package javasec.samples.ch12;
import java.io.*;
import java.net.*;
import java.security.*;
import java.util.*;
import java.util.jar.*;
public class JarLoader extends SecureClassLoader {
private URL urlBase;
public boolean printLoadMessages = true;
// These hold the classes and certificates that we read from the jar file
Hashtable classArrays;
Hashtable classIds;
public JarLoader(String base, ClassLoader parent) {
super(parent);
try {
// The base is the URL from which we read jar files; e.g.
// http://piccolo/sdo.jar is read from the base http://piccolo/
// But we can also read classes from the base directly.
if (!(base.endsWith("/")))
base = base + "/";
urlBase = new URL(base);
classArrays = new Hashtable();
classIds = new Hashtable();
} catch (Exception e) {
throw new IllegalArgumentException(base);
}
}
// Completely read the input stream and convert it into a byte array
private byte[] getClassBytes(InputStream is) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
BufferedInputStream bis = new BufferedInputStream(is);
boolean eof = false;
while (!eof) {
try {
int i = bis.read();
if (i == -1)
eof = true;
else baos.write(i);
} catch (IOException e) {
return null;
}
}
return baos.toByteArray();
}
// Find the class. This is based on the steps of our previous example
protected Class findClass(final String name) throws ClassNotFoundException {
try {
return (Class)
AccessController.doPrivileged(
new PrivilegedExceptionAction() {
public Object run() throws ClassNotFoundException {
Object o = doFindClass(name);
if (o == null)
throw new ClassNotFoundException(name);
return o;
}
}
);
} catch (PrivilegedActionException pae) {
throw (ClassNotFoundException) pae.getException();
}
}
private Class doFindClass(String name) {
String urlName = name.replace('.', '/');
byte buf[];
Class cl;
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
int i = name.lastIndexOf('.');
if (i >= 0)
sm.checkPackageDefinition(name.substring(0, i));
}
// See if the class is in a jar file we've read
buf = (byte[]) classArrays.get(urlName);
if (buf != null) {
// It was -- get the certificates (if any) and define the
// codesource and class with them.
java.security.cert.Certificate[] ids =
(java.security.cert.Certificate[]) classIds.get(urlName);
CodeSource cs = new CodeSource(urlBase, ids);
cl = defineClass(name, buf, 0, buf.length, cs);
return cl;
}
// The class wasn't in a jar file -- see if we can load it
// directly. Since it's being loaded directly, it won't have
// a signature.
try {
URL url = new URL(urlBase, urlName + ".class");
if (printLoadMessages)
System.out.println("Loading " + url);
InputStream is = url.openConnection().getInputStream();
buf = getClassBytes(is);
CodeSource cs = new CodeSource(urlBase, null);
cl = defineClass(name, buf, 0, buf.length, cs);
return cl;
} catch (Exception e) {
System.out.println("Can't load " + name + ": " + e);
return null;
}
}
// Read a jar file, storing its classes into the classArray and
// the certificates of its signatures into the classIds
public void readJarFile(String name) {
URL jarUrl = null;
JarInputStream jis;
JarEntry je;
try {
jarUrl = new URL(urlBase, name);
} catch (MalformedURLException mue) {
System.out.println("Unknown jar file " + name);
return;
}
if (printLoadMessages)
System.out.println("Loading jar file " + jarUrl);
try {
jis = new JarInputStream(
jarUrl.openConnection().getInputStream());
} catch (IOException ioe) {
System.out.println("Can't open jar file " + jarUrl);
return;
}
try {
while ((je = jis.getNextJarEntry()) != null) {
String jarName = je.getName();
if (jarName.endsWith(".class"))
loadClassBytes(jis, jarName, je);
// else ignore it; it could be an image or audio file
// Really, these type of entries need to be saved for
// the resource methods; we leave that extension to
// the reader.
jis.closeEntry();
}
} catch (IOException ioe) {
System.out.println("Badly formatted jar file");
}
}
private void loadClassBytes(JarInputStream jis,
String jarName, JarEntry je) {
if (printLoadMessages)
System.out.println("\t" + jarName);
BufferedInputStream jarBuf = new BufferedInputStream(jis);
ByteArrayOutputStream jarOut = new ByteArrayOutputStream();
int b;
try {
while ((b = jarBuf.read()) != -1)
jarOut.write(b);
String className = jarName.substring(0, jarName.length() - 6);
classArrays.put(className, jarOut.toByteArray());
// This returns the certificates from the signature file
// only if this class was signed.
java.security.cert.Certificate c[] = je.getCertificates();
if (c == null)
c = new java.security.cert.Certificate[0];
classIds.put(className, c);
} catch (IOException ioe) {
System.out.println("Error reading entry " + jarName);
}
}
}
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