Here is an example of Java code that is vulnerable to a Remote File Inclusion (RFI) Vulnerability:
🥺 Vulnerable Code
import java.io.*;
import java.net.*;
public class RFI {
public static void main(String[] args) throws Exception {
// Vulnerable code: URL is not sanitized and is directly included in the program
URL url = new URL(args[0]); // args[0] can be manipulated by attacker
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);
in.close();
}
}😎 Secure Code
Here is a version of the same code that is secured against Remote File Inclusion (RFI) attack:
import java.io.*;
import java.net.*;
import java.util.regex.*;
public class RFI {
public static void main(String[] args) throws Exception {
// Secure code: URL is sanitized using regex to only allow local files
String pattern = "^(file://)?/[A-Za-z0-9_/.-]*$"; // regex for local file URLs
Pattern p = Pattern.compile(pattern);
Matcher m = p.matcher(args[0]);
if (!m.matches()) {
System.out.println("Invalid URL");
return;
}
URL url = new URL(args[0]);
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);
in.close();
}
}The line URL “url = new URL(args[0]);” was vulnerable in the original code, as it allowed an attacker to pass in a malicious URL that could be used to execute arbitrary code on the server. In the secure code, the URL is first checked against a regex pattern to ensure that it is a local file URL before it is included in the program.