implementation of ESIA on the website

Integration steps you can hardly find anywhere. There are only guidelines and regulations for working with the ESIA, but there is no adequate description of the procedure “how to do it in C #” :)

What you received along with the response to the application is just examples of different test accounts for debugging work, i.e. it is NOT CONNECTED with the signature of your requests to the ESIA.

Here are the commands that we generate the correct certificate:

openssl req -nodes -sha256 -newkey rsa:2048 -keyout secret.key -out request.csr -subj /C=RU/ST=Rostov-na-Donu/L=city/O=COMPANY\/emailAddress=EMAIL@site.ru/ openssl x509 -req -sha256 -days 3650 -in request.csr -signkey secret.key -out cert.crt -extfile /etc/ssl/openssl.cnf -extensions v3_ca openssl x509 -in cert.crt -text 

Accordingly, in the right places you need to substitute the correct information about the company mail, etc. This command works under Linux, and in the file /etc/ssl/openssl.cnf you need to add (change) the following section:

 [ v3_ca ] # Extensions for a typical CA # PKIX recommendation. keyUsage = critical, nonRepudiation, digitalSignature, keyEncipherment, dataEncipherment extendedKeyUsage = emailProtection, clientAuth subjectKeyIdentifier=hash authorityKeyIdentifier=keyid:always,issuer 

as a result, you will receive a working certificate cert.crt and the secret.key key

But it will be only the beginning. There is also a carriage and a small truck of nuances regarding the exchange of data with the ESIA.

Here is a ready-made solution, incl. and in C #: esia.pro

It is paid, but in addition to the finished implementation, they will also consult on the integration process and organizational issues.

Our signature has earned something like this:

 public static byte[] Sign(X509Certificate2 certificate, byte[] data) { if (data == null) throw new ArgumentNullException("data"); if (certificate == null) throw new ArgumentNullException("certificate"); // setup the data to sign ContentInfo content = new ContentInfo(data); SignedCms signedCms = new SignedCms(content, true); CmsSigner signer = new CmsSigner(certificate); var sha256 = new Oid("2.16.840.1.101.3.4.2.1", "sha256"); signer.DigestAlgorithm = sha256; // create the signature signedCms.ComputeSignature(signer); var signature = signedCms.Encode(); return signature; } 

With base64, everything is not obvious there: Convert.ToBase64String is not suitable, it does not implement the standard quite accurately. I used this method here:

 public static string Base64UrlEncode(byte[] arg) { string s = Convert.ToBase64String(arg); // Regular base64 encoder s = s.Split('=')[0]; // Remove any trailing '='s s = s.Replace('+', '-'); // 62nd char of encoding s = s.Replace('/', '_'); // 63rd char of encoding return s; } 

Verifying their signatures is another rebus. It can be assumed that this process is inverse to the signing process something like this:

 public static bool ValidateCmsSignature(byte[] data, byte[] signature, X509Certificate2 certificate) { bool result = false; if (data == null) throw new ArgumentNullException("data"); if (signature == null) throw new ArgumentNullException("signature"); if (certificate == null) throw new ArgumentNullException("certificate"); // setup the data to sign ContentInfo content = new ContentInfo(data); SignedCms signedCms = new SignedCms(content, true); try { signedCms.Decode(signature); signedCms.CheckSignature(new X509Certificate2Collection(certificate), true); result = true; } catch (Exception ex) { var msg = ex.Message; } return result; } 

And this method works to verify our signature, but is not suitable for their signature. And why?

If we first form a text string, then create a detached signature on it, and then encode it all in base64, then they form two JSONs: HEADER and PAYLOAD, then they encode them separately in base64, and then they form a signature on the string HEADERbase64 .PAYLOADbase64. And then the signature is encoded in base64.

Thus, the method for verifying their signature looks something like this:

 public static bool ValidateSignature(byte[] data, byte[] signature, X509Certificate2 certificate) { bool result = false; using (var csp = (RSACryptoServiceProvider) certificate.PublicKey.Key) { using (var hasher = new SHA256Managed()) { var hash = hasher.ComputeHash(data); string id = CryptoConfig.MapNameToOID("SHA256"); bool isDataok = csp.VerifyData(data, id, signature); bool isHashOk = csp.VerifyHash(hash, id, signature); // можно ещё так //RSAPKCS1SignatureDeformatter rsaDeformatter = new RSAPKCS1SignatureDeformatter(csp); //rsaDeformatter.SetHashAlgorithm("SHA256"); //bool isHashOk2 = rsaDeformatter.VerifySignature(hash, signature); result = isDataok && isHashOk; } } return result; } 

In general, NuGet already has a useful library with which everything becomes easier:

https://www.nuget.org/packages?q=esia.net

In our times, pioneers did not indulge so :))