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Re-encrypt native methods

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This commit is contained in:
de4dot 2011-11-25 15:24:12 +01:00
parent 07f0376b45
commit 51892f62a2
2 changed files with 89 additions and 25 deletions
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9
de4dot.code/deobfuscators/dotNET_Reactor/Deobfuscator.cs
View File

@ -404,6 +404,7 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
newOne.booleanDecrypter = new BooleanDecrypter(module, booleanDecrypter);
newOne.assemblyResolver = new AssemblyResolver(module, assemblyResolver);
newOne.resourceResolver = new ResourceResolver(module, resourceResolver);
newOne.methodsDecrypter.reloaded();
return newOne;
}
@ -455,7 +456,7 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
else
canRemoveDecrypterType = false;
if (options.DecryptMethods) {
if (options.DecryptMethods && !methodsDecrypter.HasNativeMethods) {
addResourceToBeRemoved(methodsDecrypter.Resource, "Encrypted methods");
addCctorInitCallToBeRemoved(methodsDecrypter.Method);
}
@ -737,5 +738,11 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
list.Add(stringDecrypter.OtherStringDecrypter.MetadataToken.ToInt32().ToString("X8"));
return list;
}
public override void OnBeforeAddingResources(MetadataBuilder builder) {
if (!options.DecryptMethods)
return;
methodsDecrypter.encryptNativeMethods(builder);
}
}
}

