Generate a self-signed certificate on the fly

Question

I searched around, but I didn't find a clear example. I want to create a self-signed (self-)trusted certificate programmatically (C#), following these steps:

STEP 1:

Create a root CA certificate on the fly and add it to the certificate store in the folder "Trusted Root certification Authorities"

I want to do exactly what this command line tool does:

makecert.exe -sk RootCA -sky signature -pe -n CN=MY_CA -r -sr LocalMachine -ss Root MyCA.cer 

STEP 2:

Create a certificate based on the previously created root CA certificate and put it in the certificate store, in the folder "Personal"

I want to do exactly what this command line tool does:

makecert.exe -sk server -sky exchange -pe -n CN=127.0.0.1 -ir LocalMachine -is Root -ic MyCA.cer -sr LocalMachine -ss My MyCertificate.cer 

I want to obtain this:

I did that (see the following code - STEP 1). How do I make STEP 2? Target machines is Windows XP/7.

I tried both a pure .NET approach and Bouncy Castle library.

// STEP 1 mycerRoot = generateRootCertV1("MY_CA"); // Tried also generateRootCertV2(BouncyCastle) addCertToStore(mycerRoot, StoreName.Root, StoreLocation.LocalMachine);  // STEP 2 mycer = generateCert("127.0.0.1", mycerRoot); // ?????? <-- Something like that How to implement generateCert?? addCertToStore(mycer, StoreName.My, StoreLocation.LocalMachine);  public static Org.BouncyCastle.X509.X509Certificate generateRootCertV2(string certName) {     X509V1CertificateGenerator certGen = new X509V1CertificateGenerator();      X509Name CN = new X509Name("CN=" + certName);      RsaKeyPairGenerator keypairgen = new RsaKeyPairGenerator();     keypairgen.Init(new KeyGenerationParameters(new SecureRandom(new CryptoApiRandomGenerator()), 1024));      AsymmetricCipherKeyPair keypair = keypairgen.GenerateKeyPair();      certGen.SetSerialNumber(BigInteger.ProbablePrime(120, new Random()));     certGen.SetIssuerDN(CN);     certGen.SetNotAfter(DateTime.MaxValue);     certGen.SetNotBefore(DateTime.Now.Subtract(new TimeSpan(7, 0, 0, 0)));     certGen.SetSubjectDN(CN);     certGen.SetPublicKey(keypair.Public);     certGen.SetSignatureAlgorithm("MD5WithRSA");      Org.BouncyCastle.X509.X509Certificate newCert = certGen.Generate(keypair.Private);      return newCert; }  public static X509Certificate2 GenerateRootCertV1(string HostNameOrIP_or_CertName) {     X509Certificate2 cert = null;      try     {         using (CryptContext ctx = new CryptContext())         {             ctx.Open();             cert = ctx.CreateSelfSignedCertificate(                 new SelfSignedCertProperties                 {                     IsPrivateKeyExportable = true,                     KeyBitLength = 4096,                     Name = new X500DistinguishedName("cn=" + HostNameOrIP_or_CertName),                     ValidFrom = DateTime.Today.AddDays(-1),                     ValidTo = DateTime.Today.AddYears(20),                 });         }     }     catch (Exception ex)     {     }      return cert; }  public static bool addCertToStore(X509Certificate2 cert, StoreName st, StoreLocation sl) {     bool bRet = false;      try     {         X509Store store = new X509Store(st, sl);         store.Open(OpenFlags.ReadWrite);          if (cert != null)         {             byte[] pfx = cert.Export(X509ContentType.Pfx);             cert = new X509Certificate2(pfx, (string)null, X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.MachineKeySet);              if (!certExists(store, cert.SubjectName.Name))             {                 store.Add(cert);                 bRet = true;             }         }         store.Close();     }     catch     {      }     return bRet; } 

Answer 1

Ok, thanks for the help. Here it is the working code:

