jwt-authshim

jwt-authshim is a fork version from jsonwebtoken and the intention of this fork is to address the package increased size Issue.  This is useful for the below scenario,  EdgeLambda attached to the cloudfront on viewer-request event has package size limit of 1 MB

Install

$ npm install jwt-authshim

Usage

jwt.sign(payload, secretOrPrivateKey, [options, callback])

(Asynchronous) If a callback is supplied, the callback is called with the err or the JWT.

(Synchronous) Returns the JWT as string

payload could be an object literal, buffer or string representing valid JSON.

Please note that exp or any other claim is only set if the payload is an object literal. Buffer or string payloads are not checked for JSON validity.

If payload is not a buffer or a string, it will be coerced into a string using JSON.stringify.

secretOrPrivateKey is a string (utf-8 encoded), buffer, object, or KeyObject containing either the secret for HMAC algorithms or the PEM encoded private key for RSA and ECDSA. In case of a private key with passphrase an object { key, passphrase } can be used (based on crypto documentation), in this case be sure you pass the algorithm option. When signing with RSA algorithms the minimum modulus length is 2048 except when the allowInsecureKeySizes option is set to true. Private keys below this size will be rejected with an error.

options:

• algorithm (default: HS256)
• expiresIn: expressed in seconds or a string describing a time span vercel/ms.

  Eg: 60, "2 days", "10h", "7d". A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc), otherwise milliseconds unit is used by default ("120" is equal to "120ms").

• notBefore: expressed in seconds or a string describing a time span vercel/ms.

  Eg: 60, "2 days", "10h", "7d". A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc), otherwise milliseconds unit is used by default ("120" is equal to "120ms").

• audience
• issuer
• jwtid
• subject
• noTimestamp
• header
• keyid
• mutatePayload: if true, the sign function will modify the payload object directly. This is useful if you need a raw reference to the payload after claims have been applied to it but before it has been encoded into a token.
• allowInsecureKeySizes: if true allows private keys with a modulus below 2048 to be used for RSA
• allowInvalidAsymmetricKeyTypes: if true, allows asymmetric keys which do not match the specified algorithm. This option is intended only for backwards compatibility and should be avoided.

There are no default values for expiresIn, notBefore, audience, subject, issuer. These claims can also be provided in the payload directly with exp, nbf, aud, sub and iss respectively, but you can't include in both places.

Remember that exp, nbf and iat are NumericDate, see related Token Expiration (exp claim)

The header can be customized via the options.header object.

Generated jwts will include an iat (issued at) claim by default unless noTimestamp is specified. If iat is inserted in the payload, it will be used instead of the real timestamp for calculating other things like exp given a timespan in options.expiresIn.

Synchronous Sign with default (HMAC SHA256)

var jwt = require('jwt-shim');
var token = jwt.sign({ foo: 'bar' }, 'shhhhh');

Synchronous Sign with RSA SHA256

// sign with RSA SHA256
var privateKey = fs.readFileSync('private.key');
var token = jwt.sign({ foo: 'bar' }, privateKey, { algorithm: 'RS256' });

Sign asynchronously

jwt.sign({ foo: 'bar' }, privateKey, { algorithm: 'RS256' }, function(err, token) {
  console.log(token);
});

Backdate a jwt 30 seconds

var older_token = jwt.sign({ foo: 'bar', iat: Math.floor(Date.now() / 1000) - 30 }, 'shhhhh');

Token Expiration (exp claim)

The standard for JWT defines an exp claim for expiration. The expiration is represented as a NumericDate:

A JSON numeric value representing the number of seconds from 1970-01-01T00:00:00Z UTC until the specified UTC date/time, ignoring leap seconds. This is equivalent to the IEEE Std 1003.1, 2013 Edition [POSIX.1] definition "Seconds Since the Epoch", in which each day is accounted for by exactly 86400 seconds, other than that non-integer values can be represented. See RFC 3339 [RFC3339] for details regarding date/times in general and UTC in particular.

This means that the exp field should contain the number of seconds since the epoch.

Signing a token with 1 hour of expiration:

jwt.sign({
  exp: Math.floor(Date.now() / 1000) + (60 * 60),
  data: 'foobar'
}, 'secret');

Another way to generate a token like this with this library is:

jwt.sign({
  data: 'foobar'
}, 'secret', { expiresIn: 60 * 60 });

//or even better:

jwt.sign({
  data: 'foobar'
}, 'secret', { expiresIn: '1h' });

jwt.verify(token, secretOrPublicKey, [options, callback])

(Asynchronous) If a callback is supplied, function acts asynchronously. The callback is called with the decoded payload if the signature is valid and optional expiration, audience, or issuer are valid. If not, it will be called with the error.

