Hi Christian,

we do some useless signing with a fake key just to keep the give iText API 
happy. When iText has signed the PDF it can be written to disk as usual. But 
after this step we know the hash and the position of the PKCS7 signature. Once 
our own signing process is thru we replace the signature in the PDF by brute 
force ( replace byte x to byte y in file z with my content ). That's far from 
elegant but we don't need to tweak iText's code. 

Initially we don't expect our external signing problem deserves a solution 
within iText but if several people show up with such a demand, maybe we could 
make a proposal for a new interface. Or you just use our ready-build signing 
server ( http://sourceforge.net/projects/sirius-sign/ ) and we don't confuse 
people by adding more complex signing functionality to iText ;-)

Greetings

Andreas



----- Original Message ----
From: java-chris <[email protected]>
To: [email protected]
Sent: Wed, January 27, 2010 10:51:14 PM
Subject: Re: [iText-questions] Merge of detached signature


Hello Andreas, im on the same issue here.

When you talk about " store the half-baked pdf on the disk ".
Im trying to do that by making some serialization on the Stamper but nothing
is serializable in ITEXT.

So , im trying to do this way. 

[CODE]

            // write the current file.
            byte[] buf = new byte[8192];
            java.io.InputStream s = sap.getRangeStream();
          
            ByteArrayOutputStream ss = new ByteArrayOutputStream();
            
            int read = 0;
            while ((read = s.read(buf, 0, buf.length)) > 0) {
                ss.write(buf, 0, read);
            }
            // write SS to the disk.
            
            FileOutputStream fos = new FileOutputStream("blank.in_process");
            ss.writeTo(fos);
            fos.close();
            ss.close();

[/CODE]

But when im trying to read the stamper again to put the signature on : 

     PdfReader reader = new PdfReader("blank.in_process");
     PdfStamper stamper = new PdfStamper(reader,new
FileOutputStream("signedDoc.pdf"));
     PdfSignatureAppearance sa = stamper.getSignatureAppearance();

The signature PdfSignatureAppearance is null .... 
I think im missing something here ... 

How you procede to store the half-baked pdf on the disk ? 
Did i procede the right way ? 

Cheer's 

Christian Leclerc



Couldn't remember that I ever disagreed with Leonard, but now it's the time
!

Of course it's possible what your describing :

- Build a semi-signed PDF with room for the signature
- Get the hash value
- Store the half-baked PDF on disk
- Sign the hash and create a PKCS7-Signature, somtimes later, somewhere
- Insert the signature into the spare bytes in the PDF
- Ready

Due to wierd legal requirements we had to take this multi-step approach and
it works !

Greetings
Andreas


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