Add support for handling unknown protobuf fields.

app/src/main/java/org/thoughtcrime/securesms/database/RecipientDatabase.java

@@ -120,6 +120,7 @@ public class RecipientDatabase extends Database {
   private static final String PROFILE_FAMILY_NAME      = "profile_family_name";
   private static final String PROFILE_JOINED_NAME      = "profile_joined_name";
   private static final String MENTION_SETTING          = "mention_setting";
+  private static final String STORAGE_PROTO            = "storage_proto";
 
   public  static final String SEARCH_PROFILE_NAME      = "search_signal_profile";
   private static final String SORT_NAME                = "sort_name";
@@ -150,7 +151,8 @@ public class RecipientDatabase extends Database {
   private static final String[] MENTION_SEARCH_PROJECTION  = new String[]{ID, removeWhitespace("COALESCE(" + nullIfEmpty(SYSTEM_DISPLAY_NAME) + ", " + nullIfEmpty(PROFILE_JOINED_NAME) + ", " + nullIfEmpty(PROFILE_GIVEN_NAME) + ", " + nullIfEmpty(USERNAME) + ", " + nullIfEmpty(PHONE) + ")") + " AS " + SORT_NAME};
 
   private static final String[] RECIPIENT_FULL_PROJECTION = ArrayUtils.concat(
-      new String[] { TABLE_NAME + "." + ID },
+      new String[] { TABLE_NAME + "." + ID,
+                     TABLE_NAME + "." + STORAGE_PROTO },
       TYPED_RECIPIENT_PROJECTION,
       new String[] {
         IdentityDatabase.TABLE_NAME + "." + IdentityDatabase.VERIFIED + " AS " + IDENTITY_STATUS,
@@ -336,7 +338,8 @@ public class RecipientDatabase extends Database {
                                             GROUPS_V2_CAPABILITY     + " INTEGER DEFAULT " + Recipient.Capability.UNKNOWN.serialize() + ", " +
                                             STORAGE_SERVICE_ID       + " TEXT UNIQUE DEFAULT NULL, " +
                                             DIRTY                    + " INTEGER DEFAULT " + DirtyState.CLEAN.getId() + ", " +
-                                            MENTION_SETTING          + " INTEGER DEFAULT " + MentionSetting.ALWAYS_NOTIFY.getId() + ");";
+                                            MENTION_SETTING          + " INTEGER DEFAULT " + MentionSetting.ALWAYS_NOTIFY.getId() +
+                                            STORAGE_PROTO            + " TEXT DEFAULT NULL);";
 
   private static final String INSIGHTS_INVITEE_LIST = "SELECT " + TABLE_NAME + "." + ID +
       " FROM " + TABLE_NAME +
@@ -907,6 +910,12 @@ public class RecipientDatabase extends Database {
     values.put(STORAGE_SERVICE_ID, Base64.encodeBytes(update.getId().getRaw()));
     values.put(DIRTY, DirtyState.CLEAN.getId());
 
+    if (update.hasUnknownFields()) {
+      values.put(STORAGE_PROTO, Base64.encodeBytes(update.serializeUnknownFields()));
+    } else {
+      values.putNull(STORAGE_PROTO);
+    }
+
     int updateCount = db.update(TABLE_NAME, values, STORAGE_SERVICE_ID + " = ?", new String[]{Base64.encodeBytes(storageId.getRaw())});
     if (updateCount < 1) {
       throw new AssertionError("Account update didn't match any rows!");
@@ -981,6 +990,12 @@ public class RecipientDatabase extends Database {
       values.put(COLOR, ContactColors.generateFor(profileName.toString()).serialize());
     }
 
+    if (contact.hasUnknownFields()) {
+      values.put(STORAGE_PROTO, Base64.encodeBytes(contact.serializeUnknownFields()));
+    } else {
+      values.putNull(STORAGE_PROTO);
+    }
+
     return values;
   }
 
@@ -992,6 +1007,13 @@ public class RecipientDatabase extends Database {
     values.put(BLOCKED, groupV1.isBlocked() ? "1" : "0");
     values.put(STORAGE_SERVICE_ID, Base64.encodeBytes(groupV1.getId().getRaw()));
     values.put(DIRTY, DirtyState.CLEAN.getId());
+
+    if (groupV1.hasUnknownFields()) {
+      values.put(STORAGE_PROTO, Base64.encodeBytes(groupV1.serializeUnknownFields()));
+    } else {
+      values.putNull(STORAGE_PROTO);
+    }
+
     return values;
   }
   
@@ -1003,6 +1025,13 @@ public class RecipientDatabase extends Database {
     values.put(BLOCKED, groupV2.isBlocked() ? "1" : "0");
     values.put(STORAGE_SERVICE_ID, Base64.encodeBytes(groupV2.getId().getRaw()));
     values.put(DIRTY, DirtyState.CLEAN.getId());
+
+    if (groupV2.hasUnknownFields()) {
+      values.put(STORAGE_PROTO, Base64.encodeBytes(groupV2.serializeUnknownFields()));
+    } else {
+      values.putNull(STORAGE_PROTO);
+    }
+
     return values;
   }
 
@@ -1113,6 +1142,7 @@ public class RecipientDatabase extends Database {
     int     groupsV2CapabilityValue    = CursorUtil.requireInt(cursor, GROUPS_V2_CAPABILITY);
     String  storageKeyRaw              = CursorUtil.requireString(cursor, STORAGE_SERVICE_ID);
     int     mentionSettingId           = CursorUtil.requireInt(cursor, MENTION_SETTING);
+    String  storageProtoRaw            = CursorUtil.getString(cursor, STORAGE_PROTO).orNull();
 
     Optional<String>  identityKeyRaw    = CursorUtil.getString(cursor, IDENTITY_KEY);
     Optional<Integer> identityStatusRaw = CursorUtil.getInt(cursor, IDENTITY_STATUS);
@@ -1159,8 +1189,9 @@ public class RecipientDatabase extends Database {
       }
     }
 
-    byte[] storageKey  = storageKeyRaw != null ? Base64.decodeOrThrow(storageKeyRaw) : null;
+    byte[] storageKey   = storageKeyRaw != null ? Base64.decodeOrThrow(storageKeyRaw) : null;
-    byte[] identityKey = identityKeyRaw.transform(Base64::decodeOrThrow).orNull();
+    byte[] identityKey  = identityKeyRaw.transform(Base64::decodeOrThrow).orNull();
+    byte[] storageProto = storageProtoRaw != null ? Base64.decodeOrThrow(storageProtoRaw) : null;
 
     IdentityDatabase.VerifiedStatus identityStatus = identityStatusRaw.transform(IdentityDatabase.VerifiedStatus::forState).or(IdentityDatabase.VerifiedStatus.DEFAULT);
 
