference is that you need to verify the authentication response token |
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on the server after the user approves sign in to your app. |
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|
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For an example of how verification can be done server side, take a look at the |
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[blockstack-ruby](https://github.com/blockstack/blockstack-ruby#to-verify-an-auth-response) |
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library. |
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--- |
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layout: learn |
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permalink: /:collection/:path.html |
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--- |
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|
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# Understand Blockstack Auth |
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|
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{:.no_toc} |
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|
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Blockstack Auth provides single sign on and authentication without third parties or remote servers. On this page, you'll get an overview of authentication from an developer and user perspective. The following topics are covered: |
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|
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* TOC |
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{:toc} |
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|
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## User experience flow |
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|
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Blockstack Auth is a bearer token-based authentication system. From an application user's perspective, Blockstack authentication is similar to legacy third-party authentication techniques that they're familiar with. Applications present users with a **Sign in with Blockstack** button. |
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|
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 |
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|
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Assume a user, Alice, clicks the **Sign in with Blockstack** button on an app. She is |
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redirected to her copy of the Blockstack Browser. The Blockstack sign-in dialog a user sees depends on |
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whether the user already has an existing Blockstack Browser session for their current device. |
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|
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<img src="images/kingdom_notin.png" alt=""> |
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|
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Signing in with an identity is the means by which the user grants the DApp access. Access depends on the scope requested by the DApp. The default `store_write` scope allows the DApp to read the user profile and read/write user data for the DApp. Data is encrypted at a unique URL on a Gaia storage hub. |
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|
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Alice can choose to authenticate and sign into the DApp with one of her Blockstack IDs by selecting the |
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ID. The Blockstack Browser shows Alice an approval dialog with information about the access the DApp requests: |
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|
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* The origin your app was served from |
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* Your app's name |
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* Your app's logo |
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* The types of permissions and data your app is requesting |
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|
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When she chooses an ID (or creates a new one), Alice is redirected back to the DApp where she is logged in. |
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|
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## DApp authentication flow |
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|
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{% include sign_in.md %} |
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|
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## Scopes |
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|
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Scopes define the permissions requested from, and that a user accepts, through the sign-in dialog. |
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DApps may request any of the following scopes: |
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|
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| Scope | Definition| |
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|---|---| |
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| `store_write` | Read and write data to the user's Gaia hub in an app-specific storage bucket. | |
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| `publish_data` | Publish data so that other users of the app can discover and interact with the user. | |
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| `email` | Requests the user's email if available. | |
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|
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The permissions scope should be specified through the <a href="https://blockstack.github.io/blockstack.js/classes/appconfig.html" target="\_blank">AppConfig</a> object. If no `scopes` array is provided to the `redirectToSignIn` or `makeAuthRequest` |
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functions, the default is to request `['store_write']`. |
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|
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## blockstack: custom protocol handler |
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|
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The `blockstack:` custom protocol handler is how Blockstack apps send their authentication requests to the Blockstack Browser. Users can have a Blockstack Browser installed locally on their device or they can use the web version of the Blockstack Browser. If the Blockstack Browser is installed on a user's computer, it registers itself as the handler for the `blockstack:` customer protocol. |
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|
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When an application calls |
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[`redirectToSignIn`](http://blockstack.github.io/blockstack.js/index.html#redirecttosignin) |
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or |
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[`redirectToSignInWithAuthRequest`](http://blockstack.github.io/blockstack.js/index.html#redirecttosigninwithauthrequest), |
