Develop Reference

C# sign data ECDSA from smartcard

I am trying to sign some data using the private key from the smart card. The key algorithm is ECDSA. when I try to get the private key object it occurs system not supported exception.
Then after some research, I get to know that X509Certificate2 is not supporting EC Keys.
sysSec.X509Certificate2 cert = CertHelper.GetSignCertificate(serialNumber); //Get Certificate from Store var
key = cert.PrivateKey;
Then i try to use Bouncy Castle library. But in here i couldn't get ECPrivateKeyParameters after parsing X509Certificate2 . There is a code :
byte[] pkcs12Bytes = cert.Export(sysSec.X509ContentType.Pkcs12,"test");
Pkcs12Store pkcs12 = new Pkcs12StoreBuilder().Build();
pkcs12.Load(new MemoryStream(pkcs12Bytes, false), "test".ToCharArray());
ECPrivateKeyParameters privKey = null;
foreach (string alias in pkcs12.Aliases)
{
if (pkcs12.IsKeyEntry(alias))
{
privKey = (ECPrivateKeyParameters)pkcs12.GetKey(alias).Key;
break;
}
}
It also not works. But strange things happen when I create CMS file. It works.
public byte[] Sign(byte[] data , X509Certificate2 certificate ,bool detached )
{
if (data == null)
throw new ArgumentNullException("data");
if (certificate == null)
throw new ArgumentNullException("certificate");
// setup the data to sign
// ContentInfo content = new ContentInfo( new Oid("1.3.14.3.2.26"), data);
ContentInfo content = new ContentInfo( data);
SignedCms signedCms = new SignedCms(content, detached);
CmsSigner signer = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, certificate);
signer.SignedAttributes.Add(new Pkcs9DocumentName("testname"));
signer.SignedAttributes.Add(new Pkcs9SigningTime());
//signer.;
// CmsRecipientCollection recipest =new CmsRecipientCollection ()
// create the signature
signedCms.ComputeSignature(signer);
// signedCms.ComputeSignature()
byte[] res = signedCms.Encode();
foreach (SignerInfo info in signedCms.SignerInfos)
{
foreach (var item in info.SignedAttributes)
{
string frname = item.Oid.FriendlyName ?? "null";
Console.WriteLine(string.Format(" OID {0} : Value {1}", frname, item.Oid.Value.ToString()));
}
foreach (var item in info.UnsignedAttributes)
{
string frname = item.Oid.FriendlyName ?? "null";
Console.WriteLine(string.Format(" OID {0} : Value {1}", frname, item.Oid.Value.ToString()));
}
}
Console.WriteLine("Signed !");
return res;
}
So do anyone knows how to handle it?
Also how to sign from smartCard using Bouncy Castle?

According to my understanding BouncyCastle is a cryptographic library. It can sign something, if you provide the key. Smart cards however don't typically export private keys (so I have some doubts, whether your certificate contains the one from the smart card) but expect commands to sign something, e. g. by receiving the respective hash value and returning the signature (after ensuring appropriate user authentication).
This is typically accomplished using a PKCS#11 interface (assumed you have a driver for it matching the command set of your card) or by sending the appropriate command APDUs directly to the card (quite complicated) from your application. I found nothing on the bouncy castle website, suggesting that there is some support for addressing smart cards. (It may be hidden in the OpenPGP functionality, if your card is compliant to that standard.)
So without being acquainted with BouncyCastle it seems to me, that it won't match your expectations.

