'int' object has no attribute 'value' on sign_pdf

[ilpadrinohack]

Hi Matthias and everybody:

With the update of pyHanko from 0.13 o the latest one, I have a problem when trying to sign a pdf document. This is my code:

     `w = IncrementalPdfFileWriter(BytesIO(MINIMAL))
      fname = fname.replace('.pdf', '-f.pdf')
                with open(fname, 'wb') as outf:
                    
                    out = signers.PdfSigner(signature_meta=signers.PdfSignatureMetadata(
                                                    field_name='Sigdni',
                                                    reason='Firma',
                                                    location='',
                                                    use_pades_lta=True,
                                                    subfilter=fields.SigSeedSubFilter.PADES,
                                                    embed_validation_info=True,
                                                    validation_context=vc
                                                    ),
                                    signer=signerp,
                                    timestamper=None,
                                    stamp_style=style,
                                    new_field_spec=sp
                                    ).sign_pdf(w,output=outf)`

And the error is "'int' object has no attribute 'value'"
I think (not sure) that the problem is on the sign_pdf function.

If I change my code calling in a different way to IncrementaPdfFileWriter function as follow:

    `fname = fname.replace('.pdf', '-f.pdf')
                with open(fname, 'wb') as outf:
                    w = IncrementalPdfFileWriter(outf)
                    
                    out = signers.PdfSigner(signature_meta=signers.PdfSignatureMetadata(
                                                    field_name='Sigdni',
                                                    reason='Firma',
                                                    location='',
                                                    use_pades_lta=True,
                                                    subfilter=fields.SigSeedSubFilter.PADES,
                                                    embed_validation_info=True,
                                                    validation_context=vc
                                                    ),
                                    signer=signerp,
                                    timestamper=None,
                                    stamp_style=style,
                                    new_field_spec=sp
                                    ).sign_pdf(w)`

I get the error "Illegal PDF header"
I have been checking the documentation and haven't been able to notice any change in the implementation in the sign_pdf call.

Any help will be appreciated.
Thanks in advance

[MatthiasValvekens]

Hi @ilpadrinohack,

The fact that your second example doesn't work is to be expected: the stream passed into the IncrementalPdfFileWriter needs to contain the "base" file. You're invoking it on an empty stream.

As for the first example: please post the full stack trace. It's somewhat likely that the error you're seeing was present all along, but surfaced only now due to various deep changes in the validation code. Whether it's a data correctness issue or a bug is impossible to tell without a stack trace.

EDIT: moving this to a discussion. Will create an issue if/when we identify a concrete bug.

[ilpadrinohack]

Thanks Matthias:
This is the stack trace:

       `Traceback (most recent call last):
        File "/root/Descargas/programacion/firma_digital/pades_sign/ff/firma.py", line 279, in test_simple_sign
out = signers.PdfSigner(signature_meta=signers.PdfSignatureMetadata(
       File "/usr/local/lib/python3.10/site-packages/pyhanko/sign/signers/pdf_signer.py", line 1408, in sign_pdf
result = asyncio.run(
       File "/usr/lib64/python3.10/asyncio/runners.py", line 44, in run
return loop.run_until_complete(main)
       File "/usr/lib64/python3.10/asyncio/base_events.py", line 649, in run_until_complete
return future.result()
       File "/usr/local/lib/python3.10/site-packages/pyhanko/sign/signers/pdf_signer.py", line 1466, in async_sign_pdf
signing_session = self.init_signing_session(
      File "/usr/local/lib/python3.10/site-packages/pyhanko/sign/signers/pdf_signer.py", line 1152, in init_signing_session
sig_field_ref = next(cms_writer)
      File "/usr/local/lib/python3.10/site-packages/pyhanko/sign/signers/cms_embedder.py", line 453, in write_cms
field_created, sig_field_ref = _get_or_create_sigfield(
      File "/usr/local/lib/python3.10/site-packages/pyhanko/sign/signers/cms_embedder.py", line 131, in _get_or_create_sigfield
apply_sig_field_spec_properties(
      File "/usr/local/lib/python3.10/site-packages/pyhanko/sign/fields.py", line 1701, in apply_sig_field_spec_properties
sig_field_spec.seed_value_dict.as_pdf_object()
      File "/usr/local/lib/python3.10/site-packages/pyhanko/sign/fields.py", line 854, in as_pdf_object
pdf_name('/Ff'): generic.NumberObject(self.flags.value),`
      AttributeError: 'int' object has no attribute 'value'

---

     'int' object has no attribute 'value'`

Hope this can help

Thanks

[ilpadrinohack]

SOLVED
I don't know why but if I use:

 `sv = fields.SigSeedValueSpec(
                    reasons=[],            
                    flags=3,
                    )`

And after sp = fields.SigFieldSpec('Sigdni', seed_value_dict=sv, on_page=pagina_firma-1, box=(x1, y1, x2, y2),)

I get the error mentioned above.

Removing "seed_value_dict" from SigFieldSpec as follow:
sp = fields.SigFieldSpec('Sigdigp', on_page=pagina_firma-1, box=(x1, y1, x2, y2),)

works perfectly.

Thanks Matthias

[MatthiasValvekens]

Yeah, I should probably redo some needlessly general examples in the docs to no longer involve seed values, since they're a gimmick that 99.9% of users won't ever need.

For reference, the issue was that you needed to specify SigSeedValFlags(3) instead of 3. Weird that that didn't trigger a warning in your IDE, though.