CVE-2021-32817: express-hbs

express-hbs

Express handlebars template engine with multiple layouts, blocks and cached partials.

v2.0.0

Version 2 was a rewrite and cleanup, with no known breaking changes. Lots of bugs were fixed which may have subtly changed behaviour.

Full details: https://github.com/TryGhost/express-hbs/releases/tag/2.0.0

v1.0.0 Breaking Changes

If you’re upgrading from v0.8.4 to v1.0.0 there are some potentially breaking changes to be aware of:

1. Handlebars @v4.0.5 - please see the handlebars v4.0 compatibility notes
2. The file extension for partial files must now match the extension configured in extname - please see the PR

Usage

To use with express 4.

var hbs = require(‘express-hbs’);

// Use `.hbs` for extensions and find partials in `views/partials`. app.engine('hbs’, hbs.express4({ partialsDir: __dirname + ‘/views/partials’ })); app.set('view engine’, ‘hbs’); app.set('views’, __dirname + ‘/views’);

To use with express 3 is the same as above, except use hbs.express3

app.engine('hbs’, hbs.express3({ partialsDir: __dirname + ‘/views/partials’ }));

Options for #express3 and #express4

hbs.express4({ partialsDir: "{String/Array} [Required] Path to partials templates, one or several directories",

// OPTIONAL settings blockHelperName: "{String} Override ‘block’ helper name.", contentHelperName: "{String} Override ‘contentFor’ helper name.", defaultLayout: "{String} Absolute path to default layout template", extname: "{String} Extension for templates & partials, defaults to `.hbs`", handlebars: "{Module} Use external handlebars instead of express-hbs dependency", i18n: "{Object} i18n object", layoutsDir: "{String} Path to layout templates", templateOptions: "{Object} options to pass to template()", beautify: "{Boolean} whether to pretty print HTML, see github.com/einars/js-beautify .jsbeautifyrc",

// override the default compile onCompile: function(exhbs, source, filename) { var options; if (filename && filename.indexOf(‘partials’) > -1) { options = {preventIndent: true}; } return exhbs.handlebars.compile(source, options); } });

Syntax

To mark where layout should insert page

{{{body}}}

To declare a block placeholder in layout

{{{block "pageScripts"}}}

To define block content in a page

{{#contentFor "pageScripts"}}
  CONTENT HERE
{{/contentFor}}

Layouts

There are three ways to use a layout, listed in precedence order

1. Declarative within a page. Use handlebars comment

   {{!< LAYOUT}}
   

   Layout file resolution:

   If path starts with '.'
       LAYOUT is relative to template
   Else If `layoutsDir` is set
       LAYOUT is relative to `layoutsDir`
   Else
       LAYOUT from path.resolve(dirname(template), LAYOUT)
   

2. As an option to render

   ⚠️ This creates a potential security vulnerability:

   Do not use this option in conjunction with passing user submitted data to res.render e.g. res.render('index’, req.query). This allows users to read arbitrary files from your filesystem!

   res.render('veggies’, { title: 'My favorite veggies’, veggies: veggies, layout: ‘layout/veggie’ });

   This option also allows for layout suppression (both the default layout and when specified declaratively in a page) by passing in a falsey Javascript value as the value of the layout property:

   res.render('veggies’, { title: 'My favorite veggies’, veggies: veggies, layout: null // render without using a layout template });

   Layout file resolution:

   If path starts with '.'
       layout is relative to template
   Else If `layoutsDir` is set
       layout is relative to `layoutsDir`
   Else
       layout from path.resolve(viewsDir, layout)
   

3. Lastly, use defaultLayout if specified in hbs configuration options.

Layouts can be nested: just include a declarative layout tag within any layout template to have its content included in the declared “parent” layout. Be aware that too much nesting can impact performances, and stay away from infinite loops!

Helpers****Synchronous helpers

hbs.registerHelper('link’, function(text, options) { var attrs = []; for(var prop in options.hash) { attrs.push(prop + ‘="’ + options.hash[prop] + ‘"’); } return new hbs.SafeString( "<a " + attrs.join(" ") + “>” + text + “</a>” ); });

in markup

{{{link 'barc.com' href='http://barc.com'}}}

Asynchronous helpers

hbs.registerAsyncHelper('readFile’, function(filename, cb) { fs.readFile(path.join(viewsDir, filename), 'utf8’, function(err, content) { cb(new hbs.SafeString(content)); }); });

in markup

{{{readFile 'tos.txt'}}}

i18n support

Express-hbs supports i18n

var i18n = require(‘i18n’);

// minimal config i18n.configure({ locales: ['en’, ‘fr’], cookie: 'locale’, directory: __dirname + “/locales” });

app.engine('hbs’, hbs.express3({ // … options from above i18n: i18n, // registers __ and __n helpers })); app.set('view engine’, ‘hbs’); app.set('views’, viewsDir);

// cookies are needed app.use(express.cookieParser());

// init i18n module app.use(i18n.init);

Engine Instances

Create isolated engine instances with their own cache system and handlebars engine.

var hbs = require(‘express-hbs’); var instance1 = hbs.create(); var instance2 = hbs.create();

Template options

The main use case for template options is setting the handlebars “data” object - this creates global template variables accessible with an @ prefix.

Template options can be set in 3 ways. When setting global template options they can be passed as config on creation of an instance, and they can also be updated used the updateTemplateOptions(templateOptions) method of an instance. To set template options for an individual request they can be set on res.locals using the helper method updateLocalTemplateOptions(locals, templateOptions).

Both of these methods have a companion method getTemplateOptions() and getLocalTemplateOptions(locals), which should be used when extending or merging the current options.

Example

in File app.js

// http://expressjs.com/api.html#app.locals app.locals({ 'PROD_MODE’: ‘production’ === app.get(‘env’) });

File views/layout/default.hbs

<html> <head> <title>{{title}}</title> <link type="text/css" rel="stylesheet" href="/css/style.css"/> {{{block "pageStyles"}}} </head> <body> {{{body}}}

{{\> scripts}}

{{#if PROD\_MODE}}
{{{block 'googleAnalyticsScripts'}}}
{{/if}}

</body> </html>

File views/index.hbs

{{!< default}}

{{#contentFor 'pageStyles’}} <style> .clicker { color: blue; }; </style> {{/contentFor}}

<h1>{{title}}</h1> <p class="clicker">Click me!</p>

To run example project

npm install -d
node example/app.js

Testing

The test suite requires the grunt-cli package:

npm install -g grunt-cli
npm install -d

Once everything’s installed, just run:

npm test

Credits

Inspiration and code from donpark/hbs

Big thanks to all CONTRIBUTORS

License

The MIT License (MIT)

Copyright © 2012-2021 Barc, Inc., Ghost Foundation - Released under the MIT license.