Calvaweb

Select one or more user accounts that can login to the site using just their password via a custom login form supplied with the plugin. For security purposes, only user accounts with subscriber role can be selected and any accounts selected will be prevented from accessing the wordpress backend. The custom login/logout form is added to a template file using a PHP function ‘pol_showform()’. Like with the standard login form, if you pass ‘redirect_to’ on the querystring, it will use this as the url to redirect to after the login/logout.
<h3>Arbitrary section 1</h3>

Password only login

Log into the site using just your password. Restricted to specific users selected via the wordpress backend.

onelogin

This SAML plugin eliminates passwords and allows you to authenticate WordPress users (typically editors) against your existing Active Directory or LDAP server as well increase security using YubiKeys or VeriSign VIP Access via OneLogin. OneLogin is pre-integrated with thousands of apps and handles all of your SSO needs in the cloud and behind the firewall.
<ul>
<li>Eliminate passwords in WordPress</li>
<li>Allow users to sign into WordPress with their Active Directory or LDAP credentials</li>
<li>Give users one-click access from your intranet</li>
<li>Increase security using browser PKI certificates or two-factor authentication from Yubico or VeriSign</li>
<li>Easily prevent access from former employees and contractors</li>
</ul>
If you used this plugin before 2.2.0 with just-in-time provision active, Read: https://wpvulndb.com/vulnerabilities/8508 
To mitigate that bug, place the script at the root of wordpress and execute it (later remove it) https://gist.github.com/pitbulk/a8223c90a3534e9a7d5e0a93009a094f

OneLogin SAML SSO

This plugin provides single sign-on via SAML and gives users one-click access to their WordPress accounts from identity providers like OneLogin.

Password only login vs OneLogin SAML SSO