// helper methods
/// <param name="certificate">the certificate from which we need the ExtensionValue</param>
/// <param name="oid">the Object Identifier value for the extension.</param>
/// <returns>the extension value as an ASN1Primitive object</returns>
private static Asn1Object GetExtensionValue(X509Certificate certificate, String oid)
{
byte[] bytes = SignUtils.GetExtensionValueByOid(certificate, oid);
if (bytes == null)
{
return(null);
}
Asn1InputStream aIn = new Asn1InputStream(new MemoryStream(bytes));
Asn1OctetString octs = (Asn1OctetString)aIn.ReadObject();
aIn = new Asn1InputStream(new MemoryStream(octs.GetOctets()));
return(aIn.ReadObject());
}
// Time Stamp Authority
/// <summary>Gets the URL of the TSA if it's available on the certificate</summary>
/// <param name="certificate">a certificate</param>
/// <returns>a TSA URL</returns>
public static String GetTSAURL(X509Certificate certificate)
{
byte[] der = SignUtils.GetExtensionValueByOid(certificate, SecurityIDs.ID_TSA);
if (der == null)
{
return(null);
}
Asn1Object asn1obj;
try {
asn1obj = Asn1Object.FromByteArray(der);
DerOctetString octets = (DerOctetString)asn1obj;
asn1obj = Asn1Object.FromByteArray(octets.GetOctets());
Asn1Sequence asn1seq = Asn1Sequence.GetInstance(asn1obj);
return(GetStringFromGeneralName(asn1seq[1].ToAsn1Object()));
}
catch (System.IO.IOException) {
return(null);
}
}