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7f8892525f
qpdf/libqpdf/QPDF_Stream.cc
Jay Berkenbilt 7f8892525f Add precheck streams capability 
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.
2017-07-27 23:42:27 -04:00

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#include <qpdf/QPDF_Stream.hh>
#include <qpdf/QUtil.hh>
#include <qpdf/Pipeline.hh>
#include <qpdf/Pl_Flate.hh>
#include <qpdf/Pl_PNGFilter.hh>
#include <qpdf/Pl_RC4.hh>
#include <qpdf/Pl_Buffer.hh>
#include <qpdf/Pl_ASCII85Decoder.hh>
#include <qpdf/Pl_ASCIIHexDecoder.hh>
#include <qpdf/Pl_LZWDecoder.hh>
#include <qpdf/Pl_Count.hh>
#include <qpdf/QTC.hh>
#include <qpdf/QPDF.hh>
#include <qpdf/QPDFExc.hh>
#include <qpdf/Pl_QPDFTokenizer.hh>
#include <stdexcept>
std::map<std::string, std::string> QPDF_Stream::filter_abbreviations;
QPDF_Stream::QPDF_Stream(QPDF* qpdf, int objid, int generation,
QPDFObjectHandle stream_dict,
qpdf_offset_t offset, size_t length) :
qpdf(qpdf),
objid(objid),
generation(generation),
stream_dict(stream_dict),
offset(offset),
length(length)
{
if (! stream_dict.isDictionary())
{
throw std::logic_error(
"stream object instantiated with non-dictionary "
"object for dictionary");
}
}
QPDF_Stream::~QPDF_Stream()
{
}
void
QPDF_Stream::setObjGen(int objid, int generation)
{
if (! ((this->objid == 0) && (this->generation == 0)))
{
throw std::logic_error(
"attempt to set object ID and generation of a stream"
" that already has them");
}
this->objid = objid;
this->generation = generation;
}
std::string
QPDF_Stream::unparse()
{
// Unparse stream objects as indirect references
return QUtil::int_to_string(this->objid) + " " +
QUtil::int_to_string(this->generation) + " R";
}
QPDFObject::object_type_e
QPDF_Stream::getTypeCode() const
{
return QPDFObject::ot_stream;
}
char const*
QPDF_Stream::getTypeName() const
{
return "stream";
}
QPDFObjectHandle
QPDF_Stream::getDict() const
{
return this->stream_dict;
}
PointerHolder<Buffer>
QPDF_Stream::getStreamData()
{
Pl_Buffer buf("stream data buffer");
if (! pipeStreamData(&buf, true, false, false, false))
{
throw std::logic_error("getStreamData called on unfilterable stream");
}
QTC::TC("qpdf", "QPDF_Stream getStreamData");
return buf.getBuffer();
}
PointerHolder<Buffer>
QPDF_Stream::getRawStreamData()
{
Pl_Buffer buf("stream data buffer");
pipeStreamData(&buf, false, false, false, false);
QTC::TC("qpdf", "QPDF_Stream getRawStreamData");
return buf.getBuffer();
}
bool
QPDF_Stream::understandDecodeParams(
std::string const& filter, QPDFObjectHandle decode_obj,
int& predictor, int& columns, bool& early_code_change)
{
bool filterable = true;
std::set<std::string> keys = decode_obj.getKeys();
for (std::set<std::string>::iterator iter = keys.begin();
iter != keys.end(); ++iter)
{
std::string const& key = *iter;
if ((filter == "/FlateDecode") && (key == "/Predictor"))
{
QPDFObjectHandle predictor_obj = decode_obj.getKey(key);
if (predictor_obj.isInteger())
{
predictor = predictor_obj.getIntValue();
if (! ((predictor == 1) || (predictor == 12)))
{
filterable = false;
}
}
else
{
filterable = false;
}
}
else if ((filter == "/LZWDecode") && (key == "/EarlyChange"))
{
QPDFObjectHandle earlychange_obj = decode_obj.getKey(key);
if (earlychange_obj.isInteger())
{
int earlychange = earlychange_obj.getIntValue();
early_code_change = (earlychange == 1);
if (! ((earlychange == 0) || (earlychange == 1)))
{
filterable = false;
}
}
else
{
filterable = false;
}
}
else if (key == "/Columns")
{
QPDFObjectHandle columns_obj = decode_obj.getKey(key);
if (columns_obj.isInteger())
{
columns = columns_obj.getIntValue();
}
else
{
filterable = false;
}
}
else if ((filter == "/Crypt") &&
(((key == "/Type") || (key == "/Name")) &&
(decode_obj.getKey("/Type").isNull() ||
(decode_obj.getKey("/Type").isName() &&
(decode_obj.getKey("/Type").getName() ==
"/CryptFilterDecodeParms")))))
{
// we handle this in decryptStream
}
else
{
filterable = false;
}
}
return filterable;
}
bool
QPDF_Stream::filterable(std::vector<std::string>& filters,
int& predictor, int& columns,
bool& early_code_change)
{
if (filter_abbreviations.empty())
{
// The PDF specification provides these filter abbreviations
// for use in inline images, but according to table H.1 in the
// pre-ISO versions of the PDF specification, Adobe Reader
// also accepts them for stream filters.
