[Poppler-bugs] [Bug 99416] Sign PDF with digital signature

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99416

--- Comment #14 from Hans-Ulrich Jüttner <huj at froreich-bioscientia.de> ---
(In reply to Albert Astals Cid from comment #13)
> is the ASN1 thing in the PDF spec? I can't find it
> 

The document from Adobe
https://www.adobe.com/devnet-docs/acrobatetk/tools/DigSig/Acrobat_DigitalSignatures_in_PDF.pdf
describes the generation of digital signatures in PDF documents. It says
"5. The hash value is encrypted with the signer’s private key and a hex-encoded
PKCS#7 object signature object is generated.
6. The signature object is placed in the file on disk, overwriting the
placeholder /Contents value. Any space not used for the signature object is
overwritten with zeros." RFC2315 (https://tools.ietf.org/html/rfc2315)
describes PKCS#7 objects
as ASN.1 structures.

> This is only useful for documents that already have a signature field, right?
> 

Yes, I couldn't figure out how to create such a signature field with poppler.
So I content myself with the case where there is already a signature field in
the PDF document.

> Not that i'm an ultra fan of windows, but open_memstream seems not to work
> there, is there anything else we could use? (No idea if anyone has tried
> building the nss3 code in windows but maybe better if we don't make it
> harder for them than necessary)

I'm sorry about that, but I don't have access to a windows machine and,
moreover, do not know much about windows.

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