Added signature verification to Transaction.Deserialize

Each signature is verified before adding it to the transaction object. It will attempt to find the owner of the signature if the initial verification fails

Author: BifrostTitan

src/Solnet.Rpc/Models/Transaction.cs

@@ -1,3 +1,4 @@
+using Chaos.NaCl;
 using Solnet.Rpc.Builders;
 using Solnet.Rpc.Utilities;
 using Solnet.Wallet;
@@ -308,13 +309,35 @@ public static Transaction Populate(Message message, IList<byte[]> signatures = n
 
             if (signatures != null)
             {
-                for (int i = 0; i < signatures.Count; i++)
+                int i = 0;
+                foreach(byte[] signature in signatures)
                 {
-                    tx.Signatures.Add(new SignaturePubKeyPair
+                    byte[] messageBytes = message.Serialize();
+                    bool validSig = Ed25519.Verify(signature, messageBytes, message.AccountKeys[i].KeyBytes);
+                    PublicKey signer = message.AccountKeys[i];
+                    if (!validSig)
                     {
-                        PublicKey = message.AccountKeys[i],
-                        Signature = signatures[i]
-                    });
+                        foreach (var account in message.AccountKeys)
+                        {
+                            if (Ed25519.Verify(signature, messageBytes, account.KeyBytes))
+                            {
+                                validSig = true;
+                                signer = account;
+                                break;
+                            }
+                        }
+                    }
+
+                    if (validSig)
+                    {
+                        tx.Signatures.Add(new SignaturePubKeyPair
+                        {
+                            PublicKey = signer,
+                            Signature = signature
+                        });
+                    }
+
+                    i++;
                 }
             }