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Fix Stack Overflow DoS via Unbounded Recursion in idl_gen_text.cpp #9037

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Fix Stack Overflow DoS via Unbounded Recursion in idl_gen_text.cpp #9037

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13 changes: 12 additions & 1 deletion src/idl_gen_text.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -178,8 +178,16 @@ struct JsonPrinter {
return PrintContainer<Container>(tag(), arr, size, type, indent, nullptr);
}

struct DepthGuard {
int *depth_;
DepthGuard(int *depth) : depth_(depth) { --(*depth_); }
~DepthGuard() { ++(*depth_); }
};

const char* PrintOffset(const void* val, const Type& type, int indent,
const uint8_t* prev_val, soffset_t vector_index) {
if (depth_limit == 0) return "error: text generation depth limit exceeded";
DepthGuard depth_guard(&depth_limit);
switch (type.base_type) {
case BASE_TYPE_UNION: {
// If this assert hits, you have an corrupt buffer, a union type field
Expand Down Expand Up @@ -314,6 +322,8 @@ struct JsonPrinter {
// and bracketed by "{}"
const char* GenStruct(const StructDef& struct_def, const Table* table,
int indent) {
if (depth_limit == 0) return "error: text generation depth limit exceeded";
DepthGuard depth_guard(&depth_limit);
text += '{';
int fieldout = 0;
const uint8_t* prev_val = nullptr;
Expand Down Expand Up @@ -372,12 +382,13 @@ struct JsonPrinter {
}

JsonPrinter(const Parser& parser, std::string& dest)
: opts(parser.opts), text(dest) {
: opts(parser.opts), text(dest), depth_limit(FLATBUFFERS_MAX_PARSING_DEPTH) {
text.reserve(1024); // Reduce amount of inevitable reallocs.
}

const IDLOptions& opts;
std::string& text;
int depth_limit;
};

static const char* GenerateTextImpl(const Parser& parser, const Table* table,
Expand Down