Add support for sysconfig on Fedora/RHEL

This is useful for opting out from system-wide cryto policy for SSH
or configuring advanced use case (strong RNG seed).

Fixes: #141

defaults/main.yml

@@ -23,6 +23,19 @@ sshd_allow_reload: true
 # If the below is true, create a backup of the config file when the template is copied
 sshd_backup: true
 
+# If the below is true, also install the sysconfig file with the below options
+# (useful only on Fedora and RHEL)
+sshd_sysconfig: false
+
+# If the below is true the role will override also crypto policy configuration
+sshd_sysconfig_override_crypto_policy: false
+
+# If the below is set to non-zero value, the OpenSSL random generator is
+# reseeded with the given amount of random bytes (from getrandom(2)
+# with GRND_RANDOM or /dev/random). Minimum is 14 bytes when enabled.
+# This is not recommended to enable if you do not have hadware random generator
+sshd_sysconfig_use_strong_rng: 0
+
 # Empty dicts to avoid errors
 sshd: {}
 
@@ -43,3 +56,6 @@ __sshd_service: sshd
 __sshd_sftp_server: /usr/lib/openssh/sftp-server
 __sshd_defaults: {}
 __sshd_os_supported: no
+__sshd_sysconfig: false
+__sshd_sysconfig_supports_crypto_policy: false
+__sshd_sysconfig_supports_use_strong_rng: false

tasks/install.yml

@@ -20,6 +20,18 @@
     backup: "{{ sshd_backup }}"
   notify: reload_sshd
 
+- name: Sysconfig configuration
+  template:
+    src: sysconfig.j2
+    dest: "/etc/sysconfig/sshd"
+    owner: "root"
+    group: "root"
+    mode: "600"
+    backup: "{{ sshd_backup }}"
+  when:
+    - sshd_sysconfig|bool
+  notify: reload_sshd
+
 - name: Install systemd service files
   block:
     - name: Install service unit file

tasks/variables.yml

@@ -60,3 +60,7 @@
       set_fact:
         sshd_sftp_server: "{{ __sshd_sftp_server }}"
       when: sshd_sftp_server is not defined
+    - name: Define sshd_sysconfig
+      set_fact:
+        sshd_sysconfig: "{{ __sshd_sysconfig }}"
+      when: sshd_sysconfig is not defined

templates/sysconfig.j2

@@ -0,0 +1,10 @@
+# {{ ansible_managed }}
+{% if __sshd_sysconfig_supports_crypto_policy %}
+{%   if sshd_sysconfig_override_crypto_policy == true %}
+CRYPTO_POLICY=
+{%   endif %}
+{% endif %}
+
+{% if __sshd_sysconfig_supports_use_strong_rng %}
+SSH_USE_STRONG_RNG={{ sshd_sysconfig_use_strong_rng }}
+{% endif %}

vars/Fedora_31.yml

@@ -23,3 +23,4 @@ __sshd_defaults:
     - XMODIFIERS
   Subsystem: "sftp {{ sshd_sftp_server }}"
 __sshd_os_supported: yes
+__sshd_sysconfig_supports_crypto_policy: true

vars/RedHat_6.yml

@@ -19,3 +19,4 @@ __sshd_defaults:
   X11Forwarding: yes
   Subsystem: "sftp {{ sshd_sftp_server }}"
 __sshd_os_supported: yes
+__sshd_sysconfig_supports_use_strong_rng: true

vars/RedHat_7.yml

@@ -26,3 +26,4 @@ __sshd_defaults:
     - XMODIFIERS
   Subsystem: "sftp {{ sshd_sftp_server }}"
 __sshd_os_supported: yes
+__sshd_sysconfig_supports_use_strong_rng: true

vars/RedHat_8.yml

@@ -26,3 +26,5 @@ __sshd_defaults:
     - XMODIFIERS
   Subsystem: "sftp {{ sshd_sftp_server }}"
 __sshd_os_supported: yes
+__sshd_sysconfig_supports_use_strong_rng: true
+__sshd_sysconfig_supports_crypto_policy: true