Java JWT

A Java implementation of JSON Web Token (JWT) - RFC 7519.

If you're looking for an Android version of the JWT Decoder take a look at our JWTDecode.Android library.

This library requires Java 8 or higher. The last version that supported Java 7 was 3.11.0.

Installation

The library is available on both Maven Central and Bintray, and the Javadoc is published here.

Maven

<dependency>
    <groupId>com.auth0</groupId>
    <artifactId>java-jwt</artifactId>
    <version>3.18.2</version>
</dependency>

Gradle

implementation 'com.auth0:java-jwt:3.18.2'

Available Algorithms

The library implements JWT Verification and Signing using the following algorithms:

Usage

Pick the Algorithm

The Algorithm defines how a token is signed and verified. It can be instantiated with the raw value of the secret in the case of HMAC algorithms, or the key pairs or KeyProvider in the case of RSA and ECDSA algorithms. Once created, the instance is reusable for token signing and verification operations.

When using RSA or ECDSA algorithms and you just need to sign JWTs you can avoid specifying a Public Key by passing a null value. The same can be done with the Private Key when you just need to verify JWTs.

Using static secrets or keys:

//HMAC
Algorithm algorithmHS = Algorithm.HMAC256("secret");

//RSA
RSAPublicKey publicKey = //Get the key instance
RSAPrivateKey privateKey = //Get the key instance
Algorithm algorithmRS = Algorithm.RSA256(publicKey, privateKey);

Note: How you obtain or read keys is not in the scope of this library. For an example of how you might implement this, see this gist.

HMAC Key Length and Security

When using a Hash-based Message Authenticaton Code, e.g. HS256 or HS512, in order to comply with the strict requirements of the JSON Web Algorithms (JWA) specification (RFC7518), you must use a secret key which has the same (or larger) bit length as the size of the output hash. This is to avoid weakening the security strength of the authentication code (see NIST recomendations NIST SP 800-117). For example, when using HMAC256, the secret key length must be a minimum of 256 bits.

Using a KeyProvider:

By using a KeyProvider you can change in runtime the key used either to verify the token signature or to sign a new token for RSA or ECDSA algorithms. This is achieved by implementing either RSAKeyProvider or ECDSAKeyProvider methods:

• getPublicKeyById(String kid): Its called during token signature verification and it should return the key used to verify the token. If key rotation is being used, e.g. JWK it can fetch the correct rotation key using the id. (Or just return the same key all the time).
• getPrivateKey(): Its called during token signing and it should return the key that will be used to sign the JWT.
• getPrivateKeyId(): Its called during token signing and it should return the id of the key that identifies the one returned by getPrivateKey(). This value is preferred over the one set in the JWTCreator.Builder#withKeyId(String) method. If you don't need to set a kid value avoid instantiating an Algorithm using a KeyProvider.

The following example shows how this would work with JwkStore, an imaginary JWK Set implementation. For simple key rotation using JWKS, try the jwks-rsa-java library.

final JwkStore jwkStore = new JwkStore("{JWKS_FILE_HOST}");
final RSAPrivateKey privateKey = //Get the key instance
final String privateKeyId = //Create an Id for the above key

RSAKeyProvider keyProvider = new RSAKeyProvider() {
    @Override
    public RSAPublicKey getPublicKeyById(String kid) {
        //Received 'kid' value might be null if it wasn't defined in the Token's header
        RSAPublicKey publicKey = jwkStore.get(kid);
        return (RSAPublicKey) publicKey;
    }

    @Override
    public RSAPrivateKey getPrivateKey() {
        return privateKey;
    }

    @Override
    public String getPrivateKeyId() {
        return privateKeyId;
    }
};

Algorithm algorithm = Algorithm.RSA256(keyProvider);
//Use the Algorithm to create and verify JWTs.

Create and Sign a Token

You'll first need to create a JWTCreator instance by calling JWT.create(). Use the builder to define the custom Claims your token needs to have. Finally to get the String token call sign() and pass the Algorithm instance.

• Example using HS256

  try {
      Algorithm algorithm = Algorithm.HMAC256("secret");
      String token = JWT.create()
          .withIssuer("auth0")
          .sign(algorithm);
  } catch (JWTCreationException exception){
      //Invalid Signing configuration / Couldn't convert Claims.
  }

• Example using RS256

  RSAPublicKey publicKey = //Get the key instance
  RSAPrivateKey privateKey = //Get the key instance
  try {
      Algorithm algorithm = Algorithm.RSA256(publicKey, privateKey);
      String token = JWT.create()
          .withIssuer("auth0")
          .sign(algorithm);
  } catch (JWTCreationException exception){
      //Invalid Signing configuration / Couldn't convert Claims.
  }

If a Claim couldn't be converted to JSON or the Key used in the signing process was invalid a JWTCreationException will raise.

