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Add new private method QPDF::processXRefIndex

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This commit is contained in:
m-holger 2024-05-21 20:26:36 +01:00
parent 7aa5027bf8
commit 0186d60dcf
2 changed files with 51 additions and 36 deletions
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4
include/qpdf/QPDF.hh
View File

@ -1028,6 +1028,10 @@ class QPDF
qpdf_offset_t read_xrefTable(qpdf_offset_t offset);
qpdf_offset_t read_xrefStream(qpdf_offset_t offset);
qpdf_offset_t processXRefStream(qpdf_offset_t offset, QPDFObjectHandle& xref_stream);
std::pair<size_t, std::vector<long long>> processXRefIndex(
QPDFObjectHandle& dict,
size_t entry_size,
std::function<QPDFExc(std::string_view)> damaged);
void insertXrefEntry(int obj, int f0, qpdf_offset_t f1, int f2);
void insertFreeXrefEntry(QPDFObjGen);
void insertReconstructedXrefEntry(int obj, qpdf_offset_t f1, int f2);

83
libqpdf/QPDF.cc
View File

@ -968,38 +968,19 @@ QPDF::read_xrefStream(qpdf_offset_t xref_offset)
return 0; // unreachable
}
qpdf_offset_t
QPDF::processXRefStream(qpdf_offset_t xref_offset, QPDFObjectHandle& xref_obj)
// Return the expected size of the xref stream and the processed Index array.
std::pair<size_t, std::vector<long long>>
QPDF::processXRefIndex(
QPDFObjectHandle& dict, size_t entry_size, std::function<QPDFExc(std::string_view)> damaged)
{
auto damaged = [this, xref_offset](std::string_view msg) -> QPDFExc {
return damagedPDF("xref stream", xref_offset, msg.data());
};
auto max_num_entries = static_cast<unsigned long long>(-1) / entry_size;
auto dict = xref_obj.getDict();
auto W_obj = dict.getKey("/W");
auto Size_obj = dict.getKey("/Size");
auto Index_obj = dict.getKey("/Index");
if (!(W_obj.isArray() && (W_obj.getArrayNItems() >= 3) && W_obj.getArrayItem(0).isInteger() &&
W_obj.getArrayItem(1).isInteger() && W_obj.getArrayItem(2).isInteger() &&
dict.getKey("/Size").isInteger() && (Index_obj.isArray() || Index_obj.isNull()))) {
throw damaged("Cross-reference stream does not have proper /W and /Index keys");
if (!(Index_obj.isArray() || Index_obj.isNull())) {
throw damaged("Cross-reference stream does not have a proper /Index key");
}
int W[3];
size_t entry_size = 0;
int max_bytes = sizeof(qpdf_offset_t);
for (int i = 0; i < 3; ++i) {
W[i] = W_obj.getArrayItem(i).getIntValueAsInt();
if (W[i] > max_bytes) {
throw damaged("Cross-reference stream's /W contains impossibly large values");
}
entry_size += toS(W[i]);
}
if (entry_size == 0) {
throw damaged("Cross-reference stream's /W indicates entry size of 0");
}
unsigned long long max_num_entries = static_cast<unsigned long long>(-1) / entry_size;
// Process /Index entry
std::vector<long long> indx;
if (Index_obj.isArray()) {
int n_index = Index_obj.getArrayNItems();
@ -1017,9 +998,9 @@ QPDF::processXRefStream(qpdf_offset_t xref_offset, QPDFObjectHandle& xref_obj)
}
QTC::TC("qpdf", "QPDF xref /Index is array", n_index == 2 ? 0 : 1);
} else {
// We have already validayed the /Index key.
// We have already validated the /Index key.
QTC::TC("qpdf", "QPDF xref /Index is null");
long long size = dict.getKey("/Size").getIntValue();
long long size = Size_obj.getIntValue();
indx.push_back(0);
indx.push_back(size);
}
@ -1039,20 +1020,50 @@ QPDF::processXRefStream(qpdf_offset_t xref_offset, QPDFObjectHandle& xref_obj)
}
num_entries += toS(indx.at(i));
}
// entry_size and num_entries have both been validated to ensure that this multiplication does
// not cause an overflow.
size_t expected_size = entry_size * num_entries;
return {entry_size * num_entries, indx};
}
qpdf_offset_t
QPDF::processXRefStream(qpdf_offset_t xref_offset, QPDFObjectHandle& xref_obj)
{
auto damaged = [this, xref_offset](std::string_view msg) -> QPDFExc {
return damagedPDF("xref stream", xref_offset, msg.data());
};
auto dict = xref_obj.getDict();
auto W_obj = dict.getKey("/W");
auto Size_obj = dict.getKey("/Size");
if (!(W_obj.isArray() && (W_obj.getArrayNItems() >= 3) && W_obj.getArrayItem(0).isInteger() &&
W_obj.getArrayItem(1).isInteger() && W_obj.getArrayItem(2).isInteger() &&
Size_obj.isInteger())) {
throw damaged("Cross-reference stream does not have a proper /W key");
}
int W[3];
size_t entry_size = 0;
int max_bytes = sizeof(qpdf_offset_t);
for (int i = 0; i < 3; ++i) {
W[i] = W_obj.getArrayItem(i).getIntValueAsInt();
if (W[i] > max_bytes) {
throw damaged("Cross-reference stream's /W contains impossibly large values");
}
entry_size += toS(W[i]);
}
if (entry_size == 0) {
throw damaged("Cross-reference stream's /W indicates entry size of 0");
}
auto [expected_size, indx] = processXRefIndex(dict, entry_size, damaged);
std::shared_ptr<Buffer> bp = xref_obj.getStreamData(qpdf_dl_specialized);
size_t actual_size = bp->getSize();
if (expected_size != actual_size) {
QPDFExc x = damagedPDF(
"xref stream",
xref_offset,
("Cross-reference stream data has the wrong size; expected = " +
std::to_string(expected_size) + "; actual = " + std::to_string(actual_size)));
QPDFExc x = damaged(
"Cross-reference stream data has the wrong size; expected = " +
std::to_string(expected_size) + "; actual = " + std::to_string(actual_size));
if (expected_size > actual_size) {
throw x;
} else {