scp client hangs after authentication with dropbear server

[Steven Hein]

Matt Johnston wrote:

>On Wed, Feb 07, 2007 at 11:58:55AM -0600, Steven Hein wrote:
>  
>
>>Steven Hein wrote:
>>
>>    
>>
>>>I have the dropbear server running on a PPC-based embedded board.
>>>I can ssh into it just fine.   But when I try to scp to or from
>>>this dropbear server (using an openssh scp client, that's the only
>>>one I've tried), it hangs after successful authentication with
>>>a password.
>>>      
>>>
>
>I don't recall seeing this problem before - as you noted
>previous issues with scp have been it hanging after
>finishing. From the strace, can you see what the server scp
>process is doing? If you could send me the full output of
>"strace -f -o trace1.out ./dropbear -F -E ...etc" I'll see
>what I can make of it. If you compile Dropbear with
>DEBUG_TRACE set in debug.h you can use the -v flag to print
>some more verbose output of what's happening - note that
>inetd mode won't work when you're using that.
>
>The output of scp -vvv might also give some clues. One other
>thought is that it might be running out of entropy in the
>reseedrandom() call in execchild() - does using /dev/urandom
>for DROPBEAR_RANDOM_DEV in options.h help (I doubt it)?
>
>Cheers,
>Matt
>  
>
I'll try these suggestions shortly.   Just a couple more data
points from yesterday.   I get the same sort of hang if I
try to execute a command from ssh:

# ssh root at essc1 "echo hello"
root at essc1's password:
<hangs here until I CTRL-C>

So, it seems that this is related to executing a remote command
through ssh (which is what scp needs to do, right?  execute a command
on the dropbear server side?).   This seems to suggest a problem
in execchild().   But....I have /dev/random symlink'd to /dev/urandom
as I seem to have 0 entry available on my system for some reason....

One other bit:   the shell on the dropbear server side is
busybox--any problems related to that?

I'll post the results of the experiments shortly.

Steve

-- 
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Steve Hein (ssh at sgi.com)              Engineering Diagnostics/Software
Silicon Graphics, Inc.
1168 Industrial Blvd.                 Phone: (715) 726-8410
Chippewa Falls, WI 54729              Fax:   (715) 726-6715
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