[SSHD-634] Suspicious read buffer re-use in write command

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0.0
• Fix Version/s: 1.2.0
• Assignee: Lyor Goldstein
• Reporter: Eugene Petrenko
• Created: 28/Jan/16 12:44
• Updated: 03/Feb/16 11:20
• Resolved: 02/Feb/16 12:37

Description

From time to time I saw a Bad packet length ### errors from SSH clients that calls commands to the SSHD server running with Apache SSHD.
It may turn out there are some issues in the implementation.

I found one suspicious usage of buffers around org.apache.sshd.common.channel.AbstractChannel#sendResponse method. As far as I see from the code it uses the read buffer as a place to generate a write packet command. Maybe it's worth to create a fresh buffer here to avoid it be updated from the other thread while it is put to a write queue