javax.security.auth

---

1. Authenticating a User with JAAS

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

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

3. Creating a Custom Login Module

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

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

5. Using SAML with JAAS

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

6. Creating a Credential

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

7. Getting the Principal from a Credential

Principal principal = cred.getPrincipal();

8. Creating a Subject

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

9. Adding a Credential to a Subject

subject.getPrivateCredentials().add(cred);

10. Getting the Credentials from a Subject

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

11. Creating a LoginContext with Default Configuration

LoginContext lc = new LoginContext();

12. Creating a LoginContext with a Specific Configuration

LoginContext lc = new LoginContext("MyLoginContext");

13. Logging in with a LoginContext

lc.login();

14. Getting the Subject from a LoginContext

Subject subject = lc.getSubject();

15. Logout from a LoginContext

lc.logout();

16. Creating a PrivilegedAction

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

17. Executing a PrivilegedAction with a LoginContext

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

18. Creating an AccessController

AccessController ac = new AccessController();

19. Checking Permission with an AccessController

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

20. Creating a Policy

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

21. Setting a Policy with an AccessController

ac.setPolicy(policy);

22. Creating a ProtectionDomain

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

23. Getting the ProtectionDomain for a Class

ProtectionDomain pd = MyClass.class.getProtectionDomain();

24. Getting the Permissions from a ProtectionDomain

Permissions perms = pd.getPermissions();

25. Creating a CodeSource

CodeSource cs = new CodeSource(null, null);

26. Getting the CodeSource for a Class

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

27. Creating a Policy File

<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

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

30. Creating a PublicKey

PublicKey pubKey = kp.getPublic();

31. Creating a PrivateKey

PrivateKey privKey = kp.getPrivate();

32. Creating a Signature

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

33. Verifying a Signature

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

34. Creating a Message Digest

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

35. Creating a Message Digest for a File

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

36. Creating a Key Store

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

37. Getting a Key from a Key Store

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

38. Adding a Key to a Key Store

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

39. Creating a Certificate

X509Certificate cert = X509Certificate.getInstance(encodedCert);

40. Creating a Trust Manager

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

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

42. Creating a Key Pair Generator

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

43. Creating a Cipher

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

44. Encrypting Data with a Cipher

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

45. Decrypting Data with a Cipher

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

46. Creating a Secure Random

SecureRandom random = SecureRandom.getInstanceStrong();

47. Creating a Random Number

int num = random.nextInt();

48. Creating a SignedObject

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

49. Verifying a SignedObject

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

50. Creating a Certificate Authority

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