C# - Verify client certificate signed by proper root

I know there are a lot of questions on this argument but I'm stuck into this for several days now so here I am.
I've got a root certificate and a client certificate. I need to replicate in a C# web API project what the command openssl verify -CAfile ca.pem client.pem does.
This is what i know for now (hope it's actually true):
Verify() method actually validate that the certificate is signed by an authority. It's like a format control. It doesn't matter which autority signed the certificate.
X509 Chain is the way to go. Add your ca certificate inside an extra store because i'm not going to install the certificate into Windows. Then build passing the client certificate. Let's the magic happens! Unfortunately I've got some problems with the configuration.
Let me be more clear with an example
private bool VerifyCertificate(X509Certificate2 client)
{
X509Chain chain = new X509Chain();
var stringCert = WebConfigurationManager.AppSettings["CACertificate"];
var byteCert = Encoding.ASCII.GetBytes(stringCert);
var authority = new X509Certificate2(byteCert);
chain.ChainPolicy.RevocationMode = X509RevocationMode.NoCheck;
chain.ChainPolicy.VerificationFlags = X509VerificationFlags.IgnoreWrongUsage;
chain.ChainPolicy.ExtraStore.Add(authority);
// Do the preliminary validation.
if (!chain.Build(client))
return false;
return true;
}
With this example the program returns false. The build is not passed. I'm sure the problem is with the ChainPolicy properties so i tried a different configuration
chain.ChainPolicy.RevocationMode = X509RevocationMode.NoCheck;
chain.ChainPolicy.RevocationFlag = X509RevocationFlag.ExcludeRoot;
chain.ChainPolicy.VerificationFlags = X509VerificationFlags.NoFlag;
chain.ChainPolicy.VerificationTime = DateTime.Now;
chain.ChainPolicy.UrlRetrievalTimeout = new TimeSpan(0, 0, 0);
But this one is not going to verify anything, in fact using my ca cert the method returns true and using another ca certificate (which i didn't use to signed my client certificate) the method also returns true.
I Searched for an OpenSSL wrapper for C# and i found it but unfortunately is based on old libraries and the repo isn't manteined anymore. Also, i would achieve my goal using just .net framework if possible.
So guys, fast recap. I want to check that only the certificate that is firmed by my ca certificate can pass the validation, all the others must be stopped.
Thanks in advance for any help

ExtraStore isn't limiting, it provides extra certificates to help complete the chain. It provides no trust data.
In order to determine if the certificate is issued by the CA that you want you need to do something like:
private static readonly X509Certificate2 s_trustedRoot = ObtainTheRoot();
private static readonly byte[] s_normalizedRoot = s_trustedRoot.RawData;
private bool VerifyCertificate(X509Certificate2 candidate)
{
X509Chain chain = new X509Chain();
// set all the things you need to set to make it build
if (!chain.Build(candidate))
return false;
// Check that the root certificate was the expected one.
X509ChainElementCollection elements = chain.ChainElements;
return elements[elements.Count - 1].Certificate.RawData.SequenceEqual(s_normalizedRoot);
}
I promoted the cert and normalized byte form of it to statics on the assumption that they don't change once the process starts. If the cert can change dynamically then you should adjust accordingly.

Find the problem.
In my case this was the right response.
private bool VerifyCertificate(X509Certificate2 client)
{
X509Chain chain = new X509Chain();
var stringCert = WebConfigurationManager.AppSettings["CACertificate"];
var byteCert = Encoding.ASCII.GetBytes(stringCert);
var authority = new X509Certificate2(byteCert);
chain.ChainPolicy.RevocationMode = X509RevocationMode.NoCheck;
chain.ChainPolicy.VerificationFlags = X509VerificationFlags.AllowUnknownCertificateAuthority;
chain.ChainPolicy.ExtraStore.Add(authority);
// Do the preliminary validation.
if (!chain.Build(client))
return false;
// This piece makes sure it actually matches your known root
var valid = chain.ChainElements
.Cast<X509ChainElement>()
.Any(x => x.Certificate.Thumbprint == authority.Thumbprint);
if (!valid)
return false;
return true;
}
Now, debugging the application i have some considerations:
What the .Build() method is supposed to do?
I mean, using the certificate that is signed by the ca or using the self-signed certificate the method Always returns true BUT if i use the trusted one it will add the certificate inside the chain.ChainElementsotherwise nothing is added.
I need to understand this thing but all the test I've done said the method works

