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Decrypt V4.1 resources
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@wtfsck
wtfsck committed May 9, 2012
1 parent c78e77c commit dadc064
Showing 1 changed file with 221 additions and 16 deletions.
237 changes: 221 additions & 16 deletions de4dot.code/deobfuscators/DeepSea/ResourceResolver.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,17 +17,50 @@ You should have received a copy of the GNU General Public License
along with de4dot. If not, see <http://www.gnu.org/licenses/>.
*/

using System;
using System.Collections.Generic;
using Mono.Cecil;
using Mono.Cecil.Cil;
using de4dot.blocks;

namespace de4dot.code.deobfuscators.DeepSea {
class ResourceResolver : ResolverBase {
// V3
EmbeddedResource resource;

// V40
FieldDefinition resourceField;
MethodDefinition getDataMethod;
int magicV4;
bool isV3;

// V41
Data41 data41;

ResourceVersion version = ResourceVersion.Unknown;

enum ResourceVersion {
Unknown,
V3,
V40,
V41,
}

class Data41 {
public FieldDefinition resourceField;
public MethodDefinition resolveHandler2;
public int magic;
public bool isTrial;
}

class HandlerInfo {
public MethodDefinition handler;
public IList<object> args;

public HandlerInfo(MethodDefinition handler, IList<object> args) {
this.handler = handler;
this.args = args;
}
}

public MethodDefinition GetDataMethod {
get { return getDataMethod; }
Expand All @@ -47,23 +80,183 @@ protected override bool checkResolverInitMethodInternal(MethodDefinition resolve

protected override bool checkHandlerMethodDesktopInternal(MethodDefinition handler) {
if (checkHandlerV3(handler)) {
isV3 = true;
version = ResourceVersion.V3;
return true;
}

FieldDefinition resourceFieldTmp;
MethodDefinition getDataMethodTmp;
simpleDeobfuscator.deobfuscate(handler);
if (checkHandlerV4(handler, out resourceFieldTmp, out getDataMethodTmp, out magicV4)) {
isV3 = false;
if (checkHandlerV40(handler, out resourceFieldTmp, out getDataMethodTmp, out magicV4)) {
version = ResourceVersion.V40;
resourceField = resourceFieldTmp;
getDataMethod = getDataMethodTmp;
return true;
}

var info = getHandlerArgs41(handler);
Data41 data41Tmp;
if (info != null && checkHandlerV41(info, out data41Tmp)) {
version = ResourceVersion.V41;
data41 = data41Tmp;
return true;
}

return false;
}

HandlerInfo getHandlerArgs41(MethodDefinition handler) {
var instrs = handler.Body.Instructions;
for (int i = 0; i < instrs.Count; i++) {
var instr = instrs[i];
if (instr.OpCode.Code != Code.Call)
continue;
var calledMethod = instr.Operand as MethodDefinition;
if (calledMethod == null)
continue;
var args = getArgValues(DotNetUtils.getArgPushes(instrs, i));
if (args == null)
continue;

return new HandlerInfo(calledMethod, args);
}
return null;
}

bool checkHandlerV41(HandlerInfo info, out Data41 data41) {
data41 = new Data41();
data41.resolveHandler2 = info.handler;
data41.resourceField = getLdtokenField(info.handler);
if (data41.resourceField == null)
return false;
int magicArgIndex = getMagicArgIndex41Retail(info.handler);
if (magicArgIndex < 0) {
magicArgIndex = getMagicArgIndex41Trial(info.handler);
data41.isTrial = true;
}
var asmVer = module.Assembly.Name.Version;
if (magicArgIndex < 0 || magicArgIndex >= info.args.Count)
return false;
var val = info.args[magicArgIndex];
if (!(val is int))
return false;
if (data41.isTrial)
data41.magic = (int)val >> 3;
else
data41.magic = ((asmVer.Major << 3) | (asmVer.Minor << 2) | asmVer.Revision) - (int)val;
return true;
}

static int getMagicArgIndex41Retail(MethodDefinition method) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count - 3; i++) {
var add = instrs[i];
if (add.OpCode.Code != Code.Add)
continue;
var ldarg = instrs[i + 1];
if (!DotNetUtils.isLdarg(ldarg))
continue;
var sub = instrs[i + 2];
if (sub.OpCode.Code != Code.Sub)
continue;
var ldci4 = instrs[i + 3];
if (!DotNetUtils.isLdcI4(ldci4) || DotNetUtils.getLdcI4Value(ldci4) != 0xFF)
continue;

return DotNetUtils.getArgIndex(ldarg);
}
return -1;
}

static int getMagicArgIndex41Trial(MethodDefinition method) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count - 2; i++) {
var ldarg = instrs[i];
if (!DotNetUtils.isLdarg(ldarg))
continue;
if (!DotNetUtils.isLdcI4(instrs[i + 1]))
continue;
if (instrs[i + 2].OpCode.Code != Code.Shr)
continue;

return DotNetUtils.getArgIndex(ldarg);
}
return -1;
}

static FieldDefinition getLdtokenField(MethodDefinition method) {
foreach (var instr in method.Body.Instructions) {
if (instr.OpCode.Code != Code.Ldtoken)
continue;
var field = instr.Operand as FieldDefinition;
if (field == null || field.InitialValue == null || field.InitialValue.Length == 0)
continue;

