SignController.cs

SignController.cs

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Web.Http;

namespace SignGenApi.Controllers
{
    public class SignController : ApiController
    {
        public string Get(string text, string certSubject)
        {
            // Access Personal (MY) certificate store of current user
            var my = new X509Store(StoreName.My, StoreLocation.CurrentUser);

            my.Open(OpenFlags.ReadOnly);

            // Find the certificate we'll use to sign
            RSACryptoServiceProvider csp = null;

            foreach (var cert in my.Certificates)
            {
                if (cert.Subject.Contains(certSubject))
                {
                    // We found it.
                    // Get its associated CSP and private key
                    csp = (RSACryptoServiceProvider)cert.PrivateKey;
                }
            }

            if (csp == null)
            {
                return string.Empty;
                //throw new Exception("No valid cert was found");
            }

            // Hash the data
            var sha1 = new SHA1Managed();
            var encoding = new UnicodeEncoding();
            var data = encoding.GetBytes(text);
            var hash = sha1.ComputeHash(data);

            // Sign the hash
            var bytes = csp.SignHash(hash, CryptoConfig.MapNameToOID("SHA1"));

            // Convert to base64
            return Convert.ToBase64String(bytes);
        }
    }
}