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Update switch cflow deob code to handle more cases

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This commit is contained in:
de4dot 2011-10-19 09:13:27 +02:00
parent 7fe71a963a
commit f519d6f6d8
1 changed files with 129 additions and 25 deletions
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154
blocks/cflow/SwitchCflowDeobfuscator.cs
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@ -37,43 +37,44 @@ namespace de4dot.blocks.cflow {
if (switchBlock.LastInstr.OpCode.Code != Code.Switch)
continue;
if (isSwitchTopOfStack(switchBlock))
changed |= topOfstackDeobfuscate(switchBlock);
else if (isSwitchLocal(switchBlock))
changed |= localDeobfuscate(switchBlock);
changed |= deobfuscateTos(switchBlock);
else if (isLdlocBranch(switchBlock, true))
changed |= deobfuscateLdloc(switchBlock);
else if (isStLdlocBranch(switchBlock, true))
changed |= deobfuscateStLdloc(switchBlock);
}
return changed;
}
bool isSwitchTopOfStack(Block switchBlock) {
static bool isSwitchTopOfStack(Block switchBlock) {
return switchBlock.Instructions.Count == 1;
}
bool topOfstackDeobfuscate(Block switchBlock) {
static bool isLdlocBranch(Block switchBlock, bool isSwitch) {
int numInstrs = 1 + (isSwitch ? 1 : 0);
return switchBlock.Instructions.Count == numInstrs && switchBlock.Instructions[0].isLdloc();
}
bool isStLdlocBranch(Block switchBlock, bool isSwitch) {
int numInstrs = 2 + (isSwitch ? 1 : 0);
return switchBlock.Instructions.Count == numInstrs &&
switchBlock.Instructions[0].isStloc() &&
switchBlock.Instructions[1].isLdloc() &&
Instr.getLocalVar(blocks.Locals, switchBlock.Instructions[0]) == Instr.getLocalVar(blocks.Locals, switchBlock.Instructions[1]);
}
bool deobfuscateTos(Block switchBlock) {
bool changed = false;
if (switchBlock.Targets == null)
return changed;
var targets = new List<Block>(switchBlock.Targets);
foreach (var source in new List<Block>(switchBlock.Sources)) {
if (!isBranchBlock(source))
continue;
instructionEmulator.init(false, blocks.Method.Parameters, blocks.Locals);
instructionEmulator.emulate(source.Instructions);
var target = getSwitchTarget(targets, switchBlock.FallThrough, source, instructionEmulator.pop());
if (target == null)
continue;
source.replaceLastNonBranchWithBranch(0, target);
source.add(new Instr(Instruction.Create(OpCodes.Pop)));
changed = true;
}
changed |= deobfuscateTos(targets, switchBlock.FallThrough, switchBlock);
return changed;
}
bool isSwitchLocal(Block switchBlock) {
return switchBlock.Instructions.Count == 2 && switchBlock.Instructions[0].isLdloc();
}
bool localDeobfuscate(Block switchBlock) {
bool deobfuscateLdloc(Block switchBlock) {
bool changed = false;
var switchVariable = Instr.getLocalVar(blocks.Locals, switchBlock.Instructions[0]);
@ -83,22 +84,125 @@ namespace de4dot.blocks.cflow {
if (switchBlock.Targets == null)
return changed;
var targets = new List<Block>(switchBlock.Targets);
foreach (var source in new List<Block>(switchBlock.Sources)) {
changed |= deobfuscateLdloc(targets, switchBlock.FallThrough, switchBlock, switchVariable);
return changed;
}
bool deobfuscateStLdloc(Block switchBlock) {
bool changed = false;
var switchVariable = Instr.getLocalVar(blocks.Locals, switchBlock.Instructions[0]);
if (switchVariable == null)
return changed;
if (switchBlock.Targets == null)
return changed;
var targets = new List<Block>(switchBlock.Targets);
changed |= deobfuscateStLdloc(targets, switchBlock.FallThrough, switchBlock);
return changed;
}
// Switch deobfuscation when block uses stloc N, ldloc N to load switch constant
// blk1:
// ldc.i4 X
// br swblk
// swblk:
// stloc N
// ldloc N
// switch (......)
bool deobfuscateStLdloc(IList<Block> switchTargets, Block switchFallThrough, Block block) {
bool changed = false;
foreach (var source in new List<Block>(block.Sources)) {
if (!isBranchBlock(source))
continue;
instructionEmulator.init(false, blocks.Method.Parameters, blocks.Locals);
instructionEmulator.emulate(source.Instructions);
var target = getSwitchTarget(targets, switchBlock.FallThrough, source, instructionEmulator.getLocal(switchVariable));
var target = getSwitchTarget(switchTargets, switchFallThrough, source, instructionEmulator.pop());
if (target == null)
continue;
source.replaceLastNonBranchWithBranch(0, target);
source.add(new Instr(Instruction.Create(OpCodes.Pop)));
changed = true;
}
return changed;
}
// Switch deobfuscation when block uses ldloc N to load switch constant
// blk1:
// ldc.i4 X
// stloc N
// br swblk
// swblk:
// ldloc N
// switch (......)
bool deobfuscateLdloc(IList<Block> switchTargets, Block switchFallThrough, Block block, VariableDefinition switchVariable) {
bool changed = false;
foreach (var source in new List<Block>(block.Sources)) {
if (!isBranchBlock(source))
continue;
instructionEmulator.init(false, blocks.Method.Parameters, blocks.Locals);
instructionEmulator.emulate(source.Instructions);
var target = getSwitchTarget(switchTargets, switchFallThrough, source, instructionEmulator.getLocal(switchVariable));
if (target == null)
continue;
source.replaceLastNonBranchWithBranch(0, target);
changed = true;
}
return changed;
}
// Switch deobfuscation when block has switch contant on TOS:
// blk1:
// ldc.i4 X
// br swblk
// swblk:
// switch (......)
bool deobfuscateTos(IList<Block> switchTargets, Block switchFallThrough, Block block) {
bool changed = false;
foreach (var source in new List<Block>(block.Sources)) {
if (!isBranchBlock(source))
continue;
instructionEmulator.init(false, blocks.Method.Parameters, blocks.Locals);
instructionEmulator.emulate(source.Instructions);
var target = getSwitchTarget(switchTargets, switchFallThrough, source, instructionEmulator.pop());
if (target == null) {
changed |= deobfuscateTos_Ldloc(switchTargets, switchFallThrough, source);
}
else {
source.replaceLastNonBranchWithBranch(0, target);
source.add(new Instr(Instruction.Create(OpCodes.Pop)));
changed = true;
}
}
return changed;
}
// ldloc N
// br swblk
// or
// stloc N
// ldloc N
// br swblk
bool deobfuscateTos_Ldloc(IList<Block> switchTargets, Block switchFallThrough, Block block) {
if (isLdlocBranch(block, false)) {
var switchVariable = Instr.getLocalVar(blocks.Locals, block.Instructions[0]);
if (switchVariable == null)
return false;
return deobfuscateLdloc(switchTargets, switchFallThrough, block, switchVariable);
}
else if (isStLdlocBranch(block, false))
return deobfuscateStLdloc(switchTargets, switchFallThrough, block);
return false;
}
bool isBranchBlock(Block block) {
if (block.FallThrough != null)
return block.Targets == null || block.Targets.Count == 0;