Native Method Detection (#246)

Cpp2IL.Core/Cpp2IlCorePlugin.cs

@@ -51,6 +51,7 @@ public override void OnLoad()
         ProcessingLayerRegistry.Register<AttributeAnalysisProcessingLayer>();
         ProcessingLayerRegistry.Register<AttributeInjectorProcessingLayer>();
         ProcessingLayerRegistry.Register<CallAnalysisProcessingLayer>();
+        ProcessingLayerRegistry.Register<NativeMethodDetectionProcessingLayer>();
         ProcessingLayerRegistry.Register<StableRenamingProcessingLayer>();
         ProcessingLayerRegistry.Register<DeobfuscationMapProcessingLayer>();
 

Cpp2IL.Core/Model/Contexts/NativeMethodAnalysisContext.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Reflection;
+using LibCpp2IL;
+
+namespace Cpp2IL.Core.Model.Contexts;
+
+public sealed class NativeMethodAnalysisContext : MethodAnalysisContext
+{
+    public override ulong UnderlyingPointer { get; }
+
+    public override string DefaultName { get; }
+
+    public override bool IsStatic => true;
+
+    public override bool IsVoid { get; }
+
+    public override MethodAttributes Attributes => MethodAttributes.Public | MethodAttributes.Static | MethodAttributes.HideBySig;
+
+    protected override int CustomAttributeIndex => -1;
+
+    public NativeMethodAnalysisContext(TypeAnalysisContext parent, ulong address, bool voidReturn) : base(null, parent)
+    {
+        if (address == 0)
+            throw new ArgumentOutOfRangeException(nameof(address));
+
+        IsVoid = voidReturn;
+        UnderlyingPointer = address;
+        if (LibCpp2IlMain.Binary?.TryGetExportedFunctionName(UnderlyingPointer, out var name) ?? false)
+        {
+            DefaultName = name;
+        }
+        else
+        {
+            DefaultName = $"NativeMethod_0x{UnderlyingPointer:X}";
+        }
+        RawBytes = AppContext.InstructionSet.GetRawBytesForMethod(this, false);
+    }
+}

Cpp2IL.Core/ProcessingLayers/NativeMethodDetectionProcessingLayer.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Cpp2IL.Core.Api;
+using Cpp2IL.Core.ISIL;
+using Cpp2IL.Core.Model.Contexts;
+
+namespace Cpp2IL.Core.ProcessingLayers;
+
+public class NativeMethodDetectionProcessingLayer : Cpp2IlProcessingLayer
+{
+    public override string Name => "Native Method Detection";
+
+    public override string Id => "nativemethoddetector";
+
+    public override void Process(ApplicationAnalysisContext appContext, Action<int, int>? progressCallback = null)
+    {
+        var nativeMethodInfoStack = new Stack<(ulong, bool)>();
+        var cppNativeMethodsType = appContext.AssembliesByName["mscorlib"].InjectType("Cpp2ILInjected", "CppNativeMethods", null);
+        foreach (var assemblyAnalysisContext in appContext.Assemblies)
+        {
+            foreach (var m in assemblyAnalysisContext.Types.SelectMany(t => t.Methods))
+            {
+                AnalyzeMethod(appContext, m, nativeMethodInfoStack);
+            }
+        }
+        while (nativeMethodInfoStack.Count > 0)
+        {
+            (var address, var isVoid) = nativeMethodInfoStack.Pop();
+            if (!appContext.MethodsByAddress.ContainsKey(address))
+            {
+                var m = new NativeMethodAnalysisContext(cppNativeMethodsType, address, isVoid);
+                cppNativeMethodsType.Methods.Add(m);
+                m.InjectedReturnType = isVoid ? appContext.SystemTypes.SystemVoidType : appContext.SystemTypes.SystemObjectType;
+                appContext.MethodsByAddress.Add(address, new(1) { m });
+                AnalyzeMethod(appContext, m, nativeMethodInfoStack);
+            }
+        }
+    }
+
+    private static void AnalyzeMethod(ApplicationAnalysisContext appContext, MethodAnalysisContext m, Stack<(ulong, bool)> nativeMethodInfoStack)
+    {
+        if (m.UnderlyingPointer == 0)
+            return;
+
+        try
+        {
+            m.Analyze();
+        }
+        catch (Exception ex)
+        {
+#if DEBUG
+            if (ex.Message is not "Failed to convert to ISIL. Reason: Jump target not found in method. Ruh roh" && !ex.Message.StartsWith("Instruction "))
+            {
+            }
+#endif
+            m.ConvertedIsil = null;
+            return;
+        }
+
+        if (m.ConvertedIsil is { Count: 0 })
+        {
+            return;
+        }
+
+        foreach (var instruction in m.ConvertedIsil)
+        {
+            if (instruction.OpCode == InstructionSetIndependentOpCode.Call)
+            {
+                if (TryGetAddressFromInstruction(instruction, out var address) && !appContext.MethodsByAddress.ContainsKey(address))
+                {
+                    nativeMethodInfoStack.Push((address, true));
+                }
+            }
+            else if (instruction.OpCode == InstructionSetIndependentOpCode.CallNoReturn)
+            {
+                if (TryGetAddressFromInstruction(instruction, out var address) && !appContext.MethodsByAddress.ContainsKey(address))
+                {
+                    nativeMethodInfoStack.Push((address, m.IsVoid));
+                }
+            }
+        }
+    }
+
+    private static bool TryGetAddressFromInstruction(InstructionSetIndependentInstruction instruction, out ulong address)
+    {
+        if (instruction.Operands.Length > 0 && instruction.Operands[0].Data is IsilImmediateOperand operand)
+        {
+            address = operand.Value.ToUInt64(null);
+            return true;
+        }
+        address = default;
+        return false;
+    }
+}

