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Old 07-03-2012, 11:51 PM
Ralf Mardorf
 
Default Leap seconds ntp and chrony?

On Wed, 2012-07-04 at 00:21 +0100, Kevin Chadwick wrote:
> I've never seen a system crash even due to a wildly drifting clock

There's still the paradox, that using a kernel-rt we get relatively good
timing for some apps, while the "real real time" might be completely out
of timing (>= 10 seconds).

Btw. I'm running ntpdate and sntp manually (regarding to the distro) and
even when there was "negative delay" for the clock, no Linux ever
crashed.

--
Classical Latin sucks
Extra fortunam est quidquid donatur amicis
Quas dederis, solas semper habebis opes.
 
Old 07-04-2012, 01:27 AM
Gaetan Bisson
 
Default Leap seconds ntp and chrony?

[2012-07-04 00:22:25 +0100] Kevin Chadwick:
> I think I've been quite clear, similar to negative coding.

You haven't, similar to people spreading FUD.

Feel free to share your deep knowledge and thorough understanding of NTP
with us ignorants by contributing to this neat little project you might
have heard of, Wikipedia:

http://en.wikipedia.org/wiki/Network_Time_Protocol#Security_concerns

> OpenBSD has a security measure called securelevel which if raised from
> one to two prevents even root setting the clock backwards or near
> overflow as this can have consequences for the entropy pool. They also
> put in place measures to reduce client time leakage. The obvious point
> I ignored is network exploits as clock adjustment is a root process,
> which is why OpenBSDs implements priviledge seperation and chroot.

So what? You want to switch to OpenBSD? Please do.

> Explain why that matters for the usual case which is logging. I have
> servers some offline from which I can cross reference the logs. Do
> you... can you.. would you check your logs to the nanosecond and who
> said I worried. requirements, benefits and threats.

So because you don't need NTP nobody does? Educate yourself at:

http://en.wikipedia.org/wiki/Clock_synchronization#Problems

> Quas dederis solas semper habebis opes.

Subsiste sermonem statim.

--
Gaetan
 
Old 07-04-2012, 11:05 AM
Kevin Chadwick
 
Default Leap seconds ntp and chrony?

> > I think I've been quite clear, similar to negative coding.
>
> You haven't, similar to people spreading FUD.
>
> Feel free to share your deep knowledge and thorough understanding of NTP
> with us ignorants by contributing to this neat little project you might
> have heard of, Wikipedia:
>
> http://en.wikipedia.org/wiki/Network_Time_Protocol#Security_concerns
>

Funny how people read what they will. I guess you haven't looked up
negative coding. What I mean by similar to is if it doesn't benefit you,
you will have less bugs and a more stable and secure system by reducing
code usage. Therefore I wouldn't even need to know about ntp details,
or the work of some very clever people who have looked at the details to
make the right choice for me. Some security books say code redcution is
pointless, I guess rop attacks have put a pin in that but aside from
rop it has served me very well. Disabling ipv6 for example. One of
about the two remote root exploits (so far) for OpenBSD was in ipv6
ages ago and more recently this.

http://www.hackingipv6networks.com/past-trainings/hip2011-hacking-ipv6-networks.pdf

I guess I regurgitate too many thoughts at once without enough
explanation. I Wish I hadn't mentioned the alternative that would
certainly not negatively affect most users now. Who knows maybe the bug
fix will break something too. Though I'm sure they will test very well
considering.


> > OpenBSD has a security measure called securelevel which if raised from
> > one to two prevents even root setting the clock backwards or near
> > overflow as this can have consequences for the entropy pool. They also
> > put in place measures to reduce client time leakage. The obvious point
> > I ignored is network exploits as clock adjustment is a root process,
> > which is why OpenBSDs implements priviledge seperation and chroot.
>
> So what? You want to switch to OpenBSD? Please do.

I use OpenBSD more than arch actually, almost entirely for servers.

