Bug 406269 - pdf document with empty signature field is claimed to be signed
Summary: pdf document with empty signature field is claimed to be signed
Status: RESOLVED WORKSFORME
Alias: None
Product: okular
Classification: Applications
Component: general (show other bugs)
Version: unspecified
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: Okular developers
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2019-04-06 04:31 UTC by Oliver Sander
Modified: 2021-08-07 04:36 UTC (History)
2 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
File with empty signature form field (97.62 KB, application/pdf)
2019-04-06 04:31 UTC, Oliver Sander
Details

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Description Oliver Sander 2019-04-06 04:31:55 UTC
Created attachment 119266 [details]
File with empty signature form field

The attached pdf file contains an empty signature field.  When opening the file, Okular shows a blue message box claiming "This document is digitally signed.", which is not correct.

For the same file, pdfsig shows

Digital Signature Info of: Anzeige_DM_Seite_3_empty.pdf
Unimplemented Feature (0): Unable to validate this type of signature
Signature #1:
  - Signer Certificate Common Name: (null)
  - Signer full Distinguished Name: (null)
  - Signing Time: Jan 01 1970 01:00:00
  - Signing Hash Algorithm: unknown
  - Signature Type: adbe.pkcs7.detached
  - Signature Validation: Signature has not yet been verified.
Unimplemented Feature (0): Unable to validate this type of signature
Signature #2:
  - Signer Certificate Common Name: (null)
  - Signer full Distinguished Name: (null)
  - Signing Time: Jan 01 1970 01:00:00
  - Signing Hash Algorithm: unknown
  - Signature Type: adbe.pkcs7.detached
  - Signature Validation: Signature has not yet been verified.
Unimplemented Feature (0): Unable to validate this type of signature
Signature #3:
  - Signer Certificate Common Name: (null)
  - Signer full Distinguished Name: (null)
  - Signing Time: Jan 01 1970 01:00:00
  - Signing Hash Algorithm: unknown
  - Signature Type: adbe.pkcs7.detached
  - Signature Validation: Signature has not yet been verified.

That looks dubious, too, so maybe the root cause is in poppler.

This happens with Okular from today's git master on Debian testing.
Comment 1 Albert Astals Cid 2019-04-07 18:09:51 UTC
It is correct, the document is signed, it has three shitty broken signatures, but it has signatures.
Comment 2 Oliver Sander 2019-04-09 08:14:08 UTC
Okay, so not a bug.  But can we improve the text somehow to make it clearer that the signatures are shitty broken? "This document is signed" sounds too positive. Unfortunately, not being a signature or usability expert I cannot currently come up with a specific proposal.  Nate, do you have an idea?
Comment 3 Nate Graham 2019-04-09 16:24:17 UTC
Not an expert on this stuff so let me ask some questions:

- What exactly do you mean by "shitty broken signatures?"
- Are shitty broken signatures valid? Can they be legitimately used for any purpose?
Comment 4 Albert Astals Cid 2019-04-21 23:35:37 UTC
(In reply to Nate Graham from comment #3)
> Not an expert on this stuff so let me ask some questions:
> 
> - What exactly do you mean by "shitty broken signatures?"

Lots of fields are missing.

> - Are shitty broken signatures valid?

Depends on what you mean by valid :D The existing contents are not wrong, they just miss lots of fields that make them quite shitty and not very useful.

> Can they be legitimately used for any purpose?

Most probably not.
Comment 5 Nate Graham 2019-04-24 02:20:40 UTC
(In reply to Albert Astals Cid from comment #4)
> (In reply to Nate Graham from comment #3)
> > Can they be legitimately used for any purpose?
> 
> Most probably not.
In that case, for such PDFs, I would say we probably should not display the "This document is digitally signed" message widget.
Comment 6 Albert Astals Cid 2021-07-08 22:04:03 UTC
We now show a red warning about the signatures being broken, is this good enough?
Comment 7 Bug Janitor Service 2021-07-23 04:33:25 UTC
Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!
Comment 8 Bug Janitor Service 2021-08-07 04:36:05 UTC
This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!