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I would like to use ansible to manage a group of existing servers. I have created an ansible_hosts file, and tested successfully (with the -K option) with commands that only target a single host

ansible -i ansible_hosts host1 --sudo -K # + commands ...

My problem now is that the user passwords on each host are different, but I can't find a way of handling this in Ansible.

Using -K, I am only prompted for a single sudo password up-front, which then seems to be tried for all subsequent hosts without prompting:

host1 | ...
host2 | FAILED => Incorrect sudo password
host3 | FAILED => Incorrect sudo password
host4 | FAILED => Incorrect sudo password
host5 | FAILED => Incorrect sudo password

Research so far:

  • a StackOverflow question with one incorrect answer ("use -K") and one response by the author saying "Found out I needed passwordless sudo"

  • the Ansible docs, which say "Use of passwordless sudo makes things easier to automate, but it’s not required." (emphasis mine)

  • this security StackExchange question which takes it as read that NOPASSWD is required

  • article "Scalable and Understandable Provisioning..." which says:

    "running sudo may require typing a password, which is a sure way of blocking Ansible forever. A simple fix is to run visudo on the target host, and make sure that the user Ansible will use to login does not have to type a password"

  • article "Basic Ansible Playbooks", which says

    "Ansible could log into the target server as root and avoid the need for sudo, or let the ansible user have sudo without a password, but the thought of doing either makes my spleen threaten to leap up my gullet and block my windpipe, so I don’t"

    My thoughts exactly, but then how to extend beyond a single server?

  • ansible issue #1227, "Ansible should ask for sudo password for all users in a playbook", which was closed a year ago by mpdehaan with the comment "Haven't seen much demand for this, I think most people are sudoing from only one user account or using keys most of the time."

So... how are people using Ansible in situations like these? Setting NOPASSWD in /etc/sudoers, reusing password across hosts or enabling root SSH login all seem rather drastic reductions in security.

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Is there a reason you're not using SSH keys? –  Trondh Dec 18 '13 at 21:53
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I am already using SSH keys; they don't affect sudo (which should still require a password). –  supervacuo Dec 19 '13 at 9:04
    
This may not be exactly what you're looking for, but on Ubuntu boxes I still use keys, i.e. putting my public key in /root/authorized_keys to get in directly as root. Obvious drawback is allowing root logins over ssh... I also disallow password logins over ssh and run fail2ban for added security. –  senorsmile Dec 23 '13 at 20:53
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@senorsmile thanks for the response! Would you mind making it into an answer instead so I can downvote you for not reading the question? –  supervacuo Dec 29 '13 at 16:27
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i.e. the ansible_ssh_password setting only applies to the SSH password (the clue is in the name...). & I'm already using key-based SSH login. –  supervacuo Dec 29 '13 at 16:28

3 Answers 3

You've certainly done your research...

From all of my experience with ansible what you're looking to accomplish, isn't supported. As you mentioned, ansible states that it does not require passwordless sudo, and you are correct, it does not. But I have yet to see any method of using multiple sudo passwords within ansible, without of course running multiple configs.

So, I can't offer the exact solution you are looking for, but you did ask...

"So... how are people using Ansible in situations like these? Setting NOPASSWD in /etc/sudoers, reusing password across hosts or enabling root SSH login all seem rather drastic reductions in security."

I can give you one view on that. My use case is 1k nodes in multiple data centers supporting a global SaaS firm in which I have to design/implement some insanely tight security controls due to the nature of our business. Security is always balancing act, more usability less security, this process is no different if you are running 10 servers or 1,000 or 100,000.

You are absolutely correct not to use root logins either via password or ssh keys. In fact, root login should be disabled entirely if the servers have a network cable plugged into them.

Lets talk about password reuse, in a large enterprise, is it reasonable to ask sysadmins to have different passwords on each node? for a couple nodes, perhaps, but my admins/engineers would mutiny if they had to have different passwords on 1000 nodes. Implementing that would be near impossible as well, each user would have to store there own passwords somewhere, hopefully a keypass, not a spreadsheet. And every time you put a password in a location where it can be pulled out in plain text, you have greatly decreased your security. I would much rather them know, by heart, one or two really strong passwords than have to consult a keypass file every time they needed to log into or invoke sudo on a machine.