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blockstack.js checks if a `blockstack:` protocol handler is installed and, if so, |
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redirects the user to `blockstack:<authRequestToken>`. This passes the |
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authentication request token from the app to the local Blockstack Browser. If the local Blockstack Browser is not installed, the call is directed to the web version of the Blockstack Browser. |
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|
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## Manifest file |
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|
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Blockstack apps have a manifest file. This file is based on the [W3C web app manifest specification](https://w3c.github.io/manifest/). The following is an example manifest file. |
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|
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``` |
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{ |
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"name": "Todo App", |
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"start_url": "http://blockstack-todos.appartisan.com", |
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"description": "A simple todo app build on blockstack", |
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"icons": [{ |
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"src": "http://blockstack-todos.appartisan.com/logo.png", |
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"sizes": "400x400", |
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"type": "image/png" |
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}] |
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} |
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``` |
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|
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The Blockstack Browser retrieves the manifest file from the app during the |
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authentication process and displays the information in it such as the |
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app `name` and to the user during sign in. The location of the app manifest file is specific |
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in the authentication request token and **must** be on the same origin as the app |
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requesting authentication. |
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|
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The manifest file **must** have [Cross-origin resource sharing (CORS) headers](https://en.wikipedia.org/wiki/Cross-origin_resource_sharing) that allow the manifest file to be fetched from any arbitrary source. This usually means returning a header like this: |
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|
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``` |
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Access-Control-Allow-Origin: * |
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``` |
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|
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How you implement CORS depends in part on which platform/service you use to serve your application. For example, Netlify and Firebase have two different ways of configuring CORS. Consult your vendor documentation for more information. |
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|
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## Key pairs |
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|
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Blockstack Auth makes extensive use of public key cryptography. Blockstack uses ECDSA with the `secp256k1` curve. The following sections describe the three public-private key pairs used in the authentication process: |
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|
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* how they're generated |
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* where they're used |
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* to whom the private key is disclosed |
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|
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### Transit private key |
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|
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The transit private is an ephemeral key that is used to encrypt secrets that |
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need to be passed from the Blockstack Browser to the app during the |
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authentication process. It is randomly generated by the app at the beginning of |
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the authentication response. |
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|
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The public key that corresponds to the transit private key is stored in a single |
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element array in the `public_keys` key of the authentication request token. The |
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Blockstack Browser encrypts secret data such as the app private key using this |
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public key and sends it back to the app when the user signs in to the app. The |
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transit private key signs the app authentication request. |
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|
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### Blockstack ID Identity address private key |
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|
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The identity address private key is derived from the user's keychain phrase and |
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is the private key of the Blockstack ID that the user chooses to use to sign in |
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to the app. It is a secret owned by the user and never leaves the user's |
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instance of the Blockstack Browser. |
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|
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This private key signs the authentication response token for an app to indicate that the user approves sign in to that app. |
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|
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### App private key |
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|
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The app private key is an app-specific private key that is generated from the |
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user's identity address private key using the `domain_name` as input. It is |
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deterministic in that for a given Blockstack ID and `domain_name`, the same |
