fix: reject truncated native file paths

Makefile

@@ -24,6 +24,6 @@ endif
 build: $(STB_IMAGE_NIF_SO)
 	@ echo > /dev/null
 
-$(STB_IMAGE_NIF_SO):
+$(STB_IMAGE_NIF_SO): $(C_SRC)/stb_image_nif.c $(C_SRC)/nif_utils.h $(wildcard $(STB_INCLUDE_DIR)/*.h)
 	@ mkdir -p $(PRIV_DIR)
 	$(CC) $(CPPFLAGS) $(C_SRC)/stb_image_nif.c -o $(STB_IMAGE_NIF_SO)

Makefile.win

@@ -9,7 +9,7 @@ CPPFLAGS = /O2 /EHsc /I"$(ERTS_INCLUDE_DIR)" /I"$(STB_INCLUDE_DIR)"
 
 build: $(STB_IMAGE_NIF_SO)
 
-$(STB_IMAGE_NIF_SO):
+$(STB_IMAGE_NIF_SO): $(C_SRC)/stb_image_nif.c $(C_SRC)/nif_utils.h $(STB_INCLUDE_DIR)/stb_image.h $(STB_INCLUDE_DIR)/stb_image_write.h $(STB_INCLUDE_DIR)/stb_image_resize2.h
 	@ if not exist "$(PRIV_DIR)" mkdir "$(PRIV_DIR)"
 	$(CC) $(CPPFLAGS) /LD /MD /Fe$@ $(C_SRC)/stb_image_nif.c 
 

c_src/stb_image_nif.c

@@ -15,6 +15,7 @@
 #include <stb_image_resize2.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <stdint.h>
 
 #define MAX_EXTNAME_LENGTH 4
 
@@ -56,14 +57,16 @@ static ERL_NIF_TERM read_file(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[
 
     ERL_NIF_TERM ret;
 
-    if (!enif_inspect_binary(env, argv[0], &path)) {
+    if (!enif_inspect_binary(env, argv[0], &path) || path.size == SIZE_MAX ||
+        (path.size > 0 && memchr(path.data, '\0', path.size) != NULL)) {
         return error(env, "invalid path");
     }
     if(!enif_get_int(env, argv[1], &desired_channels)) {
         return error(env, "invalid channels");
     }
 
     c_path = enif_alloc(path.size + 1);
+    if (c_path == NULL) return error(env, "out of memory");
     memcpy(c_path, path.data, path.size);
     c_path[path.size] = '\0';
 
@@ -199,7 +202,8 @@ static ERL_NIF_TERM write_file(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv
     ErlNifBinary result;
     int w, h, comp;
 
-    if (!enif_inspect_binary(env, argv[0], &path)) {
+    if (!enif_inspect_binary(env, argv[0], &path) || path.size == SIZE_MAX ||
+        (path.size > 0 && memchr(path.data, '\0', path.size) != NULL)) {
         return error(env, "invalid path");
     }
     if (!enif_get_atom(env, argv[1], format, sizeof(format), ERL_NIF_LATIN1)) {
@@ -219,6 +223,7 @@ static ERL_NIF_TERM write_file(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv
     }
 
     c_path = enif_alloc(path.size + 1);
+    if (c_path == NULL) return error(env, "out of memory");
     memcpy(c_path, path.data, path.size);
     c_path[path.size] = '\0';
 

mix.exs

@@ -2,7 +2,7 @@ defmodule StbImage.MixProject do
   use Mix.Project
 
   @app :stb_image
-  @version "1.0.0"
+  @version "1.0.1-dev"
   @github_url "https://github.com/elixir-nx/stb_image"
 
   def project do
@@ -16,6 +16,7 @@ defmodule StbImage.MixProject do
       docs: docs(),
       package: package(),
       compilers: [:elixir_make] ++ Mix.compilers(),
+      make_force_build: Mix.env() == :test,
       make_precompiler: {:nif, CCPrecompiler},
       make_precompiler_url: "#{@github_url}/releases/download/v#{@version}/@{artefact_filename}",
       make_precompiler_filename: "stb_image_nif",

test/stb_image_path_validation_test.exs

@@ -0,0 +1,15 @@
+defmodule StbImagePathValidationTest do
+  use ExUnit.Case, async: true
+
+  alias StbImage.Nif
+
+  @tag :tmp_dir
+  test "paths containing null bytes are rejected without truncation", %{tmp_dir: tmp_dir} do
+    source = Path.join(__DIR__, "test.png")
+    destination = Path.join(tmp_dir, "image.png")
+
+    assert {:error, _} = Nif.read_file(source <> <<0>> <> "suffix", 0)
+    assert {:error, _} = Nif.write_file(destination <> <<0>> <> "suffix", :png, <<0>>, 1, 1, 1)
+    refute File.exists?(destination)
+  end
+end