# android-jwt
**Repository Path**: fastdroid/android-jwt
## Basic Information
- **Project Name**: android-jwt
- **Description**: Java JWT For Android
- **Primary Language**: Unknown
- **License**: MIT
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No
## Statistics
- **Stars**: 0
- **Forks**: 0
- **Created**: 2022-02-14
- **Last Updated**: 2022-02-16
## Categories & Tags
**Categories**: Uncategorized
**Tags**: None
## README
# Java JWT For Android
> [](https://jitpack.io/#com.gitee.fastdroid/android-jwt)
>
> 为`java-jwt`适配低版本的`android`系统，代码修改自：[https://github.com/auth0/java-jwt/tree/3.18.3](https://github.com/auth0/java-jwt/tree/3.18.3)
>
> 仅支持`android-21`到`android-26`，从`android-27`开始就可以正常使用[`java-jwt`](https://github.com/auth0/java-jwt)了
[](https://circleci.com/gh/auth0/java-jwt/tree/master)
[](https://codecov.io/github/auth0/java-jwt)
[](https://doge.mit-license.org)
[](https://javadoc.io/doc/com.auth0/java-jwt/latest/index.html)
A Java implementation of [JSON Web Token (JWT) - RFC 7519](https://tools.ietf.org/html/rfc7519).
If you're looking for an **Android** version of the JWT Decoder take a look at our [JWTDecode.Android](https://github.com/auth0/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](https://javadoc.io/doc/com.auth0/java-jwt/latest/index.html).
### Maven
```xml
com.auth0
java-jwt
3.18.3
```
### Gradle
```gradle
implementation 'com.auth0:java-jwt:3.18.3'
```
## Available Algorithms
The library implements JWT Verification and Signing using the following algorithms:
| JWS | Algorithm | Description |
| :-------------: | :-------------: | :----- |
| HS256 | HMAC256 | HMAC with SHA-256 |
| HS384 | HMAC384 | HMAC with SHA-384 |
| HS512 | HMAC512 | HMAC with SHA-512 |
| RS256 | RSA256 | RSASSA-PKCS1-v1_5 with SHA-256 |
| RS384 | RSA384 | RSASSA-PKCS1-v1_5 with SHA-384 |
| RS512 | RSA512 | RSASSA-PKCS1-v1_5 with SHA-512 |
| ES256 | ECDSA256 | ECDSA with curve P-256 and SHA-256 |
| ES256K | ECDSA256 | ECDSA with curve secp256k1 and SHA-256 |
| ES384 | ECDSA384 | ECDSA with curve P-384 and SHA-384 |
| ES512 | ECDSA512 | ECDSA with curve P-521 and SHA-512 |
## 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:
```java
//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](https://gist.github.com/lbalmaceda/9a0c7890c2965826c04119dcfb1a5469).
##### 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](https://tools.ietf.org/html/rfc7517) 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](https://auth0.com/docs/jwks) implementation. For simple key rotation using JWKS, try the [jwks-rsa-java](https://github.com/auth0/jwks-rsa-java) library.
```java
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`
```java
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`
```java
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`
```java
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`
```java
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.
```java
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.
```java
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.:
```java
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
```java
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.
```java
String algorithm = jwt.getAlgorithm();
```
#### Type ("typ")
Returns the Type value or null if it's not defined in the Header.
```java
String type = jwt.getType();
```
#### Content Type ("cty")
Returns the Content Type value or null if it's not defined in the Header.
```java
String contentType = jwt.getContentType();
```
#### Key Id ("kid")
Returns the Key Id value or null if it's not defined in the Header.
```java
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()`.
```java
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.
```java
Map 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.
```java
String issuer = jwt.getIssuer();
```
#### Subject ("sub")
Returns the Subject value or null if it's not defined in the Payload.
```java
String subject = jwt.getSubject();
```
#### Audience ("aud")
Returns the Audience value or null if it's not defined in the Payload.
```java
List audience = jwt.getAudience();
```
#### Expiration Time ("exp")
Returns the Expiration Time value or null if it's not defined in the Payload.
```java
Date expiresAt = jwt.getExpiresAt();
```
#### Not Before ("nbf")
Returns the Not Before value or null if it's not defined in the Payload.
```java
Date notBefore = jwt.getNotBefore();
```
#### Issued At ("iat")
Returns the Issued At value or null if it's not defined in the Payload.
```java
Date issuedAt = jwt.getIssuedAt();
```
#### JWT ID ("jti")
Returns the JWT ID value or null if it's not defined in the Payload.
```java
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()`.
```java
Map claims = jwt.getClaims(); //Key is the Claim name
Claim claim = claims.get("isAdmin");
```
or
```java
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.
```java
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:
```java
Map 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.
```java
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](https://tools.ietf.org/html/rfc7519#section-2) 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**.
* **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](https://auth0.com/docs/identityproviders), 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](https://auth0.com/docs/connections/database)**.
* Add support for **[linking different user accounts](https://auth0.com/docs/users/user-account-linking)** with the same user.
* Support for generating signed [Json Web Tokens](https://auth0.com/docs/tokens/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](https://auth0.com/docs/rules).
## Create a free account in Auth0
1. Go to [Auth0](https://auth0.com) 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](https://auth0.com/whitehat) details the procedure for disclosing security issues.
## Author
[Auth0](https://auth0.com/)
## License
This project is licensed under the MIT license. See the [LICENSE](LICENSE) file for more info.