/**
* return a checker object which can be used to retrieve the super and interfaces of a class from
* its name and classloader, identifying it from the Class instance if it the class is already
* loaded otherwise loading the corresponding bytecode and parsing it to obtain the relevant
* details.
*
* @param name the name of the superclass being checked
* @param baseLoader the class loader of the subclass's bytecode
* @return the requisite checker or null if the class does not need to be checked or cannot be
* loaded
*/
public org.jboss.byteman.agent.check.ClassChecker getClassChecker(
String name, ClassLoader baseLoader) {
// we would like to just do this
// Class superClazz = baseLoader.loadClass(name)
// and then access the details using methods of Class
// however, this fails because we are in the middle of transforming the subclass and the
// classloader
// may not have loaded the super. if we force a load now then transforms will not be performed
// on
// the super class. this may cause us to miss the chance to apply rule injection into the super
ClassLoader loader = baseLoader;
Class clazz = loadCache.lookupClass(name, loader);
if (clazz != null) {
return new org.jboss.byteman.agent.check.LoadedClassChecker(clazz);
}
// ok, instead try loading the bytecode as a resource - user-defined loaders may not support
// this but
// at least the JVM system and boot loaders should
String resourceName = name.replace('.', '/') + ".class";
try {
InputStream is;
if (baseLoader != null) {
is = baseLoader.getResourceAsStream(resourceName);
} else {
is = ClassLoader.getSystemClassLoader().getResourceAsStream(resourceName);
}
if (is != null) {
int length = is.available();
int count = 0;
byte[] bytecode = new byte[length];
while (count < length) {
int read = is.read(bytecode, count, length - count);
if (read < 0) {
throw new IOException("unexpected end of file");
}
count += read;
}
return new org.jboss.byteman.agent.check.BytecodeChecker(bytecode);
} else {
// throw new IOException("unable to load bytecode for for class " + name);
if (isVerbose()) {
System.out.println(
"Transformer.getClassChecker : unable to load bytecode for for class " + name);
}
return null;
}
} catch (IOException e) {
// log the exception and return null
e.printStackTrace();
return null;
}
}
/**
* The implementation of this method may transform the supplied class file and return a new
* replacement class file.
*
* <p>Once a transformer has been registered with {@link
* java.lang.instrument.Instrumentation#addTransformer Instrumentation.addTransformer}, the
* transformer will be called for every new class definition and every class redefinition. The
* request for a new class definition is made with {@link ClassLoader#defineClass
* ClassLoader.defineClass}. The request for a class redefinition is made with {@link
* java.lang.instrument.Instrumentation#redefineClasses Instrumentation.redefineClasses} or its
* native equivalents. The transformer is called during the processing of the request, before the
* class file bytes have been verified or applied.
*
* <p>If the implementing method determines that no transformations are needed, it should return
* <code>null</code>. Otherwise, it should create a new <code>byte[]</code> array, copy the input
* <code>classfileBuffer</code> into it, along with all desired transformations, and return the
* new array. The input <code>classfileBuffer</code> must not be modified.
*
* <p>In the redefine case, the transformer must support the redefinition semantics. If a class
* that the transformer changed during initial definition is later redefined, the transformer must
* insure that the second class output class file is a legal redefinition of the first output
* class file.
*
* <p>If the transformer believes the <code>classFileBuffer</code> does not represent a validly
* formatted class file, it should throw an <code>IllegalClassFormatException</code>. Subsequent
* transformers will still be called and the load or redefine will still be attempted. Throwing an
* <code>IllegalClassFormatException</code> thus has the same effect as returning null but
* facilitates the logging or debugging of format corruptions.
*
* @param originalLoader the defining loader of the class to be transformed, may be <code>null
* </code> if the bootstrap loader
* @param className the name of the class in the internal form of fully qualified class and
* interface names as defined in <i>The Java Virtual Machine Specification</i>. For example,
* <code>"java/util/List"</code>.
* @param classBeingRedefined if this is a redefine, the class being redefined, otherwise <code>
* null</code>
* @param protectionDomain the protection domain of the class being defined or redefined
* @param classfileBuffer the input byte buffer in class file format - must not be modified
* @return a well-formed class file buffer (the result of the transform), or <code>null</code> if
* no transform is performed.
