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Re: [TLS] Server time

Peter Gutmann <pgut001@cs.auckland.ac.nz> Mon, 06 April 2015 12:46 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "<tls@ietf.org>" <tls@ietf.org>
Thread-Topic: [TLS] Server time
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Date: Mon, 06 Apr 2015 12:45:58 +0000
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Subject: Re: [TLS] Server time
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Tom Ritter <tom@ritter.vg> writes:

>Is it better or worse than relying on a completely unauthenticated protocol
>to get the time?

If you really need a secure time source you either use NTPv4 security or run
your own stratum 1.  The problem with getting time from the server is, as
others and I have pointed out, the server may not have the correct time (or
any time at all for an embedded device), by manipulating the time the client
sees a malicious server can break the client's PKI, and so on.

Using TLS as a pseudo-NTP source makes about as much sense as using HTTP as a
pseudo-NTP source, which has happened a number of times in the past.  TLS is a
means of building a secure tunnel from A to B, not a kludgy way of avoiding
use of NTP.

Peter.

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