Puppet Class: cis_security_hardening::rules::sshd_kex

Defined in:
manifests/rules/sshd_kex.pp

Summary

Ensure only strong Key Exchange algorithms are used

Overview

Key exchange is any method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm. If the sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages received

Rationale: Key exchange methods that are considered weak should be removed. A key exchange method may be weak because too few bits are used, or the hashing algorithm is considered too weak. Using weak algorithms could expose connections to man-in-the-middle attacks.

Examples:

class { 'cis_security_hardening::rules::sshd_kex':
    enforce => true,
    kexs => ['a','b'],
}

Parameters:

  • enforce (Boolean) (defaults to: false) —

    Enforce the rule

  • kexs (Array) (defaults to: []) —

    Key exchange methods to add to config



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# File 'manifests/rules/sshd_kex.pp', line 26

class cis_security_hardening::rules::sshd_kex (
  Boolean $enforce  = false,
  Array $kexs       = [],
) {
  if $enforce {
    if (!empty($kexs)) {
      $path = ($facts['os']['name'] == 'SLES' and $facts['os']['release']['major'] == '12') ? {
        true    => '/usr/etc/ssh/sshd_config',
        default => '/etc/ssh/sshd_config',
      }
      $kexlist = $kexs.join(',')
      file_line { 'sshd-kexs':
        ensure => present,
        path   => $path,
        line   => "Kexalgorithms ${kexlist}",
        match  => '^#?Kexalgorithms.*',
        notify => Exec['reload-sshd'],
      }
    }
  }
}