Service account cannot load the X509Certificate from windows certificate store

All, I run into an issue where the service account my ASP.NET web forms application (.Net Framework 4.6.1) runs under cannot load the X509Certificate(.pfx) from the personal store on the windows 2012 R2 server .Here is how I imported the certificate to the certificate store
I Logged into the server using the service account(domain\username) ,used mmc snap in to import the certificate to Current User Personal Certificate Store (please see screenshot at the end)
This is the code I am using to load the certificate in C#.But the certificate
is null
public X509Certificate2 Load()
{
X509Certificate2 x509Certificate = null;
var store = new X509Store(StoreName.My,StoreLocation.CurrentUser);
string thumbPrint = StripTheSpacesAndMakeItUpper(ConfigurationManager.AppSettings["pfxthumbPrint"]);
store.Open(OpenFlags.ReadOnly);
var certCollection = store.Certificates;
foreach (var x509 in certCollection)
{
if (x509.Thumbprint.Equals(thumbPrint))
{
x509Certificate = x509;
break;
}
}
store.Close();
return x509Certificate;
}
private string StripTheSpacesAndMakeItUpper(string thumbPrint)
{
if(!string.IsNullOrWhiteSpace(thumbPrint))
{
return Regex.Replace(thumbPrint, #"\s|\W", "").ToUpper();
}
return thumbPrint;
}
Any suggestions on why the method Load returns null ?
]3

I don't know how you set the value of ConfigurationManager.AppSettings["pfxthumbPrint"]. I guess you double clicked the certificate in your CurrentUser store and copied the thumbprint from the Details tab, right? If that is the case, you copied also one invisible character from the beginning of the thumbprint.
The saddest thing is that this character (I don't know what it is) is not visible in your app.config/web.config. The only way to get rid of if is to delete the first quote character with the first character of the thumbprint and type them in again manually. Or delete entire thumbprint and the quotes and type them again if you wish.

Instead of
if (x509.Thumbprint.Equals(x509CertificateFriendlyName))
Shouldn't it be
if (x509.Thumbprint.Equals(thumbPrint))
...?
Also, you appear to have x509Certificate declared as a local variable and then you discard it. Did you intend to assign the value to an instance variable perhaps? I don't even see a return statement.
Also, you're not disposing your store, although that probably isn't the cause of your issue.
Here's a different version that addresses these issues, and will also eliminate any invisible characters in the configuration entry (see pepo's answer for why).
public X509Certificate2 Load()
{
var thumbPrintFromConfig = ConfigurationManager.AppSettings["pfxthumbPrint"]
var thumbPrint = Regex.Replace(thumbPrintFromConfig.ToUpper(),"[^A-F0-9]",""); //Keep only hex digits
return Load(thumbPrint);
}
private X509Certificate2 Load(string thumbPrint)
{
using (var store = new X509Store(StoreName.My,StoreLocation.CurrentUser))
{
store.Open(OpenFlags.ReadOnly);
var cert = store
.Certificates
.OfType<X509Certificate2>()
.Where(x => x.Thumbprint == thumbPrint)
.Single();
store.Close();
return cert;
}
}

How can I set PIN for a X509Certificate2 programmatically?

I need to send data to a webservice everyday so I made a scheduled task that runs my code. The problem is the webservice requires a certificate with a PIN code. I have attached the certificate but I can't find a way to set the PIN to it, therefor it shows a popup everytime to enter it manually.
Here is my code for the certificate:
private void SendData(string data)
{
using (SerWSService webService = new SerWSService())
{
string certificateSN = "serial number for the certificate";
webService.ClientCertificates.Add(FindCertificate(certificateSN));
webService.SendData(data);
}
}
private X509Certificate2 FindCertificate(string certserial)
{
X509Certificate2 WPE_UserCert = null;
X509Store wstore = default(X509Store);
wstore = new X509Store(StoreName.My, StoreLocation.CurrentUser);
wstore.Open(OpenFlags.ReadOnly);
var wcerts = wstore.Certificates;
foreach (var wcert in wcerts)
{
if (wcert.SerialNumber.ToUpper() == certserial.Replace(" ", "").ToUpper())
{
WPE_UserCert = wcert;
break;
}
}
wstore.Close();
if (WPE_UserCert != null)
{
//TO DO: add PIN code to certificate
}
return WPE_UserCert;
}
Is there any way I can set the PIN to the certificate?