return field;
}
return null;
}

static IList<object> getArgValues(IList<Instruction> argInstrs) {
if (argInstrs == null)
return null;
var args = new List<object>(argInstrs.Count);
foreach (var argInstr in argInstrs) {
object arg;
getArgValue(argInstr, out arg);
args.Add(arg);
}
return args;
}

static bool getArgValue(MethodDefinition method, int index, out object arg) {
return getArgValue(method.Body.Instructions[index], out arg);
}

static bool getArgValue(Instruction instr, out object arg) {
switch (instr.OpCode.Code) {
case Code.Ldc_I4_S: arg = (int)(sbyte)instr.Operand; return true;
case Code.Ldc_I4_M1: arg = -1; return true;
case Code.Ldc_I4_0: arg = 0; return true;
case Code.Ldc_I4_1: arg = 1; return true;
case Code.Ldc_I4_2: arg = 2; return true;
case Code.Ldc_I4_3: arg = 3; return true;
case Code.Ldc_I4_4: arg = 4; return true;
case Code.Ldc_I4_5: arg = 5; return true;
case Code.Ldc_I4_6: arg = 6; return true;
case Code.Ldc_I4_7: arg = 7; return true;
case Code.Ldc_I4_8: arg = 8; return true;
case Code.Ldnull: arg = null; return true;

case Code.Ldstr:
case Code.Ldc_I4:
case Code.Ldc_I8:
case Code.Ldc_R4:
case Code.Ldc_R8:
arg = instr.Operand;
return true;

case Code.Ldarg:
case Code.Ldarg_S:
case Code.Ldarg_0:
case Code.Ldarg_1:
case Code.Ldarg_2:
case Code.Ldarg_3:
case Code.Ldloc:
case Code.Ldloc_S:
case Code.Ldloc_0:
case Code.Ldloc_1:
case Code.Ldloc_2:
case Code.Ldloc_3:
arg = null;
return true;

default:
arg = null;
return false;
}
}

static string[] handlerLocalTypes_V3 = new string[] {
"System.AppDomain",
"System.Byte[]",
Expand All @@ -79,7 +272,7 @@ static bool checkHandlerV3(MethodDefinition handler) {
return new LocalTypes(handler).all(handlerLocalTypes_V3);
}

static bool checkHandlerV4(MethodDefinition handler, out FieldDefinition resourceField, out MethodDefinition getDataMethod, out int magic) {
static bool checkHandlerV40(MethodDefinition handler, out FieldDefinition resourceField, out MethodDefinition getDataMethod, out int magic) {
var instrs = handler.Body.Instructions;
for (int i = 0; i < instrs.Count; i++) {
int index = i;
Expand All @@ -105,7 +298,7 @@ static bool checkHandlerV4(MethodDefinition handler, out FieldDefinition resourc
// 4.0.1.18 .. 4.0.3
}

if (field.InitialValue == null || field.InitialValue.Length == 0)
if (field == null || field.InitialValue == null || field.InitialValue.Length == 0)
continue;

var ldci4_len = instrs[index++];
Expand Down Expand Up @@ -157,7 +350,7 @@ public void initialize() {
if (resolveHandler == null)
return;

if (isV3) {
if (version == ResourceVersion.V3) {
simpleDeobfuscator.deobfuscate(resolveHandler);
simpleDeobfuscator.decryptStrings(resolveHandler, deob);
resource = DeobUtils.getEmbeddedResourceFromCodeStrings(module, resolveHandler);
Expand All @@ -171,22 +364,34 @@ public void initialize() {
public bool mergeResources(out EmbeddedResource rsrc) {
rsrc = null;

if (isV3) {
switch (version) {
case ResourceVersion.V3:
if (resource == null)
return false;

DeobUtils.decryptAndAddResources(module, resource.Name, () => decryptResourceV3(resource));
rsrc = resource;
}
else {
if (resourceField == null)
return false;
return true;

case ResourceVersion.V40:
return decryptResource(resourceField, magicV4);

case ResourceVersion.V41:
return decryptResource(data41.resourceField, data41.magic);

string name = string.Format("Embedded data field {0:X8} RVA {1:X8}", resourceField.MetadataToken.ToInt32(), resourceField.RVA);
DeobUtils.decryptAndAddResources(module, name, () => decryptResourceV4(resourceField.InitialValue, magicV4));
resourceField.InitialValue = new byte[1];
resourceField.FieldType = module.TypeSystem.Byte;
default:
return true;
}
}

bool decryptResource(FieldDefinition resourceField, int magic) {
if (resourceField == null)
return false;

string name = string.Format("Embedded data field {0:X8} RVA {1:X8}", resourceField.MetadataToken.ToInt32(), resourceField.RVA);
DeobUtils.decryptAndAddResources(module, name, () => decryptResourceV4(resourceField.InitialValue, magic));
resourceField.InitialValue = new byte[1];
resourceField.FieldType = module.TypeSystem.Byte;
return true;
}
}
Expand Down

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