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  1. import java.io.ByteArrayInputStream;
  2. import java.io.ByteArrayOutputStream;
  3. import java.io.FileDescriptor;
  4. import java.io.FilePermission;
  5. import java.io.PrintStream;
  6. import java.lang.reflect.Field;
  7. import java.lang.reflect.Modifier;
  8.  
  9. public class Main {
  10.  
  11.   // Put everything in a static block so it is run before the static main method and any trailing (static) initializer-blocks:
  12.   static {
  13.     try {
  14.       initializing();
  15.     } catch (final Exception e) {
  16.     }
  17.   }
  18.  
  19.   static void initializing() throws Exception {
  20.     // Overwrite System.out, System.err and System.in:
  21.     System.setOut(new PrintStream(new ByteArrayOutputStream()));
  22.     System.setErr(new PrintStream(new ByteArrayOutputStream()));
  23.     System.setIn(new ByteArrayInputStream(new byte[0]));
  24.  
  25.     // Enable reflection for System.out, System.err and System.in:
  26.     final Field modifiersField = Field.class.getDeclaredField("modifiers");
  27.     modifiersField.setAccessible(true);
  28.     final Class<?> fdClass = java.io.FileDescriptor.class;
  29.     final Field outField = fdClass.getDeclaredField("out");
  30.     outField.setAccessible(true);
  31.     modifiersField.setInt(outField, outField.getModifiers() & ~Modifier.FINAL);
  32.     final Field errField = fdClass.getDeclaredField("err");
  33.     errField.setAccessible(true);
  34.     modifiersField.setInt(errField, errField.getModifiers() & ~Modifier.FINAL);
  35.     final Field inField = fdClass.getDeclaredField("in");
  36.     inField.setAccessible(true);
  37.     modifiersField.setInt(inField, inField.getModifiers() & ~Modifier.FINAL);
  38.  
  39.     // Replace existing System.out FileDescriptor with a new (useless) one:
  40.     outField.set(null, new FileDescriptor());
  41.     // Replace existing System.err FileDescriptor with a new (useless) one:
  42.     errField.set(null, new FileDescriptor());
  43.     // Replace existing System.in FileDescriptor with a new (useless) one:
  44.     inField.set(null, new FileDescriptor());
  45.  
  46.     // Disable reflection for System.out, System.err, System.in again:
  47.     modifiersField.setInt(outField, outField.getModifiers() & ~Modifier.FINAL);
  48.     modifiersField.setInt(errField, errField.getModifiers() & ~Modifier.FINAL);
  49.     modifiersField.setInt(inField, inField.getModifiers() & ~Modifier.FINAL);
  50.     inField.setAccessible(false);
  51.     errField.setAccessible(false);
  52.     outField.setAccessible(false);
  53.     modifiersField.setAccessible(false);
  54.  
  55.     // Overwrite the SecurityManager:
  56.     System.setSecurityManager(new SecurityManager() {
  57.  
  58.       private boolean exitAllowed = false;
  59.  
  60.       @Override
  61.       public void checkExec(final String cmd) {
  62.         throw new SecurityException();
  63.       }
  64.  
  65.       @Override
  66.       public void checkPermission(final java.security.Permission perm) {
  67.         final String name = perm.getName();
  68.         // You're not allowed to read/write files:
  69.         if (name.equals("setIO") || name.equals("writeFileDescriptor") || name.equals("readFileDescriptor")
  70.             || ((perm instanceof FilePermission) && name.startsWith("/proc/self/fd/"))) {
  71.           throw new SecurityException();
  72.         }
  73.         // You're not allowed to overwrite the Security settings:
  74.         if (name.equals("setSecurityManager") || name.equals("suppressAccessChecks")) {
  75.           throw new SecurityException();
  76.         }
  77.         // You're not allowed to use reflection anymore:
  78.         if (name.equals("getModifiers") || name.equals("get") || name.equals("set") || name.equals("setBoolean")
  79.             || name.equals("setByte") || name.equals("setChar") || name.equals("setShort") || name.equals("setInt")
  80.             || name.equals("setLong") || name.equals("setFloat") || name.equals("setDouble")
  81.             || name.equals("setFieldAccessor") || name.equals("setFieldAccessor")) {
  82.           throw new SecurityException();
  83.         }
  84.         // When you try to leave the current VM it will stop the program:
  85.         if (name.startsWith("exitVM") && !this.exitAllowed) {
  86.           this.exitAllowed = true;
  87.           System.exit(0);
  88.         }
  89.  
  90.         // You know what, nothing is allowed!
  91.         throw new SecurityException("Mhuahahahaha!");
  92.       }
  93.     });
  94.   }
  95.  
  96.   public static void main(String[] args) {
  97.     // Overwritting all given arguments:
  98.     args = new String[0];
  99.  
  100.     // Exit the program before you can do anything!
  101.     System.exit(0);
  102.   }
  103. }
  104.  
  105. // Your code goes below:
Runtime error #stdin #stdout 0.06s 711680KB
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https://ideone.com/HCdFsW
language:
Java (12.0.1)
created:
6 years ago
visibility:
public

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