LibCpp2IL/Elf/ElfFile.cs

@@ -1,5 +1,6 @@
-using System;
+using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using LibCpp2IL.Logging;
@@ -16,7 +17,8 @@ public sealed class ElfFile : Il2CppBinary
         private ElfFileHeader? _elfHeader;
         private readonly List<ElfDynamicEntry> _dynamicSection = new();
         private readonly List<ElfSymbolTableEntry> _symbolTable = new();
-        private readonly Dictionary<string, ElfSymbolTableEntry> _exportTable = new();
+        private readonly Dictionary<string, ElfSymbolTableEntry> _exportNameTable = new();
+        private readonly Dictionary<ulong, ElfSymbolTableEntry> _exportAddressTable = new();
         private List<long>? _initializerPointers;
 
         private readonly List<(ulong start, ulong end)> relocationBlocks = new(); 
@@ -405,7 +407,8 @@ private void ProcessSymbols()
             }
 
             _symbolTable.Clear();
-            _exportTable.Clear();
+            _exportNameTable.Clear();
+            _exportAddressTable.Clear();
 
             //Unify symbol tables
             foreach (var (offset, count, stringTable) in symbolTables)
@@ -440,7 +443,10 @@ private void ProcessSymbols()
                     _symbolTable.Add(entry);
 
                     if (symbol.Shndx != 0)
-                        _exportTable.TryAdd(name, entry);
+                    {
+                        _exportNameTable.TryAdd(name, entry);
+                        _exportAddressTable.TryAdd(virtualAddress, entry);
+                    }
                 }
             }
         }
@@ -707,12 +713,27 @@ public override ulong MapRawAddressToVirtual(uint offset)
 
         public override ulong GetVirtualAddressOfExportedFunctionByName(string toFind)
         {
-            if (!_exportTable.TryGetValue(toFind, out var exportedSymbol))
+            if (!_exportNameTable.TryGetValue(toFind, out var exportedSymbol))
                 return 0;
 
             return exportedSymbol.VirtualAddress;
         }
 
+        public override bool IsExportedFunction(ulong addr) => _exportAddressTable.ContainsKey(addr);
+
+        public override bool TryGetExportedFunctionName(ulong addr, [NotNullWhen(true)] out string? name)
+        {
+            if (_exportAddressTable.TryGetValue(addr, out var symbol))
+            {
+                name = symbol.Name;
+                return true;
+            }
+            else
+            {
+                return base.TryGetExportedFunctionName(addr, out name);
+            }
+        }
+
         public override ulong GetVirtualAddressOfPrimaryExecutableSection() => _elfSectionHeaderEntries.FirstOrDefault(s => s.Name == ".text")?.VirtualAddress ?? 0;
 
         public override byte[] GetEntirePrimaryExecutableSection()

LibCpp2IL/Il2CppBinary.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -459,6 +460,11 @@ public ulong GetMethodPointer(int methodIndex, int methodDefinitionIndex, int im
         public abstract byte[] GetRawBinaryContent();
         public abstract ulong GetVirtualAddressOfExportedFunctionByName(string toFind);
         public virtual bool IsExportedFunction(ulong addr) => false;
+        public virtual bool TryGetExportedFunctionName(ulong addr, [NotNullWhen(true)] out string? name)
+        {
+            name = null;
+            return false;
+        }
 
         public abstract byte[] GetEntirePrimaryExecutableSection();
 

