How to get Public Key of certificate identical to openssl output?

Question

.NET

yes, it sounds pretty stupid. but it is.
suppose we have a crt.cer certificate in Base64,
then I run openssl x509 -in crt.cer -pubkey and get the output (for example, 294 bytes long):

MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8A MIIBCgKCAQEAvUihVNnWYpu3uJmcLy PBecKu4ziVD7OIeZ + / V + + tJkXbc5 6OW8G + QDtJKuJkkuxGNLBNmLHbCyXsJ / US3kKkU7 / 7yK7jfWRNdqAKJdDTVxsWnxlo + / + 28ScGrAV6wK2bbK8GQBpsYRn1HKGCGceWIBCSqUfI7rwgwDnvqcW5PeivORd4 or5DdhgUMwiV5Vr2fvdcAiQR1CKgMphxO4 + OmZ4khpB / HT / xS4FscvfFsSBLM37jBMrnhY5yNKPeHZB2eYvehnnw22NFHJNksa + vVFXL9aJcZWJc / bqqlhlhL8eLdYSR / KA006PSInW8yWtd4IFVKJ1Moa41gCUZL81voQIDAQAB

Then I do the same in the UWP application code:

X509Certificate2 certificate = new X509Certificate2(certificateBlob);
var truePublicKey = Convert.ToBase64String(certificate.GetPublicKey());

the output is something like this (already 270 bytes long)

MIIBCgKCAQEAvUihVNnWYpu3uJmcLy + PBecKu4ziVD7OIeZ / V + tJkXbc5 + 6OW8G + QDtJKuJkkuxGNLBNmLHbCyXsJ / US3kKkU7 / 7yK7jfWRNdqAKJdDTVxsWnxlo + / 28ScGrAV6wK2bbK8GQBpsYRn1HKGCGceWIBCSqUfI7rwgwDnvqcW5PeivORd4 + or5DdhgUMwiV5Vr2fvdcAiQR1CKgMphxO4 + OmZ4khpB / HT / xS4FscvfFsSBLM37jBMrnhY5yNKPeHZB2eYvehnnw22NFHJNksa + vVFXL9aJcZWJc / bqqlhlhL8eLdYSR / KA006PSInW8yWtd4IFVKJ1Moa41gCUZL81voQIDAQAB

If you take a closer look, you can see that in the second case, a piece of data is cut off in front, but otherwise they are identical.
Using the online ASN1 data decoder, you can see that in the C # application "everything unnecessary is cut off", but this option does not suit me. Is it possible somehow to get an identical openssl result? (preferably without writing your own ASN encoder / decoder). Whatever I tried, it doesn’t work (And the key is needed exactly as in the first option, because the hash is then considered
PS: Using Chillkat, I managed to get the desired key, but it is not free. It is not suitable for my purposes.

Answer 1

Alexey Nemiro , thanks for the tip! That's pretty much what happened. Might be useful to someone:

public static IEnumerable<string> GetPublicKeysList(IReadOnlyList<Certificate> serverCertificates)
        {
            for (var i = 0; i < serverCertificates.Count; i++)
            {
                string publicKey = null;
                try
                {
                    var certificate = new X509Certificate2(serverCertificates[0].GetCertificateBlob().ToArray());
                    var ms = new MemoryStream(certificate.RawData);
                    using (var reader = new BerReader(ms))
                    {
                        var asnCert = reader.ReadToEnd(true);
                        var pkNode = asnCert.ChildNodes[0].ChildNodes[0].ChildNodes[6]; // тут лежит сам ключ
                        byte[] pkBuffer = new byte[pkNode.Length + (pkNode.DataOffsetToStream - pkNode.StartPosition)];
                        ms.Seek(pkNode.StartPosition, SeekOrigin.Begin);
                        ms.Read(pkBuffer, 0, pkNode.Length + (int)(pkNode.DataOffsetToStream - pkNode.StartPosition)); // чтобы не потерять последние 4 байта
                        publicKey = Convert.ToBase64String(pkBuffer);
                    }
                }
                catch (Exception ex)
                {
                    throw new SecurityException($"Cant get public key {ex.Message}");
                }
                yield return publicKey;
            }
        }