# javax.security.auth

***

**1. Authenticating a User with JAAS**

```java
LoginContext lc = new LoginContext("MyLoginModule", new CallbackHandler() {
  @Override
  public void handle(Callback[] callbacks) throws IOException {
    for (Callback callback : callbacks) {
      if (callback instanceof NameCallback) {
        ((NameCallback) callback).setName("username");
      } else if (callback instanceof PasswordCallback) {
        ((PasswordCallback) callback).setPassword("password".toCharArray());
      }
    }
  }
});
lc.login();
```

**2. Authorizing a User with JAAS**

```java
Subject subject = LoginContext.getCurrent().getSubject();
boolean authorized = subject.isPermitted(new Permission("my.permission"));
```

**3. Creating a Custom Login Module**

```java
public class MyLoginModule implements LoginModule {
  @Override
  public boolean login() {
    // Implement user authentication logic here
    return true;
  }

  @Override
  public boolean commit() {
    // Implement user authorization logic here
    return true;
  }

  @Override
  public boolean abort() {
    // Implement cleanup logic here
    return true;
  }
}
```

**4. Using OAuth2 with JAAS**

```java
LoginContext lc = new LoginContext("MyOAuth2LoginModule", new OAuth2CallbackHandler());
lc.login();
```

**5. Using SAML with JAAS**

```java
LoginContext lc = new LoginContext("MySAMLLoginModule", new SAMLCallbackHandler());
lc.login();
```

**6. Creating a Credential**

```java
Credential cred = new UsernamePasswordCredential("username", "password");
```

**7. Getting the Principal from a Credential**

```java
Principal principal = cred.getPrincipal();
```

**8. Creating a Subject**

```java
Subject subject = new Subject();
subject.getPrincipals().add(principal);
```

**9. Adding a Credential to a Subject**

```java
subject.getPrivateCredentials().add(cred);
```

**10. Getting the Credentials from a Subject**

```java
Set<Credential> credentials = subject.getPrivateCredentials(Credential.class);
```

**11. Creating a LoginContext with Default Configuration**

```java
LoginContext lc = new LoginContext();
```

**12. Creating a LoginContext with a Specific Configuration**

```java
LoginContext lc = new LoginContext("MyLoginContext");
```

**13. Logging in with a LoginContext**

```java
lc.login();
```

**14. Getting the Subject from a LoginContext**

```java
Subject subject = lc.getSubject();
```

**15. Logout from a LoginContext**

```java
lc.logout();
```

**16. Creating a PrivilegedAction**

```java
PrivilegedAction<String> action = new PrivilegedAction<>() {
  @Override
  public String run() {
    return System.getProperty("user.name");
  }
};
```

**17. Executing a PrivilegedAction with a LoginContext**

```java
String username = Subject.doAs(subject, action);
```

**18. Creating an AccessController**

```java
AccessController ac = new AccessController();
```

**19. Checking Permission with an AccessController**

```java
boolean permissionGranted = ac.checkPermission(new Permission("my.permission"));
```

**20. Creating a Policy**

```java
Policy policy = new Policy();
policy.addPermission(new Permission("my.permission"));
```

**21. Setting a Policy with an AccessController**

```java
ac.setPolicy(policy);
```

**22. Creating a ProtectionDomain**

```java
ProtectionDomain pd = new ProtectionDomain(null, new Permissions());
```

**23. Getting the ProtectionDomain for a Class**

```java
ProtectionDomain pd = MyClass.class.getProtectionDomain();
```

**24. Getting the Permissions from a ProtectionDomain**

```java
Permissions perms = pd.getPermissions();
```

**25. Creating a CodeSource**

```java
CodeSource cs = new CodeSource(null, null);
```

**26. Getting the CodeSource for a Class**

```java
CodeSource cs = MyClass.class.getProtectionDomain().getCodeSource();
```

**27. Creating a Policy File**

```xml
<policy>
  <grant codebase="file:<my_dir>/my_file.jar">
    <permission name="my.permission"/>
  </grant>
</policy>
```

**28. Installing a Policy File**

```
java -Djava.security.policy=<my_policy_file> <main_class>
```

**29. Creating a Private Key**

```java
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
KeyPair kp = kpg.generateKeyPair();
```

**30. Creating a PublicKey**

```java
PublicKey pubKey = kp.getPublic();
```

**31. Creating a PrivateKey**

```java
PrivateKey privKey = kp.getPrivate();
```

**32. Creating a Signature**

```java
Signature sig = Signature.getInstance("SHA256withRSA");
sig.initSign(privKey);
sig.update("data".getBytes());
byte[] signature = sig.sign();
```

**33. Verifying a Signature**

```java
sig.initVerify(pubKey);
sig.update("data".getBytes());
boolean verified = sig.verify(signature);
```

**34. Creating a Message Digest**

```java
MessageDigest md = MessageDigest.getInstance("SHA256");
byte[] digest = md.digest("data".getBytes());
```

**35. Creating a Message Digest for a File**

```java
md.update(Files.readAllBytes(Paths.get("file.txt")));
byte[] digest = md.digest();
```

**36. Creating a Key Store**

```java
KeyStore ks = KeyStore.getInstance("JKS");
ks.load(null, null);
```

**37. Getting a Key from a Key Store**

```java
Key key = ks.getKey("my_key", "password".toCharArray());
```

**38. Adding a Key to a Key Store**

```java
ks.setKey("my_key", key, "password".toCharArray(), null);
```

**39. Creating a Certificate**

```java
X509Certificate cert = X509Certificate.getInstance(encodedCert);
```

**40. Creating a Trust Manager**

```java
X509TrustManager tm = new X509TrustManager() {
  @Override
  public void checkClientTrusted(X509Certificate[] chain, String authType)
      throws CertificateException {
    // Implement trust checking logic here
  }

  @Override
  public void checkServerTrusted(X509Certificate[] chain, String authType)
      throws CertificateException {
    // Implement trust checking logic here
  }

  @Override
  public X509Certificate[] getAcceptedIssuers() {
    // Implement list of trusted issuers here
    return null;
  }
};
```

**41. Creating a Secure Socket Factory**

```java
SSLContext context = SSLContext.getInstance("TLS");
context.init(null, new TrustManager[] { tm }, new SecureRandom());
SSLSocketFactory ssf = context.getSocketFactory();
```

**42. Creating a Key Pair Generator**

```java
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
```

**43. Creating a Cipher**

```java
Cipher cipher = Cipher.getInstance("RSA");
```

**44. Encrypting Data with a Cipher**

```java
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
byte[] encryptedData = cipher.doFinal("data".getBytes());
```

**45. Decrypting Data with a Cipher**

```java
cipher.init(Cipher.DECRYPT_MODE, privKey);
byte[] decryptedData = cipher.doFinal(encryptedData);
```

**46. Creating a Secure Random**

```java
SecureRandom random = SecureRandom.getInstanceStrong();
```

**47. Creating a Random Number**

```java
int num = random.nextInt();
```

**48. Creating a SignedObject**

```java
SignedObject so = new SignedObject(
    "data", privKey, SignatureAlgorithm.RSAwithSHA256);
```

**49. Verifying a SignedObject**

```java
boolean verified = SignedObject.verify(so, pubKey);
```

**50. Creating a Certificate Authority**

```java
CertificateAuthority ca = CertificateAuthorityFactory.getInstance("X.509");
```