node_encrypt: over the wire encryption.

  1. Overview
  2. Usage
  3. Ecosystem

Overview

Do you wish your Puppet catalogs didn't contain plain text secrets? Are you tired of limiting access to your Puppet reports because of the passwords clearly visible in the change events?

This module will encrypt values for each node specifically, using their own certificates. This means that not only do you not have plain text secrets, but each node can decrypt only its own secrets.

What precisely does that mean? A resource that looks like this will never have the contents of the file in the catalog or in any reports.

node_encrypt::file { '/tmp/foo':
  owner   => 'root',
  group   => 'root',
  content => 'This string will never appear in the catalog.',
}

This also comes with a Puppet Face which can be used to generate the encrypted block ready for pasting into your manifest, and a Puppet function which can be used to programmatically generate the encrypted block.

Note: Because it requires access to each node's signed certificates, this is only useful on the CA node unless you distribute certificates or generate encrypted blocks on the CA using the puppet node encrypt face. There is a class included to automate the public certificate distribution.

Usage

  • node_encrypt::file
    • This is a defined type that wraps a standard file resource, but allows you to encrypt the content in the catalog and reports.
  • puppet node encrypt
    • This is a Puppet Face that generates encrypted ciphertext on the command line.
    • puppet node encrypt -t testhost.example.com "encrypt some text"
  • puppet node decrypt
    • This is a Puppet Face that decrypts ciphertext on the command line. It is useful in command-line scripts, or in exec statements.
  • node_encrypt()
    • This is a Puppet function used to programmatically generate encrypted text. It's used internally so you won't need to call it yourself when using the node_encrypt::file type.
    • This can be used to generate text to pass to other types if/when they add support for this module.
    • Parameters:
      • String to be encrypted.
  • redact()
    • This Puppet function allows you to remove from the catalog the value of a parameter that a class was called with.
      • The name of the parameter to redact.
      • The message to replace the parameter's value with. (optional)
  • node_encrypt::certificates
    • This class will synchronize certificates to all compile masters.

The simplest usage is like the example shown in the Overview. This defined type accepts most of the standard file parameters and simply encrypts the file contents in the catalog.

# puppet agent -t
Info: Using configured environment 'production'
Info: Retrieving pluginfacts
Info: Retrieving plugin
Info: Loading facts
Info: Caching catalog for master.puppetlabs.vm
Info: Applying configuration version '1450109738'
Notice: /Stage[main]/Main/Node[default]/Node_encrypt::File[/tmp/foo]/Node_encrypted_file[/tmp/foo]/ensure: created
Notice: Applied catalog in 9.33 seconds
# echo blah > /tmp/foo
# puppet agent -t
Info: Using configured environment 'production'
Info: Retrieving pluginfacts
Info: Retrieving plugin
Info: Loading facts
Info: Caching catalog for master.puppetlabs.vm
Info: Applying configuration version '1450109821'
Notice: /Stage[main]/Main/Node[default]/Node_encrypt::File[/tmp/foo]/Node_encrypted_file[/tmp/foo]/content: content changed '<<encrypted>>' to '<<encrypted>>'
Notice: Applied catalog in 7.61 seconds

If you'd like to pre-encrypt your data, you can pass it as the encrypted_content instead. The ciphertext can be stored directly in your manifest file, in Hiera, or anywhere else you'd like. Note that if you choose to do this, the ciphertext must be encrypted specifically for each node. You cannot share secrets amongst nodes.

node_encrypt::file { '/tmp/foo':
  owner             => 'root',
  group             => 'root',
  encrypted_content => hiera('encrypted_foo'),
}

The ciphertext can be generated on the CA using the puppet node encrypt command.

# puppet node encrypt -t testhost.puppetlabs.vm "encrypt some text"
-----BEGIN PKCS7-----
MIIMqwYJKoZIhvcNAQcDoIIMnDCCDJgCAQAxggJ7MIICdwIBADBfMFoxWDBWBgNV
BAMMT1B1cHBldCBDQSBnZW5lcmF0ZWQgb24gcHVwcGV0ZmFjdG9yeS5wdXBwZXRs
[...]
MbxinAGtO0eF4i8ova9MJykDPe600IY2b9ZY4mIskDqvHS9bVoK4fJGuRWAXiVBY
bFaZ36l90LkyLLrrSfjah/Tdqd8cHrphofsWVFWBmM1uErX1jBuuzngIehm40pN7
ClVbGy9Ow3zado1spWfDwekLoiU5imk77J9POy0X8w==
-----END PKCS7-----

Function usage:

class secret ($password) {
  $encrypted = node_encrypt($password)

  file { '/etc/something/or/other.conf:
    ensure  => file,
    owner   => 'root',
    group   => 'root',
    mode    => '0644',
    content => "password = ${encrypted}",
  }

  redact('password')

  # could be called with the optional second parameter
  # redact('password', 'The password has been removed from the catalog')
}

node_encrypt($string)

This function simply encrypts the string passed to it using the certificate belonging to the client the catalog is being compiled for.

