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Bound out-of-range Object/Enum index lookups in BinaryAnnotator #9212

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Bound out-of-range Object/Enum index lookups in BinaryAnnotator #9212

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47 changes: 38 additions & 9 deletions src/binary_annotator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -753,8 +753,16 @@ void BinaryAnnotator::BuildTable(const uint64_t table_offset,

switch (field->type()->base_type()) {
case reflection::BaseType::Obj: {
const reflection::Object* next_object =
schema_->objects()->Get(field->type()->index());
const reflection::Object* next_object = GetObject(field);
if (next_object == nullptr) {
// Field references a non-existent Object in the schema. Treat as a
// generic offset field annotation.
offset_field_comment.default_value = "(unknown)";
regions.push_back(MakeBinaryRegion(field_offset, length, region_type,
0, offset_of_next_item,
offset_field_comment));
break;
}

if (next_object->is_struct()) {
// Structs are stored inline.
Expand Down Expand Up @@ -911,9 +919,14 @@ uint64_t BinaryAnnotator::BuildStruct(const uint64_t struct_offset,
offset += type_size;
} else if (field->type()->base_type() == reflection::BaseType::Obj) {
// Structs are stored inline, even when nested.
const reflection::Object* nested = GetObject(field);
if (nested == nullptr) {
// OOB Object index; skip further traversal.
return;
}
offset = BuildStruct(offset, regions,
referring_field_name + "." + field->name()->str(),
schema_->objects()->Get(field->type()->index()));
nested);
} else if (field->type()->base_type() == reflection::BaseType::Array) {
const bool is_scalar = IsScalar(field->type()->element());
const uint64_t type_size = GetTypeSize(field->type()->element());
Expand Down Expand Up @@ -961,10 +974,15 @@ uint64_t BinaryAnnotator::BuildStruct(const uint64_t struct_offset,
// TODO(dbaileychess): This works, but the comments on the fields lose
// some context. Need to figure a way how to plumb the nested arrays
// comments together that isn't too confusing.
const reflection::Object* nested = GetObject(field);
if (nested == nullptr) {
// OOB Object index; skip further traversal.
break;
}
offset =
BuildStruct(offset, regions,
referring_field_name + "." + field->name()->str(),
schema_->objects()->Get(field->type()->index()));
nested);
}
}
}
Expand Down Expand Up @@ -1131,8 +1149,11 @@ void BinaryAnnotator::BuildVector(

switch (field->type()->element()) {
case reflection::BaseType::Obj: {
const reflection::Object* object =
schema_->objects()->Get(field->type()->index());
const reflection::Object* object = GetObject(field);
if (object == nullptr) {
// OOB Object index; cannot annotate further.
return;
}

if (object->is_struct()) {
// Vector of structs
Expand Down Expand Up @@ -1408,8 +1429,11 @@ void BinaryAnnotator::BuildVector(
std::string BinaryAnnotator::BuildUnion(const uint64_t union_offset,
const uint8_t realized_type,
const reflection::Field* const field) {
const reflection::Enum* next_enum =
schema_->enums()->Get(field->type()->index());
const reflection::Enum* next_enum = GetEnum(field);
if (next_enum == nullptr) {
// OOB Enum index; cannot annotate further.
return "";
}

const reflection::EnumVal* enum_val = next_enum->values()->Get(realized_type);

Expand All @@ -1420,8 +1444,13 @@ std::string BinaryAnnotator::BuildUnion(const uint64_t union_offset,
const reflection::Type* union_type = enum_val->union_type();

if (union_type->base_type() == reflection::BaseType::Obj) {
const int32_t union_index = union_type->index();
if (union_index < 0 ||
static_cast<uint32_t>(union_index) >= schema_->objects()->size()) {
return enum_val->name()->c_str();
}
const reflection::Object* object =
schema_->objects()->Get(union_type->index());
schema_->objects()->Get(static_cast<uint32_t>(union_index));

if (object->is_struct()) {
// Union of vectors point to a new Binary section
Expand Down
30 changes: 28 additions & 2 deletions src/binary_annotator.h
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Original file line number Diff line number Diff line change
Expand Up @@ -391,7 +391,9 @@ class BinaryAnnotator {

bool IsInlineField(const reflection::Field* const field) {
if (field->type()->base_type() == reflection::BaseType::Obj) {
return schema_->objects()->Get(field->type()->index())->is_struct();
const reflection::Object* object = GetObject(field);
if (object == nullptr) return false;
return object->is_struct();
}
return IsScalar(field->type()->base_type());
}
Expand Down Expand Up @@ -426,14 +428,38 @@ class BinaryAnnotator {
return value < enum_def->values()->size();
}

// Returns the Object referenced by `field`, or nullptr if the index is out of
// bounds. The .bfbs file is user-controlled; without this check the
// BinaryAnnotator dereferences out-of-bounds memory.
const reflection::Object* GetObject(const reflection::Field* const field) {
const int32_t index = field->type()->index();
if (index < 0 ||
static_cast<uint32_t>(index) >= schema_->objects()->size()) {
return nullptr;
}
return schema_->objects()->Get(static_cast<uint32_t>(index));
}

// Returns the Enum referenced by `field`, or nullptr if the index is out of
// bounds.
const reflection::Enum* GetEnum(const reflection::Field* const field) {
const int32_t index = field->type()->index();
if (index < 0 ||
static_cast<uint32_t>(index) >= schema_->enums()->size()) {
return nullptr;
}
return schema_->enums()->Get(static_cast<uint32_t>(index));
}

uint64_t GetElementSize(const reflection::Field* const field) {
if (IsScalar(field->type()->element())) {
return GetTypeSize(field->type()->element());
}

switch (field->type()->element()) {
case reflection::BaseType::Obj: {
auto obj = schema_->objects()->Get(field->type()->index());
const reflection::Object* obj = GetObject(field);
if (obj == nullptr) return sizeof(uint32_t);
return obj->is_struct() ? obj->bytesize() : sizeof(uint32_t);
}
default:
Expand Down