Sometimes you just need a X509Certificate2 in your C# code. For authenticating to an external webservice for instance.
This will show you how to create such a certificate right from your C# code. By the way you’ll need the Bouncy castle or Bouncy castle core library
using System; using System.Security.Cryptography.X509Certificates; using System.Security.Cryptography; using Org.BouncyCastle.X509; using Org.BouncyCastle.Utilities; using Org.BouncyCastle.Math; using Org.BouncyCastle.Security; using Org.BouncyCastle.Asn1.X509; using Org.BouncyCastle.Crypto; using Org.BouncyCastle.Crypto.Generators; using Org.BouncyCastle.Crypto.Operators; using Org.BouncyCastle.Crypto.Parameters; using Org.BouncyCastle.Pkcs; namespace Selfsigned { public static class Certificates { public static X509Certificate2 GenerateCertificate(string subject) { var random = new SecureRandom(); var certificateGenerator = new X509V3CertificateGenerator(); var serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random); certificateGenerator.SetSerialNumber(serialNumber); certificateGenerator.SetIssuerDN(new X509Name($"C=NL, O=SomeCompany, CN={subject}")); certificateGenerator.SetSubjectDN(new X509Name($"C=NL, O=SomeCompany, CN={subject}")); certificateGenerator.SetNotBefore(DateTime.UtcNow.Date); certificateGenerator.SetNotAfter(DateTime.UtcNow.Date.AddYears(1)); const int strength = 2048; var keyGenerationParameters = new KeyGenerationParameters(random, strength); var keyPairGenerator = new RsaKeyPairGenerator(); keyPairGenerator.Init(keyGenerationParameters); var subjectKeyPair = keyPairGenerator.GenerateKeyPair(); certificateGenerator.SetPublicKey(subjectKeyPair.Public); var issuerKeyPair = subjectKeyPair; const string signatureAlgorithm = "SHA256WithRSA"; var signatureFactory = new Asn1SignatureFactory(signatureAlgorithm,issuerKeyPair.Private); var bouncyCert = certificateGenerator.Generate(signatureFactory); // Lets convert it to X509Certificate2 X509Certificate2 certificate; Pkcs12Store store = new Pkcs12StoreBuilder().Build(); store.SetKeyEntry($"{subject}_key",new AsymmetricKeyEntry(subjectKeyPair.Private), new [] {new X509CertificateEntry(bouncyCert)}); string exportpw = Guid.NewGuid().ToString("x"); using(var ms = new System.IO.MemoryStream()){ store.Save(ms,exportpw.ToCharArray(),random); certificate = new X509Certificate2(ms.ToArray(),exportpw,X509KeyStorageFlags.Exportable); } //Console.WriteLine($"Generated cert with thumbprint {certificate.Thumbprint}"); return certificate; } // You can also load the certificate from to CurrentUser store private X509Certificate2 LoadCertificate(string subject) { var userStore = new X509Store(StoreName.My,StoreLocation.CurrentUser); userStore.Open(OpenFlags.OpenExistingOnly); if(userStore.IsOpen){ var collection = userStore.Certificates.Find(X509FindType.FindBySubjectName,Environment.MachineName,false); if(collection.Count > 0) { return collection[0]; } userStore.Close(); } return null; } // Or store the certificate to the local store. private void SaveCertificate(X509Certificate2 certificate) { var userStore = new X509Store(StoreName.My,StoreLocation.CurrentUser); userStore.Open(OpenFlags.ReadWrite); userStore.Add(certificate); userStore.Close(); } } }
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