[impl] Check if the file from download cache really exists before returning it

[impl] Remove downloaded update file if checksum is invalid

src/CachedDownloader.cpp

@@ -66,10 +66,13 @@ boost::filesystem::path CachedDownloader::download(const std::string & url)
     auto it = m_cache.find(url);
     if (it != m_cache.end())
     {
-        return m_cacheDir / it->second;
+        auto cachedFilename = m_cacheDir / it->second;
-    }
+        if (boost::filesystem::exists(cachedFilename))
-    else
         {
+            return cachedFilename;
+        }
+    }
+
     auto fileName = boost::filesystem::unique_path();
     auto tmpFile = m_cacheDir / fileName;
     {
@@ -80,7 +83,6 @@ boost::filesystem::path CachedDownloader::download(const std::string & url)
     addToCache(m_cacheDir / cacheListFilename, url, fileName.string());
     return tmpFile;
 }
-}
 
 void CachedDownloader::clearCache()
 {

src/ModuleManager.cpp

@@ -27,6 +27,7 @@ void ModuleManager::applyUpdate(Module & module, const ModuleUpdate & update)
     auto hash = calcSHA256(updatePath);
     if (hash != boost::algorithm::to_upper_copy(update.checksum))
     {
+        fs::remove(updatePath);
         throw std::runtime_error("Integrity check of the update has failed");
     }