Hardening Salt

This topic contains tips you can use to secure and harden your Salt environment. How you best secure and harden your Salt environment depends heavily on how you use Salt, where you use Salt, how your team is structured, where you get data from, and what kinds of access (internal and external) you require.

Important

The guidance here should be taken in combination with Salt Best Practices.

Important

Refer to the Receiving security announcements documentation in order to stay updated and secure.

Warning

For historical reasons, Salt requires PyCrypto as a "lowest common denominator". However, PyCrypto is unmaintained and best practice is to manually upgrade to use a more maintained library such as PyCryptodome. See Issue #52674 and Issue #54115 for more info

General hardening tips

  • Restrict who can directly log into your Salt master system.
  • Use SSH keys secured with a passphrase to gain access to the Salt master system.
  • Track and secure SSH keys and any other login credentials you and your team need to gain access to the Salt master system.
  • Use a hardened bastion server or a VPN to restrict direct access to the Salt master from the internet.
  • Don't expose the Salt master any more than what is required.
  • Harden the system as you would with any high-priority target.
  • Keep the system patched and up-to-date.
  • Use tight firewall rules. Pay particular attention to TCP/4505 and TCP/4506 on the salt master and avoid exposing these ports unnecessarily.

Salt hardening tips

Warning

Grains can be set by users that have access to the minion configuration files on the local system, making them less secure than other identifiers in Salt. Avoid storing sensitive data, such as passwords or keys, on minions. Instead, make use of Storing Static Data in the Pillar and/or Storing Data in Other Databases.

Important

Jinja supports a secure, sandboxed template execution environment that Salt takes advantage of. Other text Renderers do not support this functionality, so Salt highly recommends usage of jinja / jinja|yaml.

  • Subscribe to salt-users or salt-announce so you know when new Salt releases are available.
  • Keep your systems up-to-date with the latest patches.
  • Use Salt's Client ACL system to avoid having to give out root access in order to run Salt commands.
  • Use Salt's Client ACL system to restrict which users can run what commands.
  • Use external Pillar to pull data into Salt from external sources so that non-sysadmins (other teams, junior admins, developers, etc) can provide configuration data without needing access to the Salt master.
  • Make heavy use of SLS files that are version-controlled and go through a peer-review/code-review process before they're deployed and run in production. This is good advice even for "one-off" CLI commands because it helps mitigate typos and mistakes.
  • Use salt-api, SSL, and restrict authentication with the external auth system if you need to expose your Salt master to external services.
  • Make use of Salt's event system and reactor to allow minions to signal the Salt master without requiring direct access.
  • Run the salt-master daemon as non-root.
  • Disable which modules are loaded onto minions with the disable_modules setting. (for example, disable the cmd module if it makes sense in your environment.)
  • Look through the fully-commented sample master and minion config files. There are many options for securing an installation.
  • Run masterless-mode minions on particularly sensitive minions. There is also Salt SSH or the modules.sudo if you need to further restrict a minion.
  • Monitor specific security related log messages. Salt salt-master logs attempts to access methods which are not exposed to network clients. These log messages are logged at the error log level and start with Requested method not exposed.

Rotating keys

There are several reasons to rotate keys. One example is exposure or a compromised key. An easy way to rotate a key is to remove the existing keys and let the salt-master or salt-minion process generate new keys on restart.

Rotate a minion key

Run the following on the Salt minion:

salt-call saltutil.regen_keys
systemctl stop salt-minion

Run the following on the Salt master:

salt-key -d <minion-id>

Run the following on the Salt minion:

systemctl start salt-minion

Run the following on the Salt master:

salt-key -a <minion-id>

Rotate a master key

Run the following on the Salt master:

systemctl stop salt-master
rm <pki_dir>/master.{pem,pub}
systemctl start salt-master

Run the following on the Salt minion:

systemctl stop salt-minion
rm <pki_dir>/minion_master.pub
systemctl start salt-minion

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