Android authenticating with Kerberos

Android Authenticating with Kerberos

Introduction

Kerberos is a network authentication protocol that allows secure communication between clients and servers. It is commonly used in enterprise environments for authentication and authorization. This article will guide you through the process of implementing Kerberos authentication on Android.

Understanding Kerberos

• Ticket Granting Server (TGS): The TGS is responsible for issuing tickets to clients who want to access specific services.
• Key Distribution Center (KDC): The KDC is responsible for managing and distributing keys for users and services.
• Authentication Server (AS): The AS is responsible for verifying the identity of clients and issuing initial tickets.

Prerequisites

Before implementing Kerberos authentication on Android, ensure you have the following:

• A working Kerberos infrastructure (KDC, TGS, AS)
• A valid user account with Kerberos permissions
• The necessary Kerberos libraries for Android (e.g., gss-api-krb5, jcifs)

Implementation Steps

1. Setting up Kerberos Libraries

Add the necessary Kerberos libraries to your Android project’s dependencies. You can use the following libraries:

* **gss-api-krb5:** This library provides a Java interface for Kerberos authentication using the Generic Security Services API (GSS-API).
* **jcifs:** This library is commonly used for accessing network resources like SMB/CIFS shares using Kerberos.

2. Configuration File

Create a Kerberos configuration file (krb5.conf) in your Android project’s assets directory. This file contains information about your Kerberos infrastructure.

“`
[libdefaults]
default_realm = EXAMPLE.COM
dns_lookup_kdc = true
dns_lookup_realm = true
ticket_lifetime = 24h
renew_lifetime = 7d

[realms]
EXAMPLE.COM = {
kdc = kdc.example.com
admin_server = kdc.example.com
}
“`

3. Authentication Code

Use the following code snippet to authenticate a user using Kerberos:

“`java
import org.ietf.jgss.*;

public class KerberosAuthentication {

public static void main(String[] args) {
try {
// Initialize GSS context
GSSManager gssManager = GSSManager.getInstance();
GSSName serviceName = gssManager.createName(“HTTP@EXAMPLE.COM”, GSSName.NT_HOSTBASED_SERVICE);
GSSContext gssContext = gssManager.createContext(serviceName, GSS_KRB5_MECHANISM, null, 0);

// Initiate authentication
byte[] token = null;
while (true) {
token = gssContext.initSecContext(token, 0);
if (token != null) {
// Send token to the server
}
if (gssContext.isEstablished()) {
// Authentication successful
break;
}
token = gssContext.acceptSecContext(token, 0);
}

// Use authenticated connection
System.out.println(“Authenticated successfully”);

} catch (GSSException e) {
System.err.println(“Kerberos authentication failed: ” + e.getMessage());
}
}
}
“`

4. Server Communication

After successfully authenticating, you can establish a secure connection with the server using Kerberos credentials. For instance, you can use jcifs library to connect to SMB/CIFS shares.

“`java
import jcifs.smb.SmbFile;
import jcifs.smb.SmbFileInputStream;

public class KerberosFileAccess {

public static void main(String[] args) {
try {
String path = “smb://server.example.com/share/file.txt”;
SmbFile file = new SmbFile(path);

// Access the file using Kerberos credentials
SmbFileInputStream inputStream = new SmbFileInputStream(file);

// Process the file data
System.out.println(“File contents: ” + inputStream.read());
} catch (Exception e) {
System.err.println(“File access failed: ” + e.getMessage());
}
}
}
“`

Considerations

• Security: Use strong passwords and implement appropriate security measures to protect Kerberos credentials.
• Performance: Consider potential performance overhead associated with Kerberos authentication.
• Deployment: Carefully manage Kerberos configurations and ensure proper deployment for your Android application.

Conclusion

This article has provided a basic guide for implementing Kerberos authentication on Android. By following these steps and considering the important factors, you can securely authenticate Android users within your enterprise environment. Remember to consult official documentation and tutorials for further details and advanced scenarios.