xhost + is a huge security hole

Maybe you have a firewall in your company, only your PC can access the production server, only you have the root password in prod, and your company spend a lot of money in security, but you dare using xhost +.

This is a huge security hole, because it gives anyone access to your X resources, not only your display, but also your mouse and your keyboard, so anyone can read/modify/corrupt what you are typing/clicking. It is a bad habit to use xhost+. Even using xhost +localhost give access to your keyboard to anyone on localhost…

So what else could you use ?

The simplest is probably ssh tunnelling.


lsc@chltlxlsc1:$ ssh -X oracle@localhost
Last login: Fri Max 2 10:24:09 2007 from localhost
oracle@chltlxlsc1:$ if xterm -e true; then echo success; fi
success

Another way to do this is to use X cookies.

lsc@chltlxlsc1:$ xauth extract ~/my-x-cookie $DISPLAY<
lsc@chltlxlsc1:$ setfacl -m u:oracle:r ~/my-x-cookie
lsc@chltlxlsc1:$ su - oracle -c "DISPLAY=$DISPLAY bash"
Password:
oracle@chltlxlsc1:$ if xterm -e true; then echo success; fi
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

xterm Xt error: Can't open display: :0.0
oracle@chltlxlsc1:$ xauth merge ~lsc/my-x-cookie
xauth: creating new authority file ~oracle/.Xauthority
oracle@chltlxlsc1:$ if xterm -e true; then echo success; fi
success

No need to type all. Here is my alias

alias oracle='
xauth extract $HOME/my-x-cookie $DISPLAY;
setfacl -m u:oracle:r $HOME/my-x-cookie;
su - oracle -c "export DISPLAY=$DISPLAY;
xauth merge $HOME/my-x-cookie;
bash"'

3 thoughts on “xhost + is a huge security hole”

  1. In my opinion, SSH tunneling is the way to go.

    Thanks for sharing this information for those moving from Windows to Linux.

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