@companieshouse/web-security-node
v4.4.2
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Middleware for chs authentication
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web-security-node
Security for web applications in node
Authorisation
With the introduction of Verification for certain business functions, the way *-web
applications use authentication is now in two main categories - see Integrating Verification into the Authentication Service scopes and permissions for background information.
- The application needs a specific OAUTH scope, in which case authentication needs to be done using one of the functions in the
src/scopes-permissions
directory. OR - A user just needs to be logged in (or do a company login), in which case the
authMiddleware
function insrc/index.ts
is used
When a *-web
applications is architected, it will be decided if authorisation needs a specific OAuth scope or not. If it does, if one is not present then a new function needs to be developed in the src/scopes-permissions
directory.
Cross Site Request Forgery (CSRF) protection
This library provides a Express middleware Request Handler which will protect
an application from Cross Site Request Forgery (CSRF) attacks. The middleware
works by looking for a token within the request which should match a token held
within the CHS session. The middleware will expect all requests from methods
which modify data (for example POST
/DELETE
/PUT
) to include the CSRF
token. This implements a
Synchronisation Token Pattern approach
[!IMPORTANT] If you are submitting requests which are of type
multipart/form-data
then you will will need to send the CSRF token as a header, by default: this is the headerx-csrf-token
but can be customised using the options.
Installation instructions
Install the library (if not already installed).
npm i @companieshouse/web-security-node@^4.1.0
Define the options for the middleware and add the middleware to the application. Optionally, you can add the error handler too.
import { CsrfProtectionMiddleware } from " @companieshouse/web-security-node" import { SessionStore, SessionMiddleware, EnsureSessionCookiePresentMiddleware } from '@companieshouse/node-session-handler'; import express from "express"; import cookieParser from 'cookie-parser'; import Redis from 'ioredis'; const app = express(); // apply other middlewares app.use(cookieParser()); app.use(express.urlencoded({ extended: true })); const cookieName = '__SID' const cookieConfig = { cookieName, cookieSecret: config.COOKIE_SECRET, cookieDomain: config.COOKIE_DOMAIN, cookieTimeToLiveInSeconds: parseInt(config.DEFAULT_SESSION_EXPIRATION, 10) }; const sessionStore = new SessionStore(new Redis(`redis://${config.CACHE_SERVER}`)); // Important the session Middleware is required before this middleware since the // token is stored within the session app.use(SessionMiddleware(cookieConfig, sessionStore)); const csrfMiddlewareOptions = { sessionStore, enabled: true, sessionCookieName: cookieName } app.use(createLoggerMiddleware(config.applicationNamespace)); // Recommended to use the EnsureSessionCookiePresentMiddleware from // `node-session-handler` too - see subsequent note app.use(EnsureSessionCookiePresentMiddleware(cookieConfig)) // It is important that CSRF Protection follows the Sesion and urlencoded // Middlewares, maybe put at end of the middleware chain (before // controllers) app.use(CsrfProtectionMiddleware(csrfMiddlewareOptions)) app.use(helmet()); // Add other middlewares and routers
Note the addition of:
EnsureSessionCookiePresentMiddleware
ensures that there is a session cookie in the request before handling the CSRF token. This is important because the CSRF middleware cannot add the CSRF to the session without a session cookie. Without this step any mutable requests following an unauthenticated action will fail. If your application is only authenticated this may not be as applicable.Amend the
Nunjucks
configuration to add the third-party templates from this library:nunjucks .configure([ "dist/views", "node_modules/govuk-frontend/", "node_modules/govuk-frontend/components/", "node_modules/@companies-house/" ], nunjucksConfig)
In each form which submits data (or modifies data) add the following macro call
{% from "web-security-node/components/csrf-token-input/macro.njk" import csrfTokenInput %} <form action="POST"> {{ csrfTokenInput({ csrfToken: csrfToken }) }} <!-- Other form items ommitted --> </form>
Create an CSRF error page template and add the following macro call (or amend an existing template)
{% from "web-security-node/components/csrf-error/macro.njk" import csrfError %} {{ csrfError({}) }}
Create an error handler for CSRF Errors, you could start with:
import { ErrorRequestHandler, NextFunction, Request, Response } from 'express' import { CsrfError } from '@companieshouse/web-security-node' // TODO: Enter the template name here instead of <TEMPLATE NAME> const csrfErrorTemplateName = "<TEMPLATE NAME>"; const csrfErrorHandler = (err: CsrfError | Error, _: Request, res: Response, next: NextFunction) => { // handle non-CSRF Errors immediately if (!(err instanceof CsrfError)) { next(err); } return res.status(403).render( csrfErrorTemplateName, { // TODO: Complete this with any information required by your error // template, the CSRF Error component requires no information currently } ) };
Add the error handler to your application before the default Error Handler (to prevent CSRF errors being handled as normal exceptions.)
API
CsrfOptions
interface
Provides configuration to the middleware.
Properties
enabled
(boolean required) - whether or not to apply CSRF protectionssessionStore
(SessionStore required) - a SessionStore instance to manage the CHS sessionsessionCookieName
(string) - name of the cookie storing the signed Session IDcsrfTokenFactory
(supplier of string) - a callable when called will return a string to use as the session's CSRF token. Has signature:() => string
Defaults to a uuid supplier if not supplied.
createWhenCsrfTokenAbsent
(boolean) - whether to generate a new CSRF token if not present in the session. Only run on non-mutable requests (e.g. GET)headerName
(string) - name of the header to check. Defaults toX-CSRF-TOKEN
parameterName
(string) - name of the parameter in the request body to check. Defaults to_csrf
.errorWhenNoSessionCookie
(boolean) - defines the behaviour when a mutable request is received without a session cookie. When true will raise an error when the request does not contain a Cookie with Session ID, when false will do nothing and call next handler without an error (assuming this will be handled separately). This likely will be handled in a different handler therefore should not expect there to be a CSRF token to validate the request against. Defaults tofalse
.
CsrfProtectionMiddleware
function
A Request Handler capable of being used as a express Middleware function. Its
responsibility is checking that all mutable requests include a CSRF token which
indicates that they originated from the same CHS session and not an CSRF
attempt. The middleware expects that all mutable requests contain a token which
matches a token stored within the CHS session. It will add csrfToken
to
locals so that views can reference it as a variable.
Parameters
options
- (CsrfOptions
required) - the configuration for the middleware is provided as an object which implements the interfaceCsrfOptions
defaultCsrfTokenFactory
function
This function is the default CSRF issuing function, it essentially provides an uuid.
Exceptions
CsrfError
- Base class for all errors thrown by middleware
SessionUnsetError
- Thrown when a mutable request is received and the
session has not been set on the request. Likely due to application
misconfiguration. Check that the session handler is placed before the CSRF
middleware.
CsrfTokensMismatchError
- Thrown when the CSRF token is either missing
in the mutable request or does not match the CSRF token within the CHS session.
MissingCsrfSessionToken
- Thrown when there is no CSRF token within the
session to match the request's Token against.
Code Structure
For all parts of the API that this library provides, put the code in directories that have an index.ts
file so that clients can import the code from "@companieshouse/web-security-node"
.
For code private to this library, add these files in the src/private-helpers
directory (these need to be imported within this project using the filename with path).