Question on comparing array sigs

[greenozon]

I'm not sure if thats an issue, but anyway I'd like to raise it here.

I've such a method in some class (as seen in SAE for example):
myMeth1(Double[0...,0...], Double[]&&): Boolean

Now, there is a code in some assembly that calls this method
and the 1st parameter is declared as follows:

http://prntscr.com/7gj2sd

now, taking into account how dnlib compares the arraysig, the lookup fails....

module: SigComparer.cs
code:

namespace dnlib.DotNet {
......

public bool Equals(TypeSig a, TypeSig b) {
{
...........
                case ElementType.Array:
                    ArraySig ara = a as ArraySig, arb = b as ArraySig;
                    result = ara.Rank == arb.Rank &&
                            Equals(ara.Sizes, arb.Sizes) &&
Equals(ara.LowerBounds, arb.LowerBounds) &&
                        Equals(a.Next, b.Next);
                    break;

}

here is an example of the comparing code:
bool flag6 = !default(SigComparer).Equals(methodSig.Params[i], babelMethodRef.Parameters[i].Type);

I've looked around, there is interesting arcticle about this case:

Array lower bounds can be only '0'
https://msdn.microsoft.com/en-us/library/ttw7c10x%28v=vs.90%29.aspx

So the question is: does it make sense to relax the LowerBounds comparing way?
maybe it'll make sense to check if one side has 0 lower bounds and another no, then the result still may be "equal"?

Thanks

[0xd4d]

I wrote some code that tests this and peverify complains if caller's method signature doesn't include the 0 lower bounds that matches the called method's 0 lower bounds.

The reason that the code you're investigating might work is that it seems from your info above that it's a Babel.NET obfuscated assembly. The obfuscator resolves the correct method and then creates the correct code.

C:\arytest>peverify theexe.exe

Microsoft (R) .NET Framework PE Verifier.  Version  4.0.30319.0
Copyright (c) Microsoft Corporation.  All rights reserved.

[IL]: Error: [C:\arytest\theexe.exe : main.Start::Method][offset 0x00000001] Unable to resolve token.
1 Error(s) Verifying theexe.exe

C:\arytest>theexe.exe

Unhandled Exception: System.MissingMethodException: Method not found: 'Int32 ns.Class1.Method(Double[,])'.
   at main.Start.Method()

Fixing the signature results in everything working again:

C:\arytest>theexe.exe

C:\arytest>peverify theexe.exe

Microsoft (R) .NET Framework PE Verifier.  Version  4.0.30319.0
Copyright (c) Microsoft Corporation.  All rights reserved.

All Classes and Methods in theexe.exe Verified.

Here's the code I used:

using dnlib.DotNet;
using dnlib.DotNet.Emit;

....

            {
                var mod = new ModuleDefUser("themod", Guid.NewGuid());
                var asm = new AssemblyDefUser("themod", new Version(0, 0, 0, 0));
                asm.Modules.Add(mod);
                mod.Kind = ModuleKind.Dll;

                var cl = new TypeDefUser("ns", "Class1", mod.CorLibTypes.Object.TypeDefOrRef);
                mod.Types.Add(cl);
                cl.Visibility = TypeAttributes.Public;

                var arg1 = new ArraySig(mod.CorLibTypes.Double, 2);
                arg1.LowerBounds.Add(0);
                arg1.LowerBounds.Add(0);
                var meth = new MethodDefUser("Method", MethodSig.CreateStatic(mod.CorLibTypes.Int32, arg1),
                    MethodImplAttributes.IL | MethodImplAttributes.Managed,
                    MethodAttributes.Public | MethodAttributes.Static);
                cl.Methods.Add(meth);
                var body = new CilBody();
                meth.Body = body;
                body.Instructions.Add(OpCodes.Ldc_I4_3.ToInstruction());
                body.Instructions.Add(OpCodes.Ret.ToInstruction());

                mod.Write(@"C:\arytest\themod.dll");
            }
            {
                var mod = new ModuleDefUser("theexe", Guid.NewGuid());
                var asm = new AssemblyDefUser("theexe", new Version(0, 0, 0, 0));
                asm.Modules.Add(mod);
                mod.Kind = ModuleKind.Console;

                var cl = new TypeDefUser("main", "Start", mod.CorLibTypes.Object.TypeDefOrRef);
                mod.Types.Add(cl);

                var asmRef = new AssemblyRefUser("themod", new Version(0, 0, 0, 0));
                var tr = new TypeRefUser(mod, "ns", "Class1", asmRef);
                var arg1 = new ArraySig(mod.CorLibTypes.Double, 2);
// Comment these and the program will fail because the correct method can't be found
                arg1.LowerBounds.Add(0);
                arg1.LowerBounds.Add(0);
                var mr = new MemberRefUser(mod, "Method", MethodSig.CreateStatic(mod.CorLibTypes.Int32, arg1), tr);

                var meth = new MethodDefUser("Method", MethodSig.CreateStatic(mod.CorLibTypes.Void),
                    MethodImplAttributes.IL | MethodImplAttributes.Managed,
                    MethodAttributes.Public | MethodAttributes.Static);
                cl.Methods.Add(meth);
                mod.EntryPoint = meth;
                var body = new CilBody();
                meth.Body = body;
                body.Instructions.Add(OpCodes.Ldnull.ToInstruction());
                body.Instructions.Add(OpCodes.Call.ToInstruction(mr));
                body.Instructions.Add(OpCodes.Pop.ToInstruction());
                body.Instructions.Add(OpCodes.Ret.ToInstruction());

                mod.Write(@"C:\arytest\theexe.exe");
            }