Instantly share code, notes, and snippets.

Embed
What would you like to do?
JEB Plugin for decrypt DexGuard encrypted Strings.
import jeb.api.IScript;
import jeb.api.JebInstance;
import jeb.api.ast.*;
import jeb.api.ast.Class;
import jeb.api.dex.Dex;
import jeb.api.dex.DexCodeItem;
import jeb.api.dex.DexFieldData;
import jeb.api.dex.DexMethod;
import jeb.api.ui.JavaView;
import jeb.api.ui.View;
import java.util.List;
/**
* Created by AKosterin on 29/06/15.
*/
public class DexGuardStringDecoder implements IScript{
private static int encint = 0;
private static String mname_decrypt = "";
private static byte[] encbytes = new byte[0];
public void run(JebInstance jebInstance) {
jebInstance.print("DexGuardStringDecoder_Start");
if(!jebInstance.isFileLoaded()){
jebInstance.print("Please load a dex file");
return;
}
Dex dex = jebInstance.getDex();
JavaView view = (JavaView) jebInstance.getUI().getView(View.Type.JAVA);
String methodname = view.getCodePosition().getSignature();
jebInstance.print(methodname);
DexCodeItem code = dex.getMethodData(methodname).getCodeItem();
if(code == null){
jebInstance.print("MethodData not found in DEX!!!");
return;
}
jebInstance.decompileClass(getClassFromSignature(methodname));
String str1 = getClassFromSignature(methodname);
jebInstance.print(str1);
Class mClass = jebInstance.getDecompiledClassTree(str1);
for(Field mField : (List<Field>) mClass.getFields()){
if(mField.getSignature().endsWith(":[B")) {
jebInstance.print(mField.getSignature());
DexFieldData dfd = dex.getFieldData(mField.getSignature());
int wanted_flags = Dex.ACC_PRIVATE | Dex.ACC_STATIC | Dex.ACC_FINAL;
if ((dfd.getAccessFlags() & wanted_flags) == wanted_flags) {
jebInstance.print("Found field:" + mField.getSignature());
int fIndex = dfd.getFieldIndex();
for (Integer mIndex : (List<Integer>) dex.getFieldReferences(fIndex)) {
DexMethod mMethod = dex.getMethod(mIndex);
if(mMethod.getSignature(true).contains("(III)Ljava/lang/String;")){
mname_decrypt = mMethod.getName();
}
}
for (Method method : (List<Method>) mClass.getMethods()) {
if (method.getName().equals("<clinit>")) {
for (int i = 0 ; i < method.getBody().size(); i++) {
Statement st1 = method.getBody().get(i);
if (st1 instanceof Assignment) {
Assignment ass1 = (Assignment) st1;
ILeftExpression le1 = ass1.getLeft();
if ((le1 instanceof StaticField) && ((StaticField) le1).getField().getSignature().equals(mField.getSignature())) {
IExpression e1 = ass1.getRight();
if (e1 instanceof NewArray) {
NewArray na1 = (NewArray) e1;
for (IExpression e2 : ((List<IExpression>) na1.getInitialValues())) {
if (e2 instanceof Constant) {
Constant c1 = (Constant) e2;
byte b1 = c1.getByte();
byte[] c = new byte[encbytes.length + 1];
System.arraycopy(encbytes, 0, c, 0, encbytes.length);
c[encbytes.length] = b1;
encbytes = c;
}
}
}
}
}
}
}
}
}
} else if(mField.getSignature().endsWith(":I")) {
jebInstance.print(mField.getSignature());
DexFieldData dfd = dex.getFieldData(mField.getSignature());
int wanted_flags = Dex.ACC_PRIVATE | Dex.ACC_STATIC;
if ((dfd.getAccessFlags() & wanted_flags) == wanted_flags) {
jebInstance.print("Found field:" + mField.getSignature());
for (Method method : (List<Method>) mClass.getMethods()) {
if (method.getName().equals("<clinit>")) {
for (int i = 0 ; i < method.getBody().size(); i++) {
Statement st1 = method.getBody().get(i);
if (st1 instanceof Assignment) {
Assignment ass1 = (Assignment) st1;
ILeftExpression le1 = ass1.getLeft();
if ((le1 instanceof StaticField) && ((StaticField) le1).getField().getSignature().equals(mField.getSignature())) {
IExpression e1 = ass1.getRight();
if (e1 instanceof Constant) {
Constant const1 = (Constant) e1;
encint = const1.getInt();
}
}
}
}
}
}
}
}
}
if(encbytes.length == 0 ){
jebInstance.print("Encrypted strings byte array not found");
}
if (mname_decrypt.isEmpty()){
jebInstance.print("Decryption method was not found");
}
if(encint == 0 ){
jebInstance.print("May be decrypt int was not found");
}
for(Method m : (List<Method>) mClass.getMethods()){
jebInstance.print("Decrypting strings in method: " + m.getName());
for (int i = 0; i < m.getBody().size(); i++) {
Statement mStatement = m.getBody().get(i);
checkElement(jebInstance, m.getBody(), mStatement, 0);
}
}
jebInstance.getUI().getView(View.Type.JAVA).refresh();
jebInstance.print("DexGuardStringDecoder_End");
}
private static void checkElement(JebInstance jebInstance,IElement parent, IElement iElement, int level){
if (iElement instanceof Call){
Call mCall = (Call) iElement;
String methodName = mCall.getMethod().getName();
if(methodName.equals(mname_decrypt)){
int[] params = new int[0];
StringBuilder strb = new StringBuilder();
strb.append(methodName).append("(");
for (IExpression mIExpression : (List<IExpression>) mCall.getArguments()) {
if (mIExpression instanceof Constant) {
Constant mConstant = (Constant) mIExpression;
params = addToIntArray(params, mConstant.getInt());
strb.append(mConstant.getInt()).append(", ");
} else if (mIExpression instanceof ArrayElt) {
ArrayElt mArrayElt = (ArrayElt) mIExpression;
IExpression mIExpression2 = mArrayElt.getIndex();
if (mIExpression2 instanceof Constant) {
Constant mConstant = (Constant) mIExpression2;