LibCpp2IL/MachO/MachOFile.cs

@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using LibCpp2IL.Logging;
+using System.Diagnostics.CodeAnalysis;
 
 namespace LibCpp2IL.MachO
 {
@@ -15,7 +16,8 @@ public class MachOFile : Il2CppBinary
 
         private readonly MachOSegmentCommand[] Segments64;
         private readonly MachOSection[] Sections64;
-        private Dictionary<string, long> _exportsDict;
+        private readonly Dictionary<string, long> _exportAddressesDict;
+        private readonly Dictionary<long, string> _exportNamesDict;
 
         public MachOFile(MemoryStream input) : base(input)
         {
@@ -74,9 +76,10 @@ public MachOFile(MemoryStream input) : base(input)
 
             var dyldData = _loadCommands.FirstOrDefault(c => c.Command is LoadCommandId.LC_DYLD_INFO or LoadCommandId.LC_DYLD_INFO_ONLY)?.CommandData as MachODynamicLinkerCommand;
             var exports = dyldData?.Exports ?? Array.Empty<MachOExportEntry>();
-            _exportsDict = exports.ToDictionary(e => e.Name[1..], e => e.Address); //Skip the first character, which is a leading underscore inserted by the compiler
+            _exportAddressesDict = exports.ToDictionary(e => e.Name[1..], e => e.Address); //Skip the first character, which is a leading underscore inserted by the compiler
+            _exportNamesDict = _exportAddressesDict.ToDictionary(kvp => kvp.Value, kvp => kvp.Key);
 
-            LibLogger.VerboseNewline($"Found {_exportsDict.Count} exports in the DYLD info load command.");
+            LibLogger.VerboseNewline($"Found {_exportAddressesDict.Count} exports in the DYLD info load command.");
 
             LibLogger.VerboseNewline($"\tMach-O contains {Segments64.Length} segments, split into {Sections64.Length} sections.");
         }
@@ -116,12 +119,19 @@ public override ulong GetRva(ulong pointer)
 
         public override ulong GetVirtualAddressOfExportedFunctionByName(string toFind)
         {
-            if (!_exportsDict.TryGetValue(toFind, out var addr))
+            if (!_exportAddressesDict.TryGetValue(toFind, out var addr))
                 return 0;
 
             return (ulong) addr;
         }
 
+        public override bool IsExportedFunction(ulong addr) => _exportNamesDict.ContainsKey((long) addr);
+
+        public override bool TryGetExportedFunctionName(ulong addr, [NotNullWhen(true)] out string? name)
+        {
+            return _exportNamesDict.TryGetValue((long) addr, out name);
+        }
+
         private MachOSection GetTextSection64()
         {
             var textSection = Sections64.FirstOrDefault(s => s.SectionName == "__text");

LibCpp2IL/PE/PE.cs

@@ -158,7 +158,7 @@ public override ulong GetVirtualAddressOfExportedFunctionByName(string toFind)
             var index = Array.FindIndex(peExportedFunctionNamePtrs, stringAddress =>
             {
                 var rawStringAddress = MapVirtualAddressToRaw(stringAddress + peImageBase);
-                string exportName = ReadStringToNull(rawStringAddress);
+                var exportName = ReadStringToNull(rawStringAddress);
                 return exportName == toFind;
             });
 
@@ -176,7 +176,7 @@ public override bool IsExportedFunction(ulong addr)
             if (addr <= peImageBase)
                 return false;
 
-            var rva = addr - peImageBase;
+            var rva = GetRva(addr);
             if (rva > uint.MaxValue)
                 return false;
 
@@ -186,6 +186,35 @@ public override bool IsExportedFunction(ulong addr)
             return Array.IndexOf(peExportedFunctionPointers, (uint)rva) >= 0;
         }
 
+        public override bool TryGetExportedFunctionName(ulong addr, [NotNullWhen(true)] out string? name)
+        {
+            if (addr <= peImageBase)
+            {
+                return base.TryGetExportedFunctionName(addr, out name);
+            }
+
+            var rva = GetRva(addr);
+            if (rva > uint.MaxValue)
+            {
+                return base.TryGetExportedFunctionName(addr, out name);
+            }
+
+            if (peExportedFunctionPointers == null)
+                LoadPeExportTable();
+
+            var index = Array.IndexOf(peExportedFunctionPointers, (uint)rva);
+            if (index < 0)
+            {
+                return base.TryGetExportedFunctionName(addr, out name);
+            }
+            else
+            {
+                var rawStringAddress = MapVirtualAddressToRaw(peExportedFunctionNamePtrs[index] + peImageBase);
+                name = ReadStringToNull(rawStringAddress);
+                return true;
+            }
+        }
+
         public override ulong GetRva(ulong pointer)
         {
             return pointer - peImageBase;