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Fingerprinting / Hashing Dalvik Executables
import gnu.trove.map.TObjectLongMap;
import gnu.trove.map.hash.TObjectLongHashMap;
import org.jf.dexlib2.Opcode;
import org.jf.dexlib2.iface.ClassDef;
import org.jf.dexlib2.iface.DexFile;
import org.jf.dexlib2.iface.Field;
import org.jf.dexlib2.iface.Method;
import org.jf.dexlib2.iface.MethodImplementation;
import org.jf.dexlib2.iface.instruction.Instruction;
import org.jf.dexlib2.iface.instruction.NarrowLiteralInstruction;
import org.jf.dexlib2.iface.instruction.ReferenceInstruction;
import org.jf.dexlib2.iface.instruction.WideLiteralInstruction;
import org.jf.dexlib2.iface.reference.Reference;
import org.jf.dexlib2.util.ReferenceUtil;
import java.nio.charset.Charset;
public class DexFileFingerprinter {
private final DexFile dexFile;
private final TObjectLongMap<String> classTypeToHash;
private final TObjectLongMap<String> methodDescriptorToHash;
public DexFileFingerprinter(DexFile dexFile) {
this.dexFile = dexFile;
classTypeToHash = new TObjectLongHashMap<>();
methodDescriptorToHash = new TObjectLongHashMap<>();
}
public void fingerprint() {
fingerprint(true);
}
public void fingerprint(boolean strict) {
for (ClassDef classDef : dexFile.getClasses()) {
StringBuilder fp = new StringBuilder();
fingerprintClass(classDef, fp, strict);
long hash = hashString(fp.toString());
String classType = classDef.getType();
classTypeToHash.put(classType, hash);
}
}
private void fingerprintClass(ClassDef classDef, StringBuilder fp, boolean strict) {
fp.append("CLASS\n");
if (strict) {
fp.append("annotation size=").append(classDef.getAnnotations().size()).append('\n');
fp.append("interface count=").append(classDef.getInterfaces().size()).append('\n');
fp.append("access flags=").append(classDef.getAccessFlags()).append('\n');
}
for (Field field : classDef.getFields()) {
fingerprintField(field, fp, strict);
}
for (Method method : classDef.getMethods()) {
fingerprintMethod(method, fp, strict);
}
}
private void fingerprintField(Field field, StringBuilder fp, boolean strict) {
fp.append("FIELD\n");
if (strict) {
fp.append("access flags=").append(field.getAccessFlags()).append('\n');
fp.append("annotation count=").append(field.getAnnotations().size()).append('\n');
}
String typeFingerprint = buildTypeFingerprint(field.getType());
fp.append("type=").append(typeFingerprint).append('\n');
}
private static String buildTypeFingerprint(String type) {
if (type.length() == 1) {
// It's a primitive, return that type
return type;
} else {
if (type.charAt(0) == 'L') {
// Plain object, just fingerprint that it's an object
// Would be too fragile to fingerprint class names which frequently change
// Could possibly use full names for protected class paths like "java.lang", but seems a little strict
return "L";
}
// Must be an array, fingerprint array rank and type
StringBuilder sb = new StringBuilder();
for (int i = 0; i < type.length(); i++) {
char c = type.charAt(i);
if (c == '[') {
// Add another rank
sb.append(c);
} else {
// End of array
if (c == 'L') {
// Object array
sb.append('L');
} else {
// Primitive array
sb.append(c);
}
}
}
return sb.toString();
}
}
private void fingerprintMethod(Method method, StringBuilder fp, boolean strict) {
fp.append("METHOD\n");
if (strict) {
fp.append("annotation count=").append(method.getAnnotations().size()).append('\n');
fp.append("access flags=").append(method.getAccessFlags()).append('\n');
fp.append("parameter count=").append(method.getParameterTypes().size()).append('\n');
}
String returnTypeFingerprint = buildTypeFingerprint(method.getReturnType());
fp.append("return type=").append(returnTypeFingerprint).append('\n');
MethodImplementation implementation = method.getImplementation();
String methodDescriptor = ReferenceUtil.getMethodDescriptor(method);
if (implementation == null) {
fp.append("no implementation");
if (strict) {
// If strict, avoid combining counts of empty methods
fp.append(": ").append(methodDescriptor);
}
fp.append('\n');
} else {
fingerprintImplementation(method.getImplementation(), fp, strict);
}
long hash = hashString(fp.toString());
methodDescriptorToHash.put(methodDescriptor, hash);
}
private void fingerprintImplementation(MethodImplementation implementation, StringBuilder fp, boolean strict) {
if (strict) {
fp.append("register count=").append(implementation.getRegisterCount()).append('\n');
fp.append("try blocks=").append(implementation.getTryBlocks().size()).append('\n');
}
for (Instruction instruction : implementation.getInstructions()) {
Opcode op = instruction.getOpcode();
fp.append(op.toString()).append('\n');
if (strict) {
Object val = null;
if (instruction instanceof NarrowLiteralInstruction) {
val = ((NarrowLiteralInstruction) instruction).getNarrowLiteral();
} else if (instruction instanceof WideLiteralInstruction) {
val = ((WideLiteralInstruction) instruction).getWideLiteral();
} else if (instruction instanceof ReferenceInstruction) {
if (op == Opcode.CONST_STRING) {
Reference ref = ((ReferenceInstruction) instruction).getReference();
val = ReferenceUtil.getReferenceString(ref);
}
}
if (val != null) {
fp.append(val).append('\n');
}
}
}
}
private static long hashString(String string) {
byte[] key = string.getBytes(Charset.forName("UTF-8"));
int offset = 0;
int len = string.length();
int seed = 0x1337;
MurmurHash3.LongPair longPair = new MurmurHash3.LongPair();
MurmurHash3.murmurhash3_x64_128(key, offset, len, seed, longPair);
return longPair.val1;
}
public TObjectLongMap<String> getClassTypeToHash() {
return classTypeToHash;
}
public TObjectLongMap<String> getMethodDescriptorToHash() {
return methodDescriptorToHash;
}
public long getClassHash(String classType) {
return classTypeToHash.get(classType);
}
public long getClassHash(ClassDef classDef) {
return getClassHash(classDef.getType());
}
public long getMethodHash(String methodDescriptor) {
return methodDescriptorToHash.get(methodDescriptor);
}
public long getMethodHash(Method method) {
String methodDescriptor = ReferenceUtil.getMethodDescriptor(method);
return getMethodHash(methodDescriptor);
}
}
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