OAuth for Java Developers Matt Raible | @mraible March 30, 2023 Photo by František Zelinka https://unsplash.com/photos/NYpiSHcGfbw

Father, Husband, Skier, Mountain Biker, Whitewater Rafter Bus Lover Web Developer and Java Champion Okta Developer Advocate Blogger on raibledesigns.com and developer.okta.com/blog Hi, I’m Matt Raible

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01 02 03 04 What the Heck is OAuth? Java's OAuth 2.0 Support OAuth 2.0 in Action Java Security Frameworks 05 OAuth 2.0 Authorization Servers Agenda

What the Heck is OAuth?

Web Authentication GET /index.html HTTP/1.1 Host: www.example.com Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==

Federated Identity Identity Provider (IdP) Service Provider (SP) End User Trust Obtains Assertion Provides Assertion

SAML 2.0 Authentication Request Protocol Assertion

SAML 2.0 Authentication Request Protocol

SAML 2.0 Assertion https://example.okta.com ... [email protected] https://sp.example.com/saml2/sso urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport Matt Raible

SAML = Web SSO

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What’s Changed Since 2005?

An open standard for authorization; anyone can implement it Provides “secure delegated access” to client applications Works over HTTPS and authorizes: Devices APIs Servers Applications … with access tokens rather than credentials What is OAuth?

Confusion

Simple login — basic, forms, & cookies Single sign-on across sites — SAML Mobile app login — N/A Delegated authorization — N/A Identity Use Cases (circa 2006)

The Delegated Authorization Problem How can you let a website access your data (without giving it your password)?

Don’t do it this way!

Have you ever seen one of these?

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Hotel Key Cards, but for Apps

Hotel Key Cards, but for Apps OAuth Authorization Server Resource (API) Access Token

Delegated Authorization with OAuth 2.0 I trust Gmail and I kind of trust Yelp. I want Yelp to have access to my contacts only. yelp.com Connect with Google

Delegated Authorization with OAuth 2.0 yelp.com Connect with Google accounts.google.com Email ********** accounts.google.com 
 Allow Yelp to access your public profile and contacts? No Yes contacts.google yelp.com/callback

Actors Clients Authorization Server Resource Server Access Tokens Redirect URIs OAuth 2.0 Terminology

Authorization
 Server (AS) Resource Owner (RO) Client Delegates Obtains Token Uses Token Resource
 Server (RS) Actors

Authorization
 Server (AS) Resource Owner (RO) Client Delegates Obtains Token Uses Token Resource
 Server (RS) Actors

Clients Public (Client Identification) Confidential
 (Client Authentication)

Clients 
 Client Registration is the DMV of OAuth

Authorization Server Authorize Endpoint (/oauth2/authorize) Token Endpoint (/oauth2/token) Authorization Server Authorization Grant Refresh Token Access Token Introspection Endpoint (/oauth2/introspect) Revocation Endpoint (/oauth2/revoke)

Tokens • Short-lived token used by Client to access Resource Server (API) • Opaque to the Client • No client authentication required (Public Clients) • Optimized for scale and performance • Revocation is dependent on implementation Access Token (Required) • Long-lived token that is used by Client to obtain new access tokens from Authorization Server • Usually requires Confidential Clients with authentication • Forces client to rotate secrets • Can usually be revoked Refresh Token (Optional) OAuth doesn’t define the format of a token!

Self-encoded tokens Protected, time-limited data structure agreed upon between Authorization Server and Resource Server that contains metadata and claims about the identity of the user or client over the wire. Resource Server can validate the token locally by checking the signature, expected issuer name and expected audience or scope. Commonly implemented as a signed JSON Web Tokens (JWT) Reference tokens (aka opaque tokens) Infeasible-to-guess (secure-random) identifier for a token issued and stored by the OAuth 2.0 Authorization Server Resource Server must send the identifier via back-channel to the OAuth 2.0 Authorization Server’s token introspection endpoint to determine if the token is valid and obtain claims/scopes Access Token Types

OAuth 2.0 Authorization Code Flow yelp.com Connect with Google accounts.google.com 
 Allow Yelp to access your public profile and contacts? No Yes yelp.com/callback Resource owner clicks ^^ Back to redirect URI with authorization code contacts.google Talk to resource server with access token Exchange code for access token accounts.google.com Email ********** Go to authorization server Redirect URI: yelp.com/callback Response type: code Authorization Server Client

Scopes Consent Grants More OAuth 2.0 Terminology

Scopes Scopes to Deny Scopes to Allow Additive bundles of permissions asked by client when requesting a token 
 Decouples authorization policy decisions from enforcement
 Who owns the data? End user or the target service
 Who gets to specify the authorization policy? End user or application owner

OAuth 2.0 Authorization Code Flow yelp.com Connect with Google yelp.com/callback Resource owner clicks ^^ Back to redirect URI with authorization code contacts.google Talk to resource server with access token Exchange code for access token accounts.google.com Email ********** Go to authorization server Redirect URI: yelp.com/callback Scope: profile contacts Authorization Server Client accounts.google.com 
 Allow Yelp to access your public profile and contacts? No Yes Request consent from resource owner

