Adminer wrapper template for externally authenticated installations

index.php

<?php

function adminer_object() {
	class YourClass extends Adminer {

		protected $externals;

		function __construct($externals) {
			$this->externals = $externals;
		}

		function name() {
			return 'YourApp Adminer';
		}

		function credentials() {
			if (!$this->externals->authenticated) {
				auth_error('External authentication expired.');
			}
			return [
				$this->externals->host,
				$this->externals->user,
				$this->externals->pass,
			];
		}

		function database() {
			return $this->externals->database;
		}

		function loginForm() {
			if ($this->externals->authenticated) {
				$nonce = null;
				$response_headers = headers_list();
				while ($response_headers) {
					$response_header = array_pop($response_headers);
					if (preg_match('/^Content-Security-Policy:.*?\'nonce-([^\']+)/', $response_header, $nonce_matches)) {
						$nonce = $nonce_matches[1];
						break;
					}
				}
				if ($nonce !== null) {
					?>
					<style>form { display: none; }</style>
					<?php
				}
				parent::loginForm();# form fields required for login() to be triggered
				if ($nonce !== null) {
					?>
					<script nonce="<?= $nonce ?>">document.forms[0].submit()</script>
					<?php
				}
			}
			else {
				?>
				<a href="#link-to-your-log-in-page">Log in</a>
				<?php
			}
		}

		function login($login, $password) {
			return $this->externals->authenticated;
		}
	}

	# add logic to integrate with your system, here
	$host = $yourDbConfig->host;
	$database = $yourDbConfig->database;
	$user = $yourDbConfig->user;
	$password = $yourDbConfig->password;
	$authenticated = $yourAuth->isLoggedIn() && $yourAuth->hasPermissionTo('ruin_your_db');

	if (empty($_GET['db']) && $database != '') {
		$_GET['db'] = $database;
	}

	return new YourClass((object) compact('host', 'database', 'user', 'pass', 'authenticated'));
}

require 'path/to/your/adminer.php';

This is now a proper plugin.