105
de4dot.code/deobfuscators/dotNET_Reactor/MethodsDecrypter.cs
View File

@ -29,11 +29,18 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
class MethodsDecrypter {
ModuleDefinition module;
EncryptedResource encryptedResource;
Dictionary<uint, byte[]> tokenToNativeMethod = new Dictionary<uint, byte[]>();
Dictionary<MethodDefinition, byte[]> methodToNativeMethod = new Dictionary<MethodDefinition, byte[]>();
long xorKey;
public bool Detected {
get { return encryptedResource.Method != null; }
}
public bool HasNativeMethods {
get { return methodToNativeMethod.Count > 0; }
}
public TypeDefinition DecrypterType {
get { return encryptedResource.Type; }
}
@ -54,6 +61,8 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
public MethodsDecrypter(ModuleDefinition module, MethodsDecrypter oldOne) {
this.module = module;
this.encryptedResource = new EncryptedResource(module, oldOne.encryptedResource);
this.tokenToNativeMethod = oldOne.tokenToNativeMethod;
this.xorKey = oldOne.xorKey;
}
public void find() {
@ -94,6 +103,22 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
encryptedResource.Method = (MethodDefinition)callCounter.most();
}
void xorEncrypt(byte[] data) {
if (xorKey == 0)
return;
var stream = new MemoryStream(data);
var reader = new BinaryReader(stream);
var writer = new BinaryWriter(stream);
int count = data.Length / 8;
for (int i = 0; i < count; i++) {
long val = reader.ReadInt64();
val ^= xorKey;
stream.Position -= 8;
writer.Write(val);
}
}
static short[] nativeLdci4 = new short[] { 0x55, 0x8B, 0xEC, 0xB8, -1, -1, -1, -1, 0x5D, 0xC3 };
static short[] nativeLdci4_0 = new short[] { 0x55, 0x8B, 0xEC, 0x33, 0xC0, 0x5D, 0xC3 };
public bool decrypt(PE.PeImage peImage, ISimpleDeobfuscator simpleDeobfuscator, ref Dictionary<uint, DumpedMethod> dumpedMethods, Dictionary<uint,byte[]> tokenToNativeCode) {
@ -107,20 +132,8 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
bool hooksJitter = findDnrCompileMethod(encryptedResource.Method.DeclaringType) != null;
long xorKey = getXorKey();
if (xorKey != 0) {
// DNR 4.3, 4.4
var stream = new MemoryStream(methodsData);
var reader = new BinaryReader(stream);
var writer = new BinaryWriter(stream);
int count = methodsData.Length / 8;
for (int i = 0; i < count; i++) {
long val = reader.ReadInt64();
val ^= xorKey;
stream.Position -= 8;
writer.Write(val);
}
}
xorKey = getXorKey();
xorEncrypt(methodsData);
var methodsDataReader = new BinaryReader(new MemoryStream(methodsData));
int patchCount = methodsDataReader.ReadInt32();
@ -175,7 +188,6 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
patchDwords(peImage, methodsDataReader, patchCount);
int count = methodsDataReader.ReadInt32();
dumpedMethods = new Dictionary<uint, DumpedMethod>();
bool foundNativeCode = false;
while (methodsDataReader.BaseStream.Position < methodsData.Length - 1) {
uint rva = methodsDataReader.ReadUInt32();
uint index = methodsDataReader.ReadUInt32();
@ -191,13 +203,6 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
uint methodToken = 0x06000001 + (uint)methodIndex;
if (isNativeCode) {
if (!foundNativeCode) {
foundNativeCode = true;
Log.w("Found native code. Assembly won't run.");
}
//TODO: Convert to CIL code
Log.v("Found native code. Ignoring it for now... Assembly won't run. token: {0:X8}", methodToken);
if (tokenToNativeCode != null)
tokenToNativeCode[methodToken] = methodData;
@ -205,6 +210,7 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
// throw 0xDEADCODE.
if (isCode(nativeLdci4, methodData)) {
uint val = BitConverter.ToUInt32(methodData, 4);
// ldc.i4 XXXXXXXXh / ret
methodData = new byte[] { 0x20, 0, 0, 0, 0, 0x2A };
methodData[1] = (byte)val;
methodData[2] = (byte)(val >> 8);
@ -212,10 +218,15 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
methodData[4] = (byte)(val >> 24);
}
else if (isCode(nativeLdci4_0, methodData)) {
// ldc.i4.0 / ret
methodData = new byte[] { 0x16, 0x2A };
}
else
methodData = new byte[] { 0x20, 0xDE, 0xC0, 0xAD, 0xDE, 0x7A };
else {
tokenToNativeMethod[methodToken] = methodData;
// ldc.i4 0xDEADCODE / conv.u4 / throw
methodData = new byte[] { 0x20, 0xDE, 0xC0, 0xAD, 0xDE, 0x6D, 0x7A };
}
}
var dm = new DumpedMethod();
@ -284,6 +295,52 @@ namespace de4dot.deobfuscators.dotNET_Reactor {
return 0;
}
public void reloaded() {
foreach (var pair in tokenToNativeMethod) {
int token = (int)pair.Key;
var method = module.LookupToken(token) as MethodDefinition;
if (method == null)
throw new ApplicationException(string.Format("Could not find method {0:X8}", token));
methodToNativeMethod[method] = pair.Value;
}
}
public void encryptNativeMethods(MetadataBuilder builder) {
if (tokenToNativeMethod.Count == 0)
return;
var stream = new MemoryStream();
var writer = new BinaryWriter(stream);
writer.Write((uint)0); // patch count
writer.Write((uint)0); // mode
writer.Write(tokenToNativeMethod.Count);
int index = 0;
var codeWriter = builder.CodeWriter;
foreach (var pair in methodToNativeMethod) {
var method = pair.Key;
if (method.DeclaringType == null)
continue; // Method was removed
if (method.DeclaringType.Module == null)
continue; // method.DeclaringType was removed
var code = pair.Value;
uint codeRva = builder.GetMethodBodyRva((int)method.MetadataToken.RID - 1);
if ((codeWriter.ReadByteAtRva(codeRva) & 3) == 2)
codeRva++;
else
codeRva += 4 * (uint)(codeWriter.ReadByteAtRva(codeRva + 1) >> 4);
writer.Write(codeRva);
writer.Write(0x70000000 + index++);
writer.Write(code.Length);
writer.Write(code);
}
var encryptedData = stream.ToArray();
xorEncrypt(encryptedData);
encryptedResource.updateResource(encryptedResource.encrypt(encryptedData));
}
public static MethodDefinition findDnrCompileMethod(TypeDefinition type) {
foreach (var method in type.Methods) {
if (!method.IsStatic || method.Body == null)