Add APP_KEY_FILE environment variable

In lots environments having files with secrets is common (e.g. with
NixOS where static secrets in config files are not secure). This new
environment variable adds support for this. If a APP_KEY is defined it
will take precedence ofer APP_KEY_FILE
Tests have been added to show this beaviour.

.env.example

@@ -32,4 +32,4 @@ DB_PASSWORD=
 APP_KEY=
 
 # Uncomment to see errors in your browser, don't forget to comment it back when debugging finished
-#APP_DEBUG=true
+#APP_DEBUG=true

config/app.php

@@ -1,5 +1,11 @@
 <?php
 
+$key = env('APP_KEY', null);
+$key_file = env("APP_KEY_FILE", null);
+if (empty($key) && !empty($key_file)) {
+  $key = trim(file_get_contents($key_file));
+}
+
 return [
 
     /*
@@ -126,7 +132,7 @@ return [
     |
     */
 
-    'key' => env('APP_KEY'),
+    'key' => $key,
 
     'cipher' => 'AES-256-CBC',
 

phpunit.xml

@@ -28,5 +28,6 @@
         <env name="CACHE_DRIVER" value="array"/>
         <env name="SESSION_DRIVER" value="array"/>
         <env name="QUEUE_DRIVER" value="sync"/>
+        <env name="APP_KEY" value="value_from_phpunit"/>
     </php>
 </phpunit>

tests/Unit/.keyfile

@@ -0,0 +1 @@
+94SEEZqVUSdaVzC2xQLDtwspQSIrSdmR

tests/Unit/ConfigTest.php

@@ -0,0 +1,83 @@
+<?php
+
+namespace Tests\Unit;
+
+use Tests\TestCase;
+use Illuminate\Foundation\Testing\WithFaker;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+
+class ConfigTest extends TestCase
+{
+    protected $original_app_key;
+    protected $original_app_key_file;
+    protected $app_key_file = __DIR__ . "/.keyfile";
+    protected $app_key_file_content;
+
+    /**
+     * A basic test example.
+     *
+     * @return void
+     */
+    public function testExample()
+    {
+        $this->assertTrue(true);
+    }
+
+    protected function setUp()
+    {
+      $this->original_app_key = getenv("APP_KEY");
+      $this->original_app_key_file = getenv("APP_KEY_FILE");
+      # The assumption is, that file_get_contents is working
+      # So we can use this to avoid double values
+      $this->app_key_file_content = trim(file_get_contents($this->app_key_file));
+      parent::setUp();
+    }
+
+    public function tearDown() {
+      # This is to ensure tests don't influence each other
+      putenv("APP_KEY=" . $this->original_app_key);
+      putenv("APP_KEY_FILE=" . $this->original_app_key_file);
+    }
+
+    protected function assertKey($value) {
+      $config = require __DIR__.'/../../config/app.php';
+      $this->assertEquals($config["key"], $value);
+    }
+
+    protected function set_key($value, $suffix = null)
+    {
+      $key = "APP_KEY";
+      if (!empty($suffix)) {
+        $key = sprintf("APP_KEY_%s", $suffix);
+      }
+      $sep = "=";
+      if (empty($value)) {
+        # So we can unset this
+        $sep = "";
+      }
+      putenv(sprintf("%s%s%s", $key, $sep, $value));
+    }
+
+    public function test_app_key_from_environment()
+    {
+      $orig_env = getenv("APP_KEY");
+      $key = "configkeyfromenvironment";
+      $this->set_key($key);
+      $this->assertKey($key);
+    }
+
+    public function test_app_key_from_file()
+    {
+      $this->set_key(null);
+      $this->set_key($this->app_key_file, "FILE");
+      $this->assertKey($this->app_key_file_content);
+    }
+
+    public function test_environmen_takes_precedence()
+    {
+      $env_key = "configkeyfromenvironment";
+      $this->set_key($env_key);
+      $this->set_key($this->app_key_file, "FILE");
+      $this->assertKey($env_key);
+    }
+}