[Poppler-bugs] [Bug 97485] horizontal white lines on the background image

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97485

--- Comment #2 from Jakub Kucharski <jakubkucharski97 at gmail.com> ---
Your file is weird/broken. Even reading it with head,tail,more is problematic.
Only hexdump actually doesn't have a problem. The first problem is that in the
first version of this file there was a single object and then a cross-reference
table with ridiculously large number of entries... when it should only have 2
(counting in the free entry)... Or 3, because the first trailer has a reference
to an Info dictionary, but in the first version of this file there was none...

And then this file looks as if it was incrementally updated.

But generally, e.g. head shows sth like this:

$ head 014231.pdf
%PDF-1.2
0000000016 00000 n                             xref
0000029672 00000 n
0000030017 00000 n
0000030169 00000 n
0000071593 00000 n
0000096497 00000 n
0000096527 00000 n
0000096708 00000 n
0000096731 00000 n

If these were the actual contents of this file, it would be even more broken.
(hexdump shows something else...)

Now tail:

$ tail -c 10 014231.pdf
$ tail -c 50 014231.pdf
$ tail -c 80 014231.pdf
$ a5981c81b97364c3e63cb0738d>] # Here the shell has gone mad
$ tail -c 150 014231.pdf
08 00000 n
0002185958 00000 n
$ 599469d845><c6d674a5981c81b97364c3e63cb0738d>] # Again... And generally: What
the...?

And again - when I look at it with hexdump from the end it looks like a valid
PDF document. So yeah, you have a crazy file (perhaps there is even some
potential for making an exploit from it, I don't know...).

And if even head, tail & more have problems with it, then I have no idea what
we can do here. (Perhaps another poppler dev has an idea. It may be fun
debugging this thing.)

Getting back to the horizontal lines: Firefox's pdf.js shows the same. Are you
sure these lines shouldn't be there?

That's the first time I've encountered such a file, so I've thought it could be
helpful to share my discoveries here for others who are more knowledgable.
Unfortunatelly, in this situation I can't help you. Sorry.

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