cygwin sshd fails to allocate pty for some users

Posted by user115851 on Server Fault See other posts from Server Fault or by user115851
Published on 2012-03-29T21:58:11Z Indexed on 2012/03/29 23:32 UTC
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I have (finally) got sshd working under cygwin on Win7 - well, sort of.

The sshd runs as user 'cyg_server'. I'm able to successfully ssh to my computer using that same user name.

However, if I attempt to ssh using my normal (Windows) user name, it fails trying to allocate a pty for my login session. For example, output of 'sshd -D -d -d -d' contains this ..

... debug1: Entering interactive session for SSH2. debug2: fd 4 setting O_NONBLOCK debug2: fd 5 setting O_NONBLOCK debug1: server_init_dispatch_20 debug1: server_input_channel_open: ctype session rchan 0 win 1048576 max 16384 debug1: input_session_request debug1: channel 0: new [server-session] debug2: session_new: allocate (allocated 0 max 10) debug3: session_unused: session id 0 unused debug1: session_new: session 0 debug1: session_open: channel 0 debug1: session_open: session 0: link with channel 0 debug1: server_input_channel_open: confirm session debug1: server_input_global_request: rtype [email protected] want_reply 0 debug1: server_input_channel_req: channel 0 request pty-req reply 1 debug1: session_by_channel: session 0 channel 0 debug1: session_input_channel_req: session 0 req pty-req debug1: Allocating pty. debug1: session_pty_req: session 0 alloc /dev/pty1

!!! chown(/dev/pty1, 17308, 10513) failed: Invalid argument

debug1: do_cleanup debug1: session_pty_cleanup: session 0 release /dev/pty1

Currently /dev is owned by my normal account. I've tried changing its ownership to cyg_server as well as SYSTEM. In both cases the problem persists. I've also changed permissions for /dev (e.g, 700 and 777) - again problem persists.

[As a side note - it is strange that whenever I do 'ls -al /dev' the ptys do not show up. However, if I 'ls -l /dev/ptyX' for a pty I know to exist, it shows up. Is that normal for cygwin?]

-Bob Andover, MA

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