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private key is generated each time. |
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|
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The app private key is securely shared with the app on each authentication, encrypted by the Blockstack Browser with the transit public key. |
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|
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## JSON Web Token signatures |
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|
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Both the `authRequest` and the `authResponse` tokens are [JSON Web Tokens](https://jwt.io/), and they are passed via URL query strings. |
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|
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Blockstack's authentication tokens are based on the [RFC 7519 OAuth JSON Web Token (JWT)](https://tools.ietf.org/html/rfc7519) |
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with additional support for the `secp256k1` curve used by Bitcoin and many other |
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cryptocurrencies. |
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|
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This signature algorithm is indicated by specifying `ES256K` in the token's |
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`alg` key, specifying that the JWT signature uses ECDSA with the secp256k1 |
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curve. Blockstack provide both [JavaScript](https://github.com/blockstack/jsontokens-js) |
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and |
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[Ruby](https://github.com/blockstack/ruby-jwt-blockstack/tree/ruby-jwt-blockstack) |
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JWT libraries with support for this signing algorithm. |
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|
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|
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{% include note.html content="The Blockstack JWT implementation is different from other implementations because of the underlying cryptography we employ. There are libraries in <a href='https://github.com/blockstack/jsontokens-js'>Javascript</a> and <a href='https://github.com/blockstack/ruby-jwt-blockstack'>Ruby</a> available on the Blockstack Github to allow you to work with these tokens." %} |
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|
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### Example: authRequest payload schema |
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|
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``` JavaScript |
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const requestPayload = { |
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jti, // UUID |
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iat, // JWT creation time in seconds |
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exp, // JWT expiration time in seconds |
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iss, // legacy decentralized identifier generated from transit key |
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public_keys, // single entry array with public key of transit key |
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domain_name, // app origin |
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manifest_uri, // url to manifest file - must be hosted on app origin |
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redirect_uri, // url to which browser redirects user on auth approval - must be hosted on app origin |
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version, // version tuple |
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do_not_include_profile, // a boolean flag asking browser to send profile url instead of profile object |
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supports_hub_url, // a boolean flag indicating gaia hub support |
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scopes // an array of string values indicating scopes requested by the app |
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} |
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``` |
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|
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|
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### Example: authResponse payload schema |
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|
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```JavaScript |
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const responsePayload = { |
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jti, // UUID |
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iat, // JWT creation time in seconds |
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exp, // JWT expiration time in seconds |
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iss, // legacy decentralized identifier (string prefix + identity address) - this uniquely identifies the user |
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private_key, // encrypted private key payload |
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public_keys, // single entry array with public key |
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profile, // profile object or null if passed by profile_url |
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username, // blockstack id username (if any) |
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core_token, // encrypted core token payload |
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email, // email if email scope is requested & email available |
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profile_url, // url to signed profile token |
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hubUrl, // url pointing to user's gaia hub |
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version // version tuple |
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} |
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``` |
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|
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@ -0,0 +1,153 @@ |
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--- |
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layout: learn |
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permalink: /:collection/:path.html |
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--- |
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# Work with Profiles |
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|
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{:.no_toc} |
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|
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|
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|
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You can use the blockstack.js library to create and register an ID on the Stacks blockchain. This section describes the `Profile` object and contains the following topics: |
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|
