I have several setups of cygwin and XFree86. With the latest Cygwin 1.3.16-1, ssh 3.5p1-2 (or ssh 3.5p1-1), and XWin 4.2.0-16 (or 4.2.0-15), I am getting the same warning message as John:
Warning: No xauth data; using fake authentication data for X11 forwarding. However, my X clients do work fine, and I haven't found any other problem. With Cygwin 1.3.15-2, ssh 3.5p1-1, and XWin 4.2.0-16, however, there is no such warning message. This seems to suggest there is some problem involving something other than just ssh and XFree86 which generates the warning message. When I ran ssh -v, I get with Cygwin 1.3.15-2, ssh 3.5p1-1, XWin 4.2.0-16, the following as part of the startup message debug1: Entering interactive session. debug1: ssh_session2_setup: id 0 debug1: channel request 0: pty-req debug1: Requesting X11 forwarding with authentication spoofing. debug1: channel request 0: x11-req debug1: channel request 0: shell debug1: fd 4 setting TCP_NODELAY With Cygwin 1.3.16-1, ssh 3.5p1-2, XWin 4.2.0-16, the additional warning message appears just before the debug1: Requesting X11 forwarding with authentication spoofing message. I hope this may help in identifying the source of the warning message. Raymond Kwong