feat: support key id in ztdf key access object

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

@@ -30,6 +30,7 @@ public enum IntegrityAlgorithm {
     public static class KASInfo {
         public String URL;
         public String PublicKey;
+        public String KID;
     }
 
     public static class TDFConfig {

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

@@ -67,6 +67,13 @@ public String getPublicKey(Config.KASInfo kasInfo) {
                 .getPublicKey();
     }
 
+    @Override
+    public String getKid(Config.KASInfo kasInfo) {
+        return getStub(kasInfo.URL)
+                .publicKey(PublicKeyRequest.getDefaultInstance())
+                .getKid();
+    }
+
     private String normalizeAddress(String urlString) {
         URL url;
         try {

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

@@ -34,6 +34,7 @@ static public class KeyAccess {
         public String wrappedKey;
         public String policyBinding;
         public String encryptedMetadata;
+        public String kid;
     }
 
     static public class Method {

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

@@ -26,6 +26,7 @@ public void close() throws Exception {
 
     public interface KAS extends AutoCloseable {
         String getPublicKey(Config.KASInfo kasInfo);
+        String getKid(Config.KASInfo kasInfo);
         String getECPublicKey(Config.KASInfo kasInfo, NanoTDFType.ECCurve curve);
         byte[] unwrap(Manifest.KeyAccess keyAccess, String policy);
         byte[] unwrapNanoTDF(NanoTDFType.ECCurve curve, String header, String kasURL);

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

@@ -170,6 +170,7 @@ private void prepareManifest(Config.TDFConfig tdfConfig) {
                 Manifest.KeyAccess keyAccess = new Manifest.KeyAccess();
                 keyAccess.keyType = kWrapped;
                 keyAccess.url = kasInfo.URL;
+                keyAccess.kid = kasInfo.KID;
                 keyAccess.protocol = kKasProtocol;
 
                 // Add policyBinding
@@ -369,6 +370,7 @@ private void fillInPublicKeyInfo(List<Config.KASInfo> kasInfoList, SDK.KAS kas)
             }
             logger.info("no public key provided for KAS at {}, retrieving", kasInfo.URL);
             kasInfo.PublicKey = kas.getPublicKey(kasInfo);
+            kasInfo.KID = kas.getKid(kasInfo);
         }
     }
 

sdk/src/test/java/io/opentdf/platform/sdk/ConfigTest.java

@@ -32,6 +32,7 @@ void withKasInformation_shouldAddKasInfo() {
         Config.KASInfo kasInfo = new Config.KASInfo();
         kasInfo.URL = "http://example.com";
         kasInfo.PublicKey = "publicKey";
+        kasInfo.KID = "r1";
         Config.TDFConfig config = Config.newTDFConfig(Config.withKasInformation(kasInfo));
         assertEquals(1, config.kasInfoList.size());
         assertEquals(kasInfo, config.kasInfoList.get(0));

sdk/src/test/java/io/opentdf/platform/sdk/KASClientTest.java

@@ -70,6 +70,39 @@ public void publicKey(PublicKeyRequest request, StreamObserver<PublicKeyResponse
         }
     }
 
+    @Test
+    void testGettingKid() throws IOException {
+        AccessServiceGrpc.AccessServiceImplBase accessService = new AccessServiceGrpc.AccessServiceImplBase() {
+            @Override
+            public void publicKey(PublicKeyRequest request, StreamObserver<PublicKeyResponse> responseObserver) {
+                var response = PublicKeyResponse.newBuilder().setKid("r1").build();
+                responseObserver.onNext(response);
+                responseObserver.onCompleted();
+            }
+        };
+
+        Server server = null;
+        try {
+            server = startServer(accessService);
+            Function<String, ManagedChannel> channelFactory = (String url) -> ManagedChannelBuilder
+                    .forTarget(url)
+                    .usePlaintext()
+                    .build();
+
+            var keypair = CryptoUtils.generateRSAKeypair();
+            var dpopKey = new RSAKey.Builder((RSAPublicKey) keypair.getPublic()).privateKey(keypair.getPrivate()).build();
+            try (var kas = new KASClient(channelFactory, dpopKey)) {
+                Config.KASInfo kasInfo = new Config.KASInfo();
+                kasInfo.URL = "localhost:" + server.getPort();
+                assertThat(kas.getKid(kasInfo)).isEqualTo("r1");
+            }
+        } finally {
+            if (server != null) {
+                server.shutdownNow();
+            }
+        }
+    }
+
     @Test
     void testCallingRewrap() throws IOException {
         var dpopKeypair = CryptoUtils.generateRSAKeypair();

sdk/src/test/java/io/opentdf/platform/sdk/NanoTDFTest.java

@@ -43,6 +43,11 @@ public String getPublicKey(Config.KASInfo kasInfo) {
             return kasPublicKey;
         }
 
+        @Override
+        public String getKid(Config.KASInfo kasInfo) {
+            return "r1";
+        }
+
         @Override
         public String getECPublicKey(Config.KASInfo kasInfo, NanoTDFType.ECCurve curve) {
             return kasPublicKey;

sdk/src/test/java/io/opentdf/platform/sdk/TDFTest.java

@@ -35,6 +35,11 @@ public String getPublicKey(Config.KASInfo kasInfo) {
             return CryptoUtils.getRSAPublicKeyPEM(keypairs.get(index).getPublic());
         }
 
+        @Override
+        public String getKid(Config.KASInfo kasInfo) {
+            return "r1";
+        }
+
         @Override
         public byte[] unwrap(Manifest.KeyAccess keyAccess, String policy) {
             int index = Integer.parseInt(keyAccess.url);