TripleDES. Specified padding mode is not valid for this algorithm

Question

I have a net core app using core1.1 When migrating a cript/decript module from an old .NET4.6 to net core it just wont work

First TripleDES no longer (it used to) supports 128bit keys and is fixed with 192bit keys, trying to change it causes error.

Second, while trying to decript this string:

/Tk0ydguv3HauCVUWDK3Tr6U8c9BBaaRwtSt5q4/uHg=

TripleDES launches error with PKCS7 Padding saing "Specified padding mode is not valid for this algorithm." Which is strange since ti is the padding it defaults.

My project.json:

{
  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.1.0",
      "type": "platform"
    },
    "Microsoft.AspNetCore.Diagnostics": "1.1.0",
    "Microsoft.AspNetCore.Mvc": "1.0.1",
    "Microsoft.AspNetCore.Razor.Tools": {
      "version": "1.0.0-preview2-final",
      "type": "build"
    },
    "Microsoft.AspNetCore.Routing": "1.0.1",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
    "Microsoft.AspNetCore.StaticFiles": "1.0.0",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Logging": "1.0.0",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0",
    "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
    "Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0",
    "Microsoft.EntityFrameworkCore.SqlServer": "1.0.1",
    "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
    "Microsoft.EntityFrameworkCore.Design": "1.0.0-preview2-final",
    "Microsoft.EntityFrameworkCore.SqlServer.Design": "1.0.1",
    "Microsoft.AspNetCore.Mvc.WebApiCompatShim": "1.0.1",
    "Microsoft.AspNetCore.Session": "1.0.0",
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final"
  },

    "tools": {
        "BundlerMinifier.Core": "2.0.238",
        "Microsoft.EntityFrameworkCore.Tools.DotNet": "1.0.0-preview3-final",
        "Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final",
        "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final"
    },

  "frameworks": {
    "netcoreapp1.1": {
        "imports": [
            "portable-net461+win8"
        ]
    }
  },

  "buildOptions": {
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },

  "runtimeOptions": {
    "configProperties": {
      "System.GC.Server": true
    }
  },

  "publishOptions": {
    "include": [
      "wwwroot",
      "**/*.cshtml",
      "appsettings.json",
      "web.config"
    ]
  },

  "scripts": {
    "prepublish": [ "bower install", "dotnet bundle" ],
    "postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  }
}

My code:

using System;
using System.Security.Cryptography;
using System.Text;
namespace WebApp.Class
{
    public class Md5
    {
        private static readonly byte[] IV = { 240, 3, 45, 29, 0, 76, 173, 59 };

        const int NumCryptokey = 6;
        const int NumExtraClave = 8;
        const int NumsKey = 7;


        public static string Generate(int KeyChars)
        {
            int i_key = 0;
            float Random1 = 0;
            Int16 arrIndex = default(Int16);
            StringBuilder sb = new StringBuilder();
            char RandomLetter;

            string KeyLetters = "abcdefghijklmnopqrstuvwxyz";
            string KeyNumbers = "0123456789";

            char[] LettersArray = null;
            char[] NumbersArray = null;

            LettersArray = KeyLetters.ToCharArray();
            NumbersArray = KeyNumbers.ToCharArray();

            for (i_key = 1; i_key <= KeyChars; i_key++)
            {
                Random random = new Random();
                Random1 = random.Next();

                arrIndex = -1;
                if ((Convert.ToInt32(Random1 * 111)) % 2 == 0)
                {
                    while (arrIndex < 0)
                    {
                        arrIndex = Convert.ToInt16(LettersArray.GetUpperBound(0) * Random1);
                    }
                    RandomLetter = LettersArray[arrIndex];
                    if ((Convert.ToInt32(arrIndex * Random1 * 99)) % 2 != 0)
                    {
                        RandomLetter = LettersArray[arrIndex];
                        RandomLetter = char.ToUpper(RandomLetter);
                    }
                    sb.Append(RandomLetter);
                }
                else
                {
                    while (arrIndex < 0)
                    {
                        arrIndex = Convert.ToInt16(NumbersArray.GetUpperBound(0) * Random1);
                    }
                    sb.Append(NumbersArray[arrIndex]);
                }
            }
            return sb.ToString();
        }

