PuTTY semi-bug winadj-success

Home | Licence | FAQ | Docs | Download | Keys | Links
Mirrors | Updates | Feedback | Changes | Wishlist | Team

We've had a few reports of SSH connections bombing out with the following error message, reportedly under heavy load:

PuTTY Fatal Error

(X)  Disconnected: Received SSH_MSH_CHANNEL_SUCCESS for
     "winadj@putty.projects.tartarus.org"

                      [   OK   ]

Reports:

• E2E34FB668D4874FA28658B489F40BB0028F47DA@BP1XEUEX706-C.bp1.ad.bp.com
  Using "Portable PuTTY from the Xming project" (not our code)
  but also seen with 2008-12-01:r8355
  Server: SSH-2.0-OpenSSH_4.3
  Seems to happen readily -- a few "ls -ltr"s are sufficient to break it
• FileZilla ticket #3452
  (but also reported with PSFTP 2008-03-28:r7934: E00B544DC95563489A6C43CCD571EDD304EF8AFB@somodd.som.umaryland.edu)
  Reported as failure shortly after 1Gbyte of a file transfer.
• OF31BAE29C.9F8D62FE-ON862574FF.00743D6C-852574FF.007508E8@notes.wachovia.com

This message has only existed in PuTTY since the 'flow-control' feature was implemented, which was after we released 0.60; so at the time of writing, only people using development snapshots, or third-party code incorporating development code, should be seeing this. We probably want to find out what's going on before we make a release with this feature in.

On the face of it, it looks like the SSH server is incorrectly responding to our unilaterally-defined channel request message with SUCCESS, which it should never do since it's something we made up. (Our documentation mandates a FAILURE response, but that's only a restatement of the RFC 4254 requirement for a FAILURE response to requests that aren't understood -- we don't expect any server to specifically handle this message.)

However, perhaps we're getting confused about the mapping of requests to responses, or something.

Audit trail for this semi-bug.