Paper 2016/055
Attacking NTP's Authenticated Broadcast Mode
Aanchal Malhotra and Sharon Goldberg
Abstract
We identify two attacks on the Network Time Protocol (NTP)'s cryptographically-authenticated broadcast mode. First, we present a replay attack that allows an on-path attacker to indefinitely stick a broadcast client to a specific time. Second, we present a denial-of-service (DoS) attack that allows an off-path attacker to prevent a broadcast client from ever updating its system clock; to do this, the attacker sends the client a single malformed broadcast packet per query interval. Our DoS attack also applies to all other NTP modes that are `ephemeral' or `preemptable' (including manycast, pool, etc). We then use network measurements to give evidence that NTP's broadcast and other ephemeral/preemptable modes are being used in the wild. We conclude by discussing why NTP's current implementation of symmetric-key cryptographic authentication does not provide security in broadcast mode, and make some recommendations to improve the current state of affairs.
Note: Revised per comments of SIGCOMM CCR reviewers.
Metadata
- Available format(s)
-
PDF
- Category
- Applications
- Publication info
- Published elsewhere. ACM SIGCOMM Computer Communication Review. April 2016
- Keywords
- network securitynetwork time protocolNTPbroadcastoff-path attacksdenial of service
- Contact author(s)
- goldbe @ cs bu edu
- History
- 2016-02-26: last of 2 revisions
- 2016-01-25: received
- See all versions
- Short URL
- https://ia.cr/2016/055
- License
-
CC BY
BibTeX
@misc{cryptoeprint:2016/055,
author = {Aanchal Malhotra and Sharon Goldberg},
title = {Attacking {NTP}'s Authenticated Broadcast Mode},
howpublished = {Cryptology {ePrint} Archive, Paper 2016/055},
year = {2016},
url = {https://eprint.iacr.org/2016/055}
}