@@ -1180,7 +1211,8 @@ public class RecipientDatabase extends Database {
                                  Recipient.Capability.deserialize(uuidCapabilityValue),
                                  Recipient.Capability.deserialize(groupsV2CapabilityValue),
                                  InsightsBannerTier.fromId(insightsBannerTier),
-                                 storageKey, identityKey, identityStatus, MentionSetting.fromId(mentionSettingId));
+                                 storageKey, identityKey, identityStatus, MentionSetting.fromId(mentionSettingId),
+                                 storageProto);
   }
 
   public BulkOperationsHandle beginBulkSystemContactUpdate() {
@@ -2512,6 +2544,7 @@ public class RecipientDatabase extends Database {
     private final byte[]                          identityKey;
     private final IdentityDatabase.VerifiedStatus identityStatus;
     private final MentionSetting                  mentionSetting;
+    private final byte[]                          storageProto;
 
     RecipientSettings(@NonNull RecipientId id,
                       @Nullable UUID uuid,
@@ -2551,7 +2584,8 @@ public class RecipientDatabase extends Database {
                       @Nullable byte[] storageId,
                       @Nullable byte[] identityKey,
                       @NonNull IdentityDatabase.VerifiedStatus identityStatus,
-                      @NonNull MentionSetting mentionSetting)
+                      @NonNull MentionSetting mentionSetting,
+                      @Nullable byte[] storageProto)
     {
       this.id                     = id;
       this.uuid                   = uuid;
@@ -2592,6 +2626,7 @@ public class RecipientDatabase extends Database {
       this.identityKey            = identityKey;
       this.identityStatus         = identityStatus;
       this.mentionSetting         = mentionSetting;
+      this.storageProto           = storageProto;
     }
 
     public RecipientId getId() {
@@ -2752,6 +2787,10 @@ public class RecipientDatabase extends Database {
     public @NonNull MentionSetting getMentionSetting() {
       return mentionSetting;
     }
+
+    public @Nullable byte[] getStorageProto() {
+      return storageProto;
+    }
   }
 
   public static class RecipientReader implements Closeable {

app/src/main/java/org/thoughtcrime/securesms/database/helpers/SQLCipherOpenHelper.java

@@ -143,8 +143,9 @@ public class SQLCipherOpenHelper extends SQLiteOpenHelper {
   private static final int MENTIONS                         = 68;
   private static final int PINNED_CONVERSATIONS             = 69;
   private static final int MENTION_GLOBAL_SETTING_MIGRATION = 70;
+  private static final int UNKNOWN_STORAGE_FIELDS           = 71;
 
-  private static final int    DATABASE_VERSION = 70;
+  private static final int    DATABASE_VERSION = 71;
   private static final String DATABASE_NAME    = "signal.db";
 
   private final Context        context;
@@ -1008,6 +1009,10 @@ public class SQLCipherOpenHelper extends SQLiteOpenHelper {
         db.update("recipient", updateNever, "mention_setting = 2", null);
       }
 
+      if (oldVersion < UNKNOWN_STORAGE_FIELDS) {
+        db.execSQL("ALTER TABLE recipient ADD COLUMN storage_proto TEXT DEFAULT NULL");
+      }
+
       db.setTransactionSuccessful();
     } finally {
       db.endTransaction();

app/src/main/java/org/thoughtcrime/securesms/storage/AccountConflictMerger.java

@@ -3,23 +3,15 @@ package org.thoughtcrime.securesms.storage;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
-import com.annimon.stream.Stream;
-
 import org.thoughtcrime.securesms.logging.Log;
 import org.whispersystems.libsignal.util.guava.Optional;
-import org.whispersystems.signalservice.api.push.SignalServiceAddress;
 import org.whispersystems.signalservice.api.storage.SignalAccountRecord;
-import org.whispersystems.signalservice.api.storage.SignalContactRecord;
-import org.whispersystems.signalservice.internal.storage.protos.ContactRecord.IdentityState;
 
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashSet;
-import java.util.List;
 import java.util.Objects;
 import java.util.Set;
-import java.util.UUID;
 
 class AccountConflictMerger implements StorageSyncHelper.ConflictMerger<SignalAccountRecord> {
 
@@ -63,6 +55,7 @@ class AccountConflictMerger implements StorageSyncHelper.ConflictMerger<SignalAc
       familyName = local.getFamilyName().or("");
     }
 
+    byte[]  unknownFields          = remote.serializeUnknownFields();
     String  avatarUrlPath          = remote.getAvatarUrlPath().or(local.getAvatarUrlPath()).or("");
     byte[]  profileKey             = remote.getProfileKey().or(local.getProfileKey()).orNull();
     boolean noteToSelfArchived     = remote.isNoteToSelfArchived();
@@ -70,8 +63,8 @@ class AccountConflictMerger implements StorageSyncHelper.ConflictMerger<SignalAc
     boolean typingIndicators       = remote.isTypingIndicatorsEnabled();
     boolean sealedSenderIndicators = remote.isSealedSenderIndicatorsEnabled();
     boolean linkPreviews           = remote.isLinkPreviewsEnabled();
-    boolean matchesRemote          = doParamsMatch(remote, givenName, familyName, avatarUrlPath, profileKey, noteToSelfArchived, readReceipts, typingIndicators, sealedSenderIndicators, linkPreviews);
+    boolean matchesRemote          = doParamsMatch(remote, unknownFields, givenName, familyName, avatarUrlPath, profileKey, noteToSelfArchived, readReceipts, typingIndicators, sealedSenderIndicators, linkPreviews);
-    boolean matchesLocal           = doParamsMatch(local, givenName, familyName, avatarUrlPath, profileKey, noteToSelfArchived, readReceipts, typingIndicators, sealedSenderIndicators, linkPreviews);
+    boolean matchesLocal           = doParamsMatch(local, unknownFields, givenName, familyName, avatarUrlPath, profileKey, noteToSelfArchived, readReceipts, typingIndicators, sealedSenderIndicators, linkPreviews);
 
     if (matchesRemote) {
       return remote;
@@ -79,6 +72,7 @@ class AccountConflictMerger implements StorageSyncHelper.ConflictMerger<SignalAc
       return local;
     } else {
       return new SignalAccountRecord.Builder(keyGenerator.generate())
+                                    .setUnknownFields(unknownFields)
                                     .setGivenName(givenName)
                                     .setFamilyName(familyName)
                                     .setAvatarUrlPath(avatarUrlPath)
@@ -93,6 +87,7 @@ class AccountConflictMerger implements StorageSyncHelper.ConflictMerger<SignalAc
   }
 
   private static boolean doParamsMatch(@NonNull SignalAccountRecord contact,
+                                       @Nullable byte[] unknownFields,
                                        @NonNull String givenName,
                                        @NonNull String familyName,
                                        @NonNull String avatarUrlPath,
@@ -103,7 +98,8 @@ class AccountConflictMerger implements StorageSyncHelper.ConflictMerger<SignalAc
                                        boolean sealedSenderIndicators,
                                        boolean linkPreviewsEnabled)
   {
-    return Objects.equals(contact.getGivenName().or(""), givenName)            &&
+    return Arrays.equals(contact.serializeUnknownFields(), unknownFields)      &&
+           Objects.equals(contact.getGivenName().or(""), givenName)            &&
            Objects.equals(contact.getFamilyName().or(""), familyName)          &&
            Objects.equals(contact.getAvatarUrlPath().or(""), avatarUrlPath)    &&
            Arrays.equals(contact.getProfileKey().orNull(), profileKey)         &&

app/src/main/java/org/thoughtcrime/securesms/storage/ContactConflictMerger.java

@@ -75,6 +75,7 @@ class ContactConflictMerger implements StorageSyncHelper.ConflictMerger<SignalCo
       familyName = local.getFamilyName().or("");
     }
 
