EditorSecurityTest.php

<?php

namespace Drupal\Tests\editor\Functional;

use Drupal\Component\Serialization\Json;
use Drupal\editor\Entity\Editor;
use Drupal\filter\Entity\FilterFormat;
use Drupal\Tests\BrowserTestBase;

/**
 * Tests XSS protection for content creators when using text editors.
 *
 * @group editor
 */
class EditorSecurityTest extends BrowserTestBase {
    
    /**
     * The sample content to use in all tests.
     *
     * @var string
     */
    protected static $sampleContent = '<p style="color: red">Hello, Dumbo Octopus!</p><script>alert(0)</script><embed type="image/svg+xml" src="image.svg" />';
    
    /**
     * {@inheritdoc}
     */
    protected $defaultTheme = 'stark';
    
    /**
     * The secured sample content to use in most tests.
     *
     * @var string
     */
    protected static $sampleContentSecured = '<p>Hello, Dumbo Octopus!</p>alert(0)';
    
    /**
     * The secured sample content to use in tests when the <embed> tag is allowed.
     *
     * @var string
     */
    protected static $sampleContentSecuredEmbedAllowed = '<p>Hello, Dumbo Octopus!</p>alert(0)<embed type="image/svg+xml" src="image.svg" />';
    
    /**
     * Modules to enable.
     *
     * @var array
     */
    protected static $modules = [
        'filter',
        'editor',
        'editor_test',
        'node',
    ];
    
    /**
     * User with access to Restricted HTML text format without text editor.
     *
     * @var \Drupal\user\UserInterface
     */
    protected $untrustedUser;
    
    /**
     * User with access to Restricted HTML text format with text editor.
     *
     * @var \Drupal\user\UserInterface
     */
    protected $normalUser;
    
    /**
     * User with access to Restricted HTML and tags considered dangerous.
     *
     * @var \Drupal\user\UserInterface
     */
    protected $trustedUser;
    
