...for handlers of revision 6.
Since this adds U to the hash input, also trim the size of U and O to
48 bytes. The spec requires them to be 48 bytes, but all the newer PDFs
on https://cipa.jp/e/std/std-sec.html have 127 bytes -- 48 real bytes
and 79 nul padding bytes. These files were created by:
Creator: Word 用 Acrobat PDFMaker 17
Producer: Adobe PDF Library 15.0
and
Creator: Word 用 Acrobat PDFMaker 17
Producer: Adobe PDF Library 17.11.238
This is a step towards AESV3 support for PDF files.
The straight-forward way of writing this with our APIs is pretty
allocation-heavy, but this code won't run all that often for the
regular "open PDF, check password" flow.
This detects AESV3, and copies over the spec comments explaining what
needs to be done, but doesn't actually do it yet.
AESV3 is technically PDF 2.0-only, but
https://cipa.jp/std/documents/download_e.html?CIPA_DC-007-2021_E has a
1.7 PDF that uses it.
Previously we'd claim that we need a password to decrypt it.
Now, we cleanly crash with a TODO() \o/
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
Security handlers manage encryption and decription of PDF files. The
standard security handler uses RC4/MD5 to perform its crypto (AES as
well, but that is not yet implemented).