(Synchronous) If a callback is not supplied, function acts synchronously. Returns the payload decoded if the signature is valid and optional expiration, audience, or issuer are valid. If not, it will throw the error.

Warning: When the token comes from an untrusted source (e.g. user input or external requests), the returned decoded payload should be treated like any other user input; please make sure to sanitize and only work with properties that are expected

token is the JWT string

secretOrPublicKey is a string (utf-8 encoded), buffer, or KeyObject containing either the secret for HMAC algorithms, or the PEM encoded public key for RSA and ECDSA. If jwt.verify is called asynchronous, secretOrPublicKey can be a function that should fetch the secret or public key.

• algorithms: List of strings with the names of the allowed algorithms. For instance, ["HS256", "HS384"].

  If not specified a defaults will be used based on the type of key provided

  • secret - ['HS256', 'HS384', 'HS512']
  • rsa - ['RS256', 'RS384', 'RS512']
  • ec - ['ES256', 'ES384', 'ES512']
  • default - ['RS256', 'RS384', 'RS512']

• audience: if you want to check audience (aud), provide a value here. The audience can be checked against a string, a regular expression or a list of strings and/or regular expressions.

  Eg: "urn:foo", /urn:f[o]{2}/, [/urn:f[o]{2}/, "urn:bar"]

• complete: return an object with the decoded { payload, header, signature } instead of only the usual content of the payload.
• issuer (optional): string or array of strings of valid values for the iss field.
• jwtid (optional): if you want to check JWT ID (jti), provide a string value here.
• ignoreExpiration: if true do not validate the expiration of the token.
• ignoreNotBefore...
• subject: if you want to check subject (sub), provide a value here
• clockTolerance: number of seconds to tolerate when checking the nbf and exp claims, to deal with small clock differences among different servers
• maxAge: the maximum allowed age for tokens to still be valid. It is expressed in seconds or a string describing a time span vercel/ms.

  Eg: 1000, "2 days", "10h", "7d". A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc), otherwise milliseconds unit is used by default ("120" is equal to "120ms").

• clockTimestamp: the time in seconds that should be used as the current time for all necessary comparisons.
• nonce: if you want to check nonce claim, provide a string value here. It is used on Open ID for the ID Tokens. (Open ID implementation notes)
• allowInvalidAsymmetricKeyTypes: if true, allows asymmetric keys which do not match the specified algorithm. This option is intended only for backwards compatability and should be avoided.

// verify a token symmetric - synchronous
var decoded = jwt.verify(token, 'shhhhh');
console.log(decoded.foo) // bar

// verify a token symmetric
jwt.verify(token, 'shhhhh', function(err, decoded) {
  console.log(decoded.foo) // bar
});

// invalid token - synchronous
try {
  var decoded = jwt.verify(token, 'wrong-secret');
} catch(err) {
  // err
}

// invalid token
jwt.verify(token, 'wrong-secret', function(err, decoded) {
  // err
  // decoded undefined
});

// verify a token asymmetric
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, function(err, decoded) {
  console.log(decoded.foo) // bar
});

// verify audience
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo' }, function(err, decoded) {
  // if audience mismatch, err == invalid audience
});

// verify issuer
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo', issuer: 'urn:issuer' }, function(err, decoded) {
  // if issuer mismatch, err == invalid issuer
});

// verify jwt id
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo', issuer: 'urn:issuer', jwtid: 'jwtid' }, function(err, decoded) {
  // if jwt id mismatch, err == invalid jwt id
});

// verify subject
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo', issuer: 'urn:issuer', jwtid: 'jwtid', subject: 'subject' }, function(err, decoded) {
  // if subject mismatch, err == invalid subject
});

// alg mismatch
var cert = fs.readFileSync('public.pem'); // get public key
jwt.verify(token, cert, { algorithms: ['RS256'] }, function (err, payload) {
  // if token alg != RS256,  err == invalid signature
});

// Verify using getKey callback
// Example uses https://github.com/auth0/node-jwks-rsa as a way to fetch the keys.
var jwksClient = require('jwks-rsa');
var client = jwksClient({
  jwksUri: 'https://sandrino.auth0.com/.well-known/jwks.json'
});
function getKey(header, callback){
  client.getSigningKey(header.kid, function(err, key) {
    var signingKey = key.publicKey || key.rsaPublicKey;
    callback(null, signingKey);
  });
}

jwt.verify(token, getKey, options, function(err, decoded) {
  console.log(decoded.foo) // bar
});

jwt.decode(token [, options])

(Synchronous) Returns the decoded payload without verifying if the signature is valid.