    /**
     * User with access to all text formats and text editors.
     *
     * @var \Drupal\user\UserInterface
     */
    protected $privilegedUser;
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        // Create 5 text formats, to cover all potential use cases:
        // 1. restricted_without_editor (untrusted: anonymous)
        // 2. restricted_with_editor (normal: authenticated)
        // 3. restricted_plus_dangerous_tag_with_editor (privileged: trusted)
        // 4. unrestricted_without_editor (privileged: admin)
        // 5. unrestricted_with_editor (privileged: admin)
        // With text formats 2, 3 and 5, we also associate a text editor that does
        // not guarantee XSS safety. "restricted" means the text format has XSS
        // filters on output, "unrestricted" means the opposite.
        $format = FilterFormat::create([
            'format' => 'restricted_without_editor',
            'name' => 'Restricted HTML, without text editor',
            'weight' => 0,
            'filters' => [
                // A filter of the FilterInterface::TYPE_HTML_RESTRICTOR type.
'filter_html' => [
                    'status' => 1,
                    'settings' => [
                        'allowed_html' => '<h2> <h3> <h4> <h5> <h6> <p> <br> <strong> <a>',
                    ],
                ],
            ],
        ]);
        $format->save();
        $format = FilterFormat::create([
            'format' => 'restricted_with_editor',
            'name' => 'Restricted HTML, with text editor',
            'weight' => 1,
            'filters' => [
                // A filter of the FilterInterface::TYPE_HTML_RESTRICTOR type.
'filter_html' => [
                    'status' => 1,
                    'settings' => [
                        'allowed_html' => '<h2> <h3> <h4> <h5> <h6> <p> <br> <strong> <a>',
                    ],
                ],
            ],
        ]);
        $format->save();
        $editor = Editor::create([
            'format' => 'restricted_with_editor',
            'editor' => 'unicorn',
        ]);
        $editor->save();
        $format = FilterFormat::create([
            'format' => 'restricted_plus_dangerous_tag_with_editor',
            'name' => 'Restricted HTML, dangerous tag allowed, with text editor',
            'weight' => 1,
            'filters' => [
                // A filter of the FilterInterface::TYPE_HTML_RESTRICTOR type.
'filter_html' => [
                    'status' => 1,
                    'settings' => [
                        'allowed_html' => '<h2> <h3> <h4> <h5> <h6> <p> <br> <strong> <a> <embed>',
                    ],
                ],
            ],
        ]);
        $format->save();
        $editor = Editor::create([
            'format' => 'restricted_plus_dangerous_tag_with_editor',
            'editor' => 'unicorn',
        ]);
        $editor->save();
        $format = FilterFormat::create([
            'format' => 'unrestricted_without_editor',
            'name' => 'Unrestricted HTML, without text editor',
            'weight' => 0,
            'filters' => [],
        ]);
        $format->save();
        $format = FilterFormat::create([
            'format' => 'unrestricted_with_editor',
            'name' => 'Unrestricted HTML, with text editor',
            'weight' => 1,
            'filters' => [],
        ]);
        $format->save();
        $editor = Editor::create([
            'format' => 'unrestricted_with_editor',
            'editor' => 'unicorn',
        ]);
        $editor->save();
        // Create node type.
        $this->drupalCreateContentType([
            'type' => 'article',
            'name' => 'Article',
        ]);
        // Create 4 users, each with access to different text formats/editors:
        // - "untrusted": restricted_without_editor
        // - "normal": restricted_with_editor,
        // - "trusted": restricted_plus_dangerous_tag_with_editor
        // - "privileged": restricted_without_editor, restricted_with_editor,
        //   restricted_plus_dangerous_tag_with_editor,
        //   unrestricted_without_editor and unrestricted_with_editor
        $this->untrustedUser = $this->drupalCreateUser([
            'create article content',
            'edit any article content',
            'use text format restricted_without_editor',
        ]);
        $this->normalUser = $this->drupalCreateUser([
            'create article content',
            'edit any article content',
            'use text format restricted_with_editor',
        ]);
        $this->trustedUser = $this->drupalCreateUser([
            'create article content',
            'edit any article content',
            'use text format restricted_plus_dangerous_tag_with_editor',
        ]);
        $this->privilegedUser = $this->drupalCreateUser([
            'create article content',
            'edit any article content',
            'use text format restricted_without_editor',
            'use text format restricted_with_editor',
            'use text format restricted_plus_dangerous_tag_with_editor',
            'use text format unrestricted_without_editor',
            'use text format unrestricted_with_editor',
        ]);
        // Create an "article" node for each possible text format, with the same
        // sample content, to do our tests on.
        $samples = [
            [
                'author' => $this->untrustedUser
                    ->id(),
                'format' => 'restricted_without_editor',
            ],
            [
                'author' => $this->normalUser
                    ->id(),
                'format' => 'restricted_with_editor',
            ],
            [
                'author' => $this->trustedUser
                    ->id(),
                'format' => 'restricted_plus_dangerous_tag_with_editor',
            ],
            [
                'author' => $this->privilegedUser
                    ->id(),
                'format' => 'unrestricted_without_editor',
            ],
            [
                'author' => $this->privilegedUser
                    ->id(),
                'format' => 'unrestricted_with_editor',
            ],
        ];
        foreach ($samples as $sample) {
            $this->drupalCreateNode([
                'type' => 'article',
                'body' => [
                    [
                        'value' => self::$sampleContent,
                        'format' => $sample['format'],
                    ],
                ],
                'uid' => $sample['author'],
            ]);
        }
    }
    
