检查 pdf 是否已签名

Question

I would like to write a python script to check if a pdf is signed or not. After quite a bit of looking around, I saw that pyPDF2 helps extract text from pdf files, but I am not sure if it can be used to extract the signature details such as Public Key etc.

I did go through some of the open source packages like pyhanko and cryptography but I am a bit stuck as to how to do it.

I have not worked on encryptions or PDFs using python before. Could you please guide me on the best way possible to execute this?

Thanks and best regards, Raghu

I tried using cryptography package but was not quite sure how to extract the signature certificate from the pdf.

Adobe pdf offers export in PKCS7 and CER format.I would like to know how to do this using python. This is inorder to have a validation step for another process.

Also appreciate if there are other easy and smart ways to check if the pdf is signed or not.

Answer 1

disclaimer: I am the author of borb the library used in this answer

Simply load the PDF using borb , get the DocumentInfo object, and call its has_signatures function.

from borb.pdf import PDF
from borb.pdf import Document

import typing

# read the PDF
doc: typing.Optional[Document] = None
with open("input.pdf", "rb") as fh:
    doc = PDF.loads(fh)

# check whether anything has been read
# this may fail due to IO error
# or a corrupt PDF
assert doc is not None

# check whether signatures are in the PDF
doc.get_document_info().has_signatures()