Provide method to encode/decode a OAuth2InteractiveGrant to/from Stri…

…ng, closes #92

README.md

@@ -124,6 +124,19 @@ String authorization = String.format("Bearer %s", token.accessToken());
 myConnection.setRequestProperty("Authorization", authorization);
 ```
 
+### Preserving state
+
+By design, an interactive grant (Authorization Code Grant and Implicit Grant) may require multiple round trips. Sometimes an application
+needs to preserve the state between these round trips. For instance, an Android app may be suspended while the browser is in the foreground, and it may
+have to preserve the grant state in order to receive the access token when it's resumed.
+
+This can be achieved by calling `encodedState()` on the `OAuth2InteractiveGrant` instance. This method returns a String that can later be used
+to restore the grant state with
+
+```java
+OAuth2InteractiveGrant grant = new InteractiveGrantFactory(oauth2Client).value(encodedState);
+```
+
 ## Choice of HTTP client
 
 This library doesn't depend on any specific HTTP client implementation. Instead it builds upon [http-client-essentials-suite](https://github.com/dmfs/http-client-essentials-suite) to allow any 3rd party HTTP client to be used.

build.gradle

@@ -96,7 +96,7 @@ if (project.hasProperty('SONATYPE_USERNAME') && project.hasProperty('SONATYPE_PA
 }
 
 dependencies {
-    api 'org.dmfs:jems:' + JEMS_VERSION
+    api 'org.dmfs:jems:1.44'
     api 'org.dmfs:rfc3986-uri:0.8.1'
     api 'org.dmfs:rfc5545-datetime:0.3'
     api 'org.dmfs:http-client-essentials:' + HTTP_CLIENT_ESSENTIALS_VERSION
@@ -106,9 +106,13 @@ dependencies {
     implementation 'org.dmfs:http-client-types:' + HTTP_CLIENT_ESSENTIALS_VERSION
     implementation 'org.dmfs:http-client-basics:' + HTTP_CLIENT_ESSENTIALS_VERSION
     implementation 'org.dmfs:http-executor-decorators:' + HTTP_CLIENT_ESSENTIALS_VERSION
+    implementation 'org.dmfs:express-json:0.2.0'
+    implementation 'org.dmfs:jems2:' + JEMS2_VERSION
     implementation 'org.json:json:20220924'
 
-    testImplementation 'org.dmfs:jems-testing:' + JEMS_VERSION
+    testImplementation 'org.saynotobugs:confidence-core:0.8.0'
+    testImplementation 'org.saynotobugs:confidence-mockito4:0.8.0'
+    testImplementation 'org.dmfs:jems2-testing:' + JEMS2_VERSION
     testImplementation 'junit:junit:4.13.2'
     testImplementation 'org.mockito:mockito-core:4.8.0'
     testImplementation 'org.hamcrest:hamcrest-library:2.2'

gradle.properties

@@ -1,5 +1,3 @@
-
-
 #
 # Copyright 2016 dmfs GmbH
 #
@@ -15,10 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-
 HTTP_CLIENT_ESSENTIALS_VERSION=0.20
-JEMS_VERSION=1.41
-
+JEMS2_VERSION=2.14.0
 POM_DEVELOPER_ID=dmfs
 POM_DEVELOPER_NAME=Marten Gajda
 POM_DEVELOPER_EMAIL=[email protected]

src/main/java/org/dmfs/oauth2/client/OAuth2InteractiveGrant.java

@@ -20,6 +20,7 @@
 import org.dmfs.httpessentials.exceptions.ProtocolError;
 import org.dmfs.httpessentials.exceptions.ProtocolException;
 import org.dmfs.rfc3986.Uri;
+import org.json.JSONArray;
 
 import java.io.Serializable;
 import java.net.URI;
@@ -39,7 +40,7 @@ public interface OAuth2InteractiveGrant extends OAuth2Grant
      *
      * @return A {@link URI}.
