security

Angel middleware designed to enhance application security by patching common Web security holes.

• Generic Middleware
  • Sanitizing HTML
  • CSRF Tokens
  • Banning by IP/Origin
  • Trusted Proxy
  • Throttling Requests
• Helmet Port
• Service Hooks
• Permissions

Sanitizing HTML

app.before.add(sanitizeHtmlInput());

// Or:
app.chain(sanitizeHtmlInput()).get(...)

CSRF Tokens

app.chain(verifyCsrfToken()).post('/form', ...);
app.responseFinalizers.add(setCsrfToken());

Banning by IP

app.before.add(banIp('1.2.3.4'));

// Or a range:
app.before.add(banIp('1.2.3.*'));
app.before.add(banIp('1.2.*.4'));

// Or multiple filters:
app.before.add(banIp(['1.2.3.4', '192.*.*.*', RegExp(r'1\.2.\3.\4')]));

// Also can ban origins
app.before.add(banOrigin('*.known-attacker.com'));

// By default, `banOrigin` forces users to have an `Origin` header.
// Use this flag to disable it:
app.before.add(banOrigin('evil.site', allowEmptyOrigin: true));

Trusted Proxy

Works well with Apache or Nginx.

// ONLY trust localhost X-Forwarded-* headers
app.before.add(trustProxy('127.0.0.1'));

Throttling Requests

Throws a 429 error if the given rate limit is exceeded.

// Example: 5 requests per minute
app.before.add(throttleRequests(5, Duration(minutes: 1)));

Helmet

Supplementary security library

Service Hooks

Also included are a set of service hooks, some ported from FeathersJS. Others are created just for Angel.

import 'package:angel_security/hooks.dart' as hooks;

Included:

• addUserToParams
• associateCurrentUser,
• hashPassword
• queryWithCurrentUser
• restrictToAuthenticated
• restrictToOwner
• variantPermission

Also exported is the helper function isServerSide. Use this to determine whether a service method is being called by the server, or by a client.

Permissions

Permissions are a great way to restrict access to resources.

They take the form of:

• service:foo
• service:create:*
• some:arbitrary:permission:*:with:*:a:wild:*card

The specifics are up to you.

var permission = Permission('admin | users:find');

// Or:
// PermissionBuilders support + and | operators. Operands can be Strings, Permissions or PermissionBuilders.
var permission = (PermissionBuilder('admin') | (PermissionBuilder('users') + 'find')).toPermission();

// Transform into middleware
app.chain(permission.toMiddleware()).get('/protected', ...);

// Or as a service hook
app.service('protected').beforeModify(permission.toHook());

// Dynamically create a permission hook.
// This helps in situations where the resources you need to protect are dynamic.
//
// `variantPermission` is included in the `package:angel_security/hooks.dart` library.
app.service('posts').beforeModify(variantPermission((e) {
    return PermissionBuilder('posts:modify:${e.id}');
}));