ConfuserEx/Confuser.DynCipher/Utils.cs

using System.IO;
using Confuser.DynCipher.Generation;

namespace Confuser.DynCipher {
	public static class MathsUtils {
		private const ulong MODULO32 = 0x100000000;

		public static ulong modInv(ulong num, ulong mod) {
			ulong a = mod, b = num % mod;
			ulong p0 = 0, p1 = 1;
			while (b != 0) {
				if (b == 1) return p1;
				p0 += (a / b) * p1;
				a = a % b;

				if (a == 0) break;
				if (a == 1) return mod - p0;

				p1 += (b / a) * p0;
				b = b % a;
			}
			return 0;
		}

		public static uint modInv(uint num) {
			return (uint) modInv(num, MODULO32);
		}

		public static byte modInv(byte num) {
			return (byte) modInv(num, 0x100);
		}
	}

	public static class CodeGenUtils {
		public static byte[] AssembleCode(x86CodeGen codeGen, x86Register reg) {
			var stream = new MemoryStream();
			using (var writer = new BinaryWriter(stream)) {
				/* 
                 *      mov eax, esp
                 *      push ebx
                 *      push edi
                 *      push esi
                 *      sub eax, esp
                 *      cmp eax, 24             ; determine the bitness of platform
                 *      je n
                 *      mov eax, [esp + 4]      ; 32 bits => argument in stack
                 *      push eax
                 *      jmp z
                 *  n:  push ecx                ; 64 bits => argument in register
                 *  z:  XXX
                 *      pop esi
                 *      pop edi
                 *      pop ebx
                 *      pop ret
                 *      
                 */
				writer.Write(new byte[] { 0x89, 0xe0 });
				writer.Write(new byte[] { 0x53 });
				writer.Write(new byte[] { 0x57 });
				writer.Write(new byte[] { 0x56 });
				writer.Write(new byte[] { 0x29, 0xe0 });
				writer.Write(new byte[] { 0x83, 0xf8, 0x18 });
				writer.Write(new byte[] { 0x74, 0x07 });
				writer.Write(new byte[] { 0x8b, 0x44, 0x24, 0x10 });
				writer.Write(new byte[] { 0x50 });
				writer.Write(new byte[] { 0xeb, 0x01 });
				writer.Write(new byte[] { 0x51 });

				foreach (x86Instruction i in codeGen.Instructions)
					writer.Write(i.Assemble());

				if (reg != x86Register.EAX)
					writer.Write(x86Instruction.Create(x86OpCode.MOV, new x86RegisterOperand(x86Register.EAX), new x86RegisterOperand(reg)).Assemble());

				writer.Write(new byte[] { 0x5e });
				writer.Write(new byte[] { 0x5f });
				writer.Write(new byte[] { 0x5b });
				writer.Write(new byte[] { 0xc3 });
			}
			return stream.ToArray();
		}
	}
}