    /**
     * Tests initial security: is the user safe without switching text formats?
     *
     * Tests 8 scenarios. Tests only with a text editor that is not XSS-safe.
     */
    public function testInitialSecurity() {
        $expected = [
            [
                'node_id' => 1,
                'format' => 'restricted_without_editor',
                // No text editor => no XSS filtering.
'value' => self::$sampleContent,
                'users' => [
                    $this->untrustedUser,
                    $this->privilegedUser,
                ],
            ],
            [
                'node_id' => 2,
                'format' => 'restricted_with_editor',
                // Text editor => XSS filtering.
'value' => self::$sampleContentSecured,
                'users' => [
                    $this->normalUser,
                    $this->privilegedUser,
                ],
            ],
            [
                'node_id' => 3,
                'format' => 'restricted_plus_dangerous_tag_with_editor',
                // Text editor => XSS filtering.
'value' => self::$sampleContentSecuredEmbedAllowed,
                'users' => [
                    $this->trustedUser,
                    $this->privilegedUser,
                ],
            ],
            [
                'node_id' => 4,
                'format' => 'unrestricted_without_editor',
                // No text editor => no XSS filtering.
'value' => self::$sampleContent,
                'users' => [
                    $this->privilegedUser,
                ],
            ],
            [
                'node_id' => 5,
                'format' => 'unrestricted_with_editor',
                // Text editor, no security filter => no XSS filtering.
'value' => self::$sampleContent,
                'users' => [
                    $this->privilegedUser,
                ],
            ],
        ];
        // Log in as each user that may edit the content, and assert the value.
        foreach ($expected as $case) {
            foreach ($case['users'] as $account) {
                $this->drupalLogin($account);
                $this->drupalGet('node/' . $case['node_id'] . '/edit');
                // Verify that the value is correctly filtered for XSS attack vectors.
                $this->assertSession()
                    ->fieldValueEquals('edit-body-0-value', $case['value']);
            }
        }
    }
    