        public static string Encriptar(string serializedQueryString)
        {
            string functionReturnValue = null;
            string sRetorno = null;
            try
            {
                string cryptokey = "";
                string ExtraClave = "";
                string sKey = "";

                cryptokey = Generate(NumCryptokey);
                ExtraClave = Generate(NumExtraClave);
                sKey = Generate(NumsKey);

                byte[] buffer = Encoding.ASCII.GetBytes(serializedQueryString + ExtraClave);
                var des = TripleDES.Create();
                var MD5 = System.Security.Cryptography.MD5.Create();
                des.Key = MD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(sKey + cryptokey));
                des.IV = IV;

                sRetorno = cryptokey + ExtraClave + sKey + Convert.ToBase64String(des.CreateEncryptor().TransformFinalBlock(buffer, 0, buffer.Length));

                functionReturnValue = sRetorno;
            }
            catch (Exception ex)
            {
                functionReturnValue = "";
            }
            return functionReturnValue;

        }

        public static string Desencriptar(string encryptedQueryString)
        {
            string functionReturnValue = null;
            byte[] buffer = null;
            var DES = System.Security.Cryptography.TripleDES.Create();
            var Md5 = MD5.Create();
            string sRetorno = null;

            string cryptokey = "";
            string ExtraClave = "";
            string sKey = "";

            cryptokey = encryptedQueryString.Substring(0,NumCryptokey);
            ExtraClave = encryptedQueryString.Substring(NumCryptokey, NumExtraClave);
            sKey = encryptedQueryString.Substring(NumCryptokey + NumExtraClave, NumsKey);

            encryptedQueryString = encryptedQueryString.Substring(NumCryptokey + NumExtraClave + NumsKey, encryptedQueryString.Length-(NumCryptokey + NumExtraClave + NumsKey));

            try
            {
                buffer = Convert.FromBase64String(encryptedQueryString);
            byte[] by = new byte[24];
                by = Md5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(sKey + cryptokey));
            Array.Resize(ref by, 24);
                DES.Key = by;
                DES.IV = IV;

                sRetorno = Encoding.ASCII.GetString(DES.CreateDecryptor().TransformFinalBlock(buffer, 0, buffer.Length)).Replace(ExtraClave, "");
                functionReturnValue = sRetorno;
            }
            catch (Exception ex)
            {
                functionReturnValue = "";
            }
            return functionReturnValue;

        }
    }
}

Answer 1

Found it!

    public static string Encriptar(string serializedQueryString)
    {
        string functionReturnValue = null;
        string sRetorno = null;
        try
        {
            string cryptokey = "";
            string ExtraClave = "";
            string sKey = "";

            cryptokey = Generate(NumCryptokey);
            ExtraClave = Generate(NumExtraClave);
            sKey = Generate(NumsKey);

            byte[] buffer = Encoding.ASCII.GetBytes(serializedQueryString + ExtraClave);
            var des = TripleDES.Create();
            var Md5 = MD5.Create();

            byte[] by = new byte[24];
            by = Md5.ComputeHash(Encoding.ASCII.GetBytes(sKey + cryptokey));
            Array.Resize(ref by, 24);
            Array.Copy(by, 0, by, 16, 8);
            des.Key = by;
            des.IV = IV;
            //es.Padding = PaddingMode.None;
            sRetorno = cryptokey + ExtraClave + sKey + Convert.ToBase64String(des.CreateEncryptor().TransformFinalBlock(buffer, 0, buffer.Length));

            functionReturnValue = sRetorno;

        }
        catch (Exception ex)
        {
            functionReturnValue = "";
        }
        return functionReturnValue;
    }

Answer 2

I faced the same issue in ASP.NET Core. However, I was not specifying any IV.

I just added this line while encrypting as well as decrypting after specifying the key.

DES3.IV = new byte[DES3.BlockSize / 8];

Without this line, i was getting the error as described above.

As per the docs at https://msdn.microsoft.com/en-us/library/system.security.cryptography.symmetricalgorithm.iv(v=vs.110).aspx

The IV property is automatically set to a new random value whenever you create a new instance of one of the SymmetricAlgorithm classes or when you manually call the GenerateIV method.

However, I still do not understand why this worked because even i tried giving static values to the IV(like yours in question) & it failed even then.