This document summarizes a research project exploring security flaws in the Network Timing Protocol (NTP). The project goals were to set up a virtual computer network with an NTP client and server, and demonstrate a man-in-the-middle attack by fooling the NTP client. The researchers set up virtual machines running Linux, configured one as an NTP server synchronized to an external time source, and monitored network traffic. They planned to use Ettercap to intercept NTP traffic through ARP poisoning, but ran out of time before completing the attack.

1. NetworkTiming
Protocol Security
Supervisor: Michael Schukat
Interns: Andrew McGarry and Declan Brennan
Summer 2014 NUIG Research Practicum

2. Overview
• Background Information
• Project Goals
• NetworkTiming Protocol
• Stage 1
• Concept
• SoftwareTools
• Troubleshooting
• Stage 2 Research
• Authenticated NTP
• Executing the Attack
• Summary

3. Background
 “Measurement and control applications are increasingly using distributed system
technologies such as network communication, local computing, and distributed
objects.Without a standardized protocol for synchronizing the clocks in these devices,
it is unlikely that the benefits will be realized in the multivendor system component
market” (IEEE 1588, 2008).
 IEEE 1588 describes PTP, a protocol capable of greater time precision than NTP
 GPS or cellular network unusable in many cases
 However, NTP in its base form does not authenticate server/client
 Authenticated NTP used to provide secure NTP connections.
 Quite widespread, although with advent of smart grids, could be used as attack vector against
critical services.
 Has known security flaws (Autokey cookie is only 32 bits long, so it can be brute forced)

4. Project Goals
Main: to explore and demonstrate a security flaw associated with Authenticated NTP
Subgoals:
Exploration:
• Learn about NetworkTiming protocol, it’s importance, how it functions
• Utilize tools commonly used in computer science research
• Introduce ourselves to computer networking and network security
Demonstration
• Stage 1: set up a computer network which features an NTP client/server relationship and the
capability to monitor network traffic
• Stage 2: conduct a Man-in-the-Middle (MitM) attack within this network with the goal of
fooling NTP client into accepting attacker as legitimate NTP server

5. What is NTP?
 Abbreviation for 'NetworkTime Protocol'
 NTP is used for clock synchronization across data networks
 Its purpose is to synchronize the clocks participating hosts to within a few
milliseconds of UTC
 NTP utilizes layers known as strata. Each successive stratum is further and
further away from high-precision timekeeping devices
 NTP is often used in situations where accurate time stamps are essential
 NTP was originally conceived by David Mills at the University of Delaware in
1985, and is thus one of the oldest network protocols still in use

6. Stage 1: Concept
 Original concept was to establish an NTP connection between two virtual
machines (VMs)
 Wanted to contain the project within a laptop
 VM’s easier to manipulate
 NTP Server application would run on one of theVMs
 Synchronize with NUIGalway NTP server through host OS
 SecondVM would receive timing info from virtual NTP server
 Host OS
 Able to monitor all network traffic usingWireshark
 Would eventually act as MitM in a MitM attack

8. Stage 1: SoftwareTools
 To carry out this project, we needed to build a virtual network
 We usedVMware to create virtual machines which run Fedora 19, a distribution
of Linux
 We needed to learn much about the shell and familiarize ourselves with the
command terminal
 Additionally neededWireshark to sniff network traffic and Ettercap in order to
simulate man-in-the-middle attacks

9. Stage 1:Troubleshooting
 Synchronizing virtual NTP server to NUIG NTP server
 140.203.204.77 exists outside the NUIG firewall, had to synchronize over cell network
 Not a viable long-term option, data usage too high
 Synchronizing virtual NTP server to Hugh’s NTP server
 140.203.16.50 is within the NUIG firewall, but no synchronization
 Check iptables rules, ntp.conf file,Windows firewall,VMWare documentation…
 ntpd –u
 Requires that ntpq send request from/to unrestricted (< 1024) port
 However, ntpd can only synchronize through a connection over port 123…
 Ultimately decided to change the design of stage 1

11. Stage 2: Authenticated NTP
 Server secret: server seed
 Client secret: private key
 Client shares its public key with server, server uses the public key to generate cookie:
Cookie = MSBs32 (H (Client-IP || Server-IP || 0 || Server Seed)), e.g.
 Normal synchronization:
NTP Packet = NTP-Payload || KeyId || MAC
MAC = H (Autokey || NTP-Payload)
KeyId is picked by the client.
Autokey is 128 bit long and calculated as follow:
Autokey = H (Sender-IP || Receiver-IP || KeyID || Cookie)

12. Stage 2: Executing the Attack
 Ettercap proved to be a handy tool, as it provided us with a suite for
performing man-in-the-middle attacks
 Ettercap works by ARP poisoning selected targets. (ie changing the MAC
address and forging request and reply packets across a LAN)
 This allows Ettercap to act as the middle man, and enables it to perform
various styles of attack
 Our intention was to use a DNS hijack in order to fool switches which would
allow us to intercept NTP traffic sent across our virtual network.

13. Summary
 We found ourselves doing a lot of trial and error, and were unable to complete
Stage 2 in the given time
 We nonetheless managed to set up the virtual network, synchronize a virtual
NTP server with an NUIG NTP server, and explored a weakness in
Authenticated NTP
 We've learned how to intercept and monitor network traffic
 We have laid down the foundation for a new person to continue this project
from where we left it off