Bug 916

Summary: SFTP over SSH died after roughly 20MB when asking for >64k chunks
Product: Portable OpenSSH Reporter: Paul Swartz <z3p>
Component: sshdAssignee: OpenSSH Bugzilla mailing list <openssh-bugs>
Status: CLOSED WORKSFORME    
Severity: normal    
Priority: P2    
Version: 3.8.1p1   
Hardware: ix86   
OS: Linux   
Attachments:
Description Flags
Python script demonstrating bug
none
error message from test script. none

Description Paul Swartz 2004-08-20 02:32:38 AEST 
I have a SSHv2/SFTPv3 implementation written in Python.  I have been trying to
use a chunk size for SFTP downloading of 128k against the 3.8.1p1
sshd/sftp-server.  I only get 64k back, which is because of the hardcoded buffer
in sftp-server.c, but that's not the problem.  After roughly 20MB of 64kb chunks
(asking for 128kb) the server hangs and stops sending data.
Interestingly, talking directly to sftp-server does not demonstrate this bug,
which leads me to believe that the bug is somewhere in sshd, although I have no
idea how that could be.  I'm using a local window size and local maximum packet
size that is large enough for 128k packets.
I'll attach a Python script that demonstrates the bug.
Comment 1 Paul Swartz 2004-08-20 02:35:35 AEST 
Created attachment 699 [details]
Python script demonstrating bug

Requires Twisted (http://www.twistedmatrix.com/).
Comment 2 Darren Tucker 2005-01-27 18:05:56 AEDT 
Does the patch in bug #896 resolve the problem?
Comment 3 Darren Tucker 2005-02-09 22:56:56 AEDT 
Created attachment 812 [details]
error message from test script.

I tried to reproduce the problem but the test script doesn't appear to work
(even after setting the user and telling the script to use port 22).  Error
attached.  If it matters, I am using python-2.3.4 and Twisted-1.3.0.
Comment 4 Damien Miller 2006-04-03 17:13:01 AEST 
a year without feedback and a non-working test script == no bug

please reopen if you can provide a replicable demonstration or at least a trace from a failing server.
Comment 5 Darren Tucker 2006-10-07 11:36:51 AEST 
Change all RESOLVED bug to CLOSED with the exception of the ones fixed post-4.4.