--
__________________________________________________ ______

Why not do something good every day and install BOINC.
__________________________________________________ ______
 
Old 07-04-2012, 11:19 AM
Kevin Chadwick
 
Default Leap seconds ntp and chrony?

> > I think I've been quite clear, similar to negative coding.
>
> You haven't, similar to people spreading FUD.
>
> Feel free to share your deep knowledge and thorough understanding of NTP
> with us ignorants by contributing to this neat little project you might
> have heard of, Wikipedia:
>
> http://en.wikipedia.org/wiki/Network_Time_Protocol#Security_concerns


http://osvdb.org/search?search%5Bvuln_title%5D=ntp&search%5Btext_ty pe%5D=alltext

I'm sure some Windows ones are missing and probably others too. Other
concerns like securelevel 2 on OpenBSD prevents are very unlikely to
hit those lists. I should probably mention Securelevel 2 isn't
recommended by the devs on OpenBSD though for usability reasons.

This doesn't mean I am saying ntp is insecure or to be considered a
risk but what's BEST for you.

--
__________________________________________________ ______

Why not do something good every day and install BOINC.
__________________________________________________ ______
 
Old 07-04-2012, 12:31 PM
Gaetan Bisson
 
Default Leap seconds ntp and chrony?

[2012-07-04 12:05:18 +0100] Kevin Chadwick:
> What I mean by similar to is if it doesn't benefit you,
> you will have less bugs and a more stable and secure system by reducing
> code usage.

Are you just saying that people who don't need an NTP daemon are better
off not running one?


[2012-07-04 12:19:03 +0100] Kevin Chadwick:
> http://osvdb.org/search?search%5Bvuln_title%5D=ntp&search%5Btext_ty pe%5D=alltext

Those ten issues have been fixed for years...

--
Gaetan
 
Old 07-04-2012, 03:42 PM
Kevin Chadwick
 
Default Leap seconds ntp and chrony?

> > What I mean by similar to is if it doesn't benefit you,
> > you will have less bugs and a more stable and secure system by reducing
> > code usage.
>
> Are you just saying that people who don't need an NTP daemon are better
> off not running one?

Yep and many who think they do need one may well not need one. I
think stories of RTC inaccuracy are exaggerated due to those who really
need very accurate clocks and so getting rather annoyed. PC hardware is
designed with just it's RTC and no ntp in mind after all.

Some distros like Ubuntu seem to assume (or did) that no one would ever
want to switch ntp off. I wonder if any ubuntu server users have had any
issues there recently. I guess they wouldn't have known until it was
too late though?

--
__________________________________________________ ______

Why not do something good every day and install BOINC.
__________________________________________________ ______
 
Old 07-04-2012, 06:23 PM
Leonid Isaev
 
Default Leap seconds ntp and chrony?

On Wed, 4 Jul 2012 16:42:04 +0100
Kevin Chadwick <ma1l1ists@yahoo.co.uk> wrote:

> > > What I mean by similar to is if it doesn't benefit you,
> > > you will have less bugs and a more stable and secure system by reducing
> > > code usage.
> >
> > Are you just saying that people who don't need an NTP daemon are better
> > off not running one?
>
> Yep and many who think they do need one may well not need one. I
> think stories of RTC inaccuracy are exaggerated due to those who really
> need very accurate clocks and so getting rather annoyed. PC hardware is
> designed with just it's RTC and no ntp in mind after all.

But the goal of ntp is not only timekeeping, but mainly syncronization.
Potentially everyone needs precise timesync, unless you exist in a lab
isolated from the world. For example, kerberos 5 needs time syncronization
between clients and a server. I can imagine that dhcp leases do too,
especially on busy networks like those deployed in universities. If you have a
mercurial/git installation even in a small group, I am sure you'll prefer
accurate timestamps in your commit history. And the list goes on...

