Bug#896596: poppler-glib always returns 0 length for PopplerInputStream

[Simon McVittie]

Control: tags -1 + patch

On Sat, 28 Apr 2018 at 20:59:16 +0900, dai at debian.org wrote:
> original bug report: https://bugs.debian.org/896596
> previous forwarded: https://github.com/ruby-gnome2/ruby-gnome2/issues/1159
> 
> below comments and patch by Kouhei Sutou <kou at cozmixng.org>.
> 
> > Poppler adds getLength() check at
> > https://cgit.freedesktop.org/poppler/poppler/commit/?id=a59f61641fcb36859b625749afb4561557e419f6
> > for https://bugs.freedesktop.org/show_bug.cgi?id=103552 .
> > But PopplerInputStream created by poppler-glib always returns 0 for getLength():
> > https://cgit.freedesktop.org/poppler/poppler/tree/glib/poppler-document.cc#n301

Thanks for this diagnosis. It seems correct.

> > Ah, we can just use the length passed by argument:
> -    str = new PopplerInputStream(stream, cancellable, 0, gFalse, 0, Object(objNull));
> +    str = new PopplerInputStream(stream, cancellable, 0, gFalse, length, Object(objNull));

That doesn't actually work, because the function is documented to accept
-1 as a length (meaning "find the length automatically").

> > We'll be able to compute length by g_seekable_seek(0, G_SEEK_END) and
> > g_seekable_tell().

That's what I've done in the case where the caller used -1. The function
already requires that the stream is seekable, so it seems safe to assume
that this works.

Proposed patches attached. I've included a fairly minimal reproducer for
the bug, as a patch to the existing autopkgtest.

Also available as a merge request, here:
https://salsa.debian.org/freedesktop-team/poppler/merge_requests/1

Patch proposed upstream here:
https://gitlab.freedesktop.org/poppler/poppler/merge_requests/189

    smcv
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