Cryptology ePrint Archive: Report 2016/1006

The Security of NTP’s Datagram Protocol

Aanchal Malhotra and Matthew Van Gundy and Mayank Varia and Haydn Kennedy and Jonathan Gardner and Sharon Goldberg

Abstract: For decades, the Network Time Protocol (NTP) has been used to synchronize computer clocks over untrusted network paths. This work takes a new look at the security of NTP's datagram protocol. We argue that NTP's datagram protocol in RFC5905 is both underspecified and flawed. The NTP specifications do not sufficiently respect (1) the conflicting security requirements of different NTP modes, and (2) the mechanism NTP uses to prevent off-path attacks. A further problem is that (3) NTP's control-query interface reveals sensitive information that can be exploited in off-path attacks. We exploit these problems in several attacks that remote attackers can use to maliciously alter a target's time. We use network scans to find millions of IPs that are vulnerable to our attacks. Finally, we move beyond identifying attacks by developing a cryptographic model and using it to prove the security of a new backwards-compatible client/server protocol for NTP.

Category / Keywords: applications / Network Time Protocol (NTP), Network security, time synchronization

Date: received 23 Oct 2016, last revised 20 Feb 2017

Contact author: aanchal4 at bu edu

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Version: 20170220:194022 (All versions of this report)

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