filter_abbreviations["/AHx"] = "/ASCIIHexDecode";
filter_abbreviations["/A85"] = "/ASCII85Decode";
filter_abbreviations["/LZW"] = "/LZWDecode";
filter_abbreviations["/Fl"] = "/FlateDecode";
filter_abbreviations["/RL"] = "/RunLengthDecode";
filter_abbreviations["/CCF"] = "/CCITTFaxDecode";
filter_abbreviations["/DCT"] = "/DCTDecode";
}
// Check filters
QPDFObjectHandle filter_obj = this->stream_dict.getKey("/Filter");
bool filters_okay = true;
if (filter_obj.isNull())
{
// No filters
}
else if (filter_obj.isName())
{
// One filter
filters.push_back(filter_obj.getName());
}
else if (filter_obj.isArray())
{
// Potentially multiple filters
int n = filter_obj.getArrayNItems();
for (int i = 0; i < n; ++i)
{
QPDFObjectHandle item = filter_obj.getArrayItem(i);
if (item.isName())
{
filters.push_back(item.getName());
}
else
{
filters_okay = false;
}
}
}
else
{
filters_okay = false;
}
if (! filters_okay)
{
QTC::TC("qpdf", "QPDF_Stream invalid filter");
warn(QPDFExc(qpdf_e_damaged_pdf, qpdf->getFilename(),
"", this->offset,
"stream filter type is not name or array"));
return false;
}
bool filterable = true;
for (std::vector<std::string>::iterator iter = filters.begin();
iter != filters.end(); ++iter)
{
std::string& filter = *iter;
if (filter_abbreviations.count(filter))
{
QTC::TC("qpdf", "QPDF_Stream expand filter abbreviation");
filter = filter_abbreviations[filter];
}
if (! ((filter == "/Crypt") ||
(filter == "/FlateDecode") ||
(filter == "/LZWDecode") ||
(filter == "/ASCII85Decode") ||
(filter == "/ASCIIHexDecode")))
{
filterable = false;
}
}
if (! filterable)
{
return false;
}
// `filters' now contains a list of filters to be applied in
// order. See which ones we can support.
// Initialize values to their defaults as per the PDF spec
predictor = 1;
columns = 0;
early_code_change = true;
// See if we can support any decode parameters that are specified.
QPDFObjectHandle decode_obj = this->stream_dict.getKey("/DecodeParms");
std::vector<QPDFObjectHandle> decode_parms;
if (decode_obj.isArray())
{
for (int i = 0; i < decode_obj.getArrayNItems(); ++i)
{
decode_parms.push_back(decode_obj.getArrayItem(i));
}
}
else
{
for (unsigned int i = 0; i < filters.size(); ++i)
{
decode_parms.push_back(decode_obj);
}
}
// Ignore /DecodeParms entirely if /Filters is empty. At least
// one case of a file whose /DecodeParms was [ << >> ] when
// /Filters was empty has been seen in the wild.
if ((filters.size() != 0) && (decode_parms.size() != filters.size()))
{
warn(QPDFExc(qpdf_e_damaged_pdf, qpdf->getFilename(),
"", this->offset,
"stream /DecodeParms length is"
" inconsistent with filters"));
filterable = false;
}
if (! filterable)
{
return false;
}
for (unsigned int i = 0; i < filters.size(); ++i)
{
QPDFObjectHandle decode_item = decode_parms.at(i);
if (decode_item.isNull())
{
// okay
}
else if (decode_item.isDictionary())
{
if (! understandDecodeParams(
filters.at(i), decode_item,
predictor, columns, early_code_change))
{
filterable = false;
}
}
else
{
filterable = false;
}
}
if ((predictor > 1) && (columns == 0))
{
// invalid
filterable = false;
}
if (! filterable)
{
return false;
}
return filterable;
}
bool
QPDF_Stream::pipeStreamData(Pipeline* pipeline, bool filter,
bool normalize, bool compress,
bool suppress_warnings)
{
std::vector<std::string> filters;
int predictor = 1;
int columns = 0;
bool early_code_change = true;
if (filter)
{
filter = filterable(filters, predictor, columns, early_code_change);
}
if (pipeline == 0)
{
QTC::TC("qpdf", "QPDF_Stream pipeStreamData with null pipeline");
return filter;
}
// Construct the pipeline in reverse order. Force pipelines we
// create to be deleted when this function finishes.