+    byte[]               unknownFields  = remote.serializeUnknownFields();
     UUID                 uuid           = remote.getAddress().getUuid().or(local.getAddress().getUuid()).orNull();
     String               e164           = remote.getAddress().getNumber().or(local.getAddress().getNumber()).orNull();
     SignalServiceAddress address        = new SignalServiceAddress(uuid, e164);
@@ -85,8 +86,8 @@ class ContactConflictMerger implements StorageSyncHelper.ConflictMerger<SignalCo
     boolean              blocked        = remote.isBlocked();
     boolean              profileSharing = remote.isProfileSharingEnabled() || local.isProfileSharingEnabled();
     boolean              archived       = remote.isArchived();
-    boolean              matchesRemote  = doParamsMatch(remote, address, givenName, familyName, profileKey, username, identityState, identityKey, blocked, profileSharing, archived);
+    boolean              matchesRemote  = doParamsMatch(remote, unknownFields, address, givenName, familyName, profileKey, username, identityState, identityKey, blocked, profileSharing, archived);
-    boolean              matchesLocal   = doParamsMatch(local, address, givenName, familyName, profileKey, username, identityState, identityKey, blocked, profileSharing, archived);
+    boolean              matchesLocal   = doParamsMatch(local, unknownFields, address, givenName, familyName, profileKey, username, identityState, identityKey, blocked, profileSharing, archived);
 
     if (matchesRemote) {
       return remote;
@@ -94,6 +95,7 @@ class ContactConflictMerger implements StorageSyncHelper.ConflictMerger<SignalCo
       return local;
     } else {
       return new SignalContactRecord.Builder(keyGenerator.generate(), address)
+                                    .setUnknownFields(unknownFields)
                                     .setGivenName(givenName)
                                     .setFamilyName(familyName)
                                     .setProfileKey(profileKey)
@@ -107,6 +109,7 @@ class ContactConflictMerger implements StorageSyncHelper.ConflictMerger<SignalCo
   }
 
   private static boolean doParamsMatch(@NonNull SignalContactRecord contact,
+                                       @Nullable byte[] unknownFields,
                                        @NonNull SignalServiceAddress address,
                                        @NonNull String givenName,
                                        @NonNull String familyName,
@@ -118,15 +121,16 @@ class ContactConflictMerger implements StorageSyncHelper.ConflictMerger<SignalCo
                                        boolean profileSharing,
                                        boolean archived)
   {
-    return Objects.equals(contact.getAddress(), address)                 &&
+    return Arrays.equals(contact.serializeUnknownFields(), unknownFields) &&
-           Objects.equals(contact.getGivenName().or(""), givenName)      &&
+           Objects.equals(contact.getAddress(), address)                  &&
-           Objects.equals(contact.getFamilyName().or(""), familyName)    &&
+           Objects.equals(contact.getGivenName().or(""), givenName)       &&
-           Arrays.equals(contact.getProfileKey().orNull(), profileKey)   &&
+           Objects.equals(contact.getFamilyName().or(""), familyName)     &&
-           Objects.equals(contact.getUsername().or(""), username)        &&
+           Arrays.equals(contact.getProfileKey().orNull(), profileKey)    &&
-           Objects.equals(contact.getIdentityState(), identityState)     &&
+           Objects.equals(contact.getUsername().or(""), username)         &&
-           Arrays.equals(contact.getIdentityKey().orNull(), identityKey) &&
+           Objects.equals(contact.getIdentityState(), identityState)      &&
-           contact.isBlocked() == blocked                                &&
+           Arrays.equals(contact.getIdentityKey().orNull(), identityKey)  &&
-           contact.isProfileSharingEnabled() == profileSharing           &&
+           contact.isBlocked() == blocked                                 &&
+           contact.isProfileSharingEnabled() == profileSharing            &&
            contact.isArchived() == archived;
   }
 }

app/src/main/java/org/thoughtcrime/securesms/storage/GroupV1ConflictMerger.java

@@ -9,6 +9,7 @@ import org.thoughtcrime.securesms.groups.GroupId;
 import org.whispersystems.libsignal.util.guava.Optional;
 import org.whispersystems.signalservice.api.storage.SignalGroupV1Record;
 
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
@@ -33,12 +34,13 @@ class GroupV1ConflictMerger implements StorageSyncHelper.ConflictMerger<SignalGr
 
   @Override
   public @NonNull SignalGroupV1Record merge(@NonNull SignalGroupV1Record remote, @NonNull SignalGroupV1Record local, @NonNull StorageSyncHelper.KeyGenerator keyGenerator) {
+    byte[]  unknownFields  = remote.serializeUnknownFields();
     boolean blocked        = remote.isBlocked();
     boolean profileSharing = remote.isProfileSharingEnabled() || local.isProfileSharingEnabled();
     boolean archived       = remote.isArchived();
 
-    boolean matchesRemote = blocked == remote.isBlocked() && profileSharing == remote.isProfileSharingEnabled() && archived == remote.isArchived();
+    boolean matchesRemote = Arrays.equals(unknownFields, remote.serializeUnknownFields()) && blocked == remote.isBlocked() && profileSharing == remote.isProfileSharingEnabled() && archived == remote.isArchived();
-    boolean matchesLocal  = blocked == local.isBlocked()  && profileSharing == local.isProfileSharingEnabled()  && archived == local.isArchived();
+    boolean matchesLocal  = Arrays.equals(unknownFields, local.serializeUnknownFields())  && blocked == local.isBlocked()  && profileSharing == local.isProfileSharingEnabled()  && archived == local.isArchived();
 
     if (matchesRemote) {
       return remote;
@@ -46,6 +48,7 @@ class GroupV1ConflictMerger implements StorageSyncHelper.ConflictMerger<SignalGr
       return local;
     } else {
       return new SignalGroupV1Record.Builder(keyGenerator.generate(), remote.getGroupId())
+                                    .setUnknownFields(unknownFields)
                                     .setBlocked(blocked)
                                     .setProfileSharingEnabled(blocked)
                                     .build();

app/src/main/java/org/thoughtcrime/securesms/storage/GroupV2ConflictMerger.java

@@ -9,6 +9,7 @@ import org.signal.zkgroup.groups.GroupMasterKey;
 import org.whispersystems.libsignal.util.guava.Optional;
 import org.whispersystems.signalservice.api.storage.SignalGroupV2Record;
 
