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Code Issues Releases Wiki Activity

Combine stacks in QPDFParser::parse

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Part of #729
This commit is contained in:
m-holger 2022-08-30 12:53:19 +01:00
parent 74162a2d48
commit 7402c02c80
1 changed files with 35 additions and 31 deletions
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66
libqpdf/QPDFParser.cc
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@ -7,6 +7,24 @@
#include <qpdf/QUtil.hh>
#include <qpdf/SparseOHArray.hh>
namespace
{
struct StackFrame
{
StackFrame(std::shared_ptr<InputSource> input) :
offset(input->tell()),
contents_string(""),
contents_offset(-1)
{
}
std::vector<QPDFObjectHandle> olist;
qpdf_offset_t offset;
std::string contents_string;
qpdf_offset_t contents_offset;
};
} // namespace
QPDFObjectHandle
QPDFParser::parse(bool& empty, bool content_stream)
{
@ -17,8 +35,6 @@ QPDFParser::parse(bool& empty, bool content_stream)
// this, it will cause a logic error to be thrown from
// QPDF::inParse().
using OHVector = std::vector<QPDFObjectHandle>;
QPDF::ParseGuard pg(context);
empty = false;
@ -26,28 +42,22 @@ QPDFParser::parse(bool& empty, bool content_stream)
QPDFObjectHandle object;
bool set_offset = false;
std::vector<OHVector> olist_stack;
olist_stack.push_back(OHVector());
std::vector<StackFrame> stack;
stack.push_back(StackFrame(input));
std::vector<parser_state_e> state_stack;
state_stack.push_back(st_top);
std::vector<qpdf_offset_t> offset_stack;
qpdf_offset_t offset = input->tell();
offset_stack.push_back(offset);
qpdf_offset_t offset;
bool done = false;
int bad_count = 0;
int good_count = 0;
bool b_contents = false;
std::vector<std::string> contents_string_stack;
contents_string_stack.push_back("");
std::vector<qpdf_offset_t> contents_offset_stack;
contents_offset_stack.push_back(-1);
while (!done) {
bool bad = false;
auto& olist = olist_stack.back();
auto& frame = stack.back();
auto& olist = frame.olist;
parser_state_e state = state_stack.back();
offset = offset_stack.back();
std::string& contents_string = contents_string_stack.back();
qpdf_offset_t& contents_offset = contents_offset_stack.back();
offset = frame.offset;
object = QPDFObjectHandle();
set_offset = false;
@ -108,23 +118,20 @@ QPDFParser::parse(bool& empty, bool content_stream)
case QPDFTokenizer::tt_array_open:
case QPDFTokenizer::tt_dict_open:
if (olist_stack.size() > 500) {
if (stack.size() > 500) {
QTC::TC("qpdf", "QPDFParser too deep");
warn("ignoring excessively deeply nested data structure");
bad = true;
object = QPDFObjectHandle::newNull();
state = st_top;
} else {
olist_stack.push_back(OHVector());
state = st_start;
offset_stack.push_back(input->tell());
state_stack.push_back(
(token.getType() == QPDFTokenizer::tt_array_open)
? st_array
: st_dictionary);
b_contents = false;
contents_string_stack.push_back("");
contents_offset_stack.push_back(-1);
stack.push_back(StackFrame(input));
}
break;
@ -206,8 +213,8 @@ QPDFParser::parse(bool& empty, bool content_stream)
std::string val = token.getValue();
if (decrypter) {
if (b_contents) {
contents_string = val;
contents_offset = input->getLastOffset();
frame.contents_string = val;
frame.contents_offset = input->getLastOffset();
b_contents = false;
}
decrypter->decryptString(val);
@ -279,7 +286,7 @@ QPDFParser::parse(bool& empty, bool content_stream)
break;
case st_stop:
if ((state_stack.size() < 2) || (olist_stack.size() < 2)) {
if ((state_stack.size() < 2) || (stack.size() < 2)) {
throw std::logic_error(
"QPDFObjectHandle::parseInternal: st_stop encountered"
" with insufficient elements in stack");
@ -354,13 +361,13 @@ QPDFParser::parse(bool& empty, bool content_stream)
}
dict[key] = val;
}
if (!contents_string.empty() && dict.count("/Type") &&
if (!frame.contents_string.empty() && dict.count("/Type") &&
dict["/Type"].isNameAndEquals("/Sig") &&
dict.count("/ByteRange") && dict.count("/Contents") &&
dict["/Contents"].isString()) {
dict["/Contents"] =
QPDFObjectHandle::newString(contents_string);
dict["/Contents"].setParsedOffset(contents_offset);
QPDFObjectHandle::newString(frame.contents_string);
dict["/Contents"].setParsedOffset(frame.contents_offset);
}
object = QPDFObjectHandle::newDictionary(dict);
setDescriptionFromInput(object, offset);
@ -372,15 +379,12 @@ QPDFParser::parse(bool& empty, bool content_stream)
object.setParsedOffset(offset - 2);
set_offset = true;
}
olist_stack.pop_back();
offset_stack.pop_back();
stack.pop_back();
if (state_stack.back() == st_top) {
done = true;
} else {
olist_stack.back().push_back(object);
stack.back().olist.push_back(object);
}
contents_string_stack.pop_back();
contents_offset_stack.pop_back();
}
}