Aes256Decrypt.cs

using System;
using System.Security.Cryptography;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Cryptography.Functions.Encryption
{
    public class Aes256Decrypt : FunctionMultiVariate
    {
        public Aes256Decrypt(ScriptNode Content, ScriptNode Key, ScriptNode IV, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Content, Key, IV }, argumentTypes3Normal, Start, Length, Expression)
        {
        }
 
        public Aes256Decrypt(ScriptNode Content, ScriptNode Key, ScriptNode IV, ScriptNode CipherMode, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Content, Key, IV, CipherMode }, argumentTypes4Normal, Start, Length, Expression)
        {
        }
 
        public Aes256Decrypt(ScriptNode Content, ScriptNode Key, ScriptNode IV, ScriptNode CipherMode, ScriptNode PaddingMode, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Content, Key, IV, CipherMode, PaddingMode }, argumentTypes5Normal, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Aes256Decrypt);
 
        public override string[] DefaultArgumentNames => new string[] { "Content", "Key", "IV", "CipherMode", "PaddingMode" };
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            byte[] Data = Arguments[0].AssociatedObjectValue as byte[];
            if (Data is null)
                throw new ScriptRuntimeException("Data to decrypt must be binary (i.e. an array of bytes).", this);
 
            byte[] Key = Arguments[1].AssociatedObjectValue as byte[];
            if (Key is null)
                throw new ScriptRuntimeException("Key to use for decryption must be binary (i.e. an array of bytes).", this);
 
            byte[] IV = Arguments[2].AssociatedObjectValue as byte[];
            if (IV is null)
                throw new ScriptRuntimeException("Initiation Vector to use for decryption must be binary (i.e. an array of bytes).", this);
 
            int c = Arguments.Length;
            CipherMode CipherMode = c <= 3 ? CipherMode.CBC : this.ToEnum<CipherMode>(Arguments[3]);
            PaddingMode PaddingMode = c <= 4 ? PaddingMode.PKCS7 : this.ToEnum<PaddingMode>(Arguments[4]);
 
            using (Aes Aes = Aes.Create())
            {
                Aes.BlockSize = 128;
                Aes.KeySize = 256;
                Aes.Mode = CipherMode;
                Aes.Padding = PaddingMode;
 
                using (ICryptoTransform Transform = Aes.CreateDecryptor(Key, IV))
                {
                    byte[] Encrypted = Transform.TransformFinalBlock(Data, 0, Data.Length);
                    return new ObjectValue(Encrypted);
                }
            }
        }
    }
}