Verify a Token

You'll first need to create a JWTVerifier instance by calling JWT.require() and passing the Algorithm instance. If you require the token to have specific Claim values, use the builder to define them. The instance returned by the method build() is reusable, so you can define it once and use it to verify different tokens. Finally call verifier.verify() passing the token.

• Example using HS256

  String token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXUyJ9.eyJpc3MiOiJhdXRoMCJ9.AbIJTDMFc7yUa5MhvcP03nJPyCPzZtQcGEp-zWfOkEE";
  try {
      Algorithm algorithm = Algorithm.HMAC256("secret");
      JWTVerifier verifier = JWT.require(algorithm)
          .withIssuer("auth0")
          .build(); //Reusable verifier instance
      DecodedJWT jwt = verifier.verify(token);
  } catch (JWTVerificationException exception){
      //Invalid signature/claims
  }

• Example using RS256

  String token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXUyJ9.eyJpc3MiOiJhdXRoMCJ9.AbIJTDMFc7yUa5MhvcP03nJPyCPzZtQcGEp-zWfOkEE";
  RSAPublicKey publicKey = //Get the key instance
  RSAPrivateKey privateKey = //Get the key instance
  try {
      Algorithm algorithm = Algorithm.RSA256(publicKey, privateKey);
      JWTVerifier verifier = JWT.require(algorithm)
          .withIssuer("auth0")
          .build(); //Reusable verifier instance
      DecodedJWT jwt = verifier.verify(token);
  } catch (JWTVerificationException exception){
      //Invalid signature/claims
  }

If the token has an invalid signature or the Claim requirement is not met, a JWTVerificationException will raise.

Time Validation

The JWT token may include DateNumber fields that can be used to validate that:

• The token was issued in a past date "iat" < TODAY
• The token hasn't expired yet "exp" > TODAY and
• The token can already be used. "nbf" < TODAY

When verifying a token the time validation occurs automatically, resulting in a JWTVerificationException being throw when the values are invalid. If any of the previous fields are missing they won't be considered in this validation.

To specify a leeway window in which the Token should still be considered valid, use the acceptLeeway() method in the JWTVerifier builder and pass a positive seconds value. This applies to every item listed above.

JWTVerifier verifier = JWT.require(algorithm)
    .acceptLeeway(1) // 1 sec for nbf, iat and exp
    .build();

You can also specify a custom value for a given Date claim and override the default one for only that claim.

JWTVerifier verifier = JWT.require(algorithm)
    .acceptLeeway(1)   //1 sec for nbf and iat
    .acceptExpiresAt(5)   //5 secs for exp
    .build();

If you need to test this behaviour in your lib/app cast the Verification instance to a BaseVerification to gain visibility of the verification.build() method that accepts a custom Clock. e.g.:

BaseVerification verification = (BaseVerification) JWT.require(algorithm)
    .acceptLeeway(1)
    .acceptExpiresAt(5);
Clock clock = new CustomClock(); //Must implement Clock interface
JWTVerifier verifier = verification.build(clock);

Decode a Token

String token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXUyJ9.eyJpc3MiOiJhdXRoMCJ9.AbIJTDMFc7yUa5MhvcP03nJPyCPzZtQcGEp-zWfOkEE";
try {
    DecodedJWT jwt = JWT.decode(token);
} catch (JWTDecodeException exception){
    //Invalid token
}

If the token has an invalid syntax or the header or payload are not JSONs, a JWTDecodeException will raise.

Header Claims

Algorithm ("alg")

Returns the Algorithm value or null if it's not defined in the Header.

String algorithm = jwt.getAlgorithm();

Type ("typ")

Returns the Type value or null if it's not defined in the Header.

String type = jwt.getType();

Content Type ("cty")

Returns the Content Type value or null if it's not defined in the Header.

String contentType = jwt.getContentType();

Key Id ("kid")

Returns the Key Id value or null if it's not defined in the Header.

String keyId = jwt.getKeyId();

Private Claims

Additional Claims defined in the token's Header can be obtained by calling getHeaderClaim() and passing the Claim name. A Claim will always be returned, even if it can't be found. You can check if a Claim's value is null by calling claim.isNull().

Claim claim = jwt.getHeaderClaim("owner");

When creating a Token with the JWT.create() you can specify header Claims by calling withHeader() and passing both the map of claims.

Map<String, Object> headerClaims = new HashMap();
headerClaims.put("owner", "auth0");
String token = JWT.create()
        .withHeader(headerClaims)
        .sign(algorithm);

The alg and typ values will always be included in the Header after the signing process.

