Hello,
I'm using iText 4.1.6 to sign PDF documents.
What I try to achieve is to certificate document and then apply approval
signature.
I have done first step, certified document and added empty invisible
signature field.
public void SignFirstTime()
{
var reader = new PdfReader("d:\\NotSigned.pdf");
var writer = new FileStream("d:\\Signed.pdf", FileMode.Create,
FileAccess.Write);
PdfStamper st = PdfStamper.CreateSignature(reader, writer,
'\0');
PdfSignatureAppearance sap = st.SignatureAppearance;
sap.SetCrypto(Key, GetCertificatesChain(), null,
PdfName.ADOBE_PPKLITE);
sap.SetVisibleSignature(new Rectangle(0, 0, 60, 40), 1,
"CertificationSignature");
sap.Reason = "Test";
sap.CertificationLevel =
PdfSignatureAppearance.CERTIFIED_FORM_FILLING;
//Adding invisible empty signature field to be signed later
st.AddSignature("ApprovalSignature", 1, 0, 0, 0, 0);
var chain = GetCertificatesChain();
reader.Appendable = true;
var dic = new PdfSignature(PdfName.ADOBE_PPKLITE
,PdfName.ADBE_PKCS7_DETACHED);
dic.Reason = sap.Reason;
dic.Contact = sap.Contact;
dic.Location = sap.Location;
dic.Date = new PdfDate(sap.SignDate);
sap.CryptoDictionary = dic;
var exc = new Hashtable();
exc[PdfName.CONTENTS] = ContentEstimated * 2 + 2;
sap.PreClose(exc);
PdfPKCS7 sgn = new PdfPKCS7(Key, chain, null, "SHA-256", false);
IDigest messageDigest = DigestUtilities.GetDigest("SHA-256");
Stream data = sap.RangeStream;
byte[] buf = new byte[ContentEstimated];
int n;
while ((n = data.Read(buf, 0, buf.Length)) > 0)
{
messageDigest.BlockUpdate(buf, 0, n);
}
byte[] hash = new byte[messageDigest.GetDigestSize()];
messageDigest.DoFinal(hash, 0);
DateTime cal = DateTime.Now;
byte[] sh = sgn.GetAuthenticatedAttributeBytes(hash, cal, null);
sgn.Update(sh, 0, sh.Length);
byte[] encodedSig = sgn.GetEncodedPKCS7(hash, cal, null, null);
if (ContentEstimated + 2 < encodedSig.Length)
throw new Exception("Not enough space");
var paddedSig = new byte[ContentEstimated];
Array.Copy(encodedSig, 0, paddedSig, 0, encodedSig.Length);
var dic2 = new PdfDictionary();
dic2.Put(PdfName.CONTENTS, new
PdfString(paddedSig).SetHexWriting(true));
sap.Close(dic2);
}
Then I try to sign this empty invisible signature field:
public void SignSecondTime()
{
var reader = new PdfReader("d:\\Signed.pdf");
var writer = new FileStream("d:\\Signed2.pdf", FileMode.Create,
FileAccess.Write);
PdfStamper st = PdfStamper.CreateSignature(reader, writer, '\0',
null, true);
PdfSignatureAppearance sap = st.SignatureAppearance;
sap.SetCrypto(Key, GetCertificatesChain(), null,
PdfName.ADOBE_PPKLITE);
sap.SetVisibleSignature("ApprovalSignature");
sap.Reason = "Test";
sap.CertificationLevel = PdfSignatureAppearance.NOT_CERTIFIED;
var chain = GetCertificatesChain();
reader.Appendable = true;
var dic = new PdfSignature(PdfName.ADOBE_PPKLITE,
PdfName.ADBE_PKCS7_DETACHED);
dic.Reason = sap.Reason;
dic.Contact = sap.Contact;
dic.Location = sap.Location;
dic.Date = new PdfDate(sap.SignDate);
sap.CryptoDictionary = dic;
var exc = new Hashtable();
exc[PdfName.CONTENTS] = ContentEstimated * 2 + 2;
sap.PreClose(exc);
PdfPKCS7 sgn = new PdfPKCS7(Key, chain, null, "SHA-256", false);
IDigest messageDigest = DigestUtilities.GetDigest("SHA-256");
Stream data = sap.RangeStream;
byte[] buf = new byte[ContentEstimated];
int n;
while ((n = data.Read(buf, 0, buf.Length)) > 0)
{
messageDigest.BlockUpdate(buf, 0, n);
}
byte[] hash = new byte[messageDigest.GetDigestSize()];
messageDigest.DoFinal(hash, 0);
DateTime cal = DateTime.Now;
byte[] sh = sgn.GetAuthenticatedAttributeBytes(hash, cal, null);
sgn.Update(sh, 0, sh.Length);
byte[] encodedSig = sgn.GetEncodedPKCS7(hash, cal, null, null);
if (ContentEstimated + 2 < encodedSig.Length)
throw new Exception("Not enough space");
var paddedSig = new byte[ContentEstimated];
Array.Copy(encodedSig, 0, paddedSig, 0, encodedSig.Length);
var dic2 = new PdfDictionary();
dic2.Put(PdfName.CONTENTS, new
PdfString(paddedSig).SetHexWriting(true));
sap.Close(dic2);
}
but it doesn't sign it. If I add visible empty signature field, everything
works fine. I managed to sign invisible signature field only with Acrobat XI
Pro. Thanks.
--
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Sent from the iText - General mailing list archive at Nabble.com.
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