OpenSystemsDevelopment / qpdf

main() had gotten absurdly long. Split it into reasonable chunks. This
refactoring is in preparation for handling splitting output into
single pages.

When parsing content streams, allow content to be split arbitrarily
across stream boundaries.

Very badly corrupted files may not have a retrievable root dictionary.
Handle that as a special case so that a more helpful error message can
be provided.

When requested, QPDFWriter will do more aggress prechecking of streams
to make sure it can actually succeed in decoding them before
attempting to do so. This will allow preservation of raw data even
when the raw data is corrupted relative to the specified filters.

QPDFObjectHandle::parseInternal now issues warnings instead of
throwing exceptions for all error conditions that it finds (except
internal logic errors) and has stronger recovery for things like
invalid tokens and malformed dictionaries. This should improve qpdf's
ability to recover from a wide range of broken files that currently
cause it to fail.

fixes #117
fixes #118
fixes #119
fixes #120

Several other infinite loop bugs were fixed by previous changes.
Include their test files in the test suite.

During parsing of an object, sometimes parts of the object have to be
resolved. An example is stream lengths. If such an object directly or
indirectly points to the object being parsed, it can cause an infinite
loop. Guard against all cases of re-entrant resolution of objects.

This is CVE-2017-9208.

The QPDF library uses object ID 0 internally as a sentinel to
represent a direct object, but prior to this fix, was not blocking
handling of 0 0 obj or 0 0 R as a special case. Creating an object in
the file with 0 0 obj could cause various infinite loops. The PDF spec
doesn't allow for object 0. Having qpdf handle object 0 might be a
better fix, but changing all the places in the code that assumes objid
== 0 means direct would be risky.

This is CVE-2017-9209.

This is CVE-2017-9210.

The description string for an error message included unparsing an
object, which is too complex of a thing to try to do while throwing an
exception. There was only one example of this in the entire codebase,
so it is not a pervasive problem. Fixing this eliminated one class of
infinite loop errors.

Working with absolute paths makes debugging easier, but some called
scripts always need / as dir separator or won't work.

/dev/null is not portable, so use File::Spec instead, which provides
portable "paths" and especially "nul" on Windows. I changed all places
with hard coded /dev/null to be sure, while I think it only is a
problem in direct system calls, because the other executed commands go
to sh.exe from MSYS which itself should port /dev/null to NUL. The
test still pass, so shouldn't have made any harm...

expr needs ARG + ARG
quote paths to support support spaces

Shebang doesn't work well on Windows.

If xref table entries lack the spec-required trailing whitespace or
contain a small amount of extra space, handle them anyway.

For non-encrypted files, determinstic ID generation uses file contents
instead of timestamp and file name. At a small runtime cost, this
enables generation of the same /ID if the same inputs are converted in
the same way multiple times.

fix-qdf was previously hard-coding the number of bytes for the f2
field of the xref stream entry. This addresses issue #37. Thanks
aluebcke for reporting.

Pushing inherited objects to pages and getting all pages were both
prone to stack overflow infinite loops if there were loops in the
Pages dictionary. There is a general weakness in the code in that any
part of the code that traverses the Pages structure would be prone to
this and would have to implement its own loop detection. A more robust
fix may provide some general method for handling the Pages structure,
but it's probably not worth doing.

Note: addition of *Internal2 private functions was done rather than
changing signatures of existing methods to avoid breaking
compatibility.

When checking two objects preceding R while parsing, ensure that the
objects are direct. This avoids stuff like 1 0 obj containing 1 0 R 0 R
from causing an infinite loop in object resolution.

Original reported here:
https://bugs.launchpad.net/ubuntu/+source/qpdf/+bug/1397413

The PDF specification says that the /Type key for nodes in the pages
dictionary (both /Page and /Pages) is required, but some PDF files
omit them. Use the presence of other keys to determine the type of
pages tree node this is if the type key is not found.

The spec allows /Contents to be omitted for pages that are blank, but
QPDFObjectHandle::getPageContents() was throwing an exception in this
case.

QPDFWriter was trying to make /Filter and /DecodeParms direct in all
cases, but there are some cases where /DecodeParms may refer to a
stream, which can't be direct. QPDFWriter doesn't actually need
/DecodeParms to be direct in that case because it won't be able to
filter the stream. Until we can handle this type of stream, just don't
make /Filter and /DecodeParms direct if we can't filter the stream
anyway.

Fixes #34

This is a performance fix.  The output is unchanged.

Fixes #28.

Fixes #27.