Apply default umask in SetupEnvironment()

This change makes all filesystem artifacts--files and directories--being
created with the default umask.

src/i2p.cpp

@@ -336,7 +336,7 @@ void Session::GenerateAndSavePrivateKey(const Sock& sock)
 {
     DestGenerate(sock);
 
-    // umask is set to 077 in init.cpp, which is ok.
+    // umask is set to 0077 in util/system.cpp, which is ok.
     if (!WriteBinaryFile(m_private_key_file,
                          std::string(m_private_key.begin(), m_private_key.end()))) {
         throw std::runtime_error(

src/init.cpp

@@ -816,8 +816,6 @@ bool AppInitBasicSetup(const ArgsManager& args)
     }
 
 #ifndef WIN32
-    umask(077);
-
     // Clean shutdown on SIGTERM
     registerSignalHandler(SIGTERM, HandleSIGTERM);
     registerSignalHandler(SIGINT, HandleSIGTERM);

src/rpc/request.cpp

@@ -86,7 +86,7 @@ bool GenerateAuthCookie(std::string *cookie_out)
     std::string cookie = COOKIEAUTH_USER + ":" + HexStr(rand_pwd);
 
     /** the umask determines what permissions are used to create this file -
-     * these are set to 077 in init.cpp.
+     * these are set to 0077 in util/system.cpp.
      */
     std::ofstream file;
     fs::path filepath_tmp = GetAuthCookieFile(true);

src/util/system.cpp

@@ -1360,6 +1360,11 @@ void SetupEnvironment()
     SetConsoleCP(CP_UTF8);
     SetConsoleOutputCP(CP_UTF8);
 #endif
+
+#ifndef WIN32
+    constexpr mode_t private_umask = 0077;
+    umask(private_umask);
+#endif
 }
 
 bool SetupNetworking()