/// <summary>
/// Prepares an
/// <see cref="PdfPKCS7"/>
/// instance for the given signature.
/// This method handles signature parsing and might throw an exception if
/// signature is malformed.
/// <p>
/// The returned
/// <see cref="PdfPKCS7"/>
/// can be used to fetch additional info about the signature
/// and also to perform integrity check of data signed by the given signature field.
/// </p>
/// Prepared
/// <see cref="PdfPKCS7"/>
/// instance calculates digest based on signature's /ByteRange entry.
/// In order to check that /ByteRange is properly defined and given signature indeed covers the current PDF document
/// revision please use
/// <see cref="SignatureCoversWholeDocument(System.String)"/>
/// method.
/// </summary>
/// <param name="signatureFieldName">the signature field name</param>
/// <param name="securityProvider">the security provider or null for the default provider</param>
/// <returns>
/// a
/// <see cref="PdfPKCS7"/>
/// instance which can be used to fetch additional info about the signature
/// and also to perform integrity check of data signed by the given signature field.
/// </returns>
public virtual PdfPKCS7 ReadSignatureData(String signatureFieldName)
{
PdfSignature signature = GetSignature(signatureFieldName);
if (signature == null)
{
return(null);
}
try {
PdfName sub = signature.GetSubFilter();
PdfString contents = signature.GetContents();
PdfPKCS7 pk = null;
if (sub.Equals(PdfName.Adbe_x509_rsa_sha1))
{
PdfString cert = signature.GetPdfObject().GetAsString(PdfName.Cert);
if (cert == null)
{
cert = signature.GetPdfObject().GetAsArray(PdfName.Cert).GetAsString(0);
}
pk = new PdfPKCS7(PdfEncodings.ConvertToBytes(contents.GetValue(), null), cert.GetValueBytes());
}
else
{
pk = new PdfPKCS7(PdfEncodings.ConvertToBytes(contents.GetValue(), null), sub);
}
UpdateByteRange(pk, signature);
PdfString date = signature.GetDate();
if (date != null)
{
pk.SetSignDate(PdfDate.Decode(date.ToString()));
}
String signName = signature.GetName();
pk.SetSignName(signName);
String reason = signature.GetReason();
if (reason != null)
{
pk.SetReason(reason);
}
String location = signature.GetLocation();
if (location != null)
{
pk.SetLocation(location);
}
return(pk);
}
catch (Exception e) {
throw new PdfException(e);
}
}
/// <exception cref="Org.BouncyCastle.Security.SecurityUtilityException"/>
/// <exception cref="System.IO.IOException"/>
private PdfName GetSignatureHashKey(String signatureName)
{
PdfSignature sig = sgnUtil.GetSignature(signatureName);
PdfString contents = sig.GetContents();
byte[] bc = PdfEncodings.ConvertToBytes(contents.GetValue(), null);
byte[] bt = null;
if (PdfName.ETSI_RFC3161.Equals(sig.GetSubFilter()))
{
Asn1InputStream din = new Asn1InputStream(new MemoryStream(bc));
Asn1Object pkcs = din.ReadObject();
bc = pkcs.GetEncoded();
}
bt = HashBytesSha1(bc);
return(new PdfName(ConvertToHex(bt)));
}
