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From Fabricio Pombo Koch <fabriciok...@yahoo.com.br.INVALID>
Subject Re: External signature in 2 steps
Date Thu, 03 Nov 2016 19:19:47 GMT
Tilman
thank you for your effort, but the update doesn't actually help me.
I add the signature object (name, location, reason), save incremental for external signature,
then I add the empty signature and save the file on disk. Now, I could get the ByteRange with
before saving the file, but I don't have a place to store it. It's easier to get it from the
saved file in the 2nd step.

In the 2nd step, I load the pdf as a PDDocument, get the last signature and get the ByteRange.
 Anyways, your comment made it more clear to understand that we must provide an empty signature
to make it all works.


I guess that the following features would be nice:
- No need to add the empty signature byte array;
- A method from PDFBOX to replace the empty signature with the valid signature;

I don't know if it's possible, but the first time I tried to add the signature object, get
the file content for signature and discard the changes. In the second step, I added the signature
object with the same info, save incremental for external signature, add the signature and
save the file. The signature got invalid. I guess the signature object has some Date/Time
related info.

Thanks once more,Fabricio P Koch
 

    Em Quarta-feira, 2 de Novembro de 2016 16:05, Tilman Hausherr <THausherr@t-online.de>
escreveu:
 

 Am 28.10.2016 um 17:10 schrieb Fabricio Pombo Koch:
> Tilman,
> thanks to your help I was able to make it works.
>
> But, I had to add a empty signature hash to get it working. Like this:externalSigning.setSignature(new
byte[100]);
>
> Otherwise, the PDFBox would create a empty file after closing the document.And I needed
to save the file, because the ByteRange wasn't with the right value before saving. Its value
was something like this:0 1000000000000 1000000000000 1000000000000
> So, here is what I did:
> - Followed the CreateSignature example to get the content for my signature service and
added a empty signature before closing the PDDocument;- The first step created a PDF with
an invalid signature (an empty one);- Signed the content with my signature service;- Then,
I loaded the PDDocument, got the last signature, got the ByteRange and then, closed the PDDocumento;-
With the ByteRange in hands, I was able to open the PDF (with the empty signature) and replace
the empty signature with the real signature;

Hello Fabricio,

I've now updated PDFBox as explained, also added a comment in the 
"visible" example explaining my suggestion plus your important remark 
(must add a dummy signature).

This has been done in
https://issues.apache.org/jira/browse/PDFBOX-3552

You can access a snapshot at
https://repository.apache.org/content/groups/snapshots/org/apache/pdfbox/pdfbox-app/2.0.4-SNAPSHOT/

Please test it and give feedback, i.e. that you can now skip the 
"middle" step, i.e. you can now get the byterange immediately after 
adding your dummy signature.

Don't hesitate to tell whether my comment in the "visible" example is 
confusing or unclear.

Tilman


>
> Thanks again Tilman.
>
> Att,Fabricio P Koch
>
>  
>
>      Em Quinta-feira, 27 de Outubro de 2016 15:24, Fabricio Pombo Koch <fabriciokoch@yahoo.com.br.INVALID>
escreveu:
>  
>
>  Tilman,
> I'm gonna try it. And I'm sorry about the indentation of my last e-mail.
> Thank you again!Fabricio P Koch
>
>      Em Quinta-feira, 27 de Outubro de 2016 14:49, Tilman Hausherr <THausherr@t-online.de>
escreveu:
>  
>
>  Am 27.10.2016 um 15:18 schrieb Fabricio Pombo Koch:
>> Tilman, thanks for your reply.
>> I'm not familiarized with PDF structure, this way, I don't know how to insert the
signature manually into the PDF.
>> This code works for me to sign in "one step":
>> File inFile = new File("IN_PDF_FILE");PDDocument doc = PDDocument.load(inFile);PDSignature
signature = new PDSignature();signature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);signature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);signature.setName("USERNAME");signature.setLocation("LOCATION");signature.setReason("TESTING");doc.addSignature(signature);File
outFile = new File("OUT_PDF_FILE");FileOutputStream fos = new FileOutputStream(outFile);ExternalSigningSupport
externalSigning = doc.saveIncrementalForExternalSigning(fos);MessageDigest digest = MessageDigest.getInstance("SHA-256");byte[]
content= IOUtils.toByteArray(externalSigning.getContent());byte[] hash = digest.digest(content);externalSigning.setSignature(VALUE_RETURNED_FROM_MY_SIGNATURE_SERVICE);doc.close();
>>
>> But, I can't  run the following line because I recieve the "VALUE_RETURNED_FROM_MY_SIGNATURE_SERVICE"
value in a future time:externalSigning.setSignature(VALUE_RETURNED_FROM_MY_SIGNATURE_SERVICE);
>> So, I tried using all that code, except the "externalSigning.setSignature" method.
Then, in my 2nd step, I wrote it all again (from PDDocumento.load() until doc.close()).It
sign the file, but the signature is invalid.
> What you have to do is to access the PDF file, seek to the appropriate
> position, and then write the hex string of your signature.
>
> If the byterange is
>
> 0 61887 65989 21205
>
> then go to 61888, and write there.
>
> To get the byte range, as I explained yesterday, you need to access the
> PDF file with PDFBox again earlier but after the (unfinished) "signing",
> get the field (you know its name), and then the signature, then the
> ByteRange ( signature.getByteRange() ). Close again.
>
> So:
> 1) unfinished sign, close
> 2) reload with pdfbox to get the byte range, close
> 3) reload with random access class, access appropriate position, write
> sig in ascii hex, close
>
> I can't give much help now because I'm busy until mid next week.
>
> Tilman
>
>
>> It would be nice If you create the new feature.Meanwhile, how could I add the signature
manually? I have no idea.
>>
>> Thanks,Fabricio P Koch
>>
>> ---------------------------------------------------------------------------------------------------------------------------
>>
>> From: Tilman Hausherr <T...@t-online.de>Subject: Re: External signature in
2 stepsDate: 2016-10-26 18:43 (-0200)List: users@pdfbox.apache.orgAm 26.10.2016 um 21:53 schrieb
Fabricio Pombo Koch:show/hide original textYou would have to use the new "external" strategy
that exists since 2.0.3, but without writing the signature. Before closing, get the ByteRange
from the signature object.
>> HOWEVER... that one isn't available, because after being calculated the ByteRange
isn't assigned back to the PDFBox structure.
>> (Open a signed PDF with NOTEPAD++ and search for ByteRange to understand what II
mean)
>> So you'd have to reload the PDF; get the field (you know its name), and then the
signature, then the ByteRange ( signature.getByteRange() ). Close again.
>> Then write the signature that you got at the appropriate place in the file. This
can be done without PDFBox.
>> I could do a change that you can access the byte range, i.e. don't have to reload
the PDF just to get the byte range. However this will have to wait until mid next week, because
I wouldn't have the time to become active if it doens't work. (Although I just tested it).
>> Tilman
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>
>    
>
>    



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