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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);
}
}
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