params = addToIntArray(params, (int) encbytes[mConstant.getInt()]);
strb.append(encbytes[mConstant.getInt()]).append(", ");
} else {
strb.append("encbytes[").append(mIExpression2.getClass().getName()).append("], ");
}
} else if(mIExpression instanceof StaticField) {
params = addToIntArray(params, encint);
strb.append(encint).append(", ");
} else if(mIExpression instanceof Expression){
Expression mExpression = (Expression) mIExpression;
if(mExpression.getLeft() != null) {
if (mExpression.getLeft() instanceof StaticField && mExpression.getRight() instanceof Constant) {
Constant mConstant = (Constant) mExpression.getRight();
int mint;
if(mExpression.getOperator().toString().equals("&")){
mint = encint & mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("|")) {
mint = encint | mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("-")) {
mint = encint - mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("+")) {
mint = encint + mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("*")) {
mint = encint * mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else {
strb.append(encint).append(" ").append(mExpression.getOperator().toString()).append(" ").append(mConstant.getInt()).append(", ");
}
} if (mExpression.getLeft() instanceof ArrayElt && mExpression.getRight() instanceof Constant) {
ArrayElt mArrayElt = (ArrayElt) mExpression.getLeft();
Constant mConstant = (Constant) mExpression.getRight();
IExpression mIExpression2 = mArrayElt.getIndex();
if (mIExpression2 instanceof Constant) {
Constant mConstant2 = (Constant) mIExpression2;
int mint;
if(mExpression.getOperator().toString().equals("&")) {
mint = encbytes[mConstant2.getInt()] & mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("|")){
mint = encbytes[mConstant2.getInt()] | mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("-")){
mint = encbytes[mConstant2.getInt()] - mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("+")){
mint = encbytes[mConstant2.getInt()] + mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else if(mExpression.getOperator().toString().equals("*")){
mint = encbytes[mConstant2.getInt()] * mConstant.getInt();
params = addToIntArray(params, mint);
strb.append(mint).append(", ");
} else {
strb.append(encbytes[mConstant2.getInt()]).append(" ").append(mExpression.getOperator().toString()).append(" ").append(mConstant.getInt()).append(", ");
}
} else {
strb.append("jeb.api.ast.Expression(").append(mExpression.getLeft().getClass().getName()).append(" ").append(((Expression) mIExpression).getOperator().getClass().getName()).append(" ").append(mExpression.getRight().getClass().getName()).append("), ");
}
} else {
strb.append("jeb.api.ast.Expression(").append(mExpression.getLeft().getClass().getName()).append(" ").append(((Expression) mIExpression).getOperator().getClass().getName()).append(" ").append(mExpression.getRight().getClass().getName()).append("), ");
}
} else {
if(mExpression.getRight() instanceof ArrayElt){
ArrayElt mArrayElt = (ArrayElt) mExpression.getRight();
IExpression mIExpression2 = mArrayElt.getIndex();
if (mIExpression2 instanceof Constant) {
Constant mConstant = (Constant) mIExpression2;
params = addToIntArray(params, -1 * encbytes[mConstant.getInt()]);
strb.append(-1 * encbytes[mConstant.getInt()]).append(", ");
} else {
strb.append("jeb.api.ast.Expression(").append(((Expression) mIExpression).getOperator().getClass().getName()).append(" ").append(mExpression.getRight().getClass().getName()).append("), ");
}
} else {
strb.append("jeb.api.ast.Expression(").append(((Expression) mIExpression).getOperator().getClass().getName()).append(" ").append(mExpression.getRight().getClass().getName()).append("), ");
}
}
} else {
strb.append(mIExpression.getClass().getName()).append(", ");
}
}
strb.delete(strb.length() - 2, strb.length());
strb.append(");");
if (params.length == 3){
String decyptStr = decrypt_djAR(params[0], params[1], params[2]);
strb.append(" - ").append(decyptStr);
parent.replaceSubElement(iElement, (new Constant.Builder(jebInstance)).buildString(decyptStr));
}
jebInstance.print(strb.toString());
}
}
for (IElement element : (List<IElement>) iElement.getSubElements()){
if (!((element instanceof Class) || (element instanceof Field) || (element instanceof Method))){
checkElement(jebInstance, iElement, element, level + 1);
}
}
}
private static final String getClassFromSignature(String sig) {
return sig.split(";")[0].split("$")[0] + ";";//
}
private static final int[] addToIntArray(int[] array, int mint){
int[] array2 = new int[array.length + 1];
System.arraycopy(array, 0, array2, 0, array.length);
array2[array.length] = mint;
return array2;
}
//Could be determined by analyzing the decryption method
private static final String decrypt_djAR(int arg9, int arg10, int arg11) {
int v5;
byte[] v6 = encbytes;
int v1 = arg10 + 65;
int v0 = 615 - arg9;
int v3 = arg11 + 2;
byte[] v2 = new byte[v3];
int v8 = v3 - 1;
v3 = 0;
v5 = v0;
while(v3 != v8){
v2[v3] = ((byte)v1);
v0 = v6[v5];
++v3;
++v5;
v1 += -v0;
}
v2[v3] = ((byte)v1);
return new String(v2);
}
}
@AKosterin

This comment has been minimized.

Show comment
Hide comment
Owner

AKosterin commented Feb 9, 2016

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment