fix: reject traversal in audio separator paths

services/analysis-engine/src/bandscope_analysis/separation/audio_separator.py

@@ -41,6 +41,16 @@ def _read_model_profile_bytes(profile_path: Path) -> bytes:
     return profile_bytes
 
 
+def _contains_parent_path_segment(path: Path) -> bool:
+    """Return True when a raw path contains a parent traversal segment."""
+    path_text = str(path)
+    normalized_path_text = path_text
+    for separator in {os.sep, os.altsep, "\\"}:
+        if separator and separator != "/":
+            normalized_path_text = normalized_path_text.replace(separator, "/")
+    return any(part == ".." for part in normalized_path_text.split("/"))
+
+
 @dataclass(frozen=True)
 class AudioSeparationConfig:
     """Resource and band-split settings for local stem separation."""
@@ -133,6 +143,8 @@ def separate(self, audio_path: str | Path) -> AudioSeparationResult:
     def _resolve_audio_file(self, audio_path: str | Path) -> Path:
         """Normalize and validate the selected source path."""
         candidate = Path(audio_path).expanduser()
+        if _contains_parent_path_segment(candidate):
+            raise ValueError("Path traversal attempt detected in selected audio path")
         try:
             path = candidate.resolve(strict=True)
         except FileNotFoundError as error:
@@ -216,6 +228,8 @@ def _load_model_profile(self) -> dict[str, float]:
 
         if self.config.model_profile_path:
             profile_candidate = Path(self.config.model_profile_path).expanduser()
+            if _contains_parent_path_segment(profile_candidate):
+                raise ValueError("Path traversal attempt detected in selected model profile path")
             try:
                 profile_path = profile_candidate.resolve(strict=True)
             except FileNotFoundError as error:

services/analysis-engine/tests/test_separation.py

@@ -215,6 +215,36 @@ def test_audio_stem_separator_rejects_missing_audio_file(tmp_path) -> None:
         separator.separate(tmp_path / "missing.wav")
 
 
+def test_audio_stem_separator_rejects_parent_traversal_in_audio_file(tmp_path) -> None:
+    """Ensure parent path segments are rejected before source path resolution."""
+    separator = AudioStemSeparator(AudioSeparationConfig(target_sample_rate=8_000))
+
+    with pytest.raises(ValueError, match="Path traversal attempt detected"):
+        separator.separate(tmp_path / "nested" / ".." / "rehearsal.wav")
+
+
+def test_audio_stem_separator_rejects_altsep_parent_traversal_in_audio_file() -> None:
+    """Ensure backslash traversal is rejected on non-Windows hosts."""
+    separator = AudioStemSeparator(AudioSeparationConfig(target_sample_rate=8_000))
+
+    with pytest.raises(ValueError, match="Path traversal attempt detected"):
+        separator.separate("safe\\..\\rehearsal.wav")
+
+
+@pytest.mark.parametrize(
+    "audio_path",
+    ["safe/..\\rehearsal.wav", "safe\\../rehearsal.wav"],
+)
+def test_audio_stem_separator_rejects_mixed_separator_parent_traversal(
+    audio_path: str,
+) -> None:
+    """Ensure mixed-separator traversal is rejected before path resolution."""
+    separator = AudioStemSeparator(AudioSeparationConfig(target_sample_rate=8_000))
+
+    with pytest.raises(ValueError, match="Path traversal attempt detected"):
+        separator.separate(audio_path)
+
+
 def test_audio_stem_separator_rejects_directory_source(tmp_path) -> None:
     """Ensure directories are not accepted as audio files."""
     source_dir = tmp_path / "source-dir"
@@ -277,6 +307,15 @@ def fail_decode(*args, **kwargs):
     assert str(tmp_path) not in str(error.value)
 
 
+def test_audio_stem_separator_fit_length_zero() -> None:
+    """Ensure zero-length targets stay bounded and return an empty stem."""
+    separator = AudioStemSeparator(AudioSeparationConfig(target_sample_rate=8_000))
+
+    fitted = separator._fit_length(np.ones(4, dtype=np.float32), 0)
+
+    assert fitted.shape == (0,)
+
+
 def test_audio_stem_separator_uses_verified_local_model_profile(tmp_path) -> None:
     """Ensure local model profile overrides are applied only when checksum is verified."""
     profile_path = tmp_path / "profile.json"
@@ -403,6 +442,48 @@ def test_audio_stem_separator_rejects_missing_local_model_profile(tmp_path) -> N
         )
 
 
+def test_audio_stem_separator_rejects_parent_traversal_in_model_profile(tmp_path) -> None:
+    """Ensure parent path segments are rejected before profile path resolution."""
+    with pytest.raises(ValueError, match="Path traversal attempt detected"):
+        AudioStemSeparator(
+            AudioSeparationConfig(
+                target_sample_rate=8_000,
+                model_profile_path=str(tmp_path / "profiles" / ".." / "profile.json"),
+                model_profile_sha256="0" * 64,
+            )
+        )
+
+
+def test_audio_stem_separator_rejects_altsep_parent_traversal_in_model_profile() -> None:
+    """Ensure backslash traversal in profile paths is rejected on non-Windows hosts."""
+    with pytest.raises(ValueError, match="Path traversal attempt detected"):
+        AudioStemSeparator(
+            AudioSeparationConfig(
+                target_sample_rate=8_000,
+                model_profile_path="profiles\\..\\profile.json",
+                model_profile_sha256="0" * 64,
+            )
+        )
+
+
+@pytest.mark.parametrize(
+    "model_profile_path",
+    ["profiles/..\\profile.json", "profiles\\../profile.json"],
+)
+def test_audio_stem_separator_rejects_mixed_separator_parent_traversal_in_model_profile(
+    model_profile_path: str,
+) -> None:
+    """Ensure mixed-separator traversal is rejected in model profile paths."""
+    with pytest.raises(ValueError, match="Path traversal attempt detected"):
+        AudioStemSeparator(
+            AudioSeparationConfig(
+                target_sample_rate=8_000,
+                model_profile_path=model_profile_path,
+                model_profile_sha256="0" * 64,
+            )
+        )
+
+
 def test_audio_stem_separator_rejects_non_numeric_band_profile(tmp_path) -> None:
     """Ensure profile numeric coercion failures use bounded verification errors."""
     profile_path = tmp_path / "profile.json"