private void button_Click(object sender, EventArgs e) {     AsymmetricKeyParameter myCAprivateKey = null;      // Generate a root CA cert and obtain the privateKey     X509Certificate2 MyRootCAcert = GenerateCACertificate("CN=MYTESTCA", ref myCAprivateKey);      // Add CA certificate to store     addCertToStore(MyRootCAcert, StoreName.Root, StoreLocation.LocalMachine);      // Generate certificate based on the CA certificate privateKey     X509Certificate2 MyCert = GenerateSelfSignedCertificate("CN=127.0.01", "CN=MYTESTCA", myCAprivateKey);      // Add certificate to store     addCertToStore(MyCert, StoreName.My, StoreLocation.LocalMachine);      MessageBox.Show("Done!"); }   public static X509Certificate2 GenerateSelfSignedCertificate(string subjectName, string issuerName, AsymmetricKeyParameter issuerPrivKey) {     const int keyStrength = 2048;      // Generating Random Numbers     CryptoApiRandomGenerator randomGenerator = new CryptoApiRandomGenerator();     SecureRandom random = new SecureRandom(randomGenerator);      // The Certificate Generator     X509V3CertificateGenerator certificateGenerator = new X509V3CertificateGenerator();      // Serial Number     BigInteger serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);     certificateGenerator.SetSerialNumber(serialNumber);      // Signature Algorithm     const string signatureAlgorithm = "SHA256WithRSA";     certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);      // Issuer and Subject Name     X509Name subjectDN = new X509Name(subjectName);     X509Name issuerDN = new X509Name(issuerName);     certificateGenerator.SetIssuerDN(issuerDN);     certificateGenerator.SetSubjectDN(subjectDN);      // Valid For     DateTime notBefore = DateTime.UtcNow.Date;     DateTime notAfter = notBefore.AddYears(2);      certificateGenerator.SetNotBefore(notBefore);     certificateGenerator.SetNotAfter(notAfter);      // Subject Public Key     AsymmetricCipherKeyPair subjectKeyPair;     var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);     var keyPairGenerator = new RsaKeyPairGenerator();     keyPairGenerator.Init(keyGenerationParameters);     subjectKeyPair = keyPairGenerator.GenerateKeyPair();      certificateGenerator.SetPublicKey(subjectKeyPair.Public);      // Generating the Certificate     AsymmetricCipherKeyPair issuerKeyPair = subjectKeyPair;      // Selfsign certificate     Org.BouncyCastle.X509.X509Certificate certificate = certificateGenerator.Generate(issuerPrivKey, random);      // Corresponding private key     PrivateKeyInfo info = PrivateKeyInfoFactory.CreatePrivateKeyInfo(subjectKeyPair.Private);      // Merge into X509Certificate2     X509Certificate2 x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(certificate.GetEncoded());      Asn1Sequence seq = (Asn1Sequence)Asn1Object.FromByteArray(info.PrivateKey.GetDerEncoded());     if (seq.Count != 9)     {         //throw new PemException("malformed sequence in RSA private key");     }      RsaPrivateKeyStructure rsa = new RsaPrivateKeyStructure(seq);     RsaPrivateCrtKeyParameters rsaparams = new RsaPrivateCrtKeyParameters(         rsa.Modulus, rsa.PublicExponent, rsa.PrivateExponent, rsa.Prime1, rsa.Prime2, rsa.Exponent1, rsa.Exponent2, rsa.Coefficient);      x509.PrivateKey = DotNetUtilities.ToRSA(rsaparams);     return x509;  }  public static X509Certificate2 GenerateCACertificate(string subjectName, ref AsymmetricKeyParameter CaPrivateKey) {     const int keyStrength = 2048;      // Generating Random Numbers     CryptoApiRandomGenerator randomGenerator = new CryptoApiRandomGenerator();     SecureRandom random = new SecureRandom(randomGenerator);      // The Certificate Generator     X509V3CertificateGenerator certificateGenerator = new X509V3CertificateGenerator();      // Serial Number     BigInteger serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);     certificateGenerator.SetSerialNumber(serialNumber);      // Signature Algorithm     const string signatureAlgorithm = "SHA256WithRSA";     certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);      // Issuer and Subject Name     X509Name subjectDN = new X509Name(subjectName);     X509Name issuerDN = subjectDN;     certificateGenerator.SetIssuerDN(issuerDN);     certificateGenerator.SetSubjectDN(subjectDN);      // Valid For     DateTime notBefore = DateTime.UtcNow.Date;     DateTime notAfter = notBefore.AddYears(2);      certificateGenerator.SetNotBefore(notBefore);     certificateGenerator.SetNotAfter(notAfter);      // Subject Public Key     AsymmetricCipherKeyPair subjectKeyPair;     KeyGenerationParameters keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);     RsaKeyPairGenerator keyPairGenerator = new RsaKeyPairGenerator();     keyPairGenerator.Init(keyGenerationParameters);     subjectKeyPair = keyPairGenerator.GenerateKeyPair();      certificateGenerator.SetPublicKey(subjectKeyPair.Public);      // Generating the Certificate     AsymmetricCipherKeyPair issuerKeyPair = subjectKeyPair;      // Selfsign certificate     Org.BouncyCastle.X509.X509Certificate certificate = certificateGenerator.Generate(issuerKeyPair.Private, random);     X509Certificate2 x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(certificate.GetEncoded());      CaPrivateKey = issuerKeyPair.Private;      return x509;     //return issuerKeyPair.Private; }  public static bool addCertToStore(System.Security.Cryptography.X509Certificates.X509Certificate2 cert, System.Security.Cryptography.X509Certificates.StoreName st, System.Security.Cryptography.X509Certificates.StoreLocation sl) {     bool bRet = false;      try     {         X509Store store = new X509Store(st, sl);         store.Open(OpenFlags.ReadWrite);         store.Add(cert);          store.Close();     }     catch     {      }     return bRet; } 

Answer 2

I edited the answer to do the root certificate first and then issue an end entity certificate.

