fix(sdk): add methods to examine Manifest and Policy (#278)

These capabilities were removed during a previous refactoring

Also change `Manifest.readManfest` to take in a `String` since that's
the
only way it's ever used.

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: mkleene

examples/src/main/java/io/opentdf/platform/GetManifestInformation.java

@@ -0,0 +1,28 @@
+package io.opentdf.platform;
+
+import io.opentdf.platform.sdk.Manifest;
+import io.opentdf.platform.sdk.PolicyObject;
+import io.opentdf.platform.sdk.SDK;
+
+import java.io.IOException;
+import java.nio.channels.FileChannel;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+
+public class GetManifestInformation {
+    public static void main(String[] args) throws IOException {
+        if (args.length < 1) {
+            System.err.println("TDF file path must be provided as an argument.");
+            return;
+        }
+
+        try (FileChannel tdfStream = FileChannel.open(Path.of(args[0]), StandardOpenOption.READ)) {
+            Manifest manifest = SDK.readManifest(tdfStream);
+            System.out.println("loaded a TDF with key access type: " + manifest.encryptionInformation.keyAccessType);
+
+            PolicyObject policyObject = SDK.decodePolicyObject(manifest);
+            System.out.println("the policy has uuid: " + policyObject.uuid);
+        }
+    }
+}
+

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

@@ -27,7 +27,6 @@
 import org.erdtman.jcs.JsonCanonicalizer;
 
 import java.io.IOException;
-import java.io.Reader;
 import java.lang.reflect.Type;
 import java.nio.charset.StandardCharsets;
 import java.security.MessageDigest;
@@ -500,8 +499,8 @@ public AssertionConfig.Statement deserialize(JsonElement json, Type typeOfT, Jso
     public EncryptionInformation encryptionInformation;
     public Payload payload;
     public List<Assertion> assertions = new ArrayList<>();
-    protected static Manifest readManifest(Reader reader) {
-        Manifest result = gson.fromJson(reader, Manifest.class);
+    protected static Manifest readManifest(String manifestJson) {
+        Manifest result = gson.fromJson(manifestJson, Manifest.class);
         if (result.assertions == null) {
             result.assertions = new ArrayList<>();
         }
@@ -539,8 +538,7 @@ protected static Manifest readManifest(Reader reader) {
         return result;
     }
 
-    static PolicyObject readPolicyObject(Reader reader) {
-        var manifest = readManifest(reader);
+    static PolicyObject decodePolicyObject(Manifest manifest) {
         var policyBase64 = manifest.encryptionInformation.policy;
         var policyBytes = Base64.getDecoder().decode(policyBase64);
         var policyJson = new String(policyBytes, StandardCharsets.UTF_8);

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

@@ -145,6 +145,30 @@ public static boolean isTDF(SeekableByteChannel channel) {
                 && entries.stream().anyMatch(e -> "0.payload".equals(e.getName()));
     }
 
+    /**
+     * Reads the {@link Manifest} without decrypting the TDF
+     * @param tdfBytes A SeekableByteChannel containing the TDF data
+     * @return The parsed {@link Manifest} object
+     * @throws SDKException if an SDK-specific error occurs
+     * @throws IOException if an I/O error occurs
+     */
+    public static Manifest readManifest(SeekableByteChannel tdfBytes) throws SDKException, IOException {
+        TDFReader reader = new TDFReader(tdfBytes);
+        String manifestJson = reader.manifest();
+        return Manifest.readManifest(manifestJson);
+    }
+
+    /**
+     * Decodes a PolicyObject from the manifest. Use {@link SDK#readManifest(SeekableByteChannel)}
+     * to get the {@link Manifest} from a TDF.
+     * @param manifest The {@link Manifest} containing the policy.
+     * @return The decoded {@link PolicyObject}.
+     * @throws SDKException if there is an error during decoding.
+     */
+    public static PolicyObject decodePolicyObject(Manifest manifest) throws SDKException {
+        return Manifest.decodePolicyObject(manifest);
+    }
+
     public String getPlatformUrl() {
         return platformUrl;
     }

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

@@ -22,7 +22,6 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.io.StringReader;
 import java.nio.channels.SeekableByteChannel;
 import java.nio.charset.StandardCharsets;
 import java.security.*;
@@ -607,7 +606,7 @@ Reader loadTDF(SeekableByteChannel tdf, Config.TDFReaderConfig tdfReaderConfig)
         TDFReader tdfReader = new TDFReader(tdf);
         String manifestJson = tdfReader.manifest();
         // use Manifest.readManifest in order to validate the Manifest input
-        Manifest manifest = Manifest.readManifest(new StringReader(manifestJson));
+        Manifest manifest = Manifest.readManifest(manifestJson);
         byte[] payloadKey = new byte[GCM_KEY_SIZE];
         String unencryptedMetadata = null;
 