Payload Claims

Issuer ("iss")

Returns the Issuer value or null if it's not defined in the Payload.

String issuer = jwt.getIssuer();

Subject ("sub")

Returns the Subject value or null if it's not defined in the Payload.

String subject = jwt.getSubject();

Audience ("aud")

Returns the Audience value or null if it's not defined in the Payload.

List<String> audience = jwt.getAudience();

Expiration Time ("exp")

Returns the Expiration Time value or null if it's not defined in the Payload.

Date expiresAt = jwt.getExpiresAt();

Not Before ("nbf")

Returns the Not Before value or null if it's not defined in the Payload.

Date notBefore = jwt.getNotBefore();

Issued At ("iat")

Returns the Issued At value or null if it's not defined in the Payload.

Date issuedAt = jwt.getIssuedAt();

JWT ID ("jti")

Returns the JWT ID value or null if it's not defined in the Payload.

String id = jwt.getId();

Private Claims

Additional Claims defined in the token's Payload can be obtained by calling getClaims() or getClaim() and passing the Claim name. A Claim will always be returned, even if it can't be found. You can check if a Claim's value is null by calling claim.isNull().

Map<String, Claim> claims = jwt.getClaims();    //Key is the Claim name
Claim claim = claims.get("isAdmin");

or

Claim claim = jwt.getClaim("isAdmin");

When creating a Token with the JWT.create() you can specify a custom Claim by calling withClaim() and passing both the name and the value.

String token = JWT.create()
        .withClaim("name", 123)
        .withArrayClaim("array", new Integer[]{1, 2, 3})
        .sign(algorithm);

You can also create a JWT by calling withPayload() and passing a map of claim names to values:

Map<String, Object> payloadClaims = new HashMap<>();
payloadClaims.put("@context", "https://auth0.com/");
String token = JWT.create()
        .withPayload(payloadClaims)
        .sign(algorithm);

You can also verify custom Claims on the JWT.require() by calling withClaim() and passing both the name and the required value.

JWTVerifier verifier = JWT.require(algorithm)
    .withClaim("name", 123)
    .withArrayClaim("array", 1, 2, 3)
    .build();
DecodedJWT jwt = verifier.verify("my.jwt.token");

Currently supported classes for custom JWT Claim creation and verification are: Boolean, Integer, Double, String, Date and Arrays of type String and Integer.

Claim Class

The Claim class is a wrapper for the Claim values. It allows you to get the Claim as different class types. The available helpers are:

Primitives

• asBoolean(): Returns the Boolean value or null if it can't be converted.
• asInt(): Returns the Integer value or null if it can't be converted.
• asDouble(): Returns the Double value or null if it can't be converted.
• asLong(): Returns the Long value or null if it can't be converted.
• asString(): Returns the String value or null if it can't be converted.
• asDate(): Returns the Date value or null if it can't be converted. This must be a NumericDate (Unix Epoch/Timestamp). Note that the JWT Standard specified that all the NumericDate values must be in seconds.

Custom Classes and Collections

To obtain a Claim as a Collection you'll need to provide the Class Type of the contents to convert from.

• as(class): Returns the value parsed as Class Type. For collections you should use the asArray and asList methods.
• asMap(): Returns the value parsed as Map<String, Object>.
• asArray(class): Returns the value parsed as an Array of elements of type Class Type, or null if the value isn't a JSON Array.
• asList(class): Returns the value parsed as a List of elements of type Class Type, or null if the value isn't a JSON Array.

If the values can't be converted to the given Class Type a JWTDecodeException will raise.

What is Auth0?

Auth0 helps you to:

• Add authentication with multiple authentication sources, either social like Google, Facebook, Microsoft Account, LinkedIn, GitHub, Twitter, Box, Salesforce, among others, or enterprise identity systems like Windows Azure AD, Google Apps, Active Directory, ADFS or any SAML Identity Provider.
• Add authentication through more traditional username/password databases.
• Add support for linking different user accounts with the same user.
• Support for generating signed Json Web Tokens to call your APIs and flow the user identity securely.
• Analytics of how, when and where users are logging in.
• Pull data from other sources and add it to the user profile, through JavaScript rules.

Create a free account in Auth0

1. Go to Auth0 and click Sign Up.
2. Use Google, GitHub or Microsoft Account to login.

Issue Reporting

If you have found a bug or if you have a feature request, please report them at this repository issues section. Please do not report security vulnerabilities on the public GitHub issue tracker. The Responsible Disclosure Program details the procedure for disclosing security issues.

Author

Auth0

License

This project is licensed under the MIT license. See the LICENSE file for more info.