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
@@ -33,12 +34,13 @@ class GroupV2ConflictMerger implements StorageSyncHelper.ConflictMerger<SignalGr
 
   @Override
   public @NonNull SignalGroupV2Record merge(@NonNull SignalGroupV2Record remote, @NonNull SignalGroupV2Record local, @NonNull StorageSyncHelper.KeyGenerator keyGenerator) {
+    byte[]  unknownFields  = remote.serializeUnknownFields();
     boolean blocked        = remote.isBlocked();
     boolean profileSharing = remote.isProfileSharingEnabled() || local.isProfileSharingEnabled();
     boolean archived       = remote.isArchived();
 
-    boolean matchesRemote = blocked == remote.isBlocked() && profileSharing == remote.isProfileSharingEnabled() && archived == remote.isArchived();
+    boolean matchesRemote = Arrays.equals(unknownFields, remote.serializeUnknownFields()) && blocked == remote.isBlocked() && profileSharing == remote.isProfileSharingEnabled() && archived == remote.isArchived();
-    boolean matchesLocal  = blocked == local.isBlocked()  && profileSharing == local.isProfileSharingEnabled()  && archived == local.isArchived();
+    boolean matchesLocal  = Arrays.equals(unknownFields, local.serializeUnknownFields())  && blocked == local.isBlocked()  && profileSharing == local.isProfileSharingEnabled()  && archived == local.isArchived();
 
     if (matchesRemote) {
       return remote;
@@ -46,6 +48,7 @@ class GroupV2ConflictMerger implements StorageSyncHelper.ConflictMerger<SignalGr
       return local;
     } else {
       return new SignalGroupV2Record.Builder(keyGenerator.generate(), remote.getMasterKey())
+                                    .setUnknownFields(unknownFields)
                                     .setBlocked(blocked)
                                     .setProfileSharingEnabled(blocked)
                                     .build();

app/src/main/java/org/thoughtcrime/securesms/storage/StorageSyncHelper.java

@@ -385,7 +385,10 @@ public final class StorageSyncHelper {
   }
 
   public static SignalStorageRecord buildAccountRecord(@NonNull Context context, @NonNull Recipient self) {
+    RecipientSettings settings = DatabaseFactory.getRecipientDatabase(context).getRecipientSettingsForSync(self.getId());
+
     SignalAccountRecord account = new SignalAccountRecord.Builder(self.getStorageServiceId())
+                                                         .setUnknownFields(settings != null ? settings.getStorageProto() : null)
                                                          .setProfileKey(self.getProfileKey())
                                                          .setGivenName(self.getProfileName().getGivenName())
                                                          .setFamilyName(self.getProfileName().getFamilyName())

app/src/main/java/org/thoughtcrime/securesms/storage/StorageSyncModels.java

@@ -43,6 +43,7 @@ public final class StorageSyncModels {
     }
 
     return new SignalContactRecord.Builder(rawStorageId, new SignalServiceAddress(recipient.getUuid(), recipient.getE164()))
+                                  .setUnknownFields(recipient.getStorageProto())
                                   .setProfileKey(recipient.getProfileKey())
                                   .setGivenName(recipient.getProfileName().getGivenName())
                                   .setFamilyName(recipient.getProfileName().getFamilyName())
@@ -66,6 +67,7 @@ public final class StorageSyncModels {
     }
 
     return new SignalGroupV1Record.Builder(rawStorageId, groupId.getDecodedId())
+                                  .setUnknownFields(recipient.getStorageProto())
                                   .setBlocked(recipient.isBlocked())
                                   .setProfileSharingEnabled(recipient.isProfileSharing())
                                   .setArchived(archived.contains(recipient.getId()))
@@ -90,6 +92,7 @@ public final class StorageSyncModels {
     }
 
     return new SignalGroupV2Record.Builder(rawStorageId, groupMasterKey)
+                                  .setUnknownFields(recipient.getStorageProto())
                                   .setBlocked(recipient.isBlocked())
                                   .setProfileSharingEnabled(recipient.isProfileSharing())
                                   .setArchived(archived.contains(recipient.getId()))

libsignal/service/src/main/java/org/whispersystems/signalservice/api/storage/SignalAccountRecord.java

@@ -4,6 +4,7 @@ import com.google.protobuf.ByteString;
 
 import org.whispersystems.libsignal.util.guava.Optional;
 import org.whispersystems.signalservice.api.util.OptionalUtil;
+import org.whispersystems.signalservice.api.util.ProtoUtil;
 import org.whispersystems.signalservice.internal.storage.protos.AccountRecord;
 
 import java.util.Objects;
@@ -12,6 +13,7 @@ public final class SignalAccountRecord implements SignalRecord {
 
   private final StorageId     id;
   private final AccountRecord proto;
+  private final boolean       hasUnknownFields;
 
   private final Optional<String> givenName;
   private final Optional<String> familyName;
@@ -19,8 +21,9 @@ public final class SignalAccountRecord implements SignalRecord {
   private final Optional<byte[]> profileKey;
 
   public SignalAccountRecord(StorageId id, AccountRecord proto) {
-    this.id    = id;
+    this.id               = id;
-    this.proto = proto;
+    this.proto            = proto;
+    this.hasUnknownFields = ProtoUtil.hasUnknownFields(proto);
 
     this.givenName     = OptionalUtil.absentIfEmpty(proto.getGivenName());
     this.familyName    = OptionalUtil.absentIfEmpty(proto.getFamilyName());
@@ -33,6 +36,14 @@ public final class SignalAccountRecord implements SignalRecord {
     return id;
   }
 
+  public boolean hasUnknownFields() {
+    return hasUnknownFields;
+  }
+
+  public byte[] serializeUnknownFields() {
+    return hasUnknownFields ? proto.toByteArray() : null;
+  }
+
   public Optional<String> getGivenName() {
     return givenName;
   }
@@ -91,11 +102,18 @@ public final class SignalAccountRecord implements SignalRecord {
     private final StorageId             id;
     private final AccountRecord.Builder builder;
 
+    private byte[] unknownFields;
+
     public Builder(byte[] rawId) {
       this.id      = StorageId.forAccount(rawId);
       this.builder = AccountRecord.newBuilder();
     }
 