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* TOC |
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{:toc} |
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|
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## About profiels |
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|
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Profile data is stored using Gaia on the user's selected storage provider. An example of a `profile.json` file URL using Blockstack provided storage: |
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|
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``` |
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https://gaia.blockstack.org/hub/1EeZtGNdFrVB2AgLFsZbyBCF7UTZcEWhHk/profile.json |
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``` |
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|
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|
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Follow these steps to create and register a profile for a Blockstack ID: |
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|
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1. Create a JSON profile object |
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2. Split up the profile into tokens, sign the tokens, and put them in a token file |
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3. Create a zone file that points to the web location of the profile token file |
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|
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|
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Accounts can have one or more proofs. Proofs are stored under the `account` key in the user's profile data |
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|
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```js |
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"account": [ |
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{ |
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"@type": "Account", |
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"service": "twitter", |
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"identifier": "naval", |
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"proofType": "http", |
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"proofUrl": "https://twitter.com/naval/status/12345678901234567890" |
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} |
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] |
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``` |
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|
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## Create a profile |
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|
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```es6 |
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const profileOfNaval = { |
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"@context": "http://schema.org/", |
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"@type": "Person", |
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"name": "Naval Ravikant", |
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"description": "Co-founder of AngelList" |
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} |
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``` |
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|
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## Sign a profile as a single token |
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|
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```es6 |
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import { makeECPrivateKey, wrapProfileToken, Person } from 'blockstack' |
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|
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const privateKey = makeECPrivateKey() |
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|
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const person = new Person(profileOfNaval) |
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const token = person.toToken(privateKey) |
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const tokenFile = [wrapProfileToken(token)] |
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``` |
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|
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## Verify an individual token |
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|
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```js |
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import { verifyProfileToken } from 'blockstack' |
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|
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try { |
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const decodedToken = verifyProfileToken(tokenFile[0].token, publicKey) |
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} catch(e) { |
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console.log(e) |
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} |
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``` |
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|
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## Recover a profile from a token file |
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|
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```js |
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const recoveredProfile = Person.fromToken(tokenFile, publicKey) |
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``` |
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|
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## Validate profile schema |
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|
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```js |
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const validationResults = Person.validateSchema(recoveredProfile) |
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``` |
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|
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## Validate a proof |
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|
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```es6 |
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import { validateProofs } from 'blockstack' |
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|
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const domainName = "naval.id" |
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validateProofs(profile, domainName).then((proofs) => { |
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console.log(proofs) |
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}) |
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``` |
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|
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## How proofs are validated |
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|
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The `validateProofs` function checks each of the proofs listed in the |
