The security of NTP's datagram protocol

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Accepted manuscript
Date
2017
DOI
Authors
Malhotra, Aanchal
Gundy, Matthew Van
Varia, Mayank
Kennedy, Haydn
Gardner, Jonathan
Goldberg, Sharon
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Published version
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Citation
Malhotra A., Van Gundy M., Varia M., Kennedy H., Gardner J., Goldberg S. (2017) The Security of NTP’s Datagram Protocol. In: Kiayias A. (eds) Financial Cryptography and Data Security. FC 2017. Lecture Notes in Computer Science, vol 10322. Springer, Cham. DOI https://doi.org/10.1007/978-3-319-70972-7_23
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.
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