Multiple stamping

[nabinpakka]

Describe the bug
Cannot stamp previously stamped file again.

To Reproduce
Stamp a file using the text stamp and save the file. Try stamping the same file with new stamp in different position.

Expected behavior
Both stamps to appear at the designated position without any error.

Environment (please complete the following information):

• OS: [ubuntu]
• Version [20.04.4]

It is the same for signing. The signing of the same file multiple times is not permitted. Is there a way around it?

[MatthiasValvekens]

Hi @nabinpakka,

Both of those are definitely supported (and tested) features, so the problem is likely in the calling code. As such, I'm moving this to the discussion forum as it's not an actionable bug report. If we end up finding an actual, more narrowly scoped bug in pyHanko, I'll re-file it on the issue tracker then.

Can you share a sample to reproduce the problem?

[nabinpakka]

Thank you for the reply. Here is the code snippet along with errors. with open("docs_signed.pdf", 'rb') as docs: w = IncrementalPdfFileWriter(docs) fields.append_signature_field( w, sig_field_spec=fields.SigFieldSpec( 'Signature', box=(20, 20, 200, 200) ) ) meta = signers.PdfSignatureMetadata(field_name='Signature') pdfSigner = signers.PdfSigner( meta, signer=signer, stamp_style=stamp.TextStampStyle( text_box_style=text.TextBoxStyle( font_size=0 ), background=images.PdfImage("signature_test.png"), border_width=0 ) ) with open("docs_signed.pdf", "wb") as outf: pdfSigner.sign_pdf(w, output=outf) Traceback (most recent call last): File "/home/hubbleloo/PycharmProjects/pythonProject/src/PdfSigner.py", line 100, in <module> _writeTextBasedStamps(signer) File "/home/hubbleloo/PycharmProjects/pythonProject/src/PdfSigner.py", line 65, in _writeTextBasedStamps w = IncrementalPdfFileWriter(docs) File "/home/hubbleloo/PycharmProjects/pythonProject/venv/lib/python3.8/site-packages/pyhanko/pdf_utils/incremental_writer.py", line 44, in __init__ prev = PdfFileReader(input_stream, strict=strict) File "/home/hubbleloo/PycharmProjects/pythonProject/venv/lib/python3.8/site-packages/pyhanko/pdf_utils/reader.py", line 150, in __init__ self.xrefs, self.trailer = self.read() File "/home/hubbleloo/PycharmProjects/pythonProject/venv/lib/python3.8/site-packages/pyhanko/pdf_utils/reader.py", line 427, in read raise PdfReadError('Illegal PDF header') pyhanko.pdf_utils.misc.PdfReadError: Illegal PDF header You can reproduce error by signing the file and again try to sign the previously signed file On second try, it will not return an error but while opening the pdf it seems to be turned to a plain text file which cannot be opened. [image: image.png] On third try, It will reproduce above error.

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On Thu, Jun 2, 2022 at 5:03 AM Matthias Valvekens ***@***.***> wrote: Hi @nabinpakka <https://github.com/nabinpakka>, Both of those are definitely supported (and tested) features, so the problem is likely in the calling code. As such, I'm moving this to the discussion forum as it's not an actionable bug report. If we end up finding an actual, more narrowly scoped bug in pyHanko, I'll re-file it on the issue tracker then. Can you share a sample to reproduce the problem? — Reply to this email directly, view it on GitHub <#111 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AKQEMECADN2MZ5VHIO2RU43VM7VTZANCNFSM5XTCTGSQ> . You are receiving this because you were mentioned.Message ID: ***@***.*** com>

[nabinpakka]

It turns out you have to write in a different file. Can you elaborate on why this happens with the same file?
Thank you.

[MatthiasValvekens]

Yes, indeed. That's just how file handles work: you can't expect writes to a file that's being read by the same process to not result in weirdness.

What you can do, however, is open the file in rb+ mode and sign in-place by passing in_place=True to sign_pdf.

[nabinpakka]

I was so focused on the signing part that I forgot about the opened file. Thank you @MatthiasValvekens