No, because certificates don't have PINs; (private) keys do.
If you are finding a certificate with a private key and you pass that certificate to a class that expects the unified pair (e.g. SslStream, HttpClient) then there's no real/good solution.
If you are using the private key yourself, you have some leeway:
using (RSA rsa = cert.GetRSAPrivateKey())
{
RSACng rsaCng = rsa as RSACng;
RSACryptoServiceProvider rsaCsp = rsa as RSACryptoServiceProvider;
if (rsaCng != null)
{
// Set the PIN, an explicit null terminator is required to this Unicode/UCS-2 string.
byte[] propertyBytes;
if (pin[pin.Length - 1] == '\0')
{
propertyBytes = Encoding.Unicode.GetBytes(pin);
}
else
{
propertyBytes = new byte[Encoding.Unicode.GetByteCount(pin) + 2];
Encoding.Unicode.GetBytes(pin, 0, pin.Length, propertyBytes, 0);
}
const string NCRYPT_PIN_PROPERTY = "SmartCardPin";
CngProperty pinProperty = new CngProperty(
NCRYPT_PIN_PROPERTY,
propertyBytes,
CngPropertyOptions.None);
rsaCng.Key.SetProperty(pinProperty);
}
else if (rsaCsp != null)
{
// This is possible, but painful.
// Copy out the CspKeyContainerInfo data into a new CspParameters,
// build the KeyPassword value on CspParameters,
// Dispose() the existing instance,
// and open a new one to replace it.
//
// But if you really called GetRSAPrivateKey() and it has returned an RSACng for
// your device once, it pretty much will forever (until the next
// new RSA type for Windows is invented... at which point it still
// won't return an RSACryptoServiceProvider).
}
else
{
// No other built-in RSA types support setting a PIN programmatically.
}
// Use the key here.
// If you needed to return it, don't put it in a using :)
}

In the case of a CSP private key use CryptAcquireCertificatePrivateKey to acquire CryptoProv handle and then use CryptSetProvParam(h,PP_SIGNATURE_PIN,pin,0) to set the PIN.

CMS signing in .NET with certificate chain not in local trusted certificate store

I have X509 certificates that are stored on the network. I can read the chain from remote windows certificate store. I need to sign some data and include chain to the signature to make it possible to validate it later.
The problem is that I can't find a way to put certificate chain to the CsmSigner. I have read that it takes certificate from constructor parameter and tries to build a chain with X509Chain.Build. It ignores Certificates list values and fails (obviously) because no certificate can be found in the local Windows cert store.
Please find below my test code (that works only if certificates were saved locally to the windows cert store)
protected byte[] SignWithSystem(byte[] data, X509Certificate2 cert, X509Certificate[] chain)
{
ContentInfo contentInfo = new ContentInfo(data);
SignedCms signedCms = new SignedCms(contentInfo, true);
CmsSigner cmsSigner = new CmsSigner(cert);
cmsSigner.DigestAlgorithm = new Oid("2.16.840.1.101.3.4.2.1"); //sha256
cmsSigner.IncludeOption = X509IncludeOption.WholeChain;
if (chain != null)
{
//adding cert chain to signer
cmsSigner.Certificates.AddRange(chain);
signedCms.Certificates.AddRange(chain);
}
signedCms.ComputeSignature(cmsSigner); //fails here with System.Security.Cryptography.CryptographicException : A certificate chain could not be built to a trusted root authority.
byte[] signedPkcs = signedCms.Encode();
return signedPkcs;
}
Is there any way to make it work without uploading certificates to the local store? Should I use any alternative signer?
I can try to upload certificates to the store but the problems are that
I have to add and remove certificates (permissions have to be granted)
There are several processes that applies signature so cross-process synchronization have to be added.
This is not that I'd like to do.