+    public Builder setUnknownFields(byte[] serializedUnknowns) {
+      this.unknownFields = serializedUnknowns;
+      return this;
+    }
+
     public Builder setGivenName(String givenName) {
       builder.setGivenName(givenName == null ? "" : givenName);
       return this;
@@ -142,7 +160,13 @@ public final class SignalAccountRecord implements SignalRecord {
     }
 
     public SignalAccountRecord build() {
-      return new SignalAccountRecord(id, builder.build());
+      AccountRecord proto = builder.build();
+
+      if (unknownFields != null) {
+        proto = ProtoUtil.combineWithUnknownFields(proto, unknownFields);
+      }
+
+      return new SignalAccountRecord(id, proto);
     }
   }
 }

libsignal/service/src/main/java/org/whispersystems/signalservice/api/storage/SignalContactRecord.java

@@ -5,6 +5,7 @@ import com.google.protobuf.ByteString;
 import org.whispersystems.libsignal.util.guava.Optional;
 import org.whispersystems.signalservice.api.push.SignalServiceAddress;
 import org.whispersystems.signalservice.api.util.OptionalUtil;
+import org.whispersystems.signalservice.api.util.ProtoUtil;
 import org.whispersystems.signalservice.api.util.UuidUtil;
 import org.whispersystems.signalservice.internal.storage.protos.ContactRecord;
 import org.whispersystems.signalservice.internal.storage.protos.ContactRecord.IdentityState;
@@ -15,6 +16,7 @@ public final class SignalContactRecord implements SignalRecord {
 
   private final StorageId     id;
   private final ContactRecord proto;
+  private final boolean       hasUnknownFields;
 
   private final SignalServiceAddress address;
   private final Optional<String>     givenName;
@@ -24,8 +26,9 @@ public final class SignalContactRecord implements SignalRecord {
   private final Optional<byte[]>     identityKey;
 
   public SignalContactRecord(StorageId id, ContactRecord proto) {
-    this.id    = id;
+    this.id               = id;
-    this.proto = proto;
+    this.proto            = proto;
+    this.hasUnknownFields = ProtoUtil.hasUnknownFields(proto);
 
     this.address     = new SignalServiceAddress(UuidUtil.parseOrNull(proto.getServiceUuid()), proto.getServiceE164());
     this.givenName   = OptionalUtil.absentIfEmpty(proto.getGivenName());
@@ -40,6 +43,14 @@ public final class SignalContactRecord implements SignalRecord {
     return id;
   }
 
+  public boolean hasUnknownFields() {
+    return hasUnknownFields;
+  }
+
+  public byte[] serializeUnknownFields() {
+    return hasUnknownFields ? proto.toByteArray() : null;
+  }
+
   public SignalServiceAddress getAddress() {
     return address;
   }
@@ -102,6 +113,8 @@ public final class SignalContactRecord implements SignalRecord {
     private final StorageId             id;
     private final ContactRecord.Builder builder;
 
+    private byte[] unknownFields;
+
     public Builder(byte[] rawId, SignalServiceAddress address) {
       this.id      = StorageId.forContact(rawId);
       this.builder = ContactRecord.newBuilder();
@@ -110,6 +123,11 @@ public final class SignalContactRecord implements SignalRecord {
       builder.setServiceE164(address.getNumber().or(""));
     }
 
+    public Builder setUnknownFields(byte[] serializedUnknowns) {
+      this.unknownFields = serializedUnknowns;
+      return this;
+    }
+
     public Builder setGivenName(String givenName) {
       builder.setGivenName(givenName == null ? "" : givenName);
       return this;
@@ -156,7 +174,13 @@ public final class SignalContactRecord implements SignalRecord {
     }
 
     public SignalContactRecord build() {
-      return new SignalContactRecord(id, builder.build());
+      ContactRecord proto = builder.build();
+
+      if (unknownFields != null) {
+        proto = ProtoUtil.combineWithUnknownFields(proto, unknownFields);
+      }
+
+      return new SignalContactRecord(id, proto);
     }
   }
 }

libsignal/service/src/main/java/org/whispersystems/signalservice/api/storage/SignalGroupV1Record.java

@@ -2,6 +2,7 @@ package org.whispersystems.signalservice.api.storage;
 
 import com.google.protobuf.ByteString;
 
+import org.whispersystems.signalservice.api.util.ProtoUtil;
 import org.whispersystems.signalservice.internal.storage.protos.GroupV1Record;
 
 import java.util.Objects;
@@ -11,11 +12,13 @@ public final class SignalGroupV1Record implements SignalRecord {
   private final StorageId     id;
   private final GroupV1Record proto;
   private final byte[]        groupId;
+  private final boolean       hasUnknownFields;
 
   public SignalGroupV1Record(StorageId id, GroupV1Record proto) {
-    this.id      = id;
+    this.id               = id;
-    this.proto   = proto;
+    this.proto            = proto;
-    this.groupId = proto.getId().toByteArray();
+    this.groupId          = proto.getId().toByteArray();
+    this.hasUnknownFields = ProtoUtil.hasUnknownFields(proto);
   }
 
   @Override
@@ -23,6 +26,14 @@ public final class SignalGroupV1Record implements SignalRecord {
     return id;
   }
 
+  public boolean hasUnknownFields() {
+    return hasUnknownFields;
+  }
+
+  public byte[] serializeUnknownFields() {
+    return hasUnknownFields ? proto.toByteArray() : null;
+  }
+
   public byte[] getGroupId() {
     return groupId;
   }
@@ -61,6 +72,8 @@ public final class SignalGroupV1Record implements SignalRecord {
     private final StorageId             id;
     private final GroupV1Record.Builder builder;
 
+    private byte[] unknownFields;
+
     public Builder(byte[] rawId, byte[] groupId) {
       this.id      = StorageId.forGroupV1(rawId);
       this.builder = GroupV1Record.newBuilder();
@@ -68,6 +81,11 @@ public final class SignalGroupV1Record implements SignalRecord {
       builder.setId(ByteString.copyFrom(groupId));
     }
 
+    public Builder setUnknownFields(byte[] serializedUnknowns) {
+      this.unknownFields = serializedUnknowns;
+      return this;
+    }
+
     public Builder setBlocked(boolean blocked) {
       builder.setBlocked(blocked);
       return this;
@@ -84,7 +102,13 @@ public final class SignalGroupV1Record implements SignalRecord {
     }
 
     public SignalGroupV1Record build() {
-      return new SignalGroupV1Record(id, builder.build());
+      GroupV1Record proto = builder.build();
+
+      if (unknownFields != null) {
+        proto = ProtoUtil.combineWithUnknownFields(proto, unknownFields);
+      }
+
+      return new SignalGroupV1Record(id, proto);
     }
   }
 }

libsignal/service/src/main/java/org/whispersystems/signalservice/api/storage/SignalGroupV2Record.java

