iTextSharp.text.pdf.security.CertificateUtil.GetCRLURL C# (CSharp) Метод

        public static String GetCRLURL(X509Certificate certificate)
        {
            try {
                Asn1Object obj = GetExtensionValue(certificate, X509Extensions.CrlDistributionPoints.Id);
                if (obj == null) {
                    return null;
                }
                CrlDistPoint dist = CrlDistPoint.GetInstance(obj);
                DistributionPoint[] dists = dist.GetDistributionPoints();
                foreach (DistributionPoint p in dists) {
                    DistributionPointName distributionPointName = p.DistributionPointName;
                    if (DistributionPointName.FullName != distributionPointName.PointType) {
                        continue;
                    }
                    GeneralNames generalNames = (GeneralNames)distributionPointName.Name;
                    GeneralName[] names = generalNames.GetNames();
                    foreach (GeneralName name in names) {
                        if (name.TagNo != GeneralName.UniformResourceIdentifier) {
                            continue;
                        }
                        DerIA5String derStr = DerIA5String.GetInstance((Asn1TaggedObject)name.ToAsn1Object(), false);
                        return derStr.GetString();
                    }
                }
            } catch {
            }
            return null;
        }

        /**
         * Fetches the CRL bytes from an URL.
         * If no url is passed as parameter, the url will be obtained from the certificate.
         * If you want to load a CRL from a local file, subclass this method and pass an
         * URL with the path to the local file to this method. An other option is to use
         * the CrlClientOffline class.
         * @see com.itextpdf.text.pdf.security.CrlClient#getEncoded(java.security.cert.X509Certificate, java.lang.String)
         */
        public ICollection <byte[]> GetEncoded(X509Certificate checkCert, String url)
        {
            if (checkCert == null)
            {
                return(null);
            }
            if (urls.Count == 0)
            {
                LOGGER.Info("Looking for CRL for certificate " + checkCert.SubjectDN.ToString());
                try {
                    if (url == null)
                    {
                        url = CertificateUtil.GetCRLURL(checkCert);
                    }
                    if (url == null)
                    {
                        throw new ArgumentNullException();
                    }
                    urls.Add(url);
                    LOGGER.Info("Found CRL url: " + url);
                }
                catch (Exception e) {
                    LOGGER.Info("Skipped CRL url: " + e.Message);
                }
            }
            List <byte[]> ar = new List <byte[]>();

            foreach (string urlt in urls)
            {
                try {
                    LOGGER.Info("Checking CRL: " + urlt);
                    HttpWebRequest  con      = (HttpWebRequest)WebRequest.Create(urlt);
                    HttpWebResponse response = (HttpWebResponse)con.GetResponse();
                    if (response.StatusCode != HttpStatusCode.OK)
                    {
                        throw new IOException(MessageLocalization.GetComposedMessage("invalid.http.response.1", (int)response.StatusCode));
                    }
                    //Get Response
                    Stream       inp  = response.GetResponseStream();
                    byte[]       buf  = new byte[1024];
                    MemoryStream bout = new MemoryStream();
                    while (true)
                    {
                        int n = inp.Read(buf, 0, buf.Length);
                        if (n <= 0)
                        {
                            break;
                        }
                        bout.Write(buf, 0, n);
                    }
                    inp.Close();
                    ar.Add(bout.ToArray());
                    LOGGER.Info("Added CRL found at: " + urlt);
                }
                catch (Exception e) {
                    LOGGER.Info("Skipped CRL: " + e.Message + " for " + urlt);
                }
            }
            return(ar);
        }