Example CMS Signing with BouncyCastle for .NET
You could use the BouncyCastle crypto library for .NET, which contains its own X509 certificate and CMS signing machinery. A lot of the examples and documentation on the web are for Java, as BouncyCastle was a Java library first. I've used the answer to this Stackoverflow question as a starting point for the certificate and key loading, and added the CMS signing. You may have to tweak parameters to produce the results you want for your use case.
I've made the signing function look approximately like yours, but note the private key is a separate parameter now.
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Org.BouncyCastle.Cms;
using Org.BouncyCastle.Pkcs;
using Org.BouncyCastle.X509;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.X509.Store;
class Program
{
protected static byte[] SignWithSystem(byte[] data, AsymmetricKeyParameter key, X509Certificate cert, X509Certificate[] chain)
{
var generator = new CmsSignedDataGenerator();
// Add signing key
generator.AddSigner(
key,
cert,
"2.16.840.1.101.3.4.2.1"); // SHA256 digest ID
var storeCerts = new List<X509Certificate>();
storeCerts.Add(cert); // NOTE: Adding end certificate too
storeCerts.AddRange(chain); // I'm assuming the chain collection doesn't contain the end certificate already
// Construct a store from the collection of certificates and add to generator
var storeParams = new X509CollectionStoreParameters(storeCerts);
var certStore = X509StoreFactory.Create("CERTIFICATE/COLLECTION", storeParams);
generator.AddCertificates(certStore);
// Generate the signature
var signedData = generator.Generate(
new CmsProcessableByteArray(data),
false); // encapsulate = false for detached signature
return signedData.GetEncoded();
}
static void Main(string[] args)
{
try
{
// Load end certificate and signing key
AsymmetricKeyParameter key;
var signerCert = ReadCertFromFile(#"C:\Temp\David.p12", "pin", out key);
// Read CA cert
var caCert = ReadCertFromFile(#"C:\Temp\CA.cer");
var certChain = new X509Certificate[] { caCert };
var result = SignWithSystem(
Guid.NewGuid().ToByteArray(), // Any old data for sake of example
key,
signerCert,
certChain);
File.WriteAllBytes(#"C:\Temp\Signature.data", result);
}
catch (Exception ex)
{
Console.WriteLine("Failed : " + ex.ToString());
Console.ReadKey();
}
}
public static X509Certificate ReadCertFromFile(string strCertificatePath)
{
// Create file stream object to read certificate
using (var keyStream = new FileStream(strCertificatePath, FileMode.Open, FileAccess.Read))
{
var parser = new X509CertificateParser();
return parser.ReadCertificate(keyStream);
}
}
// This reads a certificate from a file.
// Thanks to: http://blog.softwarecodehelp.com/2009/06/23/CodeForRetrievePublicKeyFromCertificateAndEncryptUsingCertificatePublicKeyForBothJavaC.aspx
public static X509Certificate ReadCertFromFile(string strCertificatePath, string strCertificatePassword, out AsymmetricKeyParameter key)
{
key = null;
// Create file stream object to read certificate
using (var keyStream = new FileStream(strCertificatePath, FileMode.Open, FileAccess.Read))
{
// Read certificate using BouncyCastle component
var inputKeyStore = new Pkcs12Store();
inputKeyStore.Load(keyStream, strCertificatePassword.ToCharArray());
var keyAlias = inputKeyStore.Aliases.Cast<string>().FirstOrDefault(n => inputKeyStore.IsKeyEntry(n));
// Read Key from Aliases
if (keyAlias == null)
throw new NotImplementedException("Alias");
key = inputKeyStore.GetKey(keyAlias).Key;
//Read certificate into 509 format
return (X509Certificate)inputKeyStore.GetCertificate(keyAlias).Certificate;
}
}
}
.NET CMS (Quick-fix with rest of chain omitted from signature)
I can reproduce your problem with a certificate whose root is not in the trusted certificate store, and confirm that adding the certificate chain to the cmsSigner/signedCms Certificates collection does not avoid the A certificate chain could not be built to a trusted root authority error.
You can sign successfully by setting cmsSigner.IncludeOption = X509IncludeOption.EndCertOnly;
However, if you do this, you will not get the rest of the chain in the signature. This probably isn't what you want.
As an aside, in your example you are using X509Certificate for the array of certificates in the chain, but passing them to an X509Certificate2Collection (note the "2" in there). X509Certificate2 derives from X509Certificate, but if its not actually an X509Certificate2 that you put in one of those collections, you'll get a cast error if something iterates over the collection (you don't get an error when adding a certificate of the wrong type unfortunately, because X509Certificate2Collection also derives from X509CertificateCollection and inherits its add methods).

