Treat blank strings as null pre-keys

service/src/main/java/org/whispersystems/textsecuregcm/util/ECPublicKeyAdapter.java

@@ -42,6 +42,10 @@ public class ECPublicKeyAdapter {
         throw new JsonParseException(parser, "Could not parse EC public key as a base64-encoded value", e);
       }
 
+      if (ecPublicKeyBytes.length == 0) {
+        return null;
+      }
+
       try {
         return new ECPublicKey(ecPublicKeyBytes);
       } catch (final InvalidKeyException e) {

service/src/main/java/org/whispersystems/textsecuregcm/util/KEMPublicKeyAdapter.java

@@ -42,6 +42,10 @@ public class KEMPublicKeyAdapter {
         throw new JsonParseException(parser, "Could not parse KEM public key as a base64-encoded value", e);
       }
 
+      if (kemPublicKeyBytes.length == 0) {
+        return null;
+      }
+
       try {
         return new KEMPublicKey(kemPublicKeyBytes);
       } catch (final InvalidKeyException e) {

service/src/test/java/org/whispersystems/textsecuregcm/util/ECPublicKeyAdapterTest.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.util;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.signal.libsignal.protocol.ecc.Curve;
+import org.signal.libsignal.protocol.ecc.ECPublicKey;
+
+import javax.annotation.Nullable;
+import java.util.Base64;
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ECPublicKeyAdapterTest {
+
+  private static final ECPublicKey EC_PUBLIC_KEY = Curve.generateKeyPair().getPublicKey();
+
+  private record ECPublicKeyCarrier(@JsonSerialize(using = ECPublicKeyAdapter.Serializer.class)
+                                    @JsonDeserialize(using = ECPublicKeyAdapter.Deserializer.class)
+                                    ECPublicKey publicKey) {
+  }
+
+  @ParameterizedTest
+  @MethodSource
+  void deserialize(final String json, @Nullable final ECPublicKey expectedPublicKey) throws JsonProcessingException {
+    final ECPublicKeyCarrier publicKeyCarrier = SystemMapper.jsonMapper().readValue(json, ECPublicKeyCarrier.class);
+
+    assertEquals(expectedPublicKey, publicKeyCarrier.publicKey());
+  }
+
+  private static Stream<Arguments> deserialize() {
+    final String template = """
+        {
+          "publicKey": %s
+        }
+        """;
+
+    return Stream.of(
+        Arguments.of(String.format(template, "null"), null),
+        Arguments.of(String.format(template, "\"\""), null),
+        Arguments.of(String.format(template, "\"" + Base64.getEncoder().encodeToString(EC_PUBLIC_KEY.serialize()) + "\""), EC_PUBLIC_KEY)
+    );
+  }
+}

service/src/test/java/org/whispersystems/textsecuregcm/util/KEMPublicKeyAdapterTest.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2023 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.util;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.signal.libsignal.protocol.kem.KEMKeyPair;
+import org.signal.libsignal.protocol.kem.KEMKeyType;
+import org.signal.libsignal.protocol.kem.KEMPublicKey;
+import javax.annotation.Nullable;
+import java.util.Base64;
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class KEMPublicKeyAdapterTest {
+
+  private static final KEMPublicKey KEM_PUBLIC_KEY = KEMKeyPair.generate(KEMKeyType.KYBER_1024).getPublicKey();
+
+  private record KEMPublicKeyCarrier(@JsonSerialize(using = KEMPublicKeyAdapter.Serializer.class)
+                                    @JsonDeserialize(using = KEMPublicKeyAdapter.Deserializer.class)
+                                    KEMPublicKey publicKey) {
+  }
+
+  @ParameterizedTest
+  @MethodSource
+  void deserialize(final String json, @Nullable final KEMPublicKey expectedPublicKey) throws JsonProcessingException {
+    final KEMPublicKeyCarrier publicKeyCarrier = SystemMapper.jsonMapper().readValue(json, KEMPublicKeyAdapterTest.KEMPublicKeyCarrier.class);
+
+    assertEquals(expectedPublicKey, publicKeyCarrier.publicKey());
+  }
+
+  private static Stream<Arguments> deserialize() {
+    final String template = """
+        {
+          "publicKey": %s
+        }
+        """;
+
+    return Stream.of(
+        Arguments.of(String.format(template, "null"), null),
+        Arguments.of(String.format(template, "\"\""), null),
+        Arguments.of(String.format(template, "\"" + Base64.getEncoder().encodeToString(KEM_PUBLIC_KEY.serialize()) + "\""),
+            KEM_PUBLIC_KEY)
+    );
+  }
+}