ssh -X remote does not work due to problem with xauth

[James B. Byrne]

On Wed, May 9, 2018 06:47, Matthias Apitz wrote:
>
> When I launch 'ssh -X remote host' to get X11 forwarded to my
> workstation
> this does not work, i.e. does not produce a DISPLAY env on the remote
> host and says:
>
> $ ssh -X apitzm at srap16dxr1
> Warning: untrusted X11 forwarding setup failed: xauth key data not
> generated
> Last login: Wed May  9 12:37:17 2018 from 10.49.8.33
> apitzm at srap16dxr1:~>
>
> I digged into it with -vv options for ssh and trussing the client. It
> seems it's
> our end causing the problem:
>
> $ uname -a
> FreeBSD r314251-amd64 12.0-CURRENT FreeBSD 12.0-CURRENT #0 r314251:
> Sat Feb 25 17:14:40 CET 2017
> root at r303343-amd64:/usr/obj/usr/src/sys/GENERIC  amd64
>
> $ truss -s128 -f -o ssh.tr ssh -X -vv apitzm at srap16dxr1
> $ grep -i xauth ssh.tr > xauth.txt
>
> 20544: stat("/usr/local/bin/xauth",{ mode=-rwxr-xr-x
> ,inode=2820147,size=41056,blksize=32768 }) = 0 (0x0)
> 20544: write(2,"debug2: client_x11_get_proto: /usr/local/bin/xauth -f
> /tmp/ssh-zfFpkwHgD1qj/xauthfile generate :0 MIT-MAGIC-COOKIE-1
> untrusted t"...,153) = 153 (0x99)
> 20545: execve("/usr/local/bin/xauth",0x801459260,0x801459408) = 0
> (0x0)
> 20545: stat("/tmp/ssh-zfFpkwHgD1qj/xauthfile-c",0x7fffffffdc40) ERR#2
> 'No such file or directory'
> 20545:
> openat(AT_FDCWD,"/tmp/ssh-zfFpkwHgD1qj/xauthfile-c",O_WRONLY|O_CREAT|O_EXCL,0600)
> = 3 (0x3)
> 20545: pathconf("/tmp/ssh-zfFpkwHgD1qj/xauthfile-c",_PC_LINK_MAX) =
> 32767 (0x7fff)
> 20545:
> link("/tmp/ssh-zfFpkwHgD1qj/xauthfile-c","/tmp/ssh-zfFpkwHgD1qj/xauthfile-l")
> = 0 (0x0)
> 20545: access("/tmp/ssh-zfFpkwHgD1qj/xauthfile",F_OK) ERR#2 'No such
> file or directory'
> 20545: open("/tmp/ssh-zfFpkwHgD1qj/xauthfile",O_RDONLY,0666) ERR#2 'No
> such file or directory'
> 20545: access("/tmp/ssh-zfFpkwHgD1qj/xauthfile",F_OK) ERR#2 'No such
> file or directory'
> 20545: write(2,"/usr/local/bin/xauth:  file
> /tmp/ssh-zfFpkwHgD1qj/xauthfile does not exist\n",75) = 75 (0x4b)
> 20545: access("/tmp/kde-guru/xauth-1001-_0",R_OK) = 0 (0x0)
> 20545: open("/tmp/kde-guru/xauth-1001-_0",O_RDONLY,0666) = 4 (0x4)
> 20545: write(2,"/usr/local/bin/xauth: (argv):1:  ",33) = 33 (0x21)
> 20545: lstat("/tmp/ssh-zfFpkwHgD1qj/xauthfile-c",{ mode=-rw-------
> ,inode=8331,size=0,blksize=32768 }) = 0 (0x0)
> 20545: unlink("/tmp/ssh-zfFpkwHgD1qj/xauthfile-c") = 0 (0x0)
> 20545: lstat("/tmp/ssh-zfFpkwHgD1qj/xauthfile-l",{ mode=-rw-------
> ,inode=8331,size=0,blksize=32768 }) = 0 (0x0)
> 20545: unlink("/tmp/ssh-zfFpkwHgD1qj/xauthfile-l") = 0 (0x0)
> 20544: unlink("/tmp/ssh-zfFpkwHgD1qj/xauthfile") ERR#2 'No such file
> or directory'
> 20544: write(2,"Warning: untrusted X11 forwarding setup failed: xauth
> key data not generated\r\n",78) = 78 (0x4e)
>
> Any ideas?
>
> Thanks
>
> 	matthias

You need the xauth pkg installed on the remote to generate the
.Xauthority file for the ssh session.

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James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
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