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profile by fetching the proof URL and verifying the proof message. Currently supported proof validation services: |
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|
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- Facebook |
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- Twitter |
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- Instagram |
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- LinkedIn |
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- Hacker News |
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- GitHub |
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|
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The proof message must be of the form: |
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|
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``` |
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Verifying my Blockstack ID is secured with the address |
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1EeZtGNdFrVB2AgLFsZbyBCF7UTZcEWhHk |
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``` |
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The proof message also must appear in the required location on the |
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proof page specific to each type of social media account. |
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|
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The account from which the proof message is posted must match exactly |
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the account identifier/username claimed in the user profile. The |
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`validateProofs` function will check this in the body of the proof or |
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in the proof URL depending on the service. |
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|
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## Adding additional social account validation services |
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|
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The `Service` class can be extended to provide proof validation service |
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to additional social account types. You will need to override the |
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`getProofStatement(searchText: string)` method which parses the proof |
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body and returns the proof message text. Additionally, the identifier |
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claimed should be verified in the proof URL or in the body by implementing |
|||
`getProofIdentity(searchText: string)` and setting `shouldValidateIdentityInBody()` |
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to return true. |
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|
|||
The following snippet uses the meta tags in the proof page to retrieve the proof message. |
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```js |
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static getProofStatement(searchText: string) { |
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const $ = cheerio.load(searchText) |
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const statement = $('meta[property="og:description"]') |
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.attr('content') |
|||
|
|||
if (statement !== undefined && statement.split(':').length > 1) { |
|||
return statement.split(':')[1].trim().replace('“', '').replace('”', '') |
|||
} else { |
|||
return '' |
|||
} |
|||
} |
|||
``` |
|||
@ -0,0 +1,112 @@ |
|||
--- |
|||
layout: learn |
|||
permalink: /:collection/:path.html |
|||
--- |
|||
# Work with Storage |
|||
|
|||
{:.no_toc} |
|||
|
|||
The Blockstack Platform stores application data in the Gaia Storage System. Transactional metadata is stored on the Blockstack blockchain and user application data is stored in Gaia storage. Storing data off of the blockchain ensures that Blockstack applications can provide users with high performance and high availability for data reads and writes without introducing central trust parties. |
|||
|
|||
* TOC |
|||
{:toc} |
|||
|
|||
|
|||
{% include note.html content="<ul> <li>Blockstack Gaia Storage APIs and on-disk format will change in upcoming pre-releases breaking backward compatibility. File encryption is currently opt-in on a file by file basis.</li> <li>Certain storage features such as collections are not implemented in the current version. These features will be rolled out in future updates.</li> </ul>" %} |
|||
|
|||
|
|||
## Creating a file |
|||
|
|||
You use the <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#putfile" target="_blank">UserSession.putFile</a> |
|||
|
|||
```JavaScript |
|||
let options = { |
|||
encrypt: false |
|||
} |
|||
blockstack.UserSession.putFile("/hello.txt", "hello world!", options) |
|||
.then(() => { |
|||
// /hello.txt exists now, and has the contents "hello world!". |
|||
}) |
|||
``` |
|||
|
|||
## Creating an encrypted file |
|||
|
|||
You use the <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#putfile" target="_blank"></a> |
|||
|
|||
```JavaScript |
|||
let options = { |
|||
encrypt: true |
|||
} |
|||
|
|||
blockstack.UserSession.putFile("/message.txt", "Secret hello!", options) |
|||
.then(() => { |
|||
// message.txt exists now, and has the contents "hello world!". |
|||
}) |
|||
``` |
|||
|
|||
## Reading a file |
|||
|
|||
You use the <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#getfile" target="_blank"></a> |
|||
|
|||
```JavaScript |
|||
let options = { |
|||
decrypt: false |
|||
} |
|||
|
|||
blockstack.UserSession.getFile("/hello.txt", options) |
|||
.then((fileContents) => { |
|||
// get the contents of the file /hello.txt |
|||
assert(fileContents === "hello world!") |
|||
}); |
|||
``` |
|||
|
|||
## Reading an encrypted file |
|||
|
|||
You use the <a href="" target="_blank"></a> |
|||
|
|||
```JavaScript |
|||
let options = { |
|||
decrypt: true |
|||
} |
|||
|
|||
blockstack.UserSession.getFile("/message.txt", options) |
|||
.then((fileContents) => { |
|||
// get & decrypt the contents of the file /message.txt |
|||
assert(fileContents === "Secret hello!") |
|||
}); |
|||
``` |
|||
|
|||
## Reading another user's unencrypted file |
|||
In order for files to be publicly readable, the app must request |
|||
the `publish_data` scope during authentication. |
|||
|
|||
```JavaScript |
|||
let options = { |
|||
user: 'ryan.id', // the Blockstack ID of the user for which to lookup the file |
|||
app: 'http://BlockstackApp.com' // origin of the app this file is stored for |
|||
} |
|||
|
|||
var userSession = new UserSession() |
|||
userSession.putFile("/hello.txt", "hello world!", options) |
|||
.then((fileContents) => { |
|||
// get the contents of the file /message.txt |
|||
assert(fileContents === "hello world!") |
|||
}); |
|||
``` |
|||
|
|||
## Delete a file |
|||
|
|||
You use the <a href="https://blockstack.github.io/blockstack.js/classes/usersession.html#deletefile" target="_blank">UserSession.deleteFile</a> from the application's data store. |
|||
|
|||
|
|||
```JavaScript |
|||