@@ -4,7 +4,7 @@ import com.google.protobuf.ByteString;
 
 import org.signal.zkgroup.InvalidInputException;
 import org.signal.zkgroup.groups.GroupMasterKey;
-import org.whispersystems.signalservice.internal.storage.protos.GroupV1Record;
+import org.whispersystems.signalservice.api.util.ProtoUtil;
 import org.whispersystems.signalservice.internal.storage.protos.GroupV2Record;
 
 import java.util.Objects;
@@ -14,10 +14,12 @@ public final class SignalGroupV2Record implements SignalRecord {
   private final StorageId      id;
   private final GroupV2Record  proto;
   private final GroupMasterKey masterKey;
+  private final boolean        hasUnknownFields;
 
   public SignalGroupV2Record(StorageId id, GroupV2Record proto) {
-    this.id        = id;
+    this.id               = id;
-    this.proto     = proto;
+    this.proto            = proto;
+    this.hasUnknownFields = ProtoUtil.hasUnknownFields(proto);
     try {
       this.masterKey = new GroupMasterKey(proto.getMasterKey().toByteArray());
     } catch (InvalidInputException e) {
@@ -30,6 +32,14 @@ public final class SignalGroupV2Record implements SignalRecord {
     return id;
   }
 
+  public boolean hasUnknownFields() {
+    return hasUnknownFields;
+  }
+
+  public byte[] serializeUnknownFields() {
+    return hasUnknownFields ? proto.toByteArray() : null;
+  }
+
   public GroupMasterKey getMasterKey() {
     return masterKey;
   }
@@ -68,6 +78,8 @@ public final class SignalGroupV2Record implements SignalRecord {
     private final StorageId             id;
     private final GroupV2Record.Builder builder;
 
+    private byte[] unknownFields;
+
     public Builder(byte[] rawId, GroupMasterKey masterKey) {
       this.id      = StorageId.forGroupV2(rawId);
       this.builder = GroupV2Record.newBuilder();
@@ -75,6 +87,11 @@ public final class SignalGroupV2Record implements SignalRecord {
       builder.setMasterKey(ByteString.copyFrom(masterKey.serialize()));
     }
 
+    public Builder setUnknownFields(byte[] serializedUnknowns) {
+      this.unknownFields = serializedUnknowns;
+      return this;
+    }
+
     public Builder setBlocked(boolean blocked) {
       builder.setBlocked(blocked);
       return this;
@@ -91,7 +108,13 @@ public final class SignalGroupV2Record implements SignalRecord {
     }
 
     public SignalGroupV2Record build() {
-      return new SignalGroupV2Record(id, builder.build());
+      GroupV2Record proto = builder.build();
+
+      if (unknownFields != null) {
+        proto = ProtoUtil.combineWithUnknownFields(proto, unknownFields);
+      }
+
+      return new SignalGroupV2Record(id, proto);
     }
   }
 }

libsignal/service/src/main/java/org/whispersystems/signalservice/api/util/ProtoUtil.java

@@ -0,0 +1,134 @@
+package org.whispersystems.signalservice.api.util;
+
+import com.google.protobuf.CodedOutputStream;
+import com.google.protobuf.GeneratedMessageLite;
+import com.google.protobuf.InvalidProtocolBufferException;
+import com.google.protobuf.UnknownFieldSetLite;
+
+import org.whispersystems.libsignal.logging.Log;
+import org.whispersystems.libsignal.util.ByteUtil;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.util.LinkedList;
+import java.util.List;
+
+public final class ProtoUtil {
+
+  private static final String TAG = ProtoUtil.class.getSimpleName();
+
+  private static final String DEFAULT_INSTANCE = "DEFAULT_INSTANCE";
+
+  private ProtoUtil() { }
+
+  /**
+   * True if there are unknown fields anywhere inside the proto or its nested protos.
+   */
+  @SuppressWarnings("rawtypes")
+  public static boolean hasUnknownFields(GeneratedMessageLite rootProto) {
+    try {
+      List<GeneratedMessageLite> allProtos = getInnerProtos(rootProto);
+      allProtos.add(rootProto);
+
+      for (GeneratedMessageLite proto : allProtos) {
+        Field field = GeneratedMessageLite.class.getDeclaredField("unknownFields");
+        field.setAccessible(true);
+
+        UnknownFieldSetLite unknownFields = (UnknownFieldSetLite) field.get(proto);
+
+        if (unknownFields != null && unknownFields.getSerializedSize() > 0) {
+          return true;
+        }
+      }
+    } catch (NoSuchFieldException | IllegalAccessException e) {
+      Log.w(TAG, "Failed to read proto private fields! Assuming no unknown fields.");
+    }
+
+    return false;
+  }
+
+  /**
+   * This takes two arguments: A proto model, and the bytes of another proto model of the same type.
+   * This will take the proto model and append onto it any unknown fields from the serialized proto
+   * model. Why is this useful? Well, if you do {@code myProto.parseFrom(data).toBuilder().build()},
+   * you will lose any unknown fields that were in {@code data}. This lets you create a new model
+   * and plop the unknown fields back on from some other instance.
+   *
+   * A notable limitation of the current implementation is, however, that it does not support adding
+   * back unknown fields to *inner* messages. Unknown fields on inner messages will simply not be
+   * acknowledged.
+   */
+  @SuppressWarnings({"rawtypes", "unchecked"})
+  public static <Proto extends GeneratedMessageLite> Proto combineWithUnknownFields(Proto proto, byte[] serializedWithUnknownFields) {
+    if (serializedWithUnknownFields == null) {
+      return proto;
+    }
+
+    try {
+      Proto  protoWithUnknownFields = (Proto) proto.getParserForType().parseFrom(serializedWithUnknownFields);
+      byte[] unknownFields          = getUnknownFields(protoWithUnknownFields);
+
+      if (unknownFields == null) {
+        return proto;
+      }
+
+      byte[] combined = ByteUtil.combine(proto.toByteArray(), unknownFields);
+
+      return (Proto) proto.getParserForType().parseFrom(combined);
+    } catch (InvalidProtocolBufferException e) {
+      throw new IllegalArgumentException();
+    }
+  }
+
+  @SuppressWarnings("rawtypes")
+  private static byte[] getUnknownFields(GeneratedMessageLite proto) {
+    try {
+      Field field = GeneratedMessageLite.class.getDeclaredField("unknownFields");
+      field.setAccessible(true);
+      UnknownFieldSetLite unknownFields = (UnknownFieldSetLite) field.get(proto);
+
+      if (unknownFields == null || unknownFields.getSerializedSize() == 0) {
+        return null;
+      }
+
+      ByteArrayOutputStream byteStream   = new ByteArrayOutputStream();
+      CodedOutputStream     outputStream = CodedOutputStream.newInstance(byteStream);
+
+      unknownFields.writeTo(outputStream);
+      outputStream.flush();
+
+      return byteStream.toByteArray();
+    } catch (NoSuchFieldException | IllegalAccessException | IOException e) {
+      Log.w(TAG, "Failed to retrieve unknown fields.", e);
+      return null;
+    }
+  }
+
+  /**
+   * Recursively retrieves all inner complex proto types inside a given proto.
+   */
+  @SuppressWarnings("rawtypes")
+  private static List<GeneratedMessageLite> getInnerProtos(GeneratedMessageLite proto) {
+    List<GeneratedMessageLite> innerProtos = new LinkedList<>();
+
+    try {
+      Field[] fields = proto.getClass().getDeclaredFields();
+
+      for (Field field : fields) {
+        if (!field.getName().equals(DEFAULT_INSTANCE) && GeneratedMessageLite.class.isAssignableFrom(field.getType())) {
+          field.setAccessible(true);
+
+          GeneratedMessageLite inner = (GeneratedMessageLite) field.get(proto);
+          innerProtos.add(inner);
+          innerProtos.addAll(getInnerProtos(inner));
+        }
+      }
+
+    } catch (IllegalAccessException e) {
+      Log.w(TAG, "Failed to get inner protos!", e);
+    }
+
+    return innerProtos;
+  }
+}

