openssh bugs - Feb 2011 - [Bug 1860] New: UseDNS option ignored

https://bugzilla.mindrot.org/show_bug.cgi?id=1860

           Summary: UseDNS option ignored
           Product: Portable OpenSSH
           Version: 5.6p1
          Platform: All
        OS/Version: Other
            Status: NEW
          Severity: normal
          Priority: P2
         Component: sshd
        AssignedTo: unassigned-bugs at mindrot.org
        ReportedBy: pavel.krejci at siemens-enterprise.com


In the SCO Unix (UnixWare 7.1.4 i386 x86at) the option "UseDNS no" in
the sshd_config is ignored. Still the DNS lookup is being made when the
client connection is started.

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https://bugzilla.mindrot.org/show_bug.cgi?id=1860

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org

--- Comment #1 from Damien Miller <djm at mindrot.org> 2011-04-13 15:06:26
EST ---
You'll have to provide more information. 

Are you saying that ssh is doing a lookup? If so, this would be
unsurprising, given sshd_config doesn't not affect it.

If you mean that sshd is doing the lookup, I'm quite sure that all the
calls to getnameinfo() that aren't using NI_NUMERICHOST are disabled by
UseDNS=no. Could it be a PAM module or some library code that is making
the lookup?

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Darren Tucker <dtucker at zip.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |dtucker at zip.com.au

--- Comment #2 from Darren Tucker <dtucker at zip.com.au> 2011-05-06
11:05:04 EST ---
If it's the server, the other thing that can do it is the system login
recording libraries (try sshd -u0).

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--- Comment #3 from pavel.krejci at siemens-enterprise.com 2011-07-13 20:48:51
EST ---
Created attachment 2062
  --> https://bugzilla.mindrot.org/attachment.cgi?id=2062
sshd_config

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--- Comment #4 from pavel.krejci at siemens-enterprise.com 2011-07-13 20:49:31
EST ---
Created attachment 2063
  --> https://bugzilla.mindrot.org/attachment.cgi?id=2063
sshd-u0_truss.txt

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--- Comment #5 from pavel.krejci at siemens-enterprise.com 2011-07-13 20:49:48
EST ---
(In reply to comment #2)
> If it's the server, the other thing that can do it is the system login
> recording libraries (try sshd -u0).
The -u0 options does not help. Attached is the trace of sshd with this
option enabled. It took more than 1 minute before the "login as:"
dialog appeared in the Putty client. The NS lookup is made:

20538:   open("/etc/resolv.conf", O_RDONLY, 0666)   = 4
20538:   ioctl(4, TCGETS, 0x08046F64)         Err#25 ENOTTY
20538:   fxstat(2, 4, 0x08046FA4)         = 0
20538:   brk(0x0814ECE0)               = 0
20538:   read(4, " n a m e s e r v e r   1".., 8192)   = 20
20538:   read(4, 0x0814A090, 8192)         = 0
20538:   close(4)               = 0
20538:   nuname(0x08046B6B)            = 1
20538:   xsocket(UW71|XPG4, AF_INET, SOCK_DGRAM, 0)   = 4
20538:   xconnect(UW71|XPG4, 4, 0xBFF5D9B4, 16)      = 0
20538:   xsendmsg(UW71|XPG4, 4, 0x08046DB4, 0)      = 42
...

Also the sshd_config attached.

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