Override Script Eval Context for Elements

NBitcoin.Altcoins/Elements/ElementsOpcodeType.cs

@@ -0,0 +1,123 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using NBitcoin.Crypto;
+
+namespace NBitcoin.Altcoins.Elements
+{
+	public enum ElementsOpcodeType : byte
+	{
+		OP_CHECKSIGFROMSTACK = 0xc1,
+		OP_CHECKSIGFROMSTACKVERIFY = 0xc2
+	}
+
+	public class ElementsScriptEvaluationContext : ScriptEvaluationContext
+	{
+		protected override bool IsDisabledOpCode(OpcodeType type)
+		{
+			return type != OpcodeType.OP_CAT && base.IsDisabledOpCode(type);
+		}
+
+		protected override bool ExecuteOpCode(Script s, TransactionChecker checker, int hashversion, Op opcode, bool fRequireMinimal,
+			bool fExec, Stack<bool> vfExec, ContextStack<byte[]> altstack, ScriptReader script, ref int pbegincodehash, ref int nOpCount,
+			out bool evalScript)
+		{
+			switch (((byte)opcode.Code))
+			{
+				case (byte) ElementsOpcodeType.OP_CHECKSIGFROMSTACK:
+				case (byte)ElementsOpcodeType.OP_CHECKSIGFROMSTACKVERIFY:
+					if (_stack.Count < 3)
+					{
+						evalScript = SetError(ScriptError.InvalidStackOperation);
+						return true;
+					}
+
+					var vchSig = _stack.Top(-3);
+					var vchData = _stack.Top(-2);
+					var vchPubKey = _stack.Top(-1);
+
+					////// debug print
+					//PrintHex(vchSig.begin(), vchSig.end(), "sig: %s\n");
+					//PrintHex(vchPubKey.begin(), vchPubKey.end(), "pubkey: %s\n");
+
+					// Subset of script starting at the most recent codeseparator
+					var scriptCode = new Script(s._Script.Skip(pbegincodehash).ToArray());
+					// Drop the signature, since there's no way for a signature to sign itself
+					if (hashversion == (int) HashVersion.Original)
+						scriptCode = scriptCode.FindAndDelete(vchSig);
+
+					if (!CheckSignatureEncoding(vchSig) || !CheckPubKeyEncoding(vchPubKey, hashversion))
+					{
+						//serror is set
+						{
+							evalScript = false;
+							return true;
+						}
+					}
+
+					var publicKey = new PubKey(vchPubKey);
+					var vchHash = new uint256(Hashes.SHA256(vchData));
+					var sig = new ECDSASignature(vchSig);
+					bool fSuccess = publicKey.Verify(vchHash, sig);
+					if (!fSuccess && (ScriptVerify & ScriptVerify.NullFail) != 0 && vchSig.Length != 0)
+					{
+						evalScript = SetError(ScriptError.NullFail);
+						return true;
+					}
+
+					_stack.Pop();
+					_stack.Pop();
+					_stack.Pop();
+					_stack.Push(fSuccess ? vchTrue : vchFalse);
+					if (((byte)opcode.Code) == (byte)ElementsOpcodeType.OP_CHECKSIGFROMSTACKVERIFY)
+					{
+						_stack.Pop();
+					}
+					if (!fSuccess)
+					{
+						evalScript = SetError(ScriptError.CheckSigVerify);
+						return true;
+					}
+
+
+					break;
+
+			}
+			return base.ExecuteOpCode(s, checker, hashversion, opcode, fRequireMinimal, fExec, vfExec, altstack, script, ref pbegincodehash, ref nOpCount, out evalScript);
+		}
+	}
+
+	public class ElementsOp : Op
+	{
+		public static string GetOpName(ElementsOpcodeType opcode)
+		{
+			switch (opcode)
+			{
+				case ElementsOpcodeType.OP_CHECKSIGFROMSTACK:
+					return "OP_CHECKSIGFROMSTACK";
+				case ElementsOpcodeType.OP_CHECKSIGFROMSTACKVERIFY:
+					return "OP_CHECKSIGFROMSTACKVERIFY";
+				default:
+					return Op.GetOpName((OpcodeType) (byte) opcode);
+			}
+		}
+
+		private static bool[] GetValidOpCode()
+		{
+			var valid = new bool[256];
+			foreach (var val in Enum.GetValues(typeof(ElementsOpcodeType)))
+			{
+				valid[(byte)val] = true;
+			}
+			for (byte i = 0; ; i++)
+			{
+				if (IsPushCode((OpcodeType)i))
+					valid[i] = true;
+				if (i == 255)
+					break;
+			}
+			return valid;
+		}
+
+	}
+}