message: [wpan-service] fix pskc buffer overflow
diff: @@ -94,7 +94,7 @@ std::string WpanService::HandleFormNetworkRequest(const std::string &aFormReques
  Json::Reader reader;
  std::string response;
  ot::Psk::Pskc psk;
  - char pskcStr[OT_PSKC_MAX_LENGTH * 2];
  + char pskcStr[OT_PSKC_MAX_LENGTH * 2 + 1];
  uint8_t extPanIdBytes[OT_EXTENDED_PANID_LENGTH];
  ot::Dbus::WPANController wpanController;
  std::string networkKey;
  @@ -107,6 +107,7 @@ std::string WpanService::HandleFormNetworkRequest(const std::string &aFormReques
  bool defaultRoute;
  int ret = ot::Dbus::kWpantundStatus_Ok;
  + pskcStr[OT_PSKC_MAX_LENGTH * 2] = '\0'; // for manipulating with strlen
  VerifyOrExit(reader.parse(aFormRequest.c_str(), root) == true, ret = kWpanStatus_ParseRequestFailed);
  networkKey = root["networkKey"].asString();
  prefix = root["prefix"].asString();
  