feat: adds token exchange and general auth (#176)

Java SDK only does token exchange with client credentials. This PR
allows token exchange or general authentication using the Nimbus
Authorization Grant.

Author: imdominicreed

sdk/src/main/java/io/opentdf/platform/sdk/GRPCAuthInterceptor.java

@@ -5,7 +5,6 @@
 import com.nimbusds.jose.jwk.RSAKey;
 import com.nimbusds.jwt.SignedJWT;
 import com.nimbusds.oauth2.sdk.AuthorizationGrant;
-import com.nimbusds.oauth2.sdk.ClientCredentialsGrant;
 import com.nimbusds.oauth2.sdk.ErrorObject;
 import com.nimbusds.oauth2.sdk.TokenRequest;
 import com.nimbusds.oauth2.sdk.TokenResponse;
@@ -41,6 +40,7 @@ class GRPCAuthInterceptor implements ClientInterceptor {
     private final ClientAuthentication clientAuth;
     private final RSAKey rsaKey;
     private final URI tokenEndpointURI;
+    private final AuthorizationGrant authzGrant;
     private SSLFactory sslFactory;
     private static final Logger logger = LoggerFactory.getLogger(GRPCAuthInterceptor.class);
 
@@ -52,11 +52,12 @@ class GRPCAuthInterceptor implements ClientInterceptor {
      * @param rsaKey     the RSA key to be used by the interceptor
      * @param sslFactory Optional SSLFactory for Requests
      */
-    public GRPCAuthInterceptor(ClientAuthentication clientAuth, RSAKey rsaKey, URI tokenEndpointURI, SSLFactory sslFactory) {
+    public GRPCAuthInterceptor(ClientAuthentication clientAuth, RSAKey rsaKey, URI tokenEndpointURI, AuthorizationGrant authzGrant, SSLFactory sslFactory) {
         this.clientAuth = clientAuth;
         this.rsaKey = rsaKey;
         this.tokenEndpointURI = tokenEndpointURI;
         this.sslFactory = sslFactory;
+        this.authzGrant = authzGrant;
     }
 
     /**
@@ -110,12 +111,9 @@ private synchronized AccessToken getToken() {
 
                 logger.trace("The current access token is expired or empty, getting a new one");
 
-                // Construct the client credentials grant
-                AuthorizationGrant clientGrant = new ClientCredentialsGrant();
-
                 // Make the token request
                 TokenRequest tokenRequest = new TokenRequest(this.tokenEndpointURI,
-                        clientAuth, clientGrant, null);
+                        clientAuth, authzGrant, null);
                 HTTPRequest httpRequest = tokenRequest.toHTTPRequest();
                 if(sslFactory!=null){
                     httpRequest.setSSLSocketFactory(sslFactory.getSslSocketFactory());

sdk/src/main/java/io/opentdf/platform/sdk/SDKBuilder.java

@@ -4,12 +4,17 @@
 import com.nimbusds.jose.jwk.KeyUse;
 import com.nimbusds.jose.jwk.RSAKey;
 import com.nimbusds.jose.jwk.gen.RSAKeyGenerator;
+import com.nimbusds.oauth2.sdk.AuthorizationGrant;
+import com.nimbusds.oauth2.sdk.ClientCredentialsGrant;
 import com.nimbusds.oauth2.sdk.GeneralException;
 import com.nimbusds.oauth2.sdk.auth.ClientAuthentication;
 import com.nimbusds.oauth2.sdk.auth.ClientSecretBasic;
 import com.nimbusds.oauth2.sdk.auth.Secret;
 import com.nimbusds.oauth2.sdk.id.ClientID;
 import com.nimbusds.oauth2.sdk.id.Issuer;
+import com.nimbusds.oauth2.sdk.token.BearerAccessToken;
+import com.nimbusds.oauth2.sdk.token.TokenTypeURI;
+import com.nimbusds.oauth2.sdk.tokenexchange.TokenExchangeGrant;
 import com.nimbusds.openid.connect.sdk.op.OIDCProviderMetadata;
 import io.grpc.*;
 import io.opentdf.platform.wellknownconfiguration.GetWellKnownConfigurationRequest;
@@ -41,6 +46,7 @@ public class SDKBuilder {
     private ClientAuthentication clientAuth = null;
     private Boolean usePlainText;
     private SSLFactory sslFactory;
+    private AuthorizationGrant authzGrant;
 
     private static final Logger logger = LoggerFactory.getLogger(SDKBuilder.class);
 
@@ -49,6 +55,7 @@ public static SDKBuilder newBuilder() {
         builder.usePlainText = false;
         builder.clientAuth = null;
         builder.platformEndpoint = null;
+        builder.authzGrant = null;
 
         return builder;
     }
@@ -99,6 +106,24 @@ public SDKBuilder platformEndpoint(String platformEndpoint) {
         return this;
     }
 
+    public SDKBuilder authorizationGrant(AuthorizationGrant authzGrant) {
+        if (this.authzGrant != null) {
+            throw new RuntimeException("Authorization grant can't be specified twice");
+        }
+        this.authzGrant = authzGrant;
+        return this;
+    }
+
+    public SDKBuilder tokenExchange(String jwt) {
+        if (this.authzGrant != null) {
+            throw new RuntimeException("Authorization grant can't be specified twice");
+        }
+
+        BearerAccessToken token = new BearerAccessToken(jwt);
+        this.authzGrant = new TokenExchangeGrant(token, TokenTypeURI.ACCESS_TOKEN);
+        return this;
+    }
+
     public SDKBuilder clientSecret(String clientID, String clientSecret) {
         ClientID cid = new ClientID(clientID);
         Secret cs = new Secret(clientSecret);
@@ -168,7 +193,11 @@ private GRPCAuthInterceptor getGrpcAuthInterceptor(RSAKey rsaKey) {
             throw new SDKException("Error resolving the OIDC provider metadata", e);
         }
 
-        return new GRPCAuthInterceptor(clientAuth, rsaKey, providerMetadata.getTokenEndpointURI(), sslFactory);
+        if (this.authzGrant == null) {
+            this.authzGrant = new ClientCredentialsGrant();
+        }
+
+        return new GRPCAuthInterceptor(clientAuth, rsaKey, providerMetadata.getTokenEndpointURI(), this.authzGrant, sslFactory);
     }
 
     static class ServicesAndInternals {