      */
-    public URI authorizationUrl();
+    URI authorizationUrl();
 
     /**
      * Update the authentication flow with the redirect URI that was returned by the user agent. Unless this throws an Exception, the caller can assume that
@@ -55,7 +56,7 @@ public interface OAuth2InteractiveGrant extends OAuth2Grant
      * @throws ProtocolException
      *     If the redirectUri is invalid.
      */
-    public OAuth2InteractiveGrant withRedirect(Uri redirectUri) throws ProtocolError, ProtocolException;
+    OAuth2InteractiveGrant withRedirect(Uri redirectUri) throws ProtocolError, ProtocolException;
 
     /**
      * Return a {@link Serializable} state object that can be used to retain the current authentication flow state whenever the original {@link
@@ -68,13 +69,34 @@ public interface OAuth2InteractiveGrant extends OAuth2Grant
      *
      * @throws UnsupportedOperationException
      *     if this grant type does not support exporting the current state.
+     * @deprecated in favour of {@link #encodedState()}.
      */
-    public OAuth2GrantState state() throws UnsupportedOperationException;
+    @Deprecated
+    OAuth2GrantState state() throws UnsupportedOperationException;
+
+    /**
+     * Returns a {@link String} that can be later used to retrieve an {@link OAuth2InteractiveGrant} with the same state.
+     * <p>
+     * Note, the format of the String may be changed without further notice and may be incompatible with future versions of this library.
+     * <p>
+     * Also note, the resulting String may contain secrets used during the interactive grant. Do not persist the result in its plain
+     * text form. Make sure to encrypt it with a secure cipher.
+     * <p>
+     * Retrieve the original {@link OAuth2InteractiveGrant} like this:
+     * <pre>{@code
+     * InteractiveGrant grant = new InteractiveGrantFactory(oauth2Client).value(encodedState);
+     * }
+     * </pre>
+     */
+    String encodedState();
 
     /**
      * The interface of a simple {@link Serializable} object that represents the state of an interactive grant.
+     *
+     * @deprecated in favour of {@link OAuth2InteractiveGrant#encodedState()}.
      */
-    public interface OAuth2GrantState extends Serializable
+    @Deprecated
+    interface OAuth2GrantState extends Serializable
     {
         /**
          * Creates an {@link OAuth2InteractiveGrant} from this state for the given client.
@@ -86,6 +108,12 @@ public interface OAuth2GrantState extends Serializable
          *
          * @return An {@link OAuth2InteractiveGrant} that can be used to continue the authentication flow.
          */
-        public OAuth2InteractiveGrant grant(OAuth2Client client);
+        OAuth2InteractiveGrant grant(OAuth2Client client);
+    }
+
+
+    interface OAuth2InteractiveGrantFactory
+    {
+        OAuth2InteractiveGrant grant(OAuth2Client client, JSONArray arguments);
     }
 }

src/main/java/org/dmfs/oauth2/client/grants/AuthorizationCodeGrant.java

@@ -16,22 +16,30 @@
 
 package org.dmfs.oauth2.client.grants;
 
+import net.iharder.Base64;
+
+import org.dmfs.express.json.elementary.JsonText;
 import org.dmfs.httpessentials.client.HttpRequestExecutor;
 import org.dmfs.httpessentials.exceptions.ProtocolError;
 import org.dmfs.httpessentials.exceptions.ProtocolException;
 import org.dmfs.oauth2.client.*;
 import org.dmfs.oauth2.client.http.requests.AuthorizationCodeTokenRequest;
 import org.dmfs.oauth2.client.pkce.S256CodeChallenge;
 import org.dmfs.oauth2.client.scope.StringScope;
+import org.dmfs.oauth2.client.utils.GrantState;
 import org.dmfs.rfc3986.Uri;
 import org.dmfs.rfc3986.encoding.Precoded;
 import org.dmfs.rfc3986.encoding.XWwwFormUrlEncoded;
 import org.dmfs.rfc3986.parameters.ParameterList;
 import org.dmfs.rfc3986.parameters.adapters.XwfueParameterList;
 import org.dmfs.rfc3986.parameters.parametersets.EmptyParameterList;
+import org.dmfs.rfc3986.uris.LazyUri;
+import org.dmfs.rfc3986.uris.Text;
+import org.json.JSONArray;
 
