Can you set the number of rounds that ansible’s password_hash jinja2 filter uses

ansiblehashpasswordyaml

In ansible, it's pretty convenient to use something like this:

- name: Make sure user password is set 
  user:
    name: my_user
    password: "{{ user_password|password_hash('sha512', 'SomeSalt') }}"

where user_password is the plaintext password, stored in an ansible vault file.

On my ansible 2.5.0 running on MacOS, this generates a password hash that looks something like this:

$6$rounds=656000$SomeSalt$PlupV2TAHwwc520gHp0dL4padL5EHa50G6hdYm.JLuy4pnP5u2F.HRAHZrGY77BwdRv5UbUGqIAbuhehS00ZD0

The problem I'm having is that the device I'm trying to configure is a Raspberry Pi, and as you can see from the hash generated, rounds=656000. This requires quite a bit of processing power to generate the hash, and on a Raspberry Pi, it takes 10-15 seconds. That means once this password hash is set for a user, any action that requires the Raspberry Pi to generate a hash to compare against it, like logins, or password changes, also requires 10-15 seconds.

Even worse, once this password hash is set for a user, if that's the user that ansible is connecting as, every single task that ansible runs takes significantly longer to complete. The length of time my playbook takes to run against the Raspberry Pi the first time (when the tasks actually have work to do) with a default password was about 15 min. My playbook sets the user password at the very end. The second run (when the tasks don't have anything to do) was about 30 min.

I don't see a way to change the number of rounds in the documentation for the password_hash() filter. Is this value configurable in any way?

Best Answer

There doesn't seem to be any option to provide a rounds argument using the password_hash filter. The function that gets called by the filter only accepts the password, hash type, and salt as arguments.

If you really need to set this, you could install mkpasswd (part of the whois package on Debian/Ubuntu), and run that. This isn't total secure, if another person was watching running processes on the system you are running ansible on, they would see the password in the 'ps ax' output.

- hosts: slowremote
  gather_facts: no
  tasks:
  - shell: |
      echo 'hunter2' | mkpasswd --method=sha-512 --rounds=1000 --stdin
    register: results
    delegate_to: localhost
  - debug:
      var: results.stdout_lines
  - name: Make sure user password is set 
    user:
      name: my_user
      password: "{{results.stdout_lines}}"

Related Solutions

Security – How to implement ansible with per-host passwords, securely

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.

Reasonable performance for a simple Ansible playbook against ~100 hosts

in your ansible.cfg set the following:

[defaults]

# profile each task
callback_whitelist = profile_tasks

# [don't validate host keys](http://docs.ansible.com/ansible/intro_configuration.html#host-key-checking)
host_key_checking = False

[ssh_connection]
pipelining = True

Also, in your playbook, set the strategy as 'free'

- hosts: all
  strategy: free
  tasks: [...]

Finally, disable fact gathering on your play: gather_facts: false

If, after profiling, you are seeing a lot of this:

TASK [pip foo]
ok: [10.192.197.252] => (item=ansible)
ok: [10.192.197.252] => (item=boto)
ok: [10.192.197.252] => (item=boto3)
ok: [10.192.197.252] => (item=passlib)
ok: [10.192.197.252] => (item=cryptography)

squash those actions in ansible.cfg under [defaults]:

e.g. squash_actions = yum,pip,bar

Best Answer

Related Solutions

Security – How to implement ansible with per-host passwords, securely

Reasonable performance for a simple Ansible playbook against ~100 hosts

Related Topic