So password resuse and standardization is something that is completely acceptable and standard even in a secure environment. Otherwise ldap, keystone, and other directory services wouldn't need to exist.

When we move to automated users, ssh keys work great to get you in, but you still need to get through sudo. Your choices are a standardized password for the automated user (which is acceptable in many cases) or to enable NOPASSWD as you've pointed out. Most automated users only execute a few commands, so it's quite possible and certainly desirable to enable NOPASSWD, but only for pre-approved commands. I'd suggest using your configuration management (ansible in this case) to manage your sudoers file so that you can easily update the password-less commands list.

Now, there are some steps you can take once you start scaling to further isolate risk. While we have 1000 or so nodes, not all of them are 'production' servers, some are test environments, etc. Not all admins can access production servers, those than can though use their same SSO user/pass|key as they would elsewhere. But automated users are a bit more secure, for instance an automated tool that non-production admins can access has a user & credentials that cannot be used in production. If you want to launch ansible on all nodes, you'd have to do it in two batches, once for non-production and once for production.

We also use puppet though, since it's an enforcing configuration management tool, so most changes to all environments would get pushed out through it.

Obviously, if that feature request you cited gets reopened/completed, what you're looking to do would be entirely supported. Even then though, security is a process of risk assessment and compromise. If you only have a few nodes that you can remember the passwords for without resorting to a post-it note, separate passwords would be slightly more secure. But for most of us, it's not a feasible option.

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Thanks, @Zeb -- I had imagined that users with dozens-to-thousands of servers would use NOPASSWD for sanity reasons anyway (probably supported by tighter firewall rules etc.), but it's good to read your use-case and thoughts on the threat model. –  supervacuo Dec 31 '13 at 12:39
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One comment, though, on your suggestion about restricting to "pre-approved" sudo commands (which did occur to me when I discovered that NOPASSWD is pretty much required). Unfortunately, this seems completely unsupported as well -- ansible makes no promises about calling e.g. chown or mkdir binaries directly, and needs to be able to sudo /bin/sh for most modules to work. –  supervacuo Dec 31 '13 at 13:00
    
I seem to recall one of my engineers complaining about that a while back, that's annoying. –  Zeb Jan 1 at 1:59

From Ansible 1.5 on, it is possible to use an encrypted vault for host_vars and other variables. This does at least enable you to store a per-host (or per-group) ansible_sudo_pass variable securely. Unfortunately, --ask-vault-pass will only prompt for a single vault password per ansible invocation, so you are still constrained to a single vault password for all the hosts that you’ll use together.

Nevertheless, for some uses this may be an improvement over having a single sudo password across multiple hosts, as an attacker without access to your encrypted host_vars would still need a separate sudo password for every machine (or machine group) that he or she attacks.

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The ansible_sudo_pass option seems new, too — and seems to do what I was asking for. A single vault password is ideal for my purposes, as well. Thanks! –  supervacuo May 11 at 13:49

With Ansible 1.5, it is possible to set the ansible_sudo_pass variable using lookup('password', …):

ansible_sudo_pass: "{{ lookup('password', 'passwords/' + inventory_hostname) }}"

I find this more convenient than using files in host_vars/ for several reasons:

  • I actually use with_password: "passwords/{{ inventory_hostname}} encrypt=sha256_crypt" to provision the passwords for the deploy remote user (which is then needed for sudo), so they are already present in the files (although doing these plaintext lookups loses the salt value stored in the file when the hashed value is generated).

  • This keeps just the passwords in the file (no ansible_sudo_pass: known plaintext) for some epsilon increase in cryptographic security. More significantly, it means that you aren't encrypting all the other host-specific variables, so they can be read without the vault password.

  • Putting the passwords in a separate directory makes it easier to keep the files out of source control, or to use a tool like git-crypt to store them in encrypted form (you can use this with earlier Ansible that lacks the vault feature). I use git-crypt and since I only check out the repository in decrypted form on encrypted filesystems, I don't bother with the vault and thus don't need to type a vault password. (Using both would of course be more secure.)

You can also use the lookup function with ansible_ssh_pass; this may even be possible with earlier versions of Ansible that don't have ansible_sudo_pass.

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