fix: confine event hook scripts to the project tree

Event dispatch joined the first scripts: token onto the .specify or
extension base with Path. An absolute token discarded the base and ran
a host binary. Reject anchored tokens and require the resolved path to
stay inside the project root.

Assisted-by: Grok (model: grok-4.6, supervised)
Signed-off-by: Sebastien Tardif <sebtardif@ncf.ca>

Author: SebTardif

src/specify_cli/events.py

@@ -17,7 +17,7 @@
 import sys
 import subprocess
 import platform
-from pathlib import Path
+from pathlib import Path, PurePosixPath, PureWindowsPath
 from typing import TYPE_CHECKING, Any
 
 import yaml
@@ -83,7 +83,22 @@
 import shutil
 import subprocess
 import sys
-from pathlib import Path
+from pathlib import Path, PurePosixPath, PureWindowsPath
+
+
+def _script_under_base(base, token, project_root):
+    """Return token resolved under base, or None if it leaves the project."""
+    posix_path = PurePosixPath(token)
+    win_path = PureWindowsPath(token)
+    if posix_path.anchor or win_path.anchor:
+        return None
+    try:
+        root = project_root.resolve()
+        candidate = (base / token).resolve()
+        candidate.relative_to(root)
+    except (OSError, ValueError):
+        return None
+    return candidate
 
 
 def _find_command_template(command_name, project_root):
@@ -228,8 +243,8 @@ def _resolve_argv(template_path, project_root, ext_id):
         return None
     if not tokens:
         return None
-    script_abs = base / tokens[0]
-    if not script_abs.exists():
+    script_abs = _script_under_base(base, tokens[0], project_root)
+    if script_abs is None or not script_abs.exists():
         return None
     rest = tokens[1:]
 
@@ -541,6 +556,30 @@ def _find_command_template(command_name: str, project_root: Path) -> tuple[Path
     return None, None
 
 
+def _confine_event_script_path(
+    project_root: Path, base: Path, token: str
+) -> Path | None:
+    """Resolve *token* under *base*, or None if it leaves the project.
+
+    Rejects anchored tokens (absolute, drive, UNC) so ``Path`` cannot
+    discard *base*. ``..`` is allowed when the resolved path stays inside
+    *project_root*, which is how extension templates reach core scripts
+    via ``../../scripts/...``. Keep the generated ``_script_under_base``
+    in sync.
+    """
+    posix_path = PurePosixPath(token)
+    win_path = PureWindowsPath(token)
+    if posix_path.anchor or win_path.anchor:
+        return None
+    try:
+        root = project_root.resolve()
+        candidate = (base / token).resolve()
+        candidate.relative_to(root)
+    except (OSError, ValueError):
+        return None
+    return candidate
+
+
 def _resolve_event_command_argv(
     template_path: Path, project_root: Path, ext_id: str | None
 ) -> list[str] | None:
@@ -609,8 +648,8 @@ def _resolve_event_command_argv(
         return None
     if not tokens:
         return None
-    script_abs = base / tokens[0]
-    if not script_abs.exists():
+    script_abs = _confine_event_script_path(project_root, base, tokens[0])
+    if script_abs is None or not script_abs.exists():
         return None
     rest_args = tokens[1:]
 

tests/integrations/test_events.py

@@ -1522,6 +1522,173 @@ def test_sh_variant_uses_launcher_on_windows(self, tmp_path):
         else:
             assert PurePath(argv[0]).as_posix().endswith(".specify/scripts/bash/boot.sh")
 