blockstack.deleteFile("/hello.txt") |
|||
.then(() => { |
|||
// /hello.txt is now removed. |
|||
}) |
|||
``` |
|||
|
|||
## Related Information |
|||
{:.no_toc} |
|||
|
|||
To learn more about the guarantees provided by Gaia, see [Storage write and read]({{ site.baseurl }}/storage/write-to-read.html#) |
|||
@ -0,0 +1,19 @@ |
|||
For an application developer, the application flow is similar to the typical client-server flow used by centralized sign in services (e.g., OAuth). However, with Blockstack, the authentication flow happens entirely client-side. |
|||
|
|||
A decentralized application (DApp) and the Blockstack Browser communicate during the authentication flow by passing back and forth two tokens. The requesting application sends the Blockstack Browser an `authRequest` token. Once a user approves a sign-in, the Blockstack Browser responds to the application with an `authResponse` token. These tokens are <a href="https://jwt.io/" target="\_blank">JSON Web Tokens</a>, and they are passed via URL query strings. |
|||
|
|||
 |
|||
|
|||
When a user chooses to **Sign in with Blockstack** on a DApp, it calls the `redirectToSignIn()` method which sends an `authRequest` to the Blockstack Browser. Blockstack passes the token in via a URL query string in the `authRequest` parameter: |
|||
|
|||
`https://browser.blockstack.org/auth?authRequest=j902120cn829n1jnvoa...` |
|||
|
|||
When the Blockstack Browser receives the request, it generates an (`authResponse`) token to the application using an _ephemeral transit key_ . The ephemeral transit key is just used for the particular instance of the application, in this case, to sign the `authRequest`. The application stores the ephemeral transit key during the request generation. The public portion of the transit key is passed in the `authRequest` token. The Blockstack Browser uses the public portion of the key to encrypt an _app-private key_ which is returned via the `authResponse`. |
|||
|
|||
During sign in, the Blockstack Browser generates the app-private key from the user's _identity-address private_ key and the application's `appDomain`. The app private key serves three functions: |
|||
|
|||
* It is used to create the credentials that give an app access to the Gaia storage bucket for that specific app. |
|||
* It is used in the end-to-end encryption of files stored for the app in the user's Gaia storage. |
|||
* It serves as a cryptographic secret that apps can use to perform other cryptographic functions. |
|||
|
|||
Finally, the app private key is deterministic, meaning that for a given user ID and domain name, the same private key is generated each time. |
|||
@ -0,0 +1,332 @@ |
|||
--- |
|||
layout: learn |
|||
permalink: /:collection/:path.html |
|||
--- |
|||
# Understand Blockstack authentication |
|||
{:.no_toc} |
|||
|
|||
Blockstack Auth provides single sign on and authentication without third parties or remote servers. On this page, you'll get an overview of authentication from an developer and user perspective. |
|||
|
|||
## User experience flow |
|||
|
|||
Blockstack Auth is a bearer token-based authentication system. From an application user's perspective, Blockstack authentication is similar to legacy third-party authentication techniques that they're familiar with. Applications present users with a **Sign in with Blockstack** button. |
|||
|
|||
 |
|||
|
|||
Assume a user, Alice, clicks the **Sign in with Blockstack** button on an app. She is |
|||
redirected to her copy of the Blockstack Browser. If the user has |
|||
signed into the DApp previously. The actual Blockstack sign-in dialog depends on |
|||
whether the user already has an existing session in the Blockstack Browser. |
|||
|
|||
<img src="images/kingdom_notin.png" alt=""> |
|||
|
|||
Alice can choose to authenticate as one of her Blockstack IDs by selecting the |
|||
ID and clicking the **Approve** button. The Blockstack Browser shows Alice an approval dialog with information about your app including: |
|||
|
|||
* The origin your app was served from |
|||
* Your app's name |
|||
* Your app's logo |
|||
* The types of permissions and data your app is requesting |
|||
|
|||
Signing in with an identity is the means by which the user grants the DApp access. Access depends on the scope requested by the DApp. The default `store_write` scope allows the DApp to read the user profile and read/write user data for the DApp. Data is encrypted at a unique URL on a Gaia storage hub. |
|||
|
|||
When she clicks approve, Alice is redirected back to the DApp where she is logged in. |
|||
|
|||
## Application-authentication workflow |
|||
|
|||
For an application developer, the application flow is different from the typical client-server flow used by centralized sign in services (e.g., OAuth). Rather, with Blockstack, the authentication flow happens entirely client-side. |
|||
|
|||
A decentralized application (DApp) and the Blockstack Browser communicate during the authentication flow by passing back and forth two tokens. The requesting application sends the Blockstack Browser an `authRequest` token. Once a user approves a sign-in, the Blockstack Browser responds to the application with an `authResponse` token. These tokens are <a href="https://jwt.io/" target="\_blank">JSON Web Tokens</a>, and they are passed via URL query strings. |
|||
|
|||
 |
|||
|
|||
When a user chooses to **Sign in with Blockstack** on a DApp, calls the `redirectToSignIn()` method which sends the user to the Blockstack Browser. When Blockstack Browser is provided an ID, it generates an The browser responds with an authentication token and an _app private key_. |
|||
|
|||
The app private key is application-specific. It is generated from the user's identity address private key using the `appDomain` as input. The key is ephemeral, it is generated for each execution of a key establishment process. This key is just used for the particular instance of the application, in this case to sign a sign-in request. |
|||
|
|||
This app private key is also deterministic, meaning that for a given Blockstack ID and domain name, the same private key is generated each time. The app private key is securely shared with the app on each authentication and encrypted by the Blockstack Browser. The key serves three functions, it: |
|||
|
|||
* is used to create the credentials that give an app access to the Gaia hub storage bucket for that specific app |
|||
* is used in the end-to-end encryption of files stored for the app on the user's Gaia hub |
|||
* serves as a cryptographic secret that apps can use to perform other cryptographic functions |
|||
|
|||
A Blockstack Core node also generates a public key token which is sent to the |
|||
browser as an `authRequest` from the browser to the core node. The signed |
|||
authentication request is sent to Blockstack through a JSON Web Token (JWT). |
|||
Blocktack passes the token in via a URL query string in the `authRequest` |
|||
parameter: |
|||
|
|||
`https://browser.blockstack.org/auth?authRequest=j902120cn829n1jnvoa...` |
|||
|
|||
When the Blockstack node receives the `authRequest`, it generates a session token |
|||
and returns an authentication response (`authResponse`) to the application. Similar to the `authRequest`, the `authResponse` token includes a private key |