>
> Some distros like Ubuntu seem to assume (or did) that no one would ever
> want to switch ntp off. I wonder if any ubuntu server users have had any
> issues there recently. I guess they wouldn't have known until it was
> too late though?
>

That is a reasonable assumption (windows vista/7 makes it too, btw). The only
downside may be CPU wakeups caused by ntp, but that's the chrony story.
Regarding ubuntu servers and leap seconds, they were not any more or less
vulnerable than others. Whether or not you were affected depended on
particular applications which were run atm. For example, on my machine leap
second addition was completely seemless.

--
Leonid Isaev
GnuPG key: 0x164B5A6D
Fingerprint: C0DF 20D0 C075 C3F1 E1BE 775A A7AE F6CB 164B 5A6D
 
Old 07-04-2012, 07:06 PM
Kevin Chadwick
 
Default Leap seconds ntp and chrony?

> If you have a
> mercurial/git installation even in a small group, I am sure you'll prefer
> accurate timestamps in your commit history. And the list goes on...
>

I believe an RTC is perfectly capable of that.

> >
> > Some distros like Ubuntu seem to assume (or did) that no one would ever
> > want to switch ntp off. I wonder if any ubuntu server users have had any
> > issues there recently. I guess they wouldn't have known until it was
> > too late though?
> >
>
> That is a reasonable assumption (windows vista/7 makes it too, btw). The only
> downside may be CPU wakeups caused by ntp, but that's the chrony story.

On systems where lots is enabled by default it is perhaps a reasonable
assumption to run ntp by default, if it truly wakes the cpu then I'd
say that default is wrong too. It is not reasonable to force users to
chmod 000 ntp because init configuration is being ignored which was the
case for atleast one Ubuntu release.

Windows 7 does the same as XP, enabled by default but can be switched
off in atleast three places. Time config, Windows Time service and Group
policy.

--
__________________________________________________ ______

Why not do something good every day and install BOINC.
__________________________________________________ ______
 
Old 07-04-2012, 08:00 PM
Tom Gundersen
 
Default Leap seconds ntp and chrony?

On Wed, Jul 4, 2012 at 9:06 PM, Kevin Chadwick <ma1l1ists@yahoo.co.uk> wrote:
>> If you have a
>> mercurial/git installation even in a small group, I am sure you'll prefer
>> accurate timestamps in your commit history. And the list goes on...
>
> I believe an RTC is perfectly capable of that.

I tried to find some data on what to expect from RTC's. I was not very
successful, except finding people citing 80-100PPM as typical drift
rates (~8 secs/day).

Having a look at my own machine (a reasonably new Dell laptop) I don't
see values quite that bad. I lose about 14 PPM, which amounts to
roughly seven minutes in a year.

Having that kind of discrepancies on a network doing distributed
development would wreck absolute havoc.

-t
 
Old 07-04-2012, 09:06 PM
Mauro Santos
 
Default Leap seconds ntp and chrony?

On 04-07-2012 21:00, Tom Gundersen wrote:
> On Wed, Jul 4, 2012 at 9:06 PM, Kevin Chadwick <ma1l1ists@yahoo.co.uk> wrote:
>>> If you have a
>>> mercurial/git installation even in a small group, I am sure you'll prefer
>>> accurate timestamps in your commit history. And the list goes on...
>>
>> I believe an RTC is perfectly capable of that.
>
> I tried to find some data on what to expect from RTC's. I was not very
> successful, except finding people citing 80-100PPM as typical drift
> rates (~8 secs/day).

From data I have access to, taken from machines running ntpd, I can say
the following about the drift in PPM stored in ntpd's drift file:

my laptop: -9.699
machine 1: -8.762
machine 2: -443.266
machine 3: -35.417

Machine 1 is the newest and machine 3 is the oldest.

> Having a look at my own machine (a reasonably new Dell laptop) I don't
> see values quite that bad. I lose about 14 PPM, which amounts to
> roughly seven minutes in a year.
>
> Having that kind of discrepancies on a network doing distributed
> development would wreck absolute havoc.
>
> -t
>


--
Mauro Santos
 

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