Allow client assertion to be a callback and a per-request parameter

pom.xml

@@ -101,7 +101,7 @@
         <dependency>
             <groupId>com.azure</groupId>
             <artifactId>azure-security-keyvault-secrets</artifactId>
-            <version>4.3.6</version>
+            <version>4.3.5</version>
             <scope>test</scope>
         </dependency>
         <dependency>

src/integrationtest/java/com.microsoft.aad.msal4j/ClientCredentialsIT.java

@@ -16,6 +16,7 @@
 import java.security.UnrecoverableKeyException;
 import java.security.cert.CertificateException;
 import java.util.Collections;
+import java.util.concurrent.Callable;
 
 import static com.microsoft.aad.msal4j.TestConstants.KEYVAULT_DEFAULT_SCOPE;
 
@@ -48,16 +49,35 @@ public void acquireTokenClientCredentials_ClientSecret() throws Exception {
     public void acquireTokenClientCredentials_ClientAssertion() throws Exception {
         String clientId = "2afb0add-2f32-4946-ac90-81a02aa4550e";
 
-        ClientAssertion clientAssertion = JwtHelper.buildJwt(
-                clientId,
-                (ClientCertificate) certificate,
-                "https://login.microsoftonline.com/common/oauth2/v2.0/token",
-                true);
+        ClientAssertion clientAssertion = getClientAssertion(clientId);
+
+        IClientCredential credential = ClientCredentialFactory.createFromClientAssertion(clientAssertion.assertion());
+
+        assertAcquireTokenCommon(clientId, credential);
+    }
+
+    @Test
+    public void acquireTokenClientCredentials_Callback() throws Exception {
+        String clientId = "2afb0add-2f32-4946-ac90-81a02aa4550e";
+
+        // Creates a valid client assertion using a callback, and uses it to build the client app and make a request
+        Callable<String> callable = () -> {
+            ClientAssertion clientAssertion = getClientAssertion(clientId);
 
-        IClientCredential credential = ClientCredentialFactory.createFromClientAssertion(
-                clientAssertion.assertion());
+            return clientAssertion.assertion();
+        };
+
+        IClientCredential credential = ClientCredentialFactory.createFromCallback(callable);
 
         assertAcquireTokenCommon(clientId, credential);
+
+        // Creates an invalid client assertion to build the application, but overrides it with a valid client assertion
+        //  in the request parameters in order to make a successful token request
+        ClientAssertion invalidClientAssertion = getClientAssertion("abc");
+
+        IClientCredential invalidCredentials = ClientCredentialFactory.createFromClientAssertion(invalidClientAssertion.assertion());
+
+        assertAcquireTokenCommon_withParameters(clientId, invalidCredentials, credential);
     }
 
     @Test
@@ -98,6 +118,13 @@ public void acquireTokenClientCredentials_DefaultCacheLookup() throws Exception
         Assert.assertNotEquals(result2.accessToken(), result3.accessToken());
     }
 
+    private ClientAssertion getClientAssertion(String clientId) {
+        return JwtHelper.buildJwt(
+                clientId,
+                (ClientCertificate) certificate,
+                "https://login.microsoftonline.com/common/oauth2/v2.0/token",
+                true);
+    }
 
     private void assertAcquireTokenCommon(String clientId, IClientCredential credential) throws Exception {
         ConfidentialClientApplication cca = ConfidentialClientApplication.builder(
@@ -113,4 +140,20 @@ private void assertAcquireTokenCommon(String clientId, IClientCredential credent
         Assert.assertNotNull(result);
         Assert.assertNotNull(result.accessToken());
     }
+
+    private void assertAcquireTokenCommon_withParameters(String clientId, IClientCredential credential, IClientCredential credentialParam) throws Exception {
+
+        ConfidentialClientApplication cca = ConfidentialClientApplication.builder(
+                clientId, credential).
+                authority(TestConstants.MICROSOFT_AUTHORITY).
+                build();
+
+        IAuthenticationResult result = cca.acquireToken(ClientCredentialParameters
+                .builder(Collections.singleton(KEYVAULT_DEFAULT_SCOPE)).clientCredential(credentialParam)
+                .build())
+                .get();
+
+        Assert.assertNotNull(result);
+        Assert.assertNotNull(result.accessToken());
+    }
 }

src/main/java/com/microsoft/aad/msal4j/ClientCredentialFactory.java

@@ -9,6 +9,11 @@
 import java.security.cert.CertificateException;
 import java.security.cert.X509Certificate;
 import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 
 import static com.microsoft.aad.msal4j.ParameterValidationUtils.validateNotNull;
 