* @throws java.lang.instrument.IllegalClassFormatException if the input does not represent a
* well-formed class file
* @see java.lang.instrument.Instrumentation#redefineClasses
*/
public byte[] transform(
ClassLoader originalLoader,
String className,
Class<?> classBeingRedefined,
ProtectionDomain protectionDomain,
byte[] classfileBuffer)
throws IllegalClassFormatException {
boolean enabled = true;
ClassLoader loader = originalLoader;
try {
enabled = Rule.disableTriggersInternal();
byte[] newBuffer = classfileBuffer;
// we only transform certain classes -- we do allow bootstrap classes whose loader is null
// but we exclude byteman classes and java.lang classes
String internalName = TypeHelper.internalizeClass(className);
if (isBytemanClass(internalName) || !isTransformable(internalName)) {
return null;
}
// we will need the super class name any outer class name and the name of the interfaces the
// class implements
ClassChecker checker = getClassChecker(newBuffer); // new ClassChecker(newBuffer);
if (checker == null || checker.isInterface()) {
return null;
}
/*
if (checker.hasOuterClass()) {
// we don't transform inner classes for now
// TODO -- see if we can match and transform inner classes via the outer class
return null;
}
*/
// TODO-- reconsider this as it is a bit dodgy as far as security is concerned
if (loader == null) {
loader = ClassLoader.getSystemClassLoader();
}
// if we need to traverse the interfaces then we have a DAG to deal with so
// we had better find a way to avoid doing things twice
LinkedList<String> toVisit = null;
HashSet<String> visited = null;
// ok, we need to check whether there are any class scripts associated with this class and if
// so
// we will consider transforming the byte code
// TODO -- there are almost certainly concurrency issues to deal with here if rules are being
// loaded/unloaded
newBuffer = tryTransform(newBuffer, internalName, loader, internalName, false);
int dotIdx = internalName.lastIndexOf('.');
if (dotIdx > 0) {
newBuffer =
tryTransform(
newBuffer, internalName, loader, internalName.substring(dotIdx + 1), false);
}
if (scriptRepository.checkInterfaces()) {
// now we need to do the same for any interface scripts
// n.b. resist the temptation to call classBeingRedefined.getInterfaces() as this will
// cause the class to be resolved, losing any changes we install
// we need to check the transitive closure of the binary links
// Class implements Interface and Interface extends Interface for this class
// which in general is a DAG.
toVisit = new LinkedList<String>();
visited = new HashSet<String>();
// we start with the original list of implemented interfaces
int interfaceCount = checker.getInterfaceCount();
for (int i = 0; i < interfaceCount; i++) {
String interfaceName = checker.getInterface(i);
toVisit.add(interfaceName);
}
// ok now check each interface in turn while pushing its super interfaces
// until we no longer have any new interfaces to check
while (!toVisit.isEmpty()) {
String interfaceName = toVisit.pop();
String internalInterfaceName = TypeHelper.internalizeClass(interfaceName);
if (!visited.contains(interfaceName)) {
// avoid visiting this interface again
visited.add(interfaceName);
// now see if we have any rules for this interface
newBuffer = tryTransform(newBuffer, internalName, loader, internalInterfaceName, true);
dotIdx = internalInterfaceName.lastIndexOf('.');
if (dotIdx >= 0) {
newBuffer =
tryTransform(
newBuffer,
internalName,
loader,
internalInterfaceName.substring(dotIdx + 1),
true);
}
// check the extends list of this interface for new interfaces to consider
ClassChecker newChecker = getClassChecker(interfaceName, originalLoader);
if (newChecker != null) {
interfaceCount = newChecker.getInterfaceCount();
for (int i = 0; i < interfaceCount; i++) {
interfaceName = newChecker.getInterface(i);
toVisit.add(interfaceName);
}
}
}
}
}
// checking supers is expensive so we obey the switch which disables it
if (!skipOverrideRules()) {
// ok, now check the superclass for this class and so on
String superName = checker.getSuper();
while (superName != null) {
// we need to check the super class structure
// n.b. we use the original loader here because we don't want to search the system loader
// when we have a class in the bootstrap loader
checker = getClassChecker(superName, originalLoader);
if (checker == null || checker.hasOuterClass()) {
// we don't transform inner classes for now
// TODO -- see if we can match and transform inner classes via the outer class
break;
}
newBuffer = tryTransform(newBuffer, internalName, loader, superName, false, true);
dotIdx = superName.lastIndexOf('.');
if (dotIdx > 0) {
newBuffer =
tryTransform(
newBuffer, internalName, loader, superName.substring(dotIdx + 1), false, true);
}
if (scriptRepository.checkInterfaces()) {
// we need to do another DAG visit but only for interfaces not already considered
int interfaceCount = checker.getInterfaceCount();
for (int i = 0; i < interfaceCount; i++) {
String interfaceName = checker.getInterface(i);
toVisit.add(interfaceName);
}
// ok now check each interface in turn while pushing its super interfaces
// until we no longer have any new interfaces to check
while (!toVisit.isEmpty()) {
String interfaceName = toVisit.pop();
String internalInterfaceName = TypeHelper.internalizeClass(interfaceName);
if (!visited.contains(interfaceName)) {
// avoid visiting this interface again
visited.add(interfaceName);
// now see if we have any rules for this interface
newBuffer =
tryTransform(
newBuffer, internalName, loader, internalInterfaceName, true, true);
dotIdx = interfaceName.lastIndexOf('.');
if (dotIdx >= 0) {
newBuffer =
tryTransform(
newBuffer,
internalName,
loader,
internalInterfaceName.substring(dotIdx + 1),
true,
true);
}
// check the extends list of this interface for new interfaces to consider
ClassChecker newChecker = getClassChecker(interfaceName, originalLoader);
if (newChecker != null) {
interfaceCount = newChecker.getInterfaceCount();
for (int i = 0; i < interfaceCount; i++) {
interfaceName = newChecker.getInterface(i);
toVisit.add(interfaceName);
}
}
}
}
}
// move on to the next super
superName = checker.getSuper();
}
}
if (newBuffer != classfileBuffer) {
// see if we need to dump the transformed bytecode for checking
maybeDumpClass(internalName, newBuffer);
newBuffer =
maybeVerifyTransformedBytes(originalLoader, internalName, protectionDomain, newBuffer);
return newBuffer;
} else {
return null;
}
} finally {
if (enabled) {
Rule.enableTriggersInternal();
}
}
}
