fix: Correct null assertions when deserializing (#211)

previously this would throw null pointer exception if `"assertions":
null` was in the manifest, this should stop that error and assign
assertions and empty arraylist if it is null on deserialization

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

@@ -41,7 +41,9 @@ public class Manifest {
     private static final String kAssertionHash = "assertionHash";
     private static final String kAssertionSignature = "assertionSig";
 
-    private static final Gson gson = new Gson();
+    private static final Gson gson = new GsonBuilder()
+                                        .registerTypeAdapter(Manifest.class, new ManifestDeserializer())
+                                        .create();
 
     @Override
     public boolean equals(Object o) {
@@ -458,6 +460,19 @@ private JWSVerifier createVerifier(AssertionConfig.AssertionKey assertionKey) th
     public Payload payload;
     public List<Assertion> assertions = new ArrayList<>();
 
+    public static class ManifestDeserializer implements JsonDeserializer<Object> {
+        @Override
+        public Manifest deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
+            // Let Gson handle the default deserialization of the object first
+            Manifest manifest = new Gson().fromJson(json, typeOfT);
+            // Now check if the `assertions` field is null and replace it with an empty list if necessary
+            if (manifest.assertions == null) {
+                manifest.assertions = new ArrayList<>();  // Replace null with empty list
+            }
+            return manifest;
+        }
+    }
+
     private static Manifest readManifest(Reader reader) {
         return gson.fromJson(reader, Manifest.class);
     }

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

@@ -1,11 +1,13 @@
 package io.opentdf.platform.sdk;
 
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 import com.nimbusds.jose.*;
 
 import io.opentdf.platform.policy.Value;
 import io.opentdf.platform.policy.attributes.AttributesServiceGrpc.AttributesServiceFutureStub;
 import io.opentdf.platform.sdk.Config.TDFConfig;
+import io.opentdf.platform.sdk.Manifest.ManifestDeserializer;
 import io.opentdf.platform.sdk.Autoconfigure.AttributeValueFQN;
 import io.opentdf.platform.sdk.Config.KASInfo;
 
@@ -75,7 +77,9 @@ public TDF() {
 
     private static final SecureRandom sRandom = new SecureRandom();
 
-    private static final Gson gson = new Gson();
+    private static final Gson gson = new GsonBuilder()
+                                        .registerTypeAdapter(Manifest.class, new ManifestDeserializer())
+                                        .create();
 
     public class SplitKeyException extends IOException {
         public SplitKeyException(String errorMessage) {

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

@@ -4,11 +4,14 @@
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 
+import io.opentdf.platform.sdk.Manifest.ManifestDeserializer;
+
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Map;
 
+import static org.junit.Assert.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class ManifestTest {
@@ -62,7 +65,9 @@ void testManifestMarshalAndUnMarshal() {
                 "}";
 
         GsonBuilder gsonBuilder = new GsonBuilder();
-        Gson gson = gsonBuilder.setPrettyPrinting().create();
+        Gson gson = gsonBuilder.setPrettyPrinting()
+                        .registerTypeAdapter(Manifest.class, new ManifestDeserializer())
+                        .create();
         Manifest manifest = gson.fromJson(kManifestJsonFromTDF, Manifest.class);
 
