fix(cron): lifecycle guard crashes with 'embedded null byte' instead of failing open — kills terminal tool (#78256)

cron/lifecycle_guard.py

@@ -260,6 +260,14 @@ def _read_referenced_script(path: Path) -> tuple[Optional[str], bool]:
         descriptor = os.open(path, flags)
     except OSError:
         return None, False
+    except ValueError:
+        # A path the OS cannot even represent — an embedded NUL byte from a
+        # token parsed out of scanned content (#78256). #76762 covered the
+        # NUL-in-*contents* case below and Path.resolve, but ``os.open``
+        # itself raises ValueError (not OSError) for NUL-in-*path*, which
+        # crashed the whole guard instead of failing open. Same semantics as
+        # an unreadable file: nothing to scan.
+        return None, False
     try:
         metadata = os.fstat(descriptor)
         if not stat.S_ISREG(metadata.st_mode):
@@ -268,7 +276,7 @@ def _read_referenced_script(path: Path) -> tuple[Optional[str], bool]:
         # chunk tells us if this is a binary (NUL bytes) that should be
         # skipped as "nothing to scan" rather than failing closed (#76762).
         data = os.read(descriptor, _MAX_REFERENCED_SCRIPT_BYTES + 1)
-    except OSError:
+    except (OSError, ValueError):
         return None, False
     finally:
         os.close(descriptor)

tests/hermes_cli/test_gateway_restart_loop.py

@@ -857,3 +857,43 @@ def test_cron_nested_wrapper_script_is_scanned(self, tmp_path, capsys, monkeypat
         assert rc == 1
         out = capsys.readouterr().out
         assert "Blocked" in out
+
+
+class TestNulByteReferencedPathFailsOpen:
+    """#78256: a referenced-script path carrying an embedded NUL byte must be
+    skipped ("nothing to scan"), not crash the guard. #76762 established the
+    fail-open contract for NUL bytes in scanned *contents* and Path.resolve,
+    but ``os.open()`` raises ValueError (not OSError) for NUL in the *path*
+    itself — which escaped the OSError-only handler and took down the whole
+    terminal tool for commands like ``python -m pip --version`` whose
+    recursive scan produced such a token."""
+
+    def test_read_referenced_script_nul_path_fails_open(self):
+        from pathlib import Path
+        from cron.lifecycle_guard import _read_referenced_script
+
+        text, unsafe = _read_referenced_script(Path("x\x00y"))
+        assert text is None
+        assert unsafe is False
+
+    def test_guard_survives_nul_byte_in_referenced_script_path(self):
+        from cron.lifecycle_guard import (
+            contains_gateway_lifecycle_command_or_referenced_script,
+        )
+
+        # A sourced path with an embedded NUL: previously ValueError from
+        # os.open crashed the guard (and the terminal tool call around it).
+        assert contains_gateway_lifecycle_command_or_referenced_script(
+            "source /tmp/e\x00vil.sh"
+        ) is False
+
+    def test_guard_still_blocks_real_lifecycle_script(self, tmp_path):
+        from cron.lifecycle_guard import (
+            contains_gateway_lifecycle_command_or_referenced_script,
+        )
+
+        script = tmp_path / "restart.sh"
+        script.write_text("#!/bin/sh\nhermes gateway restart\n")
+        assert contains_gateway_lifecycle_command_or_referenced_script(
+            f"bash {script}"
+        ) is True