Here is some example of generating a self-signed certificate through Bouncy Castle:

public static X509Certificate2 GenerateSelfSignedCertificate(string subjectName, string issuerName, AsymmetricKeyParameter issuerPrivKey,  int keyStrength = 2048) {     // Generating Random Numbers     var randomGenerator = new CryptoApiRandomGenerator();     var random = new SecureRandom(randomGenerator);      // The Certificate Generator     var certificateGenerator = new X509V3CertificateGenerator();      // Serial Number     var serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);     certificateGenerator.SetSerialNumber(serialNumber);      // Signature Algorithm     const string signatureAlgorithm = "SHA256WithRSA";     certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);      // Issuer and Subject Name     var subjectDN = new X509Name(subjectName);     var issuerDN = new X509Name(issuerName);     certificateGenerator.SetIssuerDN(issuerDN);     certificateGenerator.SetSubjectDN(subjectDN);      // Valid For     var notBefore = DateTime.UtcNow.Date;     var notAfter = notBefore.AddYears(2);      certificateGenerator.SetNotBefore(notBefore);     certificateGenerator.SetNotAfter(notAfter);      // Subject Public Key     AsymmetricCipherKeyPair subjectKeyPair;     var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);     var keyPairGenerator = new RsaKeyPairGenerator();     keyPairGenerator.Init(keyGenerationParameters);     subjectKeyPair = keyPairGenerator.GenerateKeyPair();      certificateGenerator.SetPublicKey(subjectKeyPair.Public);      // Generating the Certificate     var issuerKeyPair = subjectKeyPair;      // Selfsign certificate     var certificate = certificateGenerator.Generate(issuerPrivKey, random);      // Corresponding private key     PrivateKeyInfo info = PrivateKeyInfoFactory.CreatePrivateKeyInfo(subjectKeyPair.Private);       // Merge into X509Certificate2     var x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(certificate.GetEncoded());      var seq = (Asn1Sequence)Asn1Object.FromByteArray(info.PrivateKey.GetDerEncoded());     if (seq.Count != 9)         throw new PemException("malformed sequence in RSA private key");      var rsa = new RsaPrivateKeyStructure(seq);     RsaPrivateCrtKeyParameters rsaparams = new RsaPrivateCrtKeyParameters(         rsa.Modulus, rsa.PublicExponent, rsa.PrivateExponent, rsa.Prime1, rsa.Prime2, rsa.Exponent1, rsa.Exponent2, rsa.Coefficient);      x509.PrivateKey = DotNetUtilities.ToRSA(rsaparams);     return x509; }   public static AsymmetricKeyParameter GenerateCACertificate(string subjectName, int keyStrength = 2048) {     // Generating Random Numbers     var randomGenerator = new CryptoApiRandomGenerator();     var random = new SecureRandom(randomGenerator);      // The Certificate Generator     var certificateGenerator = new X509V3CertificateGenerator();      // Serial Number     var serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);     certificateGenerator.SetSerialNumber(serialNumber);      // Signature Algorithm     const string signatureAlgorithm = "SHA256WithRSA";     certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);      // Issuer and Subject Name     var subjectDN = new X509Name(subjectName);     var issuerDN = subjectDN;     certificateGenerator.SetIssuerDN(issuerDN);     certificateGenerator.SetSubjectDN(subjectDN);      // Valid For     var notBefore = DateTime.UtcNow.Date;     var notAfter = notBefore.AddYears(2);      certificateGenerator.SetNotBefore(notBefore);     certificateGenerator.SetNotAfter(notAfter);      // Subject Public Key     AsymmetricCipherKeyPair subjectKeyPair;     var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);     var keyPairGenerator = new RsaKeyPairGenerator();     keyPairGenerator.Init(keyGenerationParameters);     subjectKeyPair = keyPairGenerator.GenerateKeyPair();      certificateGenerator.SetPublicKey(subjectKeyPair.Public);      // Generating the Certificate     var issuerKeyPair = subjectKeyPair;      // Selfsign certificate     var certificate = certificateGenerator.Generate(issuerKeyPair.Private, random);     var x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(certificate.GetEncoded());      // Add CA certificate to Root store     addCertToStore(cert, StoreName.Root, StoreLocation.CurrentUser);      return issuerKeyPair.Private; } 

And add to the store (your code slightly modified):

public static bool addCertToStore(System.Security.Cryptography.X509Certificates.X509Certificate2 cert, System.Security.Cryptography.X509Certificates.StoreName st, System.Security.Cryptography.X509Certificates.StoreLocation sl) {     bool bRet = false;      try     {         X509Store store = new X509Store(st, sl);         store.Open(OpenFlags.ReadWrite);         store.Add(cert);          store.Close();     }     catch     {      }      return bRet; } 

And usage:

var caPrivKey = GenerateCACertificate("CN=root ca"); var cert = GenerateSelfSignedCertificate("CN=127.0.01", "CN=root ca", caPrivKey); addCertToStore(cert, StoreName.My, StoreLocation.CurrentUser); 

I have not compiled this example code after @wakeupneo comments. @wakeupneo, you might have to slightly edit the code and add proper extensions to each certificate.