 import java.io.IOException;
 import java.net.URI;
+import java.nio.charset.StandardCharsets;
 
 
 /**
@@ -125,13 +133,44 @@ public OAuth2AccessToken accessToken(HttpRequestExecutor executor) throws IOExce
     }
 
 
+    @Deprecated
     @Override
     public OAuth2InteractiveGrant.OAuth2GrantState state()
     {
         return new InitialAuthorizationCodeGrantState(mScope, mState, mCodeVerifier, new XWwwFormUrlEncoded(mCustomParameters));
     }
 
 
+    @Override
+    public String encodedState()
+    {
+        return Base64.encodeBytes(
+            new JsonText(new GrantState(InitialAuthorizationCodeGrantFactory.class,
+                mScope.toString(), mState.toString(), mCodeVerifier.toString(), new XWwwFormUrlEncoded(mCustomParameters).toString()))
+                .value()
+                .getBytes(StandardCharsets.UTF_8));
+    }
+
+
+    private final static class InitialAuthorizationCodeGrantFactory implements OAuth2InteractiveGrantFactory
+    {
+
+        @Override
+        public OAuth2InteractiveGrant grant(OAuth2Client client, JSONArray arguments)
+        {
+            if (arguments.length() != 4)
+            {
+                throw new IllegalArgumentException("Can't restore grant from invalid state.");
+            }
+            return new AuthorizationCodeGrant(client,
+                new StringScope(arguments.getString(0)),
+                arguments.getString(1),
+                arguments.getString(2),
+                new XwfueParameterList(new Precoded(arguments.getString(3))));
+        }
+    }
+
+
     /**
      * An {@link OAuth2InteractiveGrant} that represents the authorized state of an Authorization Code Grant. That means, the user has granted access and an
      * auth token was issued by the server.
@@ -181,17 +220,49 @@ public OAuth2InteractiveGrant withRedirect(Uri redirectUri)
         }
 
 
+        @Deprecated
         @Override
         public OAuth2GrantState state()
         {
             return new AuthorizedAuthorizationCodeGrantState(mScope, mRedirectUri, mState, mCodeVerifier);
         }
+
+
+        @Override
+        public String encodedState()
+        {
+            return Base64.encodeBytes(
+                new JsonText(new GrantState(AuthenticatedAuthorizationCodeGrantFactory.class,
+                    new Text(mRedirectUri).toString(), mScope.toString(), mState.toString(), mCodeVerifier.toString()))
+                    .value()
+                    .getBytes(StandardCharsets.UTF_8));
+        }
+
+
+        private final static class AuthenticatedAuthorizationCodeGrantFactory implements OAuth2InteractiveGrantFactory
+        {
+
+            @Override
+            public OAuth2InteractiveGrant grant(OAuth2Client client, JSONArray arguments)
+            {
+                if (arguments.length() != 4)
+                {
+                    throw new IllegalArgumentException("Can't restore grant from invalid state.");
+                }
+                return new AuthorizedAuthorizationCodeGrant(client,
+                    new LazyUri(new Precoded(arguments.getString(0))),
+                    new StringScope(arguments.getString(1)),
+                    arguments.getString(2),
+                    arguments.getString(3));
+            }
+        }
     }
 
 
     /**
      * An {@link OAuth2GrantState} that represents the state of an Authorization Code Grant that was not confirmed by the user so far.
      */
+    @Deprecated
     private final static class InitialAuthorizationCodeGrantState implements OAuth2InteractiveGrant.OAuth2GrantState
     {
 
@@ -229,6 +300,7 @@ public AuthorizationCodeGrant grant(OAuth2Client client)
     /**
      * An {@link OAuth2GrantState} that represents the state of an Authorization Code Grant that got user consent.
      */
+    @Deprecated
     private final static class AuthorizedAuthorizationCodeGrantState implements OAuth2InteractiveGrant.OAuth2GrantState
     {
         private static final long serialVersionUID = 1L;