libsignal/service/src/test/java/org/whispersystems/signalservice/api/util/ProtoUtilTest.java

@@ -0,0 +1,229 @@
+package org.whispersystems.signalservice.api.util;
+
+import com.google.protobuf.InvalidProtocolBufferException;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.thoughtcrime.securesms.util.testprotos.TestInnerMessage;
+import org.thoughtcrime.securesms.util.testprotos.TestInnerMessageWithNewString;
+import org.thoughtcrime.securesms.util.testprotos.TestPerson;
+import org.thoughtcrime.securesms.util.testprotos.TestPersonWithNewFieldOnMessage;
+import org.thoughtcrime.securesms.util.testprotos.TestPersonWithNewMessage;
+import org.thoughtcrime.securesms.util.testprotos.TestPersonWithNewRepeatedString;
+import org.thoughtcrime.securesms.util.testprotos.TestPersonWithNewString;
+import org.thoughtcrime.securesms.util.testprotos.TestPersonWithNewStringAndInt;
+import org.whispersystems.signalservice.api.util.ProtoUtil;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+public class ProtoUtilTest {
+
+  @Test
+  public void hasUnknownFields_noUnknowns() {
+    TestPerson person = TestPerson.newBuilder()
+                                  .setName("Peter Parker")
+                                  .setAge(23)
+                                  .build();
+
+    assertFalse(ProtoUtil.hasUnknownFields(person));
+  }
+
+  @Test
+  public void hasUnknownFields_unknownString() throws InvalidProtocolBufferException {
+    TestPersonWithNewString person = TestPersonWithNewString.newBuilder()
+                                                            .setName("Peter Parker")
+                                                            .setAge(23)
+                                                            .setJob("Reporter")
+                                                            .build();
+
+    TestPerson personWithUnknowns = TestPerson.parseFrom(person.toByteArray());
+
+    assertTrue(ProtoUtil.hasUnknownFields(personWithUnknowns));
+  }
+
+  @Test
+  public void hasUnknownFields_multipleUnknowns() throws InvalidProtocolBufferException {
+    TestPersonWithNewStringAndInt person = TestPersonWithNewStringAndInt.newBuilder()
+                                                                        .setName("Peter Parker")
+                                                                        .setAge(23)
+                                                                        .setJob("Reporter")
+                                                                        .setSalary(75_000)
+                                                                        .build();
+
+    TestPerson personWithUnknowns = TestPerson.parseFrom(person.toByteArray());
+
+    assertTrue(ProtoUtil.hasUnknownFields(personWithUnknowns));
+  }
+
+  @Test
+  public void hasUnknownFields_unknownMessage() throws InvalidProtocolBufferException {
+    TestPersonWithNewMessage person = TestPersonWithNewMessage.newBuilder()
+                                                              .setName("Peter Parker")
+                                                              .setAge(23)
+                                                              .setJob(TestPersonWithNewMessage.Job.newBuilder()
+                                                                                                  .setTitle("Reporter")
+                                                                                                  .setSalary(75_000))
+                                                              .build();
+
+    TestPerson personWithUnknowns = TestPerson.parseFrom(person.toByteArray());
+
+    assertTrue(ProtoUtil.hasUnknownFields(personWithUnknowns));
+  }
+
+  @Test
+  public void hasUnknownFields_unknownInsideMessage() throws InvalidProtocolBufferException {
+    TestPersonWithNewFieldOnMessage person = TestPersonWithNewFieldOnMessage.newBuilder()
+                                                                            .setName("Peter Parker")
+                                                                            .setAge(23)
+                                                                            .setJob(TestPersonWithNewFieldOnMessage.Job.newBuilder()
+                                                                                                                       .setTitle("Reporter")
+                                                                                                                       .setSalary(75_000)
+                                                                                                                       .setStartDate(100))
+                                                                            .build();
+
+    TestPersonWithNewMessage personWithUnknowns = TestPersonWithNewMessage.parseFrom(person.toByteArray());
+
+    assertTrue(ProtoUtil.hasUnknownFields(personWithUnknowns));
+  }
+
+  @Test
+  public void combineWithUnknownFields_noUnknowns() throws InvalidProtocolBufferException {
+    TestPerson personWithUnknowns = TestPerson.newBuilder()
+                                              .setName("Peter Parker")
+                                              .setAge(23)
+                                              .build();
+
+    TestPerson localRepresentation = TestPerson.newBuilder()
+                                               .setName("Spider-Man")
+                                               .setAge(23)
+                                               .build();
+
+    TestPerson              combinedWithUnknowns = ProtoUtil.combineWithUnknownFields(localRepresentation, personWithUnknowns.toByteArray());
+    TestPersonWithNewString reparsedPerson       = TestPersonWithNewString.parseFrom(combinedWithUnknowns.toByteArray());
+
+    Assert.assertEquals("Spider-Man", reparsedPerson.getName());
+    Assert.assertEquals(23, reparsedPerson.getAge());
+  }
+
+  @Test
+  public void combineWithUnknownFields_appendedString() throws InvalidProtocolBufferException {
+    TestPersonWithNewString personWithUnknowns = TestPersonWithNewString.newBuilder()
+                                                            .setName("Peter Parker")
+                                                            .setAge(23)
+                                                            .setJob("Reporter")
+                                                            .build();
+
+    TestPerson localRepresentation = TestPerson.newBuilder()
+                                               .setName("Spider-Man")
+                                               .setAge(23)
+                                               .build();
+
+    TestPerson              combinedWithUnknowns = ProtoUtil.combineWithUnknownFields(localRepresentation, personWithUnknowns.toByteArray());
+    TestPersonWithNewString reparsedPerson       = TestPersonWithNewString.parseFrom(combinedWithUnknowns.toByteArray());
+
+    Assert.assertEquals("Spider-Man", reparsedPerson.getName());
+    Assert.assertEquals(23, reparsedPerson.getAge());
+    Assert.assertEquals("Reporter", reparsedPerson.getJob());
+  }
+
+  @Test
+  public void combineWithUnknownFields_appendedRepeatedString() throws InvalidProtocolBufferException {
+    TestPersonWithNewRepeatedString personWithUnknowns = TestPersonWithNewRepeatedString.newBuilder()
+                                                                                        .setName("Peter Parker")
+                                                                                        .setAge(23)
+                                                                                        .addJobs("Reporter")
+                                                                                        .addJobs("Super Hero")
+                                                                                        .build();
+
+    TestPerson localRepresentation = TestPerson.newBuilder()
+                                               .setName("Spider-Man")
+                                               .setAge(23)
+                                               .build();
+
+    TestPerson                      combinedWithUnknowns = ProtoUtil.combineWithUnknownFields(localRepresentation, personWithUnknowns.toByteArray());
+    TestPersonWithNewRepeatedString reparsedPerson       = TestPersonWithNewRepeatedString.parseFrom(combinedWithUnknowns.toByteArray());
+
+    Assert.assertEquals("Spider-Man", reparsedPerson.getName());
+    Assert.assertEquals(23, reparsedPerson.getAge());
+    Assert.assertEquals(2, reparsedPerson.getJobsCount());
+    Assert.assertEquals("Reporter", reparsedPerson.getJobs(0));
+    Assert.assertEquals("Super Hero", reparsedPerson.getJobs(1));
+  }
+
+  @Test
+  public void combineWithUnknownFields_appendedStringAndInt() throws InvalidProtocolBufferException {
+    TestPersonWithNewStringAndInt personWithUnknowns = TestPersonWithNewStringAndInt.newBuilder()
+                                                                                    .setName("Peter Parker")
+                                                                                    .setAge(23)
+                                                                                    .setJob("Reporter")
+                                                                                    .setSalary(75_000)
+                                                                                    .build();
+
+    TestPerson localRepresentation = TestPerson.newBuilder()
+                                               .setName("Spider-Man")
+                                               .setAge(23)
+                                               .build();
+
+    TestPerson                    combinedWithUnknowns = ProtoUtil.combineWithUnknownFields(localRepresentation, personWithUnknowns.toByteArray());
+    TestPersonWithNewStringAndInt reparsedPerson       = TestPersonWithNewStringAndInt.parseFrom(combinedWithUnknowns.toByteArray());
+
+    Assert.assertEquals("Spider-Man", reparsedPerson.getName());
+    Assert.assertEquals(23, reparsedPerson.getAge());
+    Assert.assertEquals("Reporter", reparsedPerson.getJob());
+    Assert.assertEquals(75_000, reparsedPerson.getSalary());
+  }
+
+  @Test
+  public void combineWithUnknownFields_appendedMessage() throws InvalidProtocolBufferException {
+    TestPersonWithNewMessage personWithUnknowns = TestPersonWithNewMessage.newBuilder()
+                                                                          .setName("Peter Parker")
+                                                                          .setAge(23)
+                                                                          .setJob(TestPersonWithNewMessage.Job.newBuilder()
+                                                                                                              .setTitle("Reporter")
+                                                                                                              .setSalary(75_000))
+                                                                          .build();
+
+    TestPerson localRepresentation = TestPerson.newBuilder()
+                                               .setName("Spider-Man")
+                                               .setAge(23)
+                                               .build();
+
+    TestPerson               combinedWithUnknowns = ProtoUtil.combineWithUnknownFields(localRepresentation, personWithUnknowns.toByteArray());
+    TestPersonWithNewMessage reparsedPerson       = TestPersonWithNewMessage.parseFrom(combinedWithUnknowns.toByteArray());
+
+    Assert.assertEquals("Spider-Man", reparsedPerson.getName());
+    Assert.assertEquals(23, reparsedPerson.getAge());
+    Assert.assertEquals("Reporter", reparsedPerson.getJob().getTitle());
+    Assert.assertEquals(75_000, reparsedPerson.getJob().getSalary());
+  }
+
+  /**
+   * This isn't ideal behavior. This is more to show how something works. In the future, it'd be
+   * nice to support inner unknown fields.
+   */
+  @Test
+  public void combineWithUnknownFields_innerMessagesUnknownsIgnored() throws InvalidProtocolBufferException {
+    TestInnerMessageWithNewString test = TestInnerMessageWithNewString.newBuilder()
+                                                                      .setInner(TestInnerMessageWithNewString.Inner.newBuilder()
+                                                                                                                   .setA("a1")
+                                                                                                                   .setB("b1")
+                                                                                                                   .build())
+                                                                      .build();
+
+    TestInnerMessage localRepresentation = TestInnerMessage.newBuilder()
+                                                           .setInner(TestInnerMessage.Inner.newBuilder()
+                                                                                           .setA("a2")
+                                                                                           .build())
+                                                           .build();
+
+    TestInnerMessage              combined     = ProtoUtil.combineWithUnknownFields(localRepresentation, test.toByteArray());
+    TestInnerMessageWithNewString reparsedTest = TestInnerMessageWithNewString.parseFrom(combined.toByteArray());
+
+    Assert.assertEquals("a2", reparsedTest.getInner().getA());
+    Assert.assertEquals("", reparsedTest.getInner().getB());
+  }
+}

