SSH Key Permissions chmod settings?

Question

I need to use SSH on my machine to access my website and its databases (setting up a symbolic link- but I digress).

Following problem

I enter the command:

ssh-keygen -t dsa

To generate public/private dsa key pair. I save it in the default (/home/user/.ssh/id_dsa) and enter Enter passphrase twice.

Then I get this back:

WARNING: UNPROTECTED PRIVATE KEY FILE!  
Permissions 0755 for '/home/etc.ssh/id_rsa' are too open. It is recommended that your private key files are NOT accessible by others. This private key will be ignored. bad permissions: ignore key: [then the FILE PATH in VAR/LIB/SOMEWHERE]

Now to work round this I then tried

sudo chmod 600 ~/.ssh/id_rsa         sudo chmod 600 ~/.ssh/id_rsa.pub    

But shortly after my computer froze up, and on logging back on there was a could not find .ICEauthority error.

I got round this problem and deleted the SSH files but want to be able to use the correct permissions to avoid these issues in future.

How should I set up ICEauthority, or where should I save the SSH Keys- or what permissions should they have? Would using a virtual machine be best?

This is all very new and I am on a very steep learning curve, so any help appreciated.

Answer 1

chmod 600 ~/.ssh/id_rsa; chmod 600 ~/.ssh/id_rsa.pub (i.e. chmod u=rw,go= ~/.ssh/id_rsa ~/.ssh/id_rsa.pub) are correct.

chmod 644 ~/.ssh/id_rsa.pub (i.e. chmod a=r,u+w ~/.ssh/id_rsa.pub) would also be correct, but chmod 644 ~/.ssh/id_rsa (i.e. chmod a=r,u+w ~/.ssh/id_rsa) would not be. Your public key can be public, what matters is that your private key is private.

Also your .ssh directory itself must be writable only by you: chmod 700 ~/.ssh or chmod u=rwx,go= ~/.ssh. You of course need to be able to read it and access files in it (execute permission). It isn't directly harmful if others can read it, but it isn't useful either.

You don't need sudo. Don't use sudo to manipulate your own files, that can only lead to mistakes.

The error about .ICEauthority is not related to the chmod commands you show. Either it's a coincidence or you ran some other commands that you aren't showing us.

Answer 2

    # Set public/private key permissions

    # Octal form
    chmod 600 ~/.ssh/id_rsa
    chmod 600 ~/.ssh/id_rsa.pub

    # Equivalent literal form
    chmod u=rw,go= ~/.ssh/id_rsa ~/.ssh/id_rsa.pub

    # Optional: make public key readable
    chmod 644 ~/.ssh/id_rsa.pub # chmod a=r,u+w ~/.ssh/id_rsa.pub

    # Set directory permissions
    chmod 700 ~/.ssh # chmod u=rwx,go= ~/.ssh

    # Legend for literal form
    # +: allow       -: deny         =: reset and allow
    # u: user        r: read
    # g: group       w: write
    # o: others      x: execute
    # a: all