<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

namespace core;

/**
 * Unit tests for core renderer render template exploit.
 *
 * @package core
 * @category test
 * @copyright 2019 Ryan Wyllie <ryan@moodle.com>
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
final class core_renderer_template_exploit_test extends \advanced_testcase {
    /**
     * Test cases to confirm that blacklisted helpers are stripped from the source
     * text by the helper before being passed to other another helper. This prevents
     * nested calls to helpers.
     */
    public static function get_template_testcases(): array {
        // Different helper implementations to test various combinations of nested
        // calls to render the templates.
        $norender = function($text) {
            return $text;
        };
        $singlerender = function($text, $helper) {
            return $helper->render($text);
        };
        $recursiverender = function($text, $helper) {
            $result = $helper->render($text);

            while (strpos($result, '{{') != false) {
                $result = $helper->render($result);
            }

            return $result;
        };

        return [
            'nested JS helper' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{#js}} some nasty JS {{/js}}{{/testpix}}',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $singlerender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,',
                'include' => false
            ],
            'other nested helper' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{#test1}} some text {{/test1}}{{/testpix}}',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $singlerender,
                    'test1' => $norender,
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,  some text',
                'include' => false
            ],
            'double nested helper' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{#test1}} some text {{#js}} some nasty JS {{/js}} {{/test1}}{{/testpix}}',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $singlerender,
                    'test1' => $norender,
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,  some text {{}}',
                'include' => false
            ],
            'js helper not nested' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, some text {{/testpix}}{{#js}} some nasty JS {{/js}}',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $singlerender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, some text',
                'include' => true
            ],
            'js in context not in helper' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{/testpix}}{{hack}}',
                ],
                'torender' => 'test',
                'context' => [
                    'hack' => '{{#js}} some nasty JS {{/js}}'
                ],
                'helpers' => [
                    'testpix' => $singlerender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, {{#js}} some nasty JS {{/js}}',
                'include' => false
            ],
            'js in context' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{hack}}{{/testpix}}',
                ],
                'torender' => 'test',
                'context' => [
                    'hack' => '{{#js}} some nasty JS {{/js}}'
                ],
                'helpers' => [
                    'testpix' => $singlerender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, {{}}',
                'include' => false
            ],
            'js in context double depth with single render' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{first}}{{/testpix}}',
                ],
                'torender' => 'test',
                'context' => [
                    'first' => '{{second}}',
                    'second' => '{{#js}} some nasty JS {{/js}}'
                ],
                'helpers' => [
                    'testpix' => $singlerender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, {{second}}',
                'include' => false
            ],
            'js in context double depth with recursive render' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{first}}{{/testpix}}',
                ],
                'torender' => 'test',
                'context' => [
                    'first' => '{{second}}',
                    'second' => '{{#js}} some nasty JS {{/js}}'
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,',
                'include' => false
            ],
            'partial' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, blah{{/testpix}}, {{> test2}}',
                    'test2' => 'some content',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, blah, some content',
                'include' => false
            ],
            'partial nested' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{> test2}}{{/testpix}}',
                    'test2' => 'some content',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, some content',
                'include' => false
            ],
            'partial with js' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, blah{{/testpix}}, {{> test2}}',
                    'test2' => '{{#js}} some nasty JS {{/js}}',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, blah,',
                'include' => true
            ],
            'partial nested with js' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{> test2}}{{/testpix}}',
                    'test2' => '{{#js}} some nasty JS {{/js}}',
                ],
                'torender' => 'test',
                'context' => [],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,',
                'include' => false
            ],
            'partial with js from context' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, blah{{/testpix}}, {{{foo}}}',
                    'test2' => '{{#js}} some nasty JS {{/js}}',
                ],
                'torender' => 'test',
                'context' => [
                    'foo' => '{{> test2}}'
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, blah, {{> test2}}',
                'include' => false
            ],
            'partial nested with js from context recursive render' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{foo}}{{/testpix}}',
                    'test2' => '{{#js}} some nasty JS {{/js}}',
                ],
                'torender' => 'test',
                'context' => [
                    'foo' => '{{> test2}}'
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,',
                'include' => false
            ],
            'partial nested with js from context single render' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{foo}}{{/testpix}}',
                    'test2' => '{{#js}} some nasty JS {{/js}}',
                ],
                'torender' => 'test',
                'context' => [
                    'foo' => '{{> test2}}'
                ],
                'helpers' => [
                    'testpix' => $singlerender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, {{&gt; test2}}',
                'include' => false
            ],
            'partial double nested with js from context recursive render' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{foo}}{{/testpix}}',
                    'test2' => '{{#js}} some nasty JS {{/js}}',
                ],
                'torender' => 'test',
                'context' => [
                    'foo' => '{{bar}}',
                    'bar' => '{{> test2}}'
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,',
                'include' => false
            ],
            'array context depth 1' => [
                'templates' => [
                    'test' => '{{#items}}{{#testpix}} core, move, {{.}}{{/testpix}}{{/items}}'
                ],
                'torender' => 'test',
                'context' => [
                    'items' => [
                        'legit',
                        '{{#js}}some nasty JS{{/js}}'
                    ]
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, legit core, move,',
                'include' => false
            ],
            'array context depth 2' => [
                'templates' => [
                    'test' => '{{#items}}{{#subitems}}{{#testpix}} core, move, {{.}}{{/testpix}}{{/subitems}}{{/items}}'
                ],
                'torender' => 'test',
                'context' => [
                    'items' => [
                        [
                            'subitems' => [
                                'legit',
                                '{{#js}}some nasty JS{{/js}}'
                            ]
                        ],
                    ]
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, legit core, move,',
                'include' => false
            ],
            'object context depth 1' => [
                'templates' => [
                    'test' => '{{#items}}{{#testpix}} core, move, {{.}}{{/testpix}}{{/items}}'
                ],
                'torender' => 'test',
                'context' => (object) [
                    'items' => [
                        'legit',
                        '{{#js}}some nasty JS{{/js}}'
                    ]
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, legit core, move,',
                'include' => false
            ],
            'object context depth 2' => [
                'templates' => [
                    'test' => '{{#items}}{{#subitems}}{{#testpix}} core, move, {{.}}{{/testpix}}{{/subitems}}{{/items}}'
                ],
                'torender' => 'test',
                'context' => (object) [
                    'items' => [
                        (object) [
                            'subitems' => [
                                'legit',
                                '{{#js}}some nasty JS{{/js}}'
                            ]
                        ],
                    ]
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move, legit core, move,',
                'include' => false
            ],
            'change delimeters' => [
                'templates' => [
                    'test' => '{{#testpix}} core, move, {{{foo}}}{{/testpix}}'
                ],
                'torender' => 'test',
                'context' => [
                    'foo' => '{{=<% %>=}} <%#js%>some nasty JS,<%/js%>'
                ],
                'helpers' => [
                    'testpix' => $recursiverender
                ],
                'js' => 'some nasty JS',
                'expected' => 'core, move,',
                'include' => false
            ]
        ];
    }