|||
intended only for the application. This allows the application to encrypt data |
|||
on user's personal Blockstack storage. |
|||
|
|||
{% include note.html content="The Blockstack JWT implementation is different from other implementations because of the underlying cryptography we employ. There are libraries in <a href='https://github.com/blockstack/jsontokens-js'>Javascript</a> and <a href='https://github.com/blockstack/ruby-jwt-blockstack'>Ruby</a> available on the Blockstack Github to allow you to work with these tokens." %} |
|||
|
|||
|
|||
## Manifest file |
|||
|
|||
Blockstack apps have a manifest file. This file is based on the [W3C web app manifest specification](https://w3c.github.io/manifest/). The following is an example manifest file. |
|||
|
|||
``` |
|||
{ |
|||
"name": "Todo App", |
|||
"start_url": "http://blockstack-todos.appartisan.com", |
|||
"description": "A simple todo app build on blockstack", |
|||
"icons": [{ |
|||
"src": "http://blockstack-todos.appartisan.com/logo.png", |
|||
"sizes": "400x400", |
|||
"type": "image/png" |
|||
}] |
|||
} |
|||
``` |
|||
|
|||
The Blockstack Browser retrieves the manifest file from the app during the |
|||
authentication process and displays some of the information in it such as the |
|||
app name and icon to the user. The location of the app manifest file is specific |
|||
in the authentication request token and **must** be on the same origin as the app |
|||
requesting authentication. |
|||
|
|||
The manifest file **must** have [Cross-origin resource sharing (CORS) headers](https://en.wikipedia.org/wiki/Cross-origin_resource_sharing) that allow the manifest file to be fetched from any arbitrary source. This usually means returning a header like this: |
|||
|
|||
``` |
|||
Access-Control-Allow-Origin: * |
|||
``` |
|||
|
|||
How you implement cors depends in part on which platform/service you use to serve your application. For example, Netlify and Firebase have two different ways of configuring CORS. Consult your vendor documentation for more information. |
|||
|
|||
## Key pairs |
|||
|
|||
Blockstack Auth makes extensive use of public key cryptography. Blockstack uses ECDSA with the `secp256k1` curve. The following sections describe the various public-private key pairs used in the authentication process including: |
|||
|
|||
* how they're generated, |
|||
* where they're used |
|||
* to whom the private key is disclosed. |
|||
|
|||
{% include note.html content="The Blockstack JWT implementation is different from other implementations because of the underlying cryptography we employ. There are libraries in <a href='https://github.com/blockstack/jsontokens-js'>Javascript</a> and <a href='https://github.com/blockstack/ruby-jwt-blockstack'>Ruby</a> available on the Blockstack Github to allow you to work with these tokens." %} |
|||
|
|||
### Transit private key |
|||
|
|||
The transit private is an ephemeral key that is used to encrypt secrets that |
|||
need to be passed from the Blockstack Browser to the app during the |
|||
authentication process. It is randomly generated by the app at the beginning of |
|||
the authentication response. |
|||
|
|||
The public key that corresponds to the transit private key is stored in a single |
|||
element array in the `public_keys` key of the authentication request token. The |
|||
Blockstack Browser encrypts secret data such as the app private key using this |
|||
public key and sends it back to the app when the user signs in to the app. The |
|||
transit private key signs the app authentication request. |
|||
|
|||
### Blockstack ID Identity address private key |
|||
|
|||
The identity address private key is derived from the user's keychain phrase and |
|||
is the private key of the Blockstack ID that the user chooses to use to sign in |
|||
to the app. It is a secret owned by the user and never leaves the user's |
|||
instance of the Blockstack Browser. This private key signs the authentication |
|||
response token for an app to indicate that the user approves sign in to that |
|||
app. |
|||
|
|||
### App private key |
|||
|
|||
The app private key is an app-specific private key that is generated from the |
|||
user's identity address private key using the `domain_name` as input. It is |
|||
deterministic in that for a given Blockstack ID and `domain_name`, the same |
|||
private key will be generated each time. The app private key is securely shared |
|||
with the app on each authentication, encrypted by the Blockstack Browser with |
|||
the transit public key. |
|||
|
|||
## Scopes |
|||
|
|||
Scopes define the information and permissions an app requests from the |
|||
user during authentication. Requested scopes may be any of the following: |
|||
|
|||
| Scope | Definition| |
|||
|---|---| |
|||
| `store_write` | Read and write data to the user's Gaia hub in an app-specific storage bucket. | |
|||
| `publish_data` | Publish data so that other users of the app can discover and interact with the user. | |
|||
| `email` | Requests the user's email if available. | |
|||
|
|||
If no `scopes` array is provided to the `redirectToSignIn` or `makeAuthRequest` |
|||
functions, the default is to request `['store_write']`. |
|||
|
|||
## Authentication tokens |
|||
|
|||
The app and the Blockstack Browser communicate during the authentication flow by |
|||
passing back and forth two tokens, the `authRequest` and the `authResponse` |
|||
token. The requesting application sends the Blockstack Browser an `authRequest` |
|||
token. Once a user approves a sign in, the Blockstack Browser responds to the |
|||
application with an `authResponse` token. |
|||
|
|||
These tokens are [JSON Web Tokens](https://jwt.io/), and they are passed via URL |
|||
query strings. |
|||
|
|||
### JSON Web Token signatures |
|||
|
|||
Blockstack's authentication tokens are based on the [RFC 7519 OAuth JSON Web Token (JWT)](https://tools.ietf.org/html/rfc7519) |
|||
with additional support for the `secp256k1` curve used by Bitcoin and many other |
|||
cryptocurrencies. |
|||
|
|||
This signature algorithm is indicated by specifying `ES256K` in the token's |
|||
`alg` key, specifying that the JWT signature uses ECDSA with the secp256k1 |
|||
curve. We provide both [JavaScript](https://github.com/blockstack/jsontokens-js) |
|||
and |
|||
[Ruby](https://github.com/blockstack/ruby-jwt-blockstack/tree/ruby-jwt-blockstack) |
|||
JWT libraries with support for this signing algorithm. |
|||
|
|||
### Authentication request payload schema |
|||
|
|||
``` JavaScript |
|||
const requestPayload = { |
|||
jti, // UUID |
|||
iat, // JWT creation time in seconds |
|||
exp, // JWT expiration time in seconds |
|||
iss, // legacy decentralized identifier generated from transit key |
|||
public_keys, // single entry array with public key of transit key |
|||
domain_name, // app origin |
|||
manifest_uri, // url to manifest file - must be hosted on app origin |
|||
redirect_uri, // url to which browser redirects user on auth approval - must be hosted on app origin |
|||
version, // version tuple |
|||
do_not_include_profile, // a boolean flag asking browser to send profile url instead of profile object |
