How to workaround a 2017’s Win32-OpenSSH bug by using a 1980’s unix util 😉
If you run ssh in a non-real TTY (like a popen() from mod_php, or cron) against a windows host running Win32-OpenSSH, you may receive a “read failed”.
To easily reproduce the problem you can run ssh through “nohup”:
nohup ssh -vvv user@windows-host whoami
Here’s the log:
[...] debug1: Sending command: whoami debug2: channel 0: request exec confirm 1 debug2: callback done debug2: channel 0: open confirm rwindow 0 rmax 32768 debug2: channel 0: rcvd adjust 2097152 debug2: channel_input_status_confirm: type 99 id 0 debug2: exec request accepted on channel 0 debug2: channel 0: read<=0 rfd 4 len 0 debug2: channel 0: read failed debug2: channel 0: close_read debug2: channel 0: input open -> drain debug2: channel 0: ibuf empty debug2: channel 0: send eof debug2: channel 0: input drain -> closed debug2: channel 0: rcvd eof debug2: channel 0: output open -> drain debug2: channel 0: obuf empty debug2: channel 0: close_write debug2: channel 0: output drain -> closed debug1: client_input_channel_req: channel 0 rtype exit-status reply 0 debug2: channel 0: rcvd close debug3: channel 0: will not send data after close debug2: channel 0: almost dead debug2: channel 0: gc: notify user debug2: channel 0: gc: user detached debug2: channel 0: send close debug2: channel 0: is dead debug2: channel 0: garbage collecting debug1: channel 0: free: client-session, nchannels 1 debug3: channel 0: status: The following connections are open: #0 client-session (t4 r0 i3/0 o3/0 fd -1/-1 cc -1) debug1: fd 0 clearing O_NONBLOCK debug1: fd 1 clearing O_NONBLOCK debug1: fd 2 clearing O_NONBLOCK Transferred: sent 3888, received 2748 bytes, in 0.1 seconds Bytes per second: sent 75340.2, received 53249.7 debug1: Exit status 0
A workaround which can be used to solve this issue is the running of the ssh through “script”, a 1980’s utility to log an interactive session to a file:
script makes a typescript of everything displayed on your terminal.
It is useful for students who need a hardcopy record of an
interactive session as proof of an assignment, as the typescript file
can be printed out later with lpr(1).
So, for example:
script -q -c "ssh user@windows-host whoami"
There is an open issue on GitHub.