@tsmx/express-jwt-validator

Simple express middleware for validating JWT bearer tokens.

Stop writing boilerplate code to protect express routes with JWT bearer tokens in your projects.

Supports optional log output using winston, log4js or any other compatible logger. For details refer to the log configuration section

Usage

const express = require('express');
const app = express();

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'YOUR_JWT_SECRET' 
});

app.get('/secret', verifyToken, (req, res) => {
  // token payload available in req.authData
  res.send('Only accessible with a valid JWT bearer token.');
});

For further customizing please refer to the configuration options.

How it works

This module exports a middleware function for express to check a request for a valid JSON Web token authorization. The token must be provided as a bearer token in the HTTP request header according to the RFC standard.

Requests with a failed JWT validation will be rejected with HTTP status 401 by default. If the validations succeeds, the verified JWT payload will be added to the request and it will be passed to the next element of the middleware chain.

Configuration options

When requiring in the middleware with...

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  /* configuration object */ 
});

...the passed configuration object supports the following properties.

Property	Description
secret	The JWT validation secret
header	Custom header HTTP name
strictBearerValidation	Enable/disable strict validation
rejectHttpStatus	Custom HTTP response status for failed validations
sendExpiredMessage	Enable/disable error message for expired tokens
requestAuthProp	Custom property name to store token data in req
logger	An optional logger to receive log output

secret

Type: String

Default: undefined

Mandatory: yes

The sceret used to verify the JWT bearer token. Must be present, otherwise an exception will be thrown.

Example:

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456' 
});

header

Type: String

Default: authorization

Mandatory: no

Can be used if the bearer token will be supplied in another header field than authorization (Note: HTTP header field names are case-insensitive).

Example:

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456', 
  header: 'auth' 
});

strictBearerValidation

Type: Boolean

Default: false

Mandatory: no

If set to true, the authorization header is strictly validated against the schema Bearer <JWT> (including the whitespace), like Bearer eyJhb.... If set to false (default), it is sufficient if the header consists of two strings separated by a whitespace whereas the second entry is considered to be the JWT.

Example:

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456', 
  strictBearerValidation: true
});

rejectHttpStatus

Type: Number

Default: 401

Mandatory: no

The HTTP status to be sent back to the client if the bearer token validation fails. Defaults to 401 for Unauthorized, could also be set to 403 Forbidden for example. Please note that although any status is possible here you should use an appropriate HTTP client error code.

Example:

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456',
  rejectHttpStatus: 403 
});

sendExpiredMessage

Type: Boolean

Default: true

Mandatory: no

If set to true, the rejection response will contain a JSON body with one property error and value TokenExpiredError indicating the client that the token has expired. This can be useful to allow the client to check that the token must be refreshed.

If set to false, an expired token will be rejected without any response body.

Example:

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456', 
  sendExpiredMessage: false 
});

requestAuthProp

Type: String

Default: authData

Mandatory: no

The name of the property in req where the JWT bearer token payload should be stored for further processing. Can be changed to any property name, please make sure it is unique and no other properties are overwritten.

Example:

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456', 
  requestAuthProp: 'tokenPayload' 
});

Token data would now be accessible with req.tokenPayload instead of req.authData in following middleware functions.

logger

Type: Object

Default: undefined

Mandatory: no

You can pass a winston or log4js logger instance (or any compatible) to get log output from the middleware. Compatible means that the logger must provide info, warn and error functions receiving a string to be logged.

Note: the package contains tests for winston and log4js.

The following events will be logged:

Event	Log level
Rejected - No auth header present	WARN
Rejected - No valid 'Bearer TOKEN' entry in auth header	WARN
Rejected - Strict Bearer validation failed	WARN
Rejected - Expired token was sent	WARN
Rejected - Invalid token was sent (potential attack)	ERROR
Passed - Valid Bearer token was sent	INFO

Example for winston:

const winston = require('winston');

winstonLogger = winston.createLogger({ /*... winston options ...*/ });

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456', 
  logger:  winstonLogger
});

Example for log4js:

const log4js = require('log4js');

log4js.configure({ /*... log4js options ...*/ });
log4jsLogger = log4js.getLogger();

const verifyToken = require('@tsmx/express-jwt-validator')({ 
  secret: 'MySecretKey-123456', 
  logger:  log4jsLogger
});