liteclient: Send TUF update event only if target list changes

Send the TUF update event only if a target list has changed. It helps to
avoid sending the event if TUF meta is updated while the target list
stays the same. It can happen if a customer updates target lists only
for certain subset of tags. It leads to updating TUF meta for all tags
while actual target list is updated only for the specified set of tag.

Signed-off-by: Mike Sul <mike.sul@foundries.io>

Author: mike-sul

src/liteclient.cc

@@ -448,6 +448,7 @@ void LiteClient::notifyTufUpdateStarted() {
     auto& d = tuf_update_details_[role.ToString()];
     d.from = version;
   });
+  targets_ = getTargetList(storage);
 }
 
 void LiteClient::notifyTufUpdateFinished(const std::string& err, const Uptane::Target& t) {
@@ -468,6 +469,15 @@ void LiteClient::notifyTufUpdateFinished(const std::string& err, const Uptane::T
     was_updated = d.from != d.to;
   });
 
+  if (was_updated && targets_ && targets_->isInitialized()) {
+    // If TUF meta was updated and the target list before the update is valid,
+    // then check if the target list was updated too.
+    const auto current_targets{getTargetList(storage)};
+    if (current_targets && current_targets->isInitialized()) {
+      was_updated = !Uptane::MatchTargetVector(current_targets->targets, targets_->targets);
+    }
+  }
+
   if (!err.empty() || was_updated) {
     // Compose the "details" string with info about metadata if there is an error or metadata was updated
     for (const auto& d : tuf_update_details_) {
@@ -956,3 +966,26 @@ void LiteClient::forEachRoleVersion(std::shared_ptr<const INvStorage> storage,
     func(role, ver);
   }
 }
+
+std::shared_ptr<Uptane::Targets> LiteClient::getTargetList(std::shared_ptr<const INvStorage> storage) {
+  std::shared_ptr<Uptane::Targets> targets;
+  std::string meta;
+  bool loaded;
+
+  loaded = storage->loadNonRoot(&meta, Uptane::RepositoryType::Image(), Uptane::Role::Targets());
+  if (!loaded) {
+    return targets;
+  }
+
+  const auto meta_json{Utils::parseJSON(meta)};
+  if (meta_json.empty() || !meta_json.isObject()) {
+    return targets;
+  }
+
+  try {
+    targets = std::make_shared<Uptane::Targets>(meta_json);
+  } catch (const std::exception& exc) {
+    LOG_DEBUG << "Failed to load targets meta: " << exc.what();
+  }
+  return targets;
+}

src/liteclient.h

@@ -124,6 +124,8 @@ class LiteClient {
   static void forEachRoleVersion(std::shared_ptr<const INvStorage> storage,
                                  const std::function<void(const Uptane::Role&, int)>& func);
 
+  static std::shared_ptr<Uptane::Targets> getTargetList(std::shared_ptr<const INvStorage> storage);
+
   boost::filesystem::path callback_program;
   std::unique_ptr<KeyManager> key_manager_;
   std::shared_ptr<PackageManagerInterface> package_manager_;
@@ -146,6 +148,7 @@ class LiteClient {
   Type type_{Type::Undefined};
 
   TufUpdateDetails tuf_update_details_;
+  std::shared_ptr<Uptane::Targets> targets_;
 };
 
 #endif  // AKTUALIZR_LITE_CLIENT_H_