libsignal/service/src/test/proto/Test.proto

@@ -0,0 +1,70 @@
+syntax = "proto3";
+
+package signal;
+
+option java_package        = "org.thoughtcrime.securesms.util.testprotos";
+option java_multiple_files = true;
+
+message TestPerson {
+    string name = 1;
+    int32  age  = 2;
+}
+
+message TestPersonWithNewString {
+    string name = 1;
+    int32  age  = 2;
+    string job  = 3;
+}
+
+message TestPersonWithNewRepeatedString {
+             string name = 1;
+             int32  age  = 2;
+    repeated string jobs = 3;
+}
+
+message TestPersonWithNewStringAndInt {
+    string name   = 1;
+    int32  age    = 2;
+    string job    = 3;
+    int32  salary = 4;
+}
+
+message TestPersonWithNewMessage {
+    message Job {
+        string title  = 1;
+        uint32 salary = 2;
+    }
+
+    string name = 1;
+    int32  age  = 2;
+    Job    job  = 3;
+}
+
+message TestPersonWithNewFieldOnMessage {
+    message Job {
+        string title     = 1;
+        uint32 salary    = 2;
+        uint64 startDate = 3;
+    }
+
+    string name = 1;
+    int32  age  = 2;
+    Job    job  = 3;
+}
+
+message TestInnerMessage {
+    message Inner {
+        string a = 1;
+    }
+
+    Inner inner = 1;
+}
+
+message TestInnerMessageWithNewString {
+    message Inner {
+        string a = 1;
+        string b = 2;
+    }
+
+    Inner inner = 1;
+}