std::vector<PointerHolder<Pipeline> > to_delete;
if (filter)
{
if (compress)
{
pipeline = new Pl_Flate("compress object stream", pipeline,
Pl_Flate::a_deflate);
to_delete.push_back(pipeline);
}
if (normalize)
{
pipeline = new Pl_QPDFTokenizer("normalizer", pipeline);
to_delete.push_back(pipeline);
}
for (std::vector<std::string>::reverse_iterator iter = filters.rbegin();
iter != filters.rend(); ++iter)
{
std::string const& filter = *iter;
if (filter == "/Crypt")
{
// Ignore -- handled by pipeStreamData
}
else if (filter == "/FlateDecode")
{
if (predictor == 12)
{
QTC::TC("qpdf", "QPDF_Stream PNG filter");
pipeline = new Pl_PNGFilter(
"png decode", pipeline, Pl_PNGFilter::a_decode,
columns, 0 /* not used */);
to_delete.push_back(pipeline);
}
pipeline = new Pl_Flate("stream inflate",
pipeline, Pl_Flate::a_inflate);
to_delete.push_back(pipeline);
}
else if (filter == "/ASCII85Decode")
{
pipeline = new Pl_ASCII85Decoder("ascii85 decode", pipeline);
to_delete.push_back(pipeline);
}
else if (filter == "/ASCIIHexDecode")
{
pipeline = new Pl_ASCIIHexDecoder("asciiHex decode", pipeline);
to_delete.push_back(pipeline);
}
else if (filter == "/LZWDecode")
{
pipeline = new Pl_LZWDecoder("lzw decode", pipeline,
early_code_change);
to_delete.push_back(pipeline);
}
else
{
throw std::logic_error(
"INTERNAL ERROR: QPDFStream: unknown filter "
"encountered after check");
}
}
}
if (this->stream_data.getPointer())
{
QTC::TC("qpdf", "QPDF_Stream pipe replaced stream data");
pipeline->write(this->stream_data->getBuffer(),
this->stream_data->getSize());
pipeline->finish();
}
else if (this->stream_provider.getPointer())
{
Pl_Count count("stream provider count", pipeline);
this->stream_provider->provideStreamData(
this->objid, this->generation, &count);
qpdf_offset_t actual_length = count.getCount();
qpdf_offset_t desired_length = 0;
if (this->stream_dict.hasKey("/Length"))
{
desired_length = this->stream_dict.getKey("/Length").getIntValue();
if (actual_length == desired_length)
{
QTC::TC("qpdf", "QPDF_Stream pipe use stream provider");
}
else
{
QTC::TC("qpdf", "QPDF_Stream provider length mismatch");
// This would be caused by programmer error on the
// part of a library user, not by invalid input data.
throw std::runtime_error(
"stream data provider for " +
QUtil::int_to_string(this->objid) + " " +
QUtil::int_to_string(this->generation) +
" provided " +
QUtil::int_to_string(actual_length) +
" bytes instead of expected " +
QUtil::int_to_string(desired_length) + " bytes");
}
}
else
{
QTC::TC("qpdf", "QPDF_Stream provider length not provided");
this->stream_dict.replaceKey(
"/Length", QPDFObjectHandle::newInteger(actual_length));
}
}
else if (this->offset == 0)
{
QTC::TC("qpdf", "QPDF_Stream pipe no stream data");
throw std::logic_error(
"pipeStreamData called for stream with no data");
}
else
{
QTC::TC("qpdf", "QPDF_Stream pipe original stream data");
if (! QPDF::Pipe::pipeStreamData(this->qpdf, this->objid, this->generation,
this->offset, this->length,
this->stream_dict, pipeline,
suppress_warnings))
{
filter = false;
}
}
return filter;
}
void
QPDF_Stream::replaceStreamData(PointerHolder<Buffer> data,
QPDFObjectHandle const& filter,
QPDFObjectHandle const& decode_parms)
{
this->stream_data = data;
this->stream_provider = 0;
replaceFilterData(filter, decode_parms, data->getSize());
}
void
QPDF_Stream::replaceStreamData(
PointerHolder<QPDFObjectHandle::StreamDataProvider> provider,
QPDFObjectHandle const& filter,
QPDFObjectHandle const& decode_parms)
{
this->stream_provider = provider;
this->stream_data = 0;
replaceFilterData(filter, decode_parms, 0);
}
void
QPDF_Stream::replaceFilterData(QPDFObjectHandle const& filter,
QPDFObjectHandle const& decode_parms,
size_t length)
{
this->stream_dict.replaceOrRemoveKey("/Filter", filter);
this->stream_dict.replaceOrRemoveKey("/DecodeParms", decode_parms);
if (length == 0)
{
QTC::TC("qpdf", "QPDF_Stream unknown stream length");
this->stream_dict.removeKey("/Length");
}
else
{
this->stream_dict.replaceKey(
"/Length", QPDFObjectHandle::newInteger(length));
}
}
void
QPDF_Stream::replaceDict(QPDFObjectHandle new_dict)
{
this->stream_dict = new_dict;
QPDFObjectHandle length_obj = new_dict.getKey("/Length");
if (length_obj.isInteger())
{
this->length = length_obj.getIntValue();
}
else
{
this->length = 0;
}
}
void
QPDF_Stream::warn(QPDFExc const& e)
{
QPDF::Warner::warn(this->qpdf, e);
}
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