iTextSharp.text.pdf.security.CertificateVerification.VerifyCertificate C# (CSharp) Метод

        public static String VerifyCertificate(X509Certificate cert, ICollection<X509Crl> crls, DateTime calendar)
        {
            foreach (String oid in cert.GetCriticalExtensionOids()) {
                if (oid == X509Extensions.KeyUsage.Id
                    || oid == X509Extensions.CertificatePolicies.Id
                    || oid == X509Extensions.PolicyMappings.Id
                    || oid == X509Extensions.InhibitAnyPolicy.Id
                    || oid == X509Extensions.CrlDistributionPoints.Id
                    || oid == X509Extensions.IssuingDistributionPoint.Id
                    || oid == X509Extensions.DeltaCrlIndicator.Id
                    || oid == X509Extensions.PolicyConstraints.Id
                    || oid == X509Extensions.BasicConstraints.Id
                    || oid == X509Extensions.SubjectAlternativeName.Id
                    || oid == X509Extensions.NameConstraints.Id) {
                    continue;
                }
                try {
                    // EXTENDED KEY USAGE and TIMESTAMPING is ALLOWED
                    if (oid == X509Extensions.ExtendedKeyUsage.Id && cert.GetExtendedKeyUsage().Contains("1.3.6.1.5.5.7.3.8")) {
                        continue;
                    }
                }
                catch (CertificateParsingException) {
                    // DO NOTHING;
                }
                return "Has unsupported critical extension";
            }

            try {
                if (!cert.IsValid(calendar.ToUniversalTime()))
                    return "The certificate has expired or is not yet valid";
                if (crls != null) {
                    foreach (X509Crl crl in crls) {
                        if (crl.IsRevoked(cert))
                            return "Certificate revoked";
                    }
                }
            }
            catch (Exception e) {
                return e.ToString();
            }
            return null;
        }