+    def test_absolute_script_token_returns_none(self, tmp_path):
+        """An absolute first ``scripts:`` token must not run a host binary."""
+        from specify_cli.events import _resolve_event_command_argv
+
+        outside = tmp_path.parent / "outside-event-script.sh"
+        outside.write_text("#!/bin/sh\nexit 0\n", encoding="utf-8")
+        cmd_dir = tmp_path / ".specify" / "templates" / "commands"
+        cmd_dir.mkdir(parents=True)
+        (cmd_dir / "boot.md").write_text(
+            "---\n"
+            "description: \"Boot\"\n"
+            f"scripts:\n  sh: {outside.as_posix()}\n"
+            "---\nBody\n",
+            encoding="utf-8",
+        )
+
+        argv = _resolve_event_command_argv(cmd_dir / "boot.md", tmp_path, None)
+
+        assert argv is None
+
+    def test_dotdot_script_token_outside_project_returns_none(self, tmp_path):
+        """A ``..`` walk out of the project root must not resolve."""
+        from specify_cli.events import _resolve_event_command_argv
+
+        outside = tmp_path.parent / "outside-event-script.sh"
+        outside.write_text("#!/bin/sh\nexit 0\n", encoding="utf-8")
+        cmd_dir = tmp_path / ".specify" / "templates" / "commands"
+        cmd_dir.mkdir(parents=True)
+        (cmd_dir / "boot.md").write_text(
+            "---\n"
+            "description: \"Boot\"\n"
+            "scripts:\n  sh: ../../outside-event-script.sh\n"
+            "---\nBody\n",
+            encoding="utf-8",
+        )
+
+        argv = _resolve_event_command_argv(cmd_dir / "boot.md", tmp_path, None)
+
+        assert argv is None
+
+    def test_extension_dotdot_to_core_scripts_resolves(self, tmp_path):
+        """Extension templates may reach core scripts via ``../../scripts/...``."""
+        from specify_cli.events import _resolve_event_command_argv
+
+        ext_id = "my-ext"
+        cmd_dir = tmp_path / ".specify" / "extensions" / ext_id / "commands"
+        cmd_dir.mkdir(parents=True)
+        (cmd_dir / "boot.md").write_text(
+            "---\n"
+            "description: \"Boot\"\n"
+            "scripts:\n  sh: ../../scripts/bash/helper.sh\n"
+            "---\nBody\n",
+            encoding="utf-8",
+        )
+        helper_dir = tmp_path / ".specify" / "scripts" / "bash"
+        helper_dir.mkdir(parents=True)
+        (helper_dir / "helper.sh").write_text("#!/bin/sh\nexit 0\n", encoding="utf-8")
+
+        argv = _resolve_event_command_argv(cmd_dir / "boot.md", tmp_path, ext_id)
+
+        assert argv is not None
+        script_arg = argv[1] if platform.system().lower().startswith("win") else argv[0]
+        assert PurePath(script_arg).as_posix().endswith(".specify/scripts/bash/helper.sh")
+
+    def test_symlink_escape_returns_none(self, tmp_path):
+        """A relative token that resolves through a symlink out of the project
+        must not run the host target."""
+        from specify_cli.events import _resolve_event_command_argv
+
+        host = tmp_path.parent / "host-event-script.sh"
+        host.write_text("#!/bin/sh\nexit 0\n", encoding="utf-8")
+        script_dir = tmp_path / ".specify" / "scripts"
+        script_dir.mkdir(parents=True)
+        sneak = script_dir / "sneak.sh"
+        try:
+            sneak.symlink_to(host)
+        except OSError:
+            pytest.skip("symlinks are not available")
+        cmd_dir = tmp_path / ".specify" / "templates" / "commands"
+        cmd_dir.mkdir(parents=True)
+        (cmd_dir / "boot.md").write_text(
+            "---\n"
+            "description: \"Boot\"\n"
+            "scripts:\n  sh: scripts/sneak.sh\n"
+            "---\nBody\n",
+            encoding="utf-8",
+        )
+
+        argv = _resolve_event_command_argv(cmd_dir / "boot.md", tmp_path, None)
+
+        assert argv is None
+
+    def test_windows_drive_script_token_returns_none(self, tmp_path):
+        """A Windows-anchored first token must not discard the project base."""
+        from specify_cli.events import _resolve_event_command_argv
+
+        cmd_dir = tmp_path / ".specify" / "templates" / "commands"
+        cmd_dir.mkdir(parents=True)
+        (cmd_dir / "boot.md").write_text(
+            "---\n"
+            "description: \"Boot\"\n"
+            "scripts:\n  sh: C:/Windows/System32/cmd.exe\n"
+            "---\nBody\n",
+            encoding="utf-8",
+        )
+
+        argv = _resolve_event_command_argv(cmd_dir / "boot.md", tmp_path, None)
+
+        assert argv is None
+
+    def test_dispatcher_template_confines_script_token(self):
+        """The stdlib fallback dispatcher must carry the same confinement."""
+        from specify_cli.events import _EVENTS_DISPATCHER_TEMPLATE
+
+        assert "_script_under_base" in _EVENTS_DISPATCHER_TEMPLATE
+        assert "PureWindowsPath" in _EVENTS_DISPATCHER_TEMPLATE
+
+    def test_dispatcher_inline_rejects_absolute_script(self, tmp_path):
+        """Inline fallback must not execute an absolute first ``scripts:`` token."""
+        import subprocess as _sp
+        import sys as _sys
+
+        if platform.system().lower().startswith("win"):
+            return
+
+        integration = ClaudeIntegration()
+        manifest = MagicMock(spec=IntegrationManifest)
+        manifest.files = {}
+        manifest.record_file = MagicMock()
+        manifest.record_existing = MagicMock()
+        install_integration_events(
+            integration, tmp_path, manifest,
+            {"session_start": [{"command": "speckit.boot"}]},
+        )
+        dispatcher = tmp_path / EVENTS_DISPATCHER_REL
+        marker = tmp_path / "should-not-run.out"
+        host = tmp_path.parent / "host-boot.sh"
+        host.write_text(
+            f"#!/bin/sh\necho ran > {shlex.quote(str(marker))}\nexit 0\n",
+            encoding="utf-8",
+        )
+        host.chmod(0o755)
+        cmd_dir = tmp_path / ".specify" / "templates" / "commands"
+        cmd_dir.mkdir(parents=True)
+        (cmd_dir / "boot.md").write_text(
+            "---\n"
+            "description: \"Boot\"\n"
+            f"scripts:\n  sh: {host.as_posix()}\n"
+            "---\nBody\n",
+            encoding="utf-8",
+        )
+        fake_dir = tmp_path / "_fake"
+        (fake_dir / "specify_cli").mkdir(parents=True)
+        (fake_dir / "specify_cli" / "__init__.py").write_text("", encoding="utf-8")
+        env = dict(os.environ)
+        env["PYTHONPATH"] = str(fake_dir)
+        result = _sp.run(
+            [_sys.executable, str(dispatcher), "speckit.boot", "session_start", "60"],
+            input="{}",
+            capture_output=True,
+            text=True,
+            env=env,
+            cwd=str(tmp_path),
+        )
+        assert result.returncode == 0, result.stderr
+        assert not marker.exists()
+
 
 # -- Merge/teardown idempotency & safety (Tier 3) ----------------------------