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

@@ -1,10 +1,8 @@
 package io.opentdf.platform.sdk;
 
-import java.io.BufferedReader;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.InputStreamReader;
 import java.nio.channels.SeekableByteChannel;
 import java.nio.charset.StandardCharsets;
 import java.util.Map;
@@ -64,10 +62,8 @@ int readPayloadBytes(byte[] buf) {
     }
 
     PolicyObject readPolicyObject() {
-        try (var reader = new BufferedReader(new InputStreamReader(manifestEntry.getData()))){
-            return Manifest.readPolicyObject(reader);
-        } catch (IOException e) {
-            throw new SDKException("error reading policy object", e);
-        }
+        String manifestJson = manifest();
+        Manifest manifest = Manifest.readManifest(manifestJson);
+        return Manifest.decodePolicyObject(manifest);
     }
 }

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

@@ -4,8 +4,7 @@
 import org.junit.jupiter.api.Test;
 
 import java.io.IOException;
-import java.io.InputStreamReader;
-import java.io.StringReader;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Map;
 
@@ -62,7 +61,7 @@ void testManifestMarshalAndUnMarshal() {
                 "  }\n" +
                 "}";
 
-        Manifest manifest = Manifest.readManifest(new StringReader(kManifestJsonFromTDF));
+        Manifest manifest = Manifest.readManifest(kManifestJsonFromTDF);
 
         // Test payload
         assertEquals(manifest.payload.url, "0.payload");
@@ -85,7 +84,7 @@ void testManifestMarshalAndUnMarshal() {
         assertEquals(manifest.encryptionInformation.integrityInformation.segments.get(0).segmentSize, 1048576);
 
         var serialized = Manifest.toJson(manifest);
-        var deserializedAgain = Manifest.readManifest(new StringReader(serialized));
+        var deserializedAgain = Manifest.readManifest(serialized);
 
         assertEquals(manifest, deserializedAgain, "something changed when we deserialized -> serialized -> deserialized");
     }
@@ -140,7 +139,7 @@ void testAssertionNull() {
                 "   \"assertions\": null\n"+
                 "}";
 
-        Manifest manifest = Manifest.readManifest(new StringReader(kManifestJsonFromTDF));
+        Manifest manifest = Manifest.readManifest(kManifestJsonFromTDF);
 
         // Test payload for sanity check
         assertEquals(manifest.payload.url, "0.payload");
@@ -155,7 +154,8 @@ void testReadingManifestWithObjectStatementValue() throws IOException {
         final Manifest manifest;
         try (var mStream = getClass().getResourceAsStream("/io.opentdf.platform.sdk.TestData/manifest-with-object-statement-value.json")) {
             assert mStream != null;
-            manifest = Manifest.readManifest(new InputStreamReader(mStream)) ;
+            var manifestJson = new String(mStream.readAllBytes(), StandardCharsets.UTF_8);
+            manifest = Manifest.readManifest(manifestJson);
         }
 
         assertThat(manifest.assertions).hasSize(2);

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

@@ -77,6 +77,21 @@ public SeekableByteChannel truncate(long size) {
         assertThat(SDK.isTDF(chan)).isFalse();
     }
 
+    @Test
+    void testExaminingManifest() throws IOException {
+        try (var tdfStream = SDKTest.class.getClassLoader().getResourceAsStream("sample.txt.tdf")) {
+            assertThat(tdfStream)
+                    .withFailMessage("sample.txt.tdf not found in classpath")
+                    .isNotNull();
+            var manifest = SDK.readManifest(new SeekableInMemoryByteChannel(tdfStream.readAllBytes()));
+            assertThat(manifest).isNotNull();
+            assertThat(manifest.encryptionInformation.integrityInformation.encryptedSegmentSizeDefault)
+                    .isEqualTo(1048604);
+            var policyObject = SDK.decodePolicyObject(manifest);
+            assertThat(policyObject.uuid).isEqualTo("98bb8a81-5217-4a31-8852-932d29d71aac");
+        }
+    }
+
     @Test
     void testReadingRandomBytes() {
         var tdf = new byte[2023];