@@ -29,7 +34,7 @@ public static IClientSecret createFromSecret(String secret) {
     }
 
     /**
-     * Static method to create a {@link ClientCertificate} instance from a certificate
+     * Static method to create a {@link ClientCertificate} instance from a password-protected certificate.
      *
      * @param pkcs12Certificate InputStream containing PCKS12 formatted certificate
      * @param password          certificate password
@@ -48,7 +53,7 @@ public static IClientCertificate createFromCertificate(final InputStream pkcs12C
     }
 
     /**
-     * Static method to create a {@link ClientCertificate} instance.
+     * Static method to create a {@link ClientCertificate} instance from a private key/public certificate pair.
      *
      * @param key                  RSA private key to sign the assertion.
      * @param publicKeyCertificate x509 public certificate used for thumbprint
@@ -61,7 +66,7 @@ public static IClientCertificate createFromCertificate(final PrivateKey key, fin
     }
 
     /**
-     * Static method to create a {@link ClientCertificate} instance.
+     * Static method to create a {@link ClientCertificate} instance from a certificate chain.
      *
      * @param key                       RSA private key to sign the assertion.
      * @param publicKeyCertificateChain ordered with the user's certificate first followed by zero or more certificate authorities
@@ -75,12 +80,26 @@ public static IClientCertificate createFromCertificateChain(PrivateKey key, List
     }
 
     /**
-     * Static method to create a {@link ClientAssertion} instance.
+     * Static method to create a {@link ClientAssertion} instance from a JWT token encoded as a base64 URL encoded string.
      *
-     * @param clientAssertion Jwt token encoded as a base64 URL encoded string
+     * @param clientAssertion JWT token encoded as a base64 URL encoded string
      * @return {@link ClientAssertion}
      */
     public static IClientAssertion createFromClientAssertion(String clientAssertion) {
         return new ClientAssertion(clientAssertion);
     }
+
+    /**
+     * Static method to create a {@link ClientAssertion} instance from a provided Callable.
+     *
+     * @param callable Callable that produces a JWT token encoded as a base64 URL encoded string
+     * @return {@link ClientAssertion}
+     */
+    public static IClientAssertion createFromCallback(Callable<String> callable) throws ExecutionException, InterruptedException {
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+
+        Future<String> future = executor.submit(callable);
+
+        return new ClientAssertion(future.get());
+    }
 }

src/main/java/com/microsoft/aad/msal4j/ClientCredentialParameters.java

@@ -49,6 +49,11 @@ public class ClientCredentialParameters implements IAcquireTokenParameters {
      */
     private String tenant;
 
+    /**
+     * Overrides the client credentials for this request
+     */
+    private IClientCredential clientCredential;
+
     private static ClientCredentialParametersBuilder builder() {
 
         return new ClientCredentialParametersBuilder();

src/main/java/com/microsoft/aad/msal4j/ConfidentialClientApplication.java

@@ -125,7 +125,7 @@ private ClientAuthentication buildValidClientCertificateAuthority() {
         return createClientAuthFromClientAssertion(clientAssertion);
     }
 
-    private ClientAuthentication createClientAuthFromClientAssertion(
+    protected ClientAuthentication createClientAuthFromClientAssertion(
             final ClientAssertion clientAssertion) {
         final Map<String, List<String>> map = new HashMap<>();
         try {

src/main/java/com/microsoft/aad/msal4j/TokenRequestExecutor.java

@@ -73,7 +73,15 @@ OAuthHttpRequest createOauthHttpRequest() throws SerializeException, MalformedUR
         oauthHttpRequest.setQuery(URLUtils.serializeParameters(params));
 
         if (msalRequest.application().clientAuthentication() != null) {
-            msalRequest.application().clientAuthentication().applyTo(oauthHttpRequest);
+            // If the client application has a client assertion to apply to the request, check if a new client assertion
+            //  was supplied as a request parameter. If so, use the request's assertion instead of the application's
+            if (msalRequest instanceof ClientCredentialRequest && ((ClientCredentialRequest) msalRequest).parameters.clientCredential() != null) {
+                ((ConfidentialClientApplication) msalRequest.application())
+                        .createClientAuthFromClientAssertion((ClientAssertion) ((ClientCredentialRequest) msalRequest).parameters.clientCredential())
+                        .applyTo(oauthHttpRequest);
+            } else {
+                msalRequest.application().clientAuthentication().applyTo(oauthHttpRequest);
+            }
         }
         return oauthHttpRequest;
     }