RSACryptoServiceProvider Extension to add FromXmlString and ToXmlString methods for ASP.NET Core

RSACryptoServiceProviderExtensions.cs

using System;
using System.Security.Cryptography;
using System.Xml;

namespace RSACryptoServiceProviderExtensions
{
    public static class RSACryptoServiceProviderExtensions
    {
        public static void FromXmlString(this RSACryptoServiceProvider rsa, string xmlString)
        {
            RSAParameters parameters = new RSAParameters();

            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(xmlString);

            if (xmlDoc.DocumentElement.Name.Equals("RSAKeyValue"))
            {
                foreach (XmlNode node in xmlDoc.DocumentElement.ChildNodes)
                {
                    switch (node.Name)
                    {
                        case "Modulus":     parameters.Modulus =    Convert.FromBase64String(node.InnerText); break;
                        case "Exponent":    parameters.Exponent =   Convert.FromBase64String(node.InnerText); break;
                        case "P":           parameters.P =          Convert.FromBase64String(node.InnerText); break;
                        case "Q":           parameters.Q =          Convert.FromBase64String(node.InnerText); break;
                        case "DP":          parameters.DP =         Convert.FromBase64String(node.InnerText); break;
                        case "DQ":          parameters.DQ =         Convert.FromBase64String(node.InnerText); break;
                        case "InverseQ":    parameters.InverseQ =   Convert.FromBase64String(node.InnerText); break;
                        case "D":           parameters.D =          Convert.FromBase64String(node.InnerText); break;
                    }
                }
            } else
            {
                throw new Exception("Invalid XML RSA key.");
            }

            rsa.ImportParameters(parameters);
        }

        public static string ToXmlString(this RSACryptoServiceProvider rsa)
        {
            RSAParameters parameters = rsa.ExportParameters(true);

            return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent><P>{2}</P><Q>{3}</Q><DP>{4}</DP><DQ>{5}</DQ><InverseQ>{6}</InverseQ><D>{7}</D></RSAKeyValue>",
                Convert.ToBase64String(parameters.Modulus),
                Convert.ToBase64String(parameters.Exponent),
                Convert.ToBase64String(parameters.P),
                Convert.ToBase64String(parameters.Q),
                Convert.ToBase64String(parameters.DP),
                Convert.ToBase64String(parameters.DQ),
                Convert.ToBase64String(parameters.InverseQ),
                Convert.ToBase64String(parameters.D));
        }
    }
}

The ToXmlString method could be written as:

public static string ToXmlString(this RSACryptoServiceProvider rsa, bool includePrivateParameters)
{
    RSAParameters parameters = rsa.ExportParameters(includePrivateParameters);

    . . . .  same code . . . .

This would be preferable:

        public static string ToXmlString(this RSACryptoServiceProvider rsa, bool includePrivateParameters = false)
        {
            RSAParameters parameters = rsa.ExportParameters(includePrivateParameters);

            if (includePrivateParameters)
            {
                return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent><P>{2}</P><Q>{3}</Q><DP>{4}</DP><DQ>{5}</DQ><InverseQ>{6}</InverseQ><D>{7}</D></RSAKeyValue>",
                    Convert.ToBase64String(parameters.Modulus),
                    Convert.ToBase64String(parameters.Exponent),
                    Convert.ToBase64String(parameters.P),
                    Convert.ToBase64String(parameters.Q),
                    Convert.ToBase64String(parameters.DP),
                    Convert.ToBase64String(parameters.DQ),
                    Convert.ToBase64String(parameters.InverseQ),
                    Convert.ToBase64String(parameters.D));
            }

            return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent></RSAKeyValue>",
                Convert.ToBase64String(parameters.Modulus),
                Convert.ToBase64String(parameters.Exponent));
        }

It's no longer necessary since .NET Core 3.0. But it was pretty useful at the time. Thanks for posting!

I'm going to try this. The fact that the MS version does not support Framework is a problem because .NET identity in .NET Core is too difficult to modify for API work. I'll stick with Framework and this module will help.