|||
supports_hub_url, // a boolean flag indicating gaia hub support |
|||
scopes // an array of string values indicating scopes requested by the app |
|||
} |
|||
``` |
|||
|
|||
|
|||
### Authentication response payload schema |
|||
|
|||
```JavaScript |
|||
const responsePayload = { |
|||
jti, // UUID |
|||
iat, // JWT creation time in seconds |
|||
exp, // JWT expiration time in seconds |
|||
iss, // legacy decentralized identifier (string prefix + identity address) - this uniquely identifies the user |
|||
private_key, // encrypted private key payload |
|||
public_keys, // single entry array with public key |
|||
profile, // profile object or null if passed by profile_url |
|||
username, // blockstack id username (if any) |
|||
core_token, // encrypted core token payload |
|||
email, // email if email scope is requested & email available |
|||
profile_url, // url to signed profile token |
|||
hubUrl, // url pointing to user's gaia hub |
|||
version // version tuple |
|||
} |
|||
``` |
|||
|
|||
## `blockstack:` custom protocol handler |
|||
|
|||
The `blockstack:` custom protocol handler is how Blockstack apps send their |
|||
authentication requests to the Blockstack Browser. When the Blockstack Browser |
|||
is installed on a user's computer, it registers itself as the handler for the |
|||
`blockstack:` customer protocol. |
|||
|
|||
When an application calls |
|||
[`redirectToSignIn`](http://blockstack.github.io/blockstack.js/index.html#redirecttosignin) |
|||
or |
|||
[`redirectToSignInWithAuthRequest`](http://blockstack.github.io/blockstack.js/index.html#redirecttosigninwithauthrequest), |
|||
blockstack.js checks if a `blockstack:` protocol handler is installed and, if so, |
|||
redirects the user to `blockstack:<authRequestToken>`. This passes the |
|||
authentication request token from the app to the Blockstack Browser, which will |
|||
in turn validate the request and display an authentication dialog. |
|||
|
|||
|
|||
## Adding Blockstack Authentication to your app |
|||
|
|||
The way you can add Blockstack Authentication to you app depends on whether your |
|||
app is a modern decentralized Blockstack App where code runs client-side without |
|||
trusted servers or a legacy client-server app where a server is trusted. |
|||
|
|||
### Authentication in Client-side apps |
|||
|
|||
This method is appropriate for decentralized client-side apps where the user's |
|||
zone of trust - the parts of the app that the user is trusting - begins and ends |
|||
with the code running on their own computer. In apps like these, any code the |
|||
app interacts with that's not on their own computer such as external servers |
|||
does not need to know who she is. |
|||
|
|||
[Blockstack.js](https://github.com/blockstack/blockstack.js) provides API |
|||
methods that help you to implement Blockstack Authentication in your client-side |
|||
app. |
|||
|
|||
#### Standard flow |
|||
The preferred way to implement authentication in these apps is to use the |
|||
standard flow. This flow hides much of the process behind a few easy function |
|||
calls and makes it very fast to get up and running. |
|||
|
|||
In this process you'll use these four functions: |
|||
|
|||
- [[redirectToSignIn]] |
|||
- [[isSignInPending]] |
|||
- [[handlePendingSignIn]] |
|||
- [[loadUserData]] |
|||
|
|||
##### Starting the sign in process |
|||
|
|||
When your app wants to start the sign in process, typically when the user clicks |
|||
a "Sign in with Blockstack" button, your app will call the [[redirectToSignIn]] |
|||
method of [blockstack.js](https://github.com/blockstack/blockstack.js). |
|||
|
|||
This creates an ephemeral transit key, stores it in the web browser's |
|||
`localStorage`, uses it to create an authentication request token and finally |
|||
redirects the user to the Blockstack Browser to approve the sign in request. |
|||
|
|||
##### Handling an authentication response |
|||
|
|||
When a user approves a sign in request, the Blockstack Browser will return the signed authentication response token to the `redirectURI` specified in `redirectToSignIn`. |
|||
|
|||
To check for the presence of this token, your app should call `isSignInPending`. If this returns `true`, the app should then call `handlePendingSignIn`. This decodes the token, returns the signed-in-user's data, and simultaneously storing it to `localStorage` so that it can be retrieved later with `loadUserData`. |
|||
|
|||
```js |
|||
import * as blockstack from 'blockstack' |
|||
|
|||
if (blockstack.UserSession.isSignInPending()) { |
|||
blockstack.UserSession.handlePendingSignIn() |
|||
.then(userData => { |
|||
const profile = userData.profile |
|||
}) |
|||
} |
|||
|
|||
``` |
|||
|
|||
#### Manual flow |
|||
|
|||
Alternatively, you can manually generate your own transit private key and/or |
|||
authentication request token. This gives you more control over the experience. |
|||
|
|||
For example, you could use the following code to generate an authentication |
|||
request on `https://alice.example.com` or `https://bob.example.com` for an app |
|||
running on origin `https://example.com`. |
|||
|
|||
```js |
|||
|
|||
const transitPrivateKey = generateAndStoreTransitKey() |
|||
const redirectURI = 'https://example.com/authLandingPage' |
|||
const manifestURI = 'https://example.com/manifest.json' |
|||
const scopes = ['scope_write', 'publish_data'] |
|||
const appDomain = 'https://example.com' |
|||
|
|||
const authRequest = makeAuthRequest(transitPrivateKey, redirectURI, manifestURI, scopes, appDomain) |
|||
|
|||
redirectToSignInWithAuthRequest(authRequest) |
|||
``` |
|||
|
|||
### Authentication in client-server apps |
|||
|
|||
*Note: Client-server authentication requires using a library written in the |
|||
language of your server app. There are private methods in blockstack.js that can |
|||
be accomplish this on node.js server apps, but they are not currently part of |
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our public, supported API.* |
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|
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Using Blockstack Authentication in client-server apps is very similar to |
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client-side apps. You generate the authentication request using the same code in |
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the client as described above. |
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|
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The main difference is that you need to verify the authentication response token |
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on the server after the user approves sign in to your app. |
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|
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For an example of how verification can be done server side, take a look at the |
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[blockstack-ruby](https://github.com/blockstack/blockstack-ruby#to-verify-an-auth-response) |
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library. |
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Reference in new issue