$encrypted = node_encrypt($password)

redact($parameter, $replacewith)

This function will modify the catalog during compilation to remove the named parameter from the class from which it was called. For example, if you wrote a class named foo and called redact('bar') from within that class, then the catalog would not record the value of bar that foo was called with.

class foo($bar) {
  # this call will display the proper output, but because it's not a resource
  # the string won't exist in the catalog.
  notice("Class['foo'] was called with param ${bar}")

  # but the catalog won't record what the passed in param was.
  redact('bar')
}

class { 'foo':
  bar => 'this will not appear in the catalog',
}

Warning: If you use that parameter to declare other classes or resources, then you must take further action to remove the parameter from those declarations!

This takes an optional second parameter of the value to replace the original parameter declaration with. This parameter is required if the class declares a type that is not String for the parameter you're redacting.

Using the command line decryption tool

This comes with a Puppet Face that can decrypt ciphertext on the command line, using the same agent certs as the encrypted file resource type. You can use this in your own scripts via several methods. Assume that we've set a variable like such:

# export SECRET=$(puppet node encrypt -t testhost.puppetlabs.vm "your mother was a hamster")
  • Passing data directly using the --data option:
    • puppet node decrypt --data "${SECRET}"
    • On some platforms, this may exceed command length limits!
  • Setting data in an environment variable and passing the name:
    • puppet node decrypt --env SECRET
  • Piping data to STDIN:
    • echo "${SECRET}" | puppet node decrypt
    • cat /file/with/encrypted/blob.txt | puppet node decrypt

This can be useful when running exec resources with embedded secrets. Note the careful use of single quotes to prevent variable expansion in Puppet:

exec { 'set service passphrase':
  command     => 'some-service --set-passphrase="$(puppet node decrypt --env SECRET)"',
  path        => '/opt/puppetlabs/bin:/usr/bin',
  environment => "SECRET=${node_encrypt('and your father smelt of elderberries')}",
}

Automatically distributing certificates to compile masters

The node_encrypt::certificates class can synchronize certificates across your infrastructure so that encryption works from all compile masters. Please be aware that this class will create a fileserver mount on the CA node making public certificates available for download by nodes listed in the $whitelist.

Classify all your masters, including the CA or Master of Masters, with this class. This will ensure that all masters have all agents' public certificates. Limit access to the certificates by passing a comma-separated list of compile master nodes as the $whitelist parameter.

Note:
If this is applied to nodes in a flat hierarchy (i.e., non Master of Masters), then all agents will have all public certificates synched. This is not a security risk, as public certificates are designed to be shared widely, but it is something you should be aware of.

Parameters:

  • [*whitelist*]
    • This is a comma-separated list of all nodes who are authorized to synchronize all certificates from the CA node. Defaults to *, or all nodes.

Using on masterless infrastructures

For the most part, node_encrypt doesn't have as much value in a masterless setup. When the agent is compiling its own catalog, there's no cached catalog or network transfer. Nevertheless, there are use cases for it. For example, if you have a report server configured, or are submitting catalogs & reports to PuppetDB, you likely want to keep secrets hidden.

node_encrypt won't work out of the box on a masterless node because it relies on the existence of the CA certificates. But it's easy to generate these certificates so that it will work. Keep in mind that without the full CA infrastructure, no other node will be able to decrypt these secrets.

$ rm -rf $(puppet master --configprint ssldir)/*
$ puppet cert list -a
$ puppet cert --generate ${puppet master --configprint certname} --dns_alt_names "$(puppet master --configprint dns_alt_names)"

Ecosystem

What about Hiera eyaml?

Does this project replace that tool?

Not at all. They exist in different problem spaces. Hiera eyaml is intended to protect your secrets on-disk and in your repository. With Hiera eyaml, you can add secrets to your codebase without having to secure the entire codebase. Having access to the code doesn't mean having access to the secrets in that code.

But the secrets are still exposed in the catalog and in reports. This means you should be protecting them as well. node_encrypt addresses that problem. The two projects happily coexist. You can (and should) use eyaml to store your secrets on disk, while you use node_encrypt to protect the rest of the pipeline.

Integration with other tools

This was designed to make it easy to integrate support into other tooling. For example, this pull request adds transparent encryption support to _rc's popular datacat module.

Disclaimer

I take no liability for the use of this module. As this uses standard Ruby and OpenSSL libraries, it should work anywhere Puppet itself does. I have not yet validated on anything other than CentOS, though.

Contact

binford2k@gmail.com