[Bug 1479652] Re: [patch] ntpd rejects source UDP ports less than 123 as bogus

[Robie Basak]

Thanks Eric, the debdiffs look good to me. I added Origin and Bug-Ubuntu
dep3 headers as discussed on IRC. Apart from that I've uploaded all
three unmodified. Now awaiting SRU team review.

** Description changed:

  [Impact]
  
  If an NTP client sends a request with a source port less than 123, the
  packet is silently ignored by ntpd. This is occurring in our environment
  due to NAT.
+ 
+ [Development Fix]
+ 
+ Fixed by merge of NTP of newer upstream release that includes the fix.
+ Stuck in dep-wait in xenial-proposed due to an unrelated issue (pps-
+ tools MIR or other resolution).
  
  [Test Case]
  
  The problem can easily be reproduced by having an iptable postrouting
  nat forcing the source port to be under 123 set on the client.
  
  Setup:
   ==> NTP server = y.y.y.y
   ntp.conf configured to be a server.
  
   ==> NTP client = x.x.x.x
   "ntpdate" used to submmit requests
  
   #iptable setup to force src port to be lower than 123
   iptables -t nat -A POSTROUTING -p UDP --dport 123  -j SNAT --to-source x.x.x.x:100-122
  
  ## On the client, set to force src port < 123 (without patch)
  
  $ ntpdate y.y.y.y
  ntpdate[<PID>]: no server suitable for synchronization found
  
  ## On the client, set to force src port < 123 (with patch)
  
  $ ntpdate y.y.y.y
  ntpdate[<PID>]: adjust time server y.y.y.y offset -0.028483 sec
  
  [Regression Potential]
  
  The patch comes from upstream: http://bugs.ntp.org/show_bug.cgi?id=2174
  
  A testfix[1] package has been provided to the community before the SRU
  process to bring more confidence for the patch. Positive feedbacks has
  been given by the community to confirm the patch addressed the bug
  [comment #7]
  
  [1]- https://launchpad.net/~slashd/+archive/ubuntu/bug1479652
  
  [Original description]
  
  [Title copied from Debian bug, which was not filed by me. Description
  below is mine.]
  
  If an NTP client sends a request with a source port less than 123, the
  packet is silently ignored by ntpd. This is occurring in our environment
  due to NAT.
  
  Attached is the patch already accepted upstream which fixes the issue.
  I've verified it fixes the problem. Debian has been ignoring this patch
  for almost 3 years. Can we get this in Ubuntu please?

** Changed in: ntp (Ubuntu Xenial)
       Status: In Progress => Fix Committed

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Title:
  [patch] ntpd rejects source UDP ports less than 123 as bogus

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