    /**
     * Test that the mustache_helper_collection class correctly strips.
     *
     * @dataProvider get_template_testcases
     * @param array $templates The template to add
     * @param string $torender The name of the template to render
     * @param array $context The template context
     * @param array $helpers Mustache helpers to add
     * @param string $js The JS string from the template
     * @param string $expected The expected output of the string after stripping JS
     * @param bool $include If the JS should be added to the page or not
     */
    public function test_core_mustache_engine_strips_js_helper(
        $templates,
        $torender,
        $context,
        $helpers,
        $js,
        $expected,
        $include
    ) {
        $page = new \moodle_page();
        $renderer = $page->get_renderer('core');

        // Get the mustache engine from the renderer.
        $reflection = new \ReflectionMethod($renderer, 'get_mustache');
        $reflection->setAccessible(true);
        $engine = $reflection->invoke($renderer);

        // Swap the loader out with an array loader so that we can set some
        // inline templates for testing.
        $loader = new \Mustache_Loader_ArrayLoader([]);
        $engine->setLoader($loader);

        // Add our test helpers.
        $helpercollection = $engine->getHelpers();
        foreach ($helpers as $name => $function) {
            $helpercollection->add($name, $function);
        }

        // Add our test template to be rendered.
        foreach ($templates as $name => $template) {
            $loader->setTemplate($name, $template);
        }

        // Confirm that the rendered template matches what we expect.
        $this->assertEquals($expected, trim($engine->render($torender, $context)));

        if ($include) {
            // Confirm that the JS was added to the page.
            $this->assertStringContainsString($js, $page->requires->get_end_code());
        } else {
            // Confirm that the JS wasn't added to the page.
            $this->assertStringNotContainsString($js, $page->requires->get_end_code());
        }
    }
}
