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Support trial string encrypter

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This commit is contained in:
de4dot 2012-05-09 17:30:31 +02:00
parent 3572bdfdcc
commit 1aaa5df9ce
1 changed files with 79 additions and 10 deletions
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89
de4dot.code/deobfuscators/DeepSea/StringDecrypter.cs
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@ -46,6 +46,12 @@ namespace de4dot.code.deobfuscators.DeepSea {
}
static short[] findKey(MethodDefinition initMethod, FieldDefinition keyField) {
var fields = new FieldDefinitionAndDeclaringTypeDict<bool>();
fields.add(keyField, true);
return findKey(initMethod, fields);
}
static short[] findKey(MethodDefinition initMethod, FieldDefinitionAndDeclaringTypeDict<bool> fields) {
var instrs = initMethod.Body.Instructions;
for (int i = 0; i < instrs.Count - 2; i++) {
var ldci4 = instrs[i];
@ -71,7 +77,7 @@ namespace de4dot.code.deobfuscators.DeepSea {
var field = getStoreField(initMethod, startInitIndex, local);
if (field == null)
continue;
if (keyField == field)
if (fields.find(field))
return array;
}
@ -128,7 +134,9 @@ namespace de4dot.code.deobfuscators.DeepSea {
FieldDefinitionAndDeclaringTypeDict<bool> fields;
ArrayInfo arrayInfo;
ushort[] encryptedData;
ushort[] key;
short[] key;
int keyShift;
bool isTrial;
class ArrayInfo {
public int sizeInElems;
@ -208,6 +216,8 @@ namespace de4dot.code.deobfuscators.DeepSea {
encryptedData = new ushort[arrayInfo.initField.InitialValue.Length / 2];
Buffer.BlockCopy(arrayInfo.initField.InitialValue, 0, encryptedData, 0, arrayInfo.initField.InitialValue.Length);
isTrial = !DeobUtils.hasInteger(Method, 0xFFF0);
keyShift = findKeyShift(cctor);
key = findKey();
if (key == null || key.Length == 0)
return false;
@ -215,6 +225,49 @@ namespace de4dot.code.deobfuscators.DeepSea {
return true;
}
int findKeyShift(MethodDefinition method) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count - 3; i++) {
int index = i;
var ldci4 = instrs[index++];
if (!DotNetUtils.isLdcI4(ldci4))
continue;
if (DotNetUtils.getLdcI4Value(ldci4) != 0xFF)
continue;
if (instrs[index++].OpCode.Code != Code.And)
continue;
if (instrs[index++].OpCode.Code != Code.Dup)
continue;
var ldci4_2 = instrs[index++];
if (!DotNetUtils.isLdcI4(ldci4_2))
continue;
if (findNextFieldUse(method, index) < 0)
continue;
return DotNetUtils.getLdcI4Value(ldci4_2);
}
return -1;
}
int findNextFieldUse(MethodDefinition method, int index) {
var instrs = method.Body.Instructions;
for (int i = index; i < instrs.Count; i++) {
var instr = instrs[i];
if (instr.OpCode.Code != Code.Ldsfld && instr.OpCode.Code != Code.Stsfld)
continue;
var field = instr.Operand as FieldReference;
if (!fields.find(field))
return -1;
return i;
}
return -1;
}
ArrayInfo getArrayInfo(MethodDefinition method) {
var instructions = method.Body.Instructions;
for (int i = 0; i < instructions.Count; i++) {
@ -242,7 +295,7 @@ namespace de4dot.code.deobfuscators.DeepSea {
return null;
}
ushort[] findKey() {
short[] findKey() {
if (cctor.Module.Assembly == null)
return null;
var pkt = cctor.Module.Assembly.Name.PublicKeyToken;
@ -251,24 +304,40 @@ namespace de4dot.code.deobfuscators.DeepSea {
return findKey(cctor);
}
ushort[] findKey(MethodDefinition initMethod) {
throw new NotImplementedException(); //TODO:
short[] findKey(MethodDefinition initMethod) {
return StringDecrypter.findKey(initMethod, fields);
}
static ushort[] getPublicKeyTokenKey(byte[] publicKeyToken) {
var key = new ushort[publicKeyToken.Length];
short[] getPublicKeyTokenKey(byte[] publicKeyToken) {
if (keyShift < 0)
throw new ApplicationException("Could not find shift value");
var key = new short[publicKeyToken.Length];
for (int i = 0; i < publicKeyToken.Length; i++) {
int b = publicKeyToken[i];
key[i] = (ushort)((b << 7) ^ b);
key[i] = (short)((b << keyShift) ^ b);
}
return key;
}
public string decrypt(object[] args) {
return decrypt((int)args[arg1], (int)args[arg2]);
if (isTrial)
return decryptTrial((int)args[arg1], (int)args[arg2]);
return decryptRetail((int)args[arg1], (int)args[arg2]);
}
string decrypt(int magic2, int magic3) {
string decryptTrial(int magic2, int magic3) {
int offset = magic ^ magic2 ^ magic3;
var keyChar = encryptedData[offset + 1];
int cachedIndex = encryptedData[offset] ^ keyChar;
int numChars = ((keyChar ^ encryptedData[offset + 2]) << 16) + (keyChar ^ encryptedData[offset + 3]);
offset += 4;
var sb = new StringBuilder(numChars);
for (int i = 0; i < numChars; i++)
sb.Append((char)(keyChar ^ encryptedData[offset + i] ^ key[(offset + i) % key.Length]));
return sb.ToString();
}
string decryptRetail(int magic2, int magic3) {
int offset = magic ^ magic2 ^ magic3;
var keyChar = encryptedData[offset + 2];
int cachedIndex = encryptedData[offset + 1] ^ keyChar;