    /**
     * Tests administrator security: is the user safe when switching text formats?
     *
     * Tests 24 scenarios. Tests only with a text editor that is not XSS-safe.
     *
     * When changing from a more restrictive text format with a text editor (or a
     * text format without a text editor) to a less restrictive text format, it is
     * possible that a malicious user could trigger an XSS.
     *
     * E.g. when switching a piece of text that uses the Restricted HTML text
     * format and contains a <script> tag to the Full HTML text format, the
     * <script> tag would be executed. Unless we apply appropriate filtering.
     */
    public function testSwitchingSecurity() {
        $expected = [
            [
                'node_id' => 1,
                // No text editor => no XSS filtering.
'value' => self::$sampleContent,
                'format' => 'restricted_without_editor',
                'switch_to' => [
                    'restricted_with_editor' => self::$sampleContentSecured,
                    // Intersection of restrictions => most strict XSS filtering.
'restricted_plus_dangerous_tag_with_editor' => self::$sampleContentSecured,
                    // No text editor => no XSS filtering.
'unrestricted_without_editor' => FALSE,
                    'unrestricted_with_editor' => self::$sampleContentSecured,
                ],
            ],
            [
                'node_id' => 2,
                // Text editor => XSS filtering.
'value' => self::$sampleContentSecured,
                'format' => 'restricted_with_editor',
                'switch_to' => [
                    // No text editor => no XSS filtering.
'restricted_without_editor' => FALSE,
                    // Intersection of restrictions => most strict XSS filtering.
'restricted_plus_dangerous_tag_with_editor' => self::$sampleContentSecured,
                    // No text editor => no XSS filtering.
'unrestricted_without_editor' => FALSE,
                    'unrestricted_with_editor' => self::$sampleContentSecured,
                ],
            ],
            [
                'node_id' => 3,
                // Text editor => XSS filtering.
'value' => self::$sampleContentSecuredEmbedAllowed,
                'format' => 'restricted_plus_dangerous_tag_with_editor',
                'switch_to' => [
                    // No text editor => no XSS filtering.
'restricted_without_editor' => FALSE,
                    // Intersection of restrictions => most strict XSS filtering.
'restricted_with_editor' => self::$sampleContentSecured,
                    // No text editor => no XSS filtering.
'unrestricted_without_editor' => FALSE,
                    // Intersection of restrictions => most strict XSS filtering.
'unrestricted_with_editor' => self::$sampleContentSecured,
                ],
            ],
            [
                'node_id' => 4,
                // No text editor => no XSS filtering.
'value' => self::$sampleContent,
                'format' => 'unrestricted_without_editor',
                'switch_to' => [
                    // No text editor => no XSS filtering.
'restricted_without_editor' => FALSE,
                    'restricted_with_editor' => self::$sampleContentSecured,
                    // Intersection of restrictions => most strict XSS filtering.
'restricted_plus_dangerous_tag_with_editor' => self::$sampleContentSecured,
                    // From no editor, no security filters, to editor, still no security
                    // filters: resulting content when viewed was already vulnerable, so
                    // it must be intentional.
'unrestricted_with_editor' => FALSE,
                ],
            ],
            [
                'node_id' => 5,
                // Text editor => XSS filtering.
'value' => self::$sampleContentSecured,
                'format' => 'unrestricted_with_editor',
                'switch_to' => [
                    // From editor, no security filters to security filters, no editor: no
                    // risk.
'restricted_without_editor' => FALSE,
                    'restricted_with_editor' => self::$sampleContentSecured,
                    // Intersection of restrictions => most strict XSS filtering.
'restricted_plus_dangerous_tag_with_editor' => self::$sampleContentSecured,
                    // From no editor, no security filters, to editor, still no security
                    // filters: resulting content when viewed was already vulnerable, so
                    // it must be intentional.
'unrestricted_without_editor' => FALSE,
                ],
            ],
        ];
        // Log in as the privileged user, and for every sample, do the following:
        // - switch to every other text format/editor
        // - assert the XSS-filtered values that we get from the server
        $this->drupalLogin($this->privilegedUser);
        $cookies = $this->getSessionCookies();
        foreach ($expected as $case) {
            $this->drupalGet('node/' . $case['node_id'] . '/edit');
            // Verify data- attributes.
            $body = $this->assertSession()
                ->fieldExists('edit-body-0-value');
            $this->assertSame(self::$sampleContent, $body->getAttribute('data-editor-value-original'), 'The data-editor-value-original attribute is correctly set.');
            $this->assertSame('false', (string) $body->getAttribute('data-editor-value-is-changed'), 'The data-editor-value-is-changed attribute is correctly set.');
            // Switch to every other text format/editor and verify the results.
            foreach ($case['switch_to'] as $format => $expected_filtered_value) {
                $post = [
                    'value' => self::$sampleContent,
                    'original_format_id' => $case['format'],
                ];
                $client = $this->getHttpClient();
                $response = $client->post($this->buildUrl('/editor/filter_xss/' . $format), [
                    'body' => http_build_query($post),
                    'cookies' => $cookies,
                    'headers' => [
                        'Accept' => 'application/json',
                        'Content-Type' => 'application/x-www-form-urlencoded',
                    ],
                    'http_errors' => FALSE,
                ]);
                $this->assertEquals(200, $response->getStatusCode());
                $json = Json::decode($response->getBody());
                $this->assertSame($expected_filtered_value, $json, 'The value was correctly filtered for XSS attack vectors.');
            }
        }
    }
    
    /**
     * Tests the standard text editor XSS filter being overridden.
     */
    public function testEditorXssFilterOverride() {
        // First: the Standard text editor XSS filter.
        $this->drupalLogin($this->normalUser);
        $this->drupalGet('node/2/edit');
        $this->assertSession()
            ->fieldValueEquals('edit-body-0-value', self::$sampleContentSecured);
        // Enable editor_test.module's hook_editor_xss_filter_alter() implementation
        // to alter the text editor XSS filter class being used.
        \Drupal::state()->set('editor_test_editor_xss_filter_alter_enabled', TRUE);
        // First: the Insecure text editor XSS filter.
        $this->drupalGet('node/2/edit');
        $this->assertSession()
            ->fieldValueEquals('edit-body-0-value', self::$sampleContent);
    }

}