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Date:      Wed, 9 May 2018 12:47:00 +0200
From:      Matthias Apitz <guru@unixarea.de>
To:        freebsd-questions@freebsd.org
Subject:   ssh -X remote does not work due to problem with xauth
Message-ID:  <20180509104700.GA3259@c720-r314251>

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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@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@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@r303343-amd64:/usr/obj/usr/src/sys/GENERIC  amd64

$ truss -s128 -f -o ssh.tr ssh -X -vv apitzm@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
-- 
Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045
Public GnuPG key: http://www.unixarea.de/key.pub
May, 9: Спаси́бо освободители! Thank you very much, Russian liberators!



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