         // Test payload
@@ -90,4 +95,69 @@ void testManifestMarshalAndUnMarshal() {
 
         assertEquals(manifest, deserializedAgain, "something changed when we deserialized -> serialized -> deserialized");
     }
+
+    @Test
+    void testAssertionNull() {
+        String kManifestJsonFromTDF = "{\n" +
+                "  \"encryptionInformation\": {\n" +
+                "    \"integrityInformation\": {\n" +
+                "      \"encryptedSegmentSizeDefault\": 1048604,\n" +
+                "      \"rootSignature\": {\n" +
+                "        \"alg\": \"HS256\",\n" +
+                "        \"sig\": \"N2Y1ZjJlYWE4N2EzNjc2Nzc3NzgxNGU2ZGE1NmI4NDNhZTI5ZWY5NDc2OGI1ZTMzYTIyMTU4MDBlZTY3NzQzNA==\"\n" +
+                "      },\n" +
+                "      \"segmentHashAlg\": \"GMAC\",\n" +
+                "      \"segmentSizeDefault\": 1048576,\n" +
+                "      \"segments\": [\n" +
+                "        {\n" +
+                "          \"encryptedSegmentSize\": 41,\n" +
+                "          \"hash\": \"ZWEyZTkwYjZiZThmYWZhNzg5ZmNjOWIyZTA2Njg5OTQ=\",\n" +
+                "          \"segmentSize\": 1048576\n" +
+                "        }\n" +
+                "      ]\n" +
+                "    },\n" +
+                "    \"keyAccess\": [\n" +
+                "      {\n" +
+                "        \"policyBinding\": {\n" +
+                "          \"alg\": \"HS256\",\n" +
+                "          \"hash\": \"YTgzNThhNzc5NWRhMjdjYThlYjk4ZmNmODliNzc2Y2E5ZmZiZDExZDQ3OTM5ODFjZTRjNmE3MmVjOTUzZTFlMA==\"\n" +
+                "        },\n" +
+                "        \"protocol\": \"kas\",\n" +
+                "        \"type\": \"wrapped\",\n" +
+                "        \"url\": \"http://localhost:65432/kas\",\n" +
+                "        \"wrappedKey\": \"dJ3PdscXWvLv/juSkL7EMhl4lgLSBfI9EeoG2ct6NeSwPkPm/ieMF6ryDQjGeqZttoLlx2qBCVpik/BooGd/FtpYMIF/7a5RFTJ3G+o4Lww/zG6zIgV2APEPO+Gp7ORlFyMNJfn6Tj8ChTweKBqfXEXLihTV6sTZFtsWjdV96Z4KXbLe8tGpkXBpUAsSlmjcDJ920vrqnp3dvt2GwfmAiRWYCMXxnqUECqN5kVXMJywcvHatv2ZJSA/ixjDOrix+MocDJ69K/yFA17DXgfjf5X4SLyS0XgaZcXsdACBb+ogBlPw6vAbBrAyqI0Vi1msMRYNDS+FTl1yWEXl1HpyyCw==\"\n" +
+                "      }\n" +
+                "    ],\n" +
+                "    \"method\": {\n" +
+                "      \"algorithm\": \"AES-256-GCM\",\n" +
+                "      \"isStreamable\": true,\n" +
+                "      \"iv\": \"tozen81HLtZktNOP\"\n" +
+                "    },\n" +
+                "    \"policy\": \"eyJib2R5Ijp7ImRhdGFBdHRyaWJ1dGVzIjpbXSwiZGlzc2VtIjpbXX0sInV1aWQiOiJiNTM3MDllMy03NmE3LTRmYzctOGEwZi1mZDBhNjcyNmVhM2YifQ==\",\n" +
+                "    \"type\": \"split\"\n" +
+                "  },\n" +
+                "  \"payload\": {\n" +
+                "    \"isEncrypted\": true,\n" +
+                "    \"mimeType\": \"application/octet-stream\",\n" +
+                "    \"protocol\": \"zip\",\n" +
+                "    \"type\": \"reference\",\n" +
+                "    \"url\": \"0.payload\"\n" +
+                "  },\n" +
+                "   \"assertions\": null\n"+
+                "}";
+
+        GsonBuilder gsonBuilder = new GsonBuilder();
+        Gson gson = gsonBuilder.setPrettyPrinting()
+                        .registerTypeAdapter(Manifest.class, new ManifestDeserializer())
+                        .create();
+        Manifest manifest = gson.fromJson(kManifestJsonFromTDF, Manifest.class);
+
+        // Test payload for sanity check
+        assertEquals(manifest.payload.url, "0.payload");
+        assertEquals(manifest.payload.isEncrypted, true);
+        // Test assertion deserialization
+        assertNotNull(manifest.assertions);
+        assertEquals(manifest.assertions.size(), 0);
+
+    }
 }

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

@@ -1,5 +1,9 @@
 package io.opentdf.platform.sdk;
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+import io.opentdf.platform.sdk.Manifest.ManifestDeserializer;
+
 import org.apache.commons.compress.archivers.zip.Zip64Mode;
 import org.apache.commons.compress.archivers.zip.ZipArchiveEntry;
 import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream;
@@ -36,7 +40,11 @@ public void testReadingExistingZip() throws Exception {
                 if (entry.getName().endsWith(".json")) {
                     entry.getData().transferTo(stream);
                     var data = stream.toString(StandardCharsets.UTF_8);
-                    var map = new Gson().fromJson(data, Map.class);
+                    var gson = new GsonBuilder()
+                                        .registerTypeAdapter(Manifest.class, new ManifestDeserializer())
+                                        .create();
+                    var map = gson.fromJson(data, Map.class);
+
                     assertThat(map.get("encryptionInformation")).isNotNull();
                 }
             }