linux - Sudo Cmnd_Alias Optional Arguments

07
2014-07
  • James Madison

    I would like to allow a command to be run under sudo with or without arguements. For example, both of these should work:

     rm -f /etc/stuff
     rm /etc/stuff/item.txt
    

    To get this to work, I need this in sudoers:

     Cmnd_Alias ITEM_RM = /bin/rm * /etc/*, /bin/rm /etc/*
    

    Which I then assign to a group. This works. But it makes me double-up on every command. I would like a way to have only one entry that does both:

     Cmnd_Alias ITEM_RM = /bin/rm {something goes here that does both} /etc/*
    

    I know that one approach is to wrap this in a script. I don't want to do that. I have dozens of these entries and I need all of them to work with and without knowing the arguements in advance.

    I also accept that I'm asking for something that is a bit of a security risk. No value in reminding me of that. I'm going for some security, not tight security. I need to keep peole from causing too much harm to the server, but we have a killer firewall and this server is not accessible from it, so the tight security is at the corporate level.

    Thoughts welcome!

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    Related Question

    linux - a safer no password sudo?
  • V_H

    Ok, here's my problem - Please don't yell at me for being insecure! :) This is on my host machine. I'm the only one using it so it's fairly safe, but I have a very complex password that is hard to type over and over. I use the console for moving files around and executing arbitrary commands a LOT, and I switch terminals, so sudo remembering for the console isn't enough (AND I still have to type in my terrible password at least once!) In the past I have used the NOPASSWD trick in sudoers but I've decided to be more secure. Is there any sort of compromise besides allowing no password access to certain apps? (which can still be insecure) Something that will stop malware and remote logins from sudo rm -rf /-ing me, but in my terminals I can type happily away? Can I have this per terminal, perhaps, so just random commands won't make it through? I've tried running the terminal emulations as sudo, but that puts me as root.


  • Related Answers
  • whitequark

    Try adding this to your sudo options:

    Defaults timestamp_timeout=0, tty_tickets
    

    tty_tickets option (on by default) will make sudo ask password if it was not asked previously in that particular tty (including terminal emulators ptys), and timestamp_timeout=0 option will make it not ask it again in the whole session.

    So, when you want to do some administrative operations, you can open terminal, sudo something, close it, and you will be safe again.

  • Rory Alsop

    The obvious solution to me is to reduce the complexity of your password. You seem happy to go for no password rather than a long, complex one, so why not look at this middle ground as a valid option?

    If your machine is connected to a network then there is a risk of compromise. With no password, you do open yourself up to opportunistic exploitation, so even a simple password offers extra security.

  • ewindisch

    The most secure alternative to using no password is to use an alternative authentication method via PAM. You could, for instance, use a smartcard reader. You'd simply insert the card before using 'sudo', and remove it when done. There is even a PAM module for voice authentication. If you can't find a PAM module that you like and you're not comfortable with C, there are Python bindings.

    Check out this list of PAM modules.

  • user39559

    Set rootpw on your /etc/sudoers:

     Defaults        rootpw
    

    Give root a simpler password than yours.

    Remember to forbid root on ssh, in case you have installed an ssh server.

    If your horrible password is to protect your files, then they are really protected only if they are encrypted, otherwise this is just "security theater". Assuming this is why you wanto to keep the big one, you will be safe: breaking root's password still won't be enough to decrypt your files, and any kind of malware will fry our CPU before guessing the password.

  • Boldewyn

    A different approach to /etc/sudoers and such would be sudo -i and staying root. For example, if you use GNU screen, you can have one window as regular user and a second, where you issue sudo -i and stay root.

    If your ~/.screenrc looks like this, issuing screen automatically opens you two "tabs" accordingly:

    hardstatus alwayslastline "%w"
    screen -t normal
    screen -t root sudo -i
    
  • UberJim

    in /etc/sudoers (visudo) add a line like this:

    uberjim ALL = (ALL) NOPASSWD:ALL

    then as your user, once logged in (with your secure password) you can just type:

    sudo /cmd/you/want/to/run
    

    No password required :) Have fun