[Bug 262892] Re: Possible bug found in SSHD and tunneling(Based on question number 43605)

Tue Dec 10 21:41:09 UTC 2013

tldr; Can you give this a more sensible title?

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https://bugs.launchpad.net/bugs/262892

Title:
  Possible bug found in SSHD and tunneling(Based on question number
  43605)

Status in “openssh” package in Ubuntu:
  Confirmed

Bug description:
  I've run into a very strange phenomenom that I'm hoping someone can
  help me with. I've debugged it from all angles and everything points
  back to ubuntu and sshd (or a library it depends on). Here's the
  scenario:

  At my office, I am sshing to my home machine using putty and setting
  up a dynamic socks proxy on port 8080. When I point my firefox 3 (or
  firefox 2, or ie 7, I tried them all) to the localhost:8080 and surf
  the web (specifically lifehacker.com due to it's massive number of
  external links), the web pages renders through once. Then if I do a
  shift-refresh, it starts to load again, then hangs. My putty ssh
  session is hung also. I can however fire up a second putty session
  into my home machine and it responds fine. My home linux machine can
  also still go out on the internet, surf from the console (vnc) etc
  just fine.

  So.. after trying out all the browsers, I thought, well, maybe it's my
  router.. (whr-g125 running dd-wrt 2.4sp1). So .. I made my router
  itself open via ssh to the internet, and tunneled (ssh'd) in directly
  to my router. The socks proxy using Firefox worked just fine,
  refreshing over and over without incident.

  So now I thought "It must be the sshd on ubuntu". So I downloaded the
  latest Openssh Portable 5.1p1 and compiled it from source. Fired up a
  new putty session to tunnel, refreshed the browser, same hang..
  browser quits pulling up website, putty session hung.

  So finally, I fired up a brand new Fedora 9 instance in my ubuntu
  server (using vbox), told my router to redirect to it's sshd, and
  connected from my work machine directly to Fedora 9 VM. Lo and behold,
  it worked just fine refreshing lifehacker.com over and over.

  So .. the $64,000 question is what library or networking code does ssh
  compile against that could be causing the ssh channels via socks to
  not free up (or get overloaded)? I have attached a snipped of the sshd
  running in debug mode to glean some insight (the final entry is the
  last time returned before hang). The only difference I can see from
  the ubuntu sshd logs vs the fedora sshd logs is fedora seems to
  instantly free up the 'nchannels' as soon as the browser has finished
  loading the page. I did not see that same behavior from the ubuntu
  sshd dump (stuck upwards of 33 nchannels).

  Thanks!

  -----snip from tail end of log before hang-----
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 14: connected Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 15: connected Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 16: connected Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 17: connected Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 18: connected Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 19: connected Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 20: connected Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 277 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 22: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 278 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 23: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 279 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 24: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 280 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 25: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 281 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 26: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 282 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 27: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 283 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 28: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 284 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 29: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 285 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 30: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 286 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target tags.lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 31: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 287 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target lifehacker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 32: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 288 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.gawker.com port 80 Aug 29 17:50:47 trinity sshd[28749]: debug1: channel 33: new [direct-tcpip] Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:47 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 289 win 16384 max 16384 Aug 29 17:50:47 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.gawker.com port 80 Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 34: new [direct-tcpip] Aug 29 17:50:48 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:48 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 290 win 16384 max 16384 Aug 29 17:50:48 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.gawker.com port 80 Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 35: new [direct-tcpip] Aug 29 17:50:48 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 4: free: 
  direct-tcpip, nchannels 37
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 5: free: 
  direct-tcpip, nchannels 36
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 6: free: 
  direct-tcpip, nchannels 35
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 11: free: 
  direct-tcpip, nchannels 34
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 45: free: 
  direct-tcpip, nchannels 33
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 21: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 22: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 23: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 24: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 25: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 26: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 27: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 28: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 29: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 30: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 31: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 32: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 33: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 34: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 35: connected Aug 29 17:50:48 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 259 win 16384 max 16384 Aug 29 17:50:48 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.gawker.com port 80 Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 4: new [direct-tcpip] Aug 29 17:50:48 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 7: free: 
  direct-tcpip, nchannels 33
  Aug 29 17:50:48 trinity sshd[28749]: debug1: channel 8: free: 
  direct-tcpip, nchannels 32
  Aug 29 17:50:48 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 260 win 16384 max 16384 Aug 29 17:50:48 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.gawker.com port 80 Aug 29 17:50:49 trinity sshd[28749]: debug1: channel 5: new [direct-tcpip] Aug 29 17:50:49 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:49 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 261 win 16384 max 16384 Aug 29 17:50:49 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.gawker.com port 80 Aug 29 17:50:49 trinity sshd[28749]: debug1: channel 6: new [direct-tcpip] Aug 29 17:50:49 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip
  Aug 29 17:50:49 trinity sshd[28749]: debug1: channel 2: free: 
  direct-tcpip, nchannels 33
  Aug 29 17:50:49 trinity sshd[28749]: debug1: channel 19: free: 
  direct-tcpip, nchannels 32
  Aug 29 17:50:49 trinity sshd[28749]: debug1: server_input_channel_open: 
  ctype direct-tcpip rchan 266 win 16384 max 16384 Aug 29 17:50:49 trinity sshd[28749]: debug1: server_request_direct_tcpip: 
  originator 0.0.0.0 port 0, target cache.gawker.com port 80 Aug 29 17:50:49 trinity sshd[28749]: debug1: channel 2: new [direct-tcpip] Aug 29 17:50:49 trinity sshd[28749]: debug1: server_input_channel_open: 
  confirm direct-tcpip

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