Flow Channels Resource
 Server (RS) Authorization
 Server (AS) Resource Owner (RO) Client Delegates Obtains Token Uses Token Front Channel Back Channel

Authorization Request HTTP/1.1 302 Found
 Location: https://app.example.com/oauth2/callback?
 code=MsCeLvIaQm6bTrgtp7&
 state=af0ifjsldkj Request Response Note: Parameters are not URL-encoded for example purposes GET https://accounts.google.com/o/oauth2/auth?
 scope=gmail.insert gmail.send&
 redirect_uri=https://app.example.com/oauth2/callback&
 response_type=code&
 client_id=812741506391&
 state=af0ifjsldkj

Token Request Note: Parameters are not URL-encoded for example purposes POST /oauth2/v3/token HTTP/1.1 Host: www.googleapis.com Content-Type: application/x-www-form-urlencoded code=MsCeLvIaQm6bTrgtp7& client_id=812741506391& client_secret={client_secret}& redirect_uri=https://app.example.com/oauth2/callback& grant_type=authorization_code

Token Response { "access_token": "2YotnFZFEjr1zCsicMWpAA", "token_type": "Bearer", "expires_in": 3600, "refresh_token": "tGzv3JOkF0XG5Qx2TlKWIA" }

Making Protected Resource Requests curl -H "Authorization: Bearer 2YotnFZFEjr1zCsicMWpAA" \ https://www.googleapis.com/gmail/v1/users/1444587525/messages

OAuth 2.0 Authorization Code Flow yelp.com Connect with Google yelp.com/callback Resource owner clicks ^^ Back to redirect URI with authorization code (front channel) contacts.google Talk to resource server (back channel) Exchange code for access token (back channel) accounts.google.com Email ********** Go to authorization server Redirect URI: yelp.com/callback (front channel) Authorization Server Client accounts.google.com 
 Allow Yelp to access your public profile and contacts? No Yes Request consent from resource owner

OAuth 2.0 Grant Types (Flows) • Optimized for browser-only Public Clients • Access token returned directly from authorization request (Front-channel only) • Does not support refresh tokens • Assumes Resource Owner and Public Client are on the same device • Most vulnerable to security threats Implicit • Front channel flow used by Client to obtain authorization code grant • Back channel flow used by Client to exchange authorization code grant for access token and optionally refresh token • Assumes Resource Owner and Client are on separate devices • Most secure flow as tokens never passes through user- agent Authorization Code • Optimized for server-only Confidential Clients acting on behalf of itself or a user • Back-channel only flow to obtain an access token using the Client’s credentials • Supports shared secrets or assertions as Client credentials signed with either symmetric or asymmetric keys Client Credential

OAuth 2.0 Grant Types (Flows) • Legacy grant type for native username/password apps such as desktop apps • Username/password is authorization grant to obtain access token from Authorization Server • Does not support refresh tokens • Assumes Resource Owner and Public Client or on the same device Resource Owner Password • Optimized for devices that do not have access to web- browsers • User code is returned from authorization request that must be redeemed by visiting a URL on a device with a browser to authorize • Back channel flow used by Client to poll for authorization approval for access token and optionally refresh token Device • Allows Authorization Server to trust authorization grants from third party such as SAML IdP (Federation) • Assertion is used to obtain access token with token request • Does not support refresh tokens Assertion

Six different flows Necessary because of: How you get consent from client? Who is making consent? Adds a lot of complexity to OAuth OAuth Flows

OAuth 2.0 Playground https://oauth.com/playground

Not backward compatible with OAuth 1.0 Interoperability issues exists as its not a protocol but rather an authorization framework OAuth 2.0 is not an authentication protocol OAuth 2.0 alone says absolutely nothing about the user OAuth 2.0 Facts

OAuth 2.0 and OpenID Connect OpenID Connect OAuth 2.0 HTTP OpenID Connect is for authentication
 
 OAuth 2.0 is for authorization

Extends OAuth 2.0 with new signed id_token for the Client and UserInfo endpoint to fetch user attributes Provides a standard set of scopes and claims for identities profile email address phone Built-in registration, discovery & metadata for dynamic federations Bring Your Own Identity (BYOI) Supports high assurance levels and key SAML use cases (enterprise) OpenID Connect OAuth 2.0 + Facebook Connect + SAML 2.0 (good parts)

Authorization Request HTTP/1.1 302 Found
 Location: https://app.example.com/oauth2/callback?
 code=MsCeLvIaQm6bTrgtp7&
 state=af0ifjsldkj Request Response Note: Parameters are not URL-encoded for example purposes GET https://accounts.google.com/o/oauth2/auth?
 scope=openid email&
 redirect_uri=https://app.example.com/oauth2/callback&
 response_type=code&
 client_id=812741506391&
 state=af0ifjsldkj