Warning: This will not verify whether the signature is valid. You should not use this for untrusted messages. You most likely want to use jwt.verify instead.

Warning: When the token comes from an untrusted source (e.g. user input or external request), the returned decoded payload should be treated like any other user input; please make sure to sanitize and only work with properties that are expected

token is the JWT string

options:

• json: force JSON.parse on the payload even if the header doesn't contain "typ":"JWT".
• complete: return an object with the decoded payload and header.

Example

// get the decoded payload ignoring signature, no secretOrPrivateKey needed
var decoded = jwt.decode(token);

// get the decoded payload and header
var decoded = jwt.decode(token, {complete: true});
console.log(decoded.header);
console.log(decoded.payload)

Errors & Codes

Possible thrown errors during verification. Error is the first argument of the verification callback.

TokenExpiredError

Thrown error if the token is expired.

Error object:

• name: 'TokenExpiredError'
• message: 'jwt expired'
• expiredAt: [ExpDate]

jwt.verify(token, 'shhhhh', function(err, decoded) {
  if (err) {
    /*
      err = {
        name: 'TokenExpiredError',
        message: 'jwt expired',
        expiredAt: 1408621000
      }
    */
  }
});

JsonWebTokenError

Error object:

• name: 'JsonWebTokenError'
• message:
  • 'invalid token' - the header or payload could not be parsed
  • 'jwt malformed' - the token does not have three components (delimited by a .)
  • 'jwt signature is required'
  • 'invalid signature'
  • 'jwt audience invalid. expected: [OPTIONS AUDIENCE]'
  • 'jwt issuer invalid. expected: [OPTIONS ISSUER]'
  • 'jwt id invalid. expected: [OPTIONS JWT ID]'
  • 'jwt subject invalid. expected: [OPTIONS SUBJECT]'

jwt.verify(token, 'shhhhh', function(err, decoded) {
  if (err) {
    /*
      err = {
        name: 'JsonWebTokenError',
        message: 'jwt malformed'
      }
    */
  }
});

NotBeforeError

Thrown if current time is before the nbf claim.

Error object:

• name: 'NotBeforeError'
• message: 'jwt not active'
• date: 2018-10-04T16:10:44.000Z

jwt.verify(token, 'shhhhh', function(err, decoded) {
  if (err) {
    /*
      err = {
        name: 'NotBeforeError',
        message: 'jwt not active',
        date: 2018-10-04T16:10:44.000Z
      }
    */
  }
});

Algorithms supported

Array of supported algorithms. The following algorithms are currently supported.

| alg Parameter Value | Digital Signature or MAC Algorithm | |---------------------|------------------------------------------------------------------------| | HS256 | HMAC using SHA-256 hash algorithm | | HS384 | HMAC using SHA-384 hash algorithm | | HS512 | HMAC using SHA-512 hash algorithm | | RS256 | RSASSA-PKCS1-v1_5 using SHA-256 hash algorithm | | RS384 | RSASSA-PKCS1-v1_5 using SHA-384 hash algorithm | | RS512 | RSASSA-PKCS1-v1_5 using SHA-512 hash algorithm | | PS256 | RSASSA-PSS using SHA-256 hash algorithm (only node ^6.12.0 OR >=8.0.0) | | PS384 | RSASSA-PSS using SHA-384 hash algorithm (only node ^6.12.0 OR >=8.0.0) | | PS512 | RSASSA-PSS using SHA-512 hash algorithm (only node ^6.12.0 OR >=8.0.0) | | ES256 | ECDSA using P-256 curve and SHA-256 hash algorithm | | ES384 | ECDSA using P-384 curve and SHA-384 hash algorithm | | ES512 | ECDSA using P-521 curve and SHA-512 hash algorithm | | none | No digital signature or MAC value included |

Refreshing JWTs

First of all, we recommend you to think carefully if auto-refreshing a JWT will not introduce any vulnerability in your system.

TODO

• X.509 certificate chain is not checked

Author

jwtAuth