Adding sample code that creates detached PKCS7 signature using BouncyCastle (thanks to softwariness) without Certificate store.
It uses .net X509Certificate2 instances as input parameter. First certificate in collection have to be linked with private key to sign data.
Also I'd like to note that it is not possible to read private key associated with certificate from remote Windows cert store using .net X509Certificate2.PrivateKey property. By default private key is not loaded with certificate using X509Store(#"\\remotemachine\MY", StoreLocation.LocalMachine) and when X509Certificate2.PrivateKey property is accessed on local machine it fails with error "Keyset does not exist".
public void SignWithBouncyCastle(Collection<X509Certificate2> netCertificates)
{
// first cert have to be linked with private key
var signCert = netCertificates[0];
var Cert = Org.BouncyCastle.Security.DotNetUtilities.FromX509Certificate(signCert);
var data = Encoding.ASCII.GetBytes(Cert.SubjectDN.ToString());
var bcCertificates = netCertificates.Select(_ => Org.BouncyCastle.Security.DotNetUtilities.FromX509Certificate(_)).ToList();
var x509Certs = X509StoreFactory.Create("Certificate/Collection", new X509CollectionStoreParameters(bcCertificates));
var msg = new CmsProcessableByteArray(data);
var gen = new CmsSignedDataGenerator();
var privateKey = Org.BouncyCastle.Security.DotNetUtilities.GetKeyPair(signCert.PrivateKey).Private;
gen.AddSigner(privateKey, Cert, CmsSignedDataGenerator.DigestSha256);
gen.AddCertificates(x509Certs);
var signature = gen.Generate(msg, false).GetEncoded();
Trace.TraceInformation("signed");
CheckSignature(data, signature);
Trace.TraceInformation("checked");
try
{
CheckSignature(new byte[100], signature);
}
catch (CryptographicException cex)
{
Trace.TraceInformation("signature was checked for modified data '{0}'", cex.Message);
}
}
void CheckSignature(byte[] data, byte[] signature)
{
var ci = new ContentInfo(data);
SignedCms signedCms = new SignedCms(ci, true);
signedCms.Decode(signature);
foreach (X509Certificate cert in signedCms.Certificates)
Trace.TraceInformation("certificate found {0}", cert.Subject);
signedCms.CheckSignature(true);
}

To be clear, I am no security or cryptography expert.. but per my knowledge, for receiver to be able to validate the signature, the root certificate in the certificate chain you used for signing, must already be a trusted root for the receiver.
If the receiver does not have the root certificate already in their store, and marked as a trusted root... then doesn't matter how you sign the data.. it will fail validation on receiver end. And this is by design.
See more at Chain of trust
Hence the only real solution to your problem I see is to ensure that the root certificate is provisioned as trusted root on both ends... Typically done by a Certificate Authority.
Enterprise application scenario - Typically in an enterprise some group in IT department (who have access to all machines in the domain - like domain admins) would enable this scenario by ensuring that every computer in the domain has root certificate owned by this group, present on every machine as trusted root, and an application developer in the enterprise typically requests a new certificate for use with their application, which has the chain of trust going back to the root certificate already distributed to all machines in the domain.
Found out contact person for this group in your company, and have them issue a certificate you can use for signature.
Internet application scenario - There are established Certificate Authorities, who own their root certificates, and work with OS vendors to ensure that their root certificates are in trusted store, as the OS vendor ships the OS to it's customers. (One reason why using pirated OS can be harmful. It's not just about viruses / malware..). And that is why when you use a certificate issued by VeriSign to sign the data, the signature can be validated by most other machines in the world.