论文标题
在NTP的广播模式下防止时间同步
Preventing Time Synchronization in NTP's Broadcast Mode
论文作者
论文摘要
当今的Internet中有数百万主机使用网络时间协议（NTP）来同步其时钟。对于许多网络应用程序，时钟同步是必要的。非同步时钟可能会导致各种核心互联网服务的失败，包括DNS和基于RPKI的域间路由，并为更复杂的攻击打开了路径。在本文中，我们描述了一种新的攻击，该攻击可以防止以NTP的广播模式配置的客户端与服务器同步。我们测试了真实网络中的攻击，并表明它在NTP的身份验证和未经身份验证的广播/多播模式中都有效。我们还通过扫描整个IPv4地址空间来执行实验以测量整体攻击表面，并表明NTP广播模式在野外使用了几个低层（高度准确）的主机。我们还建议很少有对策来减轻拟议的攻击。
Network Time Protocol (NTP) is used by millions of hosts in Internet today to synchronize their clocks. Clock synchronization is necessary for many network applications to function correctly. Unsynchronized clock may lead to failure of various core Internet services including DNS and RPKI based interdomain routing and opens path for more sophisticated attacks. In this paper, we describe a new attack which can prevent a client configured in NTP's broadcast mode from synchronizing its clock with the server. We test the attack in real networks and show that it is effective in both authenticated and unauthenticated broadcast/multicast modes of NTP. We also perform experiments to measure the overall attack surface by scanning the entire IPv4 address space and show that NTP broadcast mode is being used in the wild by several low stratum (highly accurate) hosts. We also suggest few countermeasures to mitigate the proposed attack.
