Chapter 14. Configuring secure communication by using the ssh and sshd RHEL System Roles

Variables for the sshd System Role

sshd_enable

If set to False, the role is completely disabled. Defaults to True.

sshd_skip_defaults

If set to True, the System Role does not apply default values. Instead, you specify the complete set of configuration defaults by using either the sshd dict, or sshd_Key variables. Defaults to False.

sshd_manage_service

If set to False, the service is not managed, which means it is not enabled on boot and does not start or reload. Defaults to True except when running inside a container or AIX, because the Ansible service module does not currently support enabled for AIX.

sshd_allow_reload

If set to False, sshd does not reload after a change of configuration. This can help with troubleshooting. To apply the changed configuration, reload sshd manually. Defaults to the same value as sshd_manage_service except on AIX, where sshd_manage_service defaults to False but sshd_allow_reload defaults to True.

sshd_install_service

If set to True, the role installs service files for the sshd service. This overrides files provided in the operating system. Do not set to True unless you are configuring a second instance and you also change the sshd_service variable. Defaults to False.

The role uses the files pointed by the following variables as templates:

sshd_service_template_service (default: templates/sshd.service.j2)
sshd_service_template_at_service (default: templates/sshd@.service.j2)
sshd_service_template_socket (default: templates/sshd.socket.j2)

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sshd_service

This variable changes the sshd service name, which is useful for configuring a second sshd service instance.

sshd

A dict that contains configuration. For example:

sshd:
  Compression: yes
  ListenAddress:
    - 0.0.0.0

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sshd_OptionName

You can define options by using simple variables consisting of the sshd_ prefix and the option name instead of a dict. The simple variables override values in the sshd dict.. For example:

sshd_Compression: no

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sshd_match and sshd_match_1 to sshd_match_9

A list of dicts or just a dict for a Match section. Note that these variables do not override match blocks as defined in the sshd dict. All of the sources will be reflected in the resulting configuration file.

sshd_packages

You can override the default list of installed packages using this variable.

sshd_config_owner, sshd_config_group, and sshd_config_mode

You can set the ownership and permissions for the openssh configuration file that this role produces using these variables.

sshd_config_file

The path where this role saves the openssh server configuration produced.

sshd_config_namespace

The default value of this variable is null, which means that the role defines the entire content of the configuration file including system defaults. Alternatively, you can use this variable to invoke this role from other roles or from multiple places in a single playbook on systems that do not support drop-in directory. The sshd_skip_defaults variable is ignored and no system defaults are used in this case.

When this variable is set, the role places the configuration that you specify to configuration snippets in an existing configuration file under the given namespace. If your scenario requires applying the role several times, you need to select a different namespace for each application.

Note

Limitations of the openssh configuration file still apply. For example, only the first option specified in a configuration file is effective for most of the configuration options.

Technically, the role places snippets in "Match all" blocks, unless they contain other match blocks, to ensure they are applied regardless of the previous match blocks in the existing configuration file. This allows configuring any non-conflicting options from different roles invocations.

sshd_binary

The path to the sshd executable of openssh.

sshd_service

The name of the sshd service. By default, this variable contains the name of the sshd service that the target platform uses. You can also use it to set the name of the custom sshd service when the role uses the sshd_install_service variable.

sshd_verify_hostkeys

Defaults to auto. When set to auto, this lists all host keys that are present in the produced configuration file, and generates any paths that are not present. Additionally, permissions and file owners are set to default values. This is useful if the role is used in the deployment stage to make sure the service is able to start on the first attempt. To disable this check, set this variable to an empty list [].

sshd_hostkey_owner, sshd_hostkey_group, sshd_hostkey_mode

Use these variables to set the ownership and permissions for the host keys from sshd_verify_hostkeys.

sshd_sysconfig

On RHEL-based systems, this variable configures additional details of the sshd service. If set to true, this role manages also the /etc/sysconfig/sshd configuration file based on the following configuration. Defaults to false.

sshd_sysconfig_override_crypto_policy

In RHEL, when set to true, this variable overrides the system-wide crypto policy. Defaults to false.

sshd_sysconfig_use_strong_rng

On RHEL-based systems, this variable can force sshd to reseed the openssl random number generator with the number of bytes given as the argument. The default is 0, which disables this functionality. Do not turn this on if the system does not have a hardware random number generator.

Variables for the ssh System Role

ssh_user

You can define an existing user name for which the System Role modifies user-specific configuration. The user-specific configuration is saved in ~/.ssh/config of the given user. The default value is null, which modifies global configuration for all users.

ssh_skip_defaults

Defaults to auto. If set to auto, the System Role writes the system-wide configuration file /etc/ssh/ssh_config and keeps the RHEL defaults defined there. Creating a drop-in configuration file, for example by defining the ssh_drop_in_name variable, automatically disables the ssh_skip_defaults variable.

ssh_drop_in_name

Defines the name for the drop-in configuration file, which is placed in the system-wide drop-in directory. The name is used in the template /etc/ssh/ssh_config.d/{ssh_drop_in_name}.conf to reference the configuration file to be modified. If the system does not support drop-in directory, the default value is null. If the system supports drop-in directories, the default value is 00-ansible.

Warning

If the system does not support drop-in directories, setting this option will make the play fail.

The suggested format is NN-name, where NN is a two-digit number used for ordering the configuration files and name is any descriptive name for the content or the owner of the file.

ssh

A dict that contains configuration options and their respective values.

ssh_OptionName

You can define options by using simple variables consisting of the ssh_ prefix and the option name instead of a dict. The simple variables override values in the ssh dict.

ssh_additional_packages

This role automatically installs the openssh and openssh-clients packages, which are needed for the most common use cases. If you need to install additional packages, for example, openssh-keysign for host-based authentication, you can specify them in this variable.

ssh_config_file

The path to which the role saves the configuration file produced. Default value:

• If the system has a drop-in directory, the default value is defined by the template /etc/ssh/ssh_config.d/{ssh_drop_in_name}.conf.
• If the system does not have a drop-in directory, the default value is /etc/ssh/ssh_config.
• if the ssh_user variable is defined, the default value is ~/.ssh/config.

ssh_config_owner, ssh_config_group, ssh_config_mode

The owner, group and modes of the created configuration file. By default, the owner of the file is root:root, and the mode is 0644. If ssh_user is defined, the mode is 0600, and the owner and group are derived from the user name specified in the ssh_user variable.