Token Request POST /oauth2/v3/token HTTP/1.1 Host: www.googleapis.com Content-Type: application/x-www-form-urlencoded code=MsCeLvIaQm6bTrgtp7& client_id=812741506391& client_secret={client_secret}& redirect_uri=https://app.example.com/oauth2/callback& grant_type=authorization_code

Token Response { "access_token": "2YotnFZFEjr1zCsicMWpAA", "token_type": "Bearer", "expires_in": 3600, "refresh_token": "tGzv3JOkF0XG5Qx2TlKWIA", "id_token": "eyJhbGciOiJSUzI1NiIsImtpZCI6IjFlOWdkazcifQ..." }

Validate ID Token Token Endpoint Authorization Endpoint /.well-known/
 openid-configuration JWKS Endpoint UserInfo Endpoint OAuth 2.0 Authorization Server & OpenID Connect Provider (OP) OAuth 2.0 Resource Server Client (Relying Party) 1 3 2 5 4 1 Discover OpenID Provider Metadata 2 Perform OAuth flow to obtain a ID token and/or access token 3 Get JSON Web Key Set (JWKS) for signature keys 4 Validate ID token
 (JSON Web Token) 5 Get additional user attributes with access token from UserInfo endpoint OpenID Connect

OIDC Authorization Code Flow yelp.com Connect with Google yelp.com/callback Resource owner clicks ^^ Back to redirect URI with authorization code accounts.google /userinfo Get user info 
 with access token Exchange code for access token and ID token accounts.google.com Email ********** Go to authorization server Redirect URI: yelp.com/callback Scope: openid profile Authorization Server Client accounts.google.com 
 Allow Yelp to access your public profile and contacts? No Yes Request consent from resource owner Hello Matt!

JSON Web Token (JWT) eyJhbGciOiJSUzI1NiJ9.eyJpc3MiOiJodHRwczovL2V4Y W1wbGUub2t0YS5jb20iLCJzdWIiOiIwMHVncmVuTWV xdllsYTRIVzBnMyIsImF1ZCI6IncyNTVIRVdpU1U0QXV OeEVqZWlqIiwiaWF0IjoxNDQ2MzA1MjgyLCJleHAiOjE 0NDYzMDg4ODIsImFtciI6WyJwd2QiXSwiYXV0aF90a W1lIjoxNDQ2MzA1MjgyLCJlbWFpbCI6ImthcmxAZXhhb XBsZS5jb20iLCJlbWFpbF92ZXJpZmllZCI6dHJ1ZX0.Xc NXs4C7DqpR22LLti777AMMVCxM7FjEPKZQnd- AS_Cc6R54wuQ5EApuY6GVFCkIlnfbNmYSbHMkO4H- L3uoeXVOPQmcqhNPDLLEChj00jQwZDjhPD9uBoNw GyiZ9_YKwsRpzbg9NEeY8xEwXJFIdk6SRktTFrVNHA OIhEQsgm8 { "alg": "RS256”
 "kid": "123456789" } { "iss": "https://example.okta.com", "sub": "00ugrenMeqvYla4HW0g3", "aud": "w255HEWiSU4AuNxEjeij", "iat": 1446305282, "exp": 1446308882, "amr": [ "pwd" ], "auth_time": 1446305282, "email": "[email protected]", "email_verified": true } Header Claims Signature Header Claims base64url(Header) + “.” + base64url(Claims) + “.” + base64url(Signature)

jwt.io https://jwt.io

No. A browser is required. Three options if a user is involved: 1. Web app: handle a redirect 2. CLI, TV, etc: use the Device Grant 3. Native app: use a custom URL handler Can you do OAuth without a browser?

PKCE is required for all clients using the authorization code flow Redirect URIs must be compared using exact string matching The Implicit grant is omitted from this specification The Resource Owner Password Credentials grant is omitted from this specification Bearer token usage omits the use of bearer tokens in the query string of URIs Refresh tokens for public clients must either be sender-constrained or one-time use OAuth 2.1 https://oauth.net/2.1/

Java's OAuth 2.0 Support

Java, the language, does not have OAuth support The JDK doesn't contain APIs to write a web app Building blocks are provided by Servlet API and Jakarta EE Jakarta Security 3.0 supports OpenID Connect! Java's OAuth 2.0 Support

OAuth in Java Frameworks

MicroProfile JWT Authentication

Quarkus

Helidon

Micronaut

Spring Boot

What about JSF and Wicket?

OAuth 2.0 in Action

https://github.com/oktadev/auth0-java-oauth-examples Java OAuth Demos

Java Security Frameworks

Java Security Frameworks

OAuth 2.0 Authorization Servers

Open Source OAuth 2.0 Authorization Servers Keycloak Spring Authorization Server WSO2 Identity Server

What about JavaFX?

Do Scala and Kotlin support OAuth?

Learn more about Java and OAuth https://developer.okta.com/blog/2022/06/16/oauth-java

Play with OAuth 2.0 and OpenID Connect developer.auth0.com

Join us as an Auth0 Ambassador! auth0.com/ambassador-program

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