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Fix heap OOB read in STL decoder from missing buffer bounds checks #1203

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Fix heap OOB read in STL decoder from missing buffer bounds checks #1203

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22 changes: 19 additions & 3 deletions src/draco/io/stl_decoder.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -37,13 +37,25 @@ StatusOr<std::unique_ptr<Mesh>> StlDecoder::DecodeFromFile(

StatusOr<std::unique_ptr<Mesh>> StlDecoder::DecodeFromBuffer(
DecoderBuffer *buffer) {
// Binary STL requires at least an 80-byte header + 4-byte face count.
if (buffer->remaining_size() < 84) {
return Status(Status::IO_ERROR, "STL file too small.");
}
if (!strncmp(buffer->data_head(), "solid ", 6)) {
return Status(Status::IO_ERROR,
"Currently only binary STL files are supported.");
}
buffer->Advance(80);
uint32_t face_count;
buffer->Decode(&face_count, 4);
if (!buffer->Decode(&face_count, 4)) {
return Status(Status::IO_ERROR, "Failed to read STL face count.");
}
// Each face is 50 bytes (12 floats = 48 bytes + 2-byte attribute).
constexpr int64_t kBytesPerFace = 50;
if (face_count >
static_cast<uint64_t>(buffer->remaining_size()) / kBytesPerFace) {
return Status(Status::IO_ERROR, "STL face count exceeds available data.");
}

TriangleSoupMeshBuilder builder;
builder.Start(face_count);
Expand All @@ -55,9 +67,13 @@ StatusOr<std::unique_ptr<Mesh>> StlDecoder::DecodeFromBuffer(

for (uint32_t i = 0; i < face_count; i++) {
float data[48];
buffer->Decode(data, 48);
if (!buffer->Decode(data, 48)) {
return Status(Status::IO_ERROR, "Failed to read STL face data.");
}
uint16_t unused;
buffer->Decode(&unused, 2);
if (!buffer->Decode(&unused, 2)) {
return Status(Status::IO_ERROR, "Failed to read STL face attribute.");
}

builder.SetPerFaceAttributeValueForFace(
norm_att_id, draco::FaceIndex(i),
Expand Down