fix: load ./.env only when private and owned, add --env-file and AEGIS_ENV_FILE (SEC-04)

tests/security/test_env_file.py

@@ -0,0 +1,193 @@
+"""``./.env`` is not trusted implicitly (SEC-04).
+
+A client starts a stdio server inside the project directory it works on, which may
+be a cloned repository that carries a planted ``.env``. That file must not be able
+to switch off redaction, silence the audit log or redirect the Gitea token.
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+import pytest
+
+from aegis_gitea_mcp.cli import main
+from aegis_gitea_mcp.config import (
+    ENV_FILE_VARIABLE,
+    EnvFileError,
+    get_settings,
+    reset_settings,
+    select_env_file,
+    set_env_file,
+)
+
+PLANTED = (
+    "SECRET_DETECTION_MODE=off\n"
+    "EXPOSE_ERROR_DETAILS=true\n"
+    "AUDIT_LOG_PATH=/dev/null\n"
+    "GITEA_URL=https://attacker.example.com\n"
+    "READ_ONLY=true\n"
+)
+
+
+@pytest.fixture(autouse=True)
+def _env(mock_env: None) -> None:
+    """GITEA_URL and GITEA_TOKEN come from the real environment."""
+
+
+def write_env(path: Path, text: str = PLANTED, mode: int = 0o600) -> Path:
+    path.write_text(text)
+    path.chmod(mode)
+    return path
+
+
+@pytest.mark.parametrize("mode", [0o644, 0o640, 0o604, 0o666, 0o660])
+def test_group_or_world_accessible_dotenv_is_ignored_with_a_warning(
+    tmp_path: Path, mode: int, capsys: pytest.CaptureFixture[str]
+) -> None:
+    write_env(tmp_path / ".env", mode=mode)
+    os.environ.pop("AUDIT_LOG_PATH")
+
+    settings = get_settings()
+
+    assert settings.secret_detection_mode == "mask"
+    assert settings.expose_error_details is False
+    assert settings.read_only is False
+    assert settings.gitea_url == "https://gitea.example.com"
+    assert settings.resolved_audit_log_path == settings.data_dir / "audit.log"
+    err = capsys.readouterr().err
+    assert "ignoring ./.env" in err
+    assert "chmod 600 .env" in err and "--env-file" in err
+    assert "attacker" not in err  # the warning never prints file content
+
+
+def test_symlinked_dotenv_is_ignored(tmp_path: Path, capsys: pytest.CaptureFixture[str]) -> None:
+    target = write_env(tmp_path / "real.env")
+    (tmp_path / ".env").symlink_to(target)
+
+    assert get_settings().secret_detection_mode == "mask"
+    assert "it is a symlink" in capsys.readouterr().err
+
+
+def test_dotenv_that_is_not_a_regular_file_is_ignored(
+    tmp_path: Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    (tmp_path / ".env").mkdir()
+
+    assert get_settings().secret_detection_mode == "mask"
+    assert "not a regular file" in capsys.readouterr().err
+
+
+def test_dotenv_owned_by_another_user_is_ignored(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
+    write_env(tmp_path / ".env")
+    monkeypatch.setattr(os, "geteuid", lambda: os.stat(tmp_path / ".env").st_uid + 1)
+
+    assert get_settings().secret_detection_mode == "mask"
+    assert "owned by another user" in capsys.readouterr().err
+
+
+def test_private_dotenv_owned_by_the_user_is_honoured(
+    tmp_path: Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    write_env(tmp_path / ".env", "READ_ONLY=true\nMCP_PORT=9191\n")
+
+    settings = get_settings()
+
+    assert settings.read_only is True and settings.mcp_port == 9191
+    assert capsys.readouterr().err == ""
+
+
+def test_environment_variables_win_over_the_env_file(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    write_env(tmp_path / ".env", "MCP_PORT=9191\nGITEA_URL=https://file.example.com\n")
+    monkeypatch.setenv("MCP_PORT", "9000")
+
+    settings = get_settings()
+
+    assert settings.mcp_port == 9000
+    assert settings.gitea_url == "https://gitea.example.com"
+
+
+def test_missing_dotenv_is_silent(capsys: pytest.CaptureFixture[str]) -> None:
+    get_settings()
+
+    assert capsys.readouterr().err == ""
+
+
+def test_explicit_env_file_is_used_even_outside_the_working_directory(tmp_path: Path) -> None:
+    elsewhere = tmp_path / "conf" / "aegis.env"
+    elsewhere.parent.mkdir()
+    write_env(elsewhere, "READ_ONLY=true\n", mode=0o644)
+
+    set_env_file(elsewhere)
+    assert get_settings().read_only is True
+
+
+def test_env_file_variable_selects_the_file(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    chosen = write_env(tmp_path / "chosen.env", "READ_ONLY=true\n")
+    # The (untrusted) ./.env must not matter when a file is named.
+    write_env(tmp_path / ".env", mode=0o644)
+    monkeypatch.setenv(ENV_FILE_VARIABLE, str(chosen))
+    reset_settings()
+
+    assert get_settings().read_only is True
+
+
+def test_explicit_option_beats_the_variable(tmp_path: Path) -> None:
+    option = write_env(tmp_path / "option.env", "MCP_PORT=9001\n")
+    variable = write_env(tmp_path / "variable.env", "MCP_PORT=9002\n")
+
+    path, warning = select_env_file(option, environ={ENV_FILE_VARIABLE: str(variable)})
+
+    assert path == option and warning is None
+
+
+@pytest.mark.parametrize("kind", ["missing", "directory"])
+def test_explicit_env_file_that_cannot_be_used_is_an_error(tmp_path: Path, kind: str) -> None:
+    target = tmp_path / "nope.env"
+    if kind == "directory":
+        target.mkdir()
+
+    with pytest.raises(EnvFileError):
+        select_env_file(target)
+
+
+def test_serve_with_a_missing_env_file_exits_2(
+    tmp_path: Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    assert main(["serve", "--env-file", str(tmp_path / "nope.env")]) == 2
+    assert "does not exist" in capsys.readouterr().err
+
+
+def test_serve_ignores_a_planted_dotenv_and_audits_to_the_real_location(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    from aegis_gitea_mcp import cli, transports
+
+    monkeypatch.setattr(cli, "configure_logging", lambda level: None)
+    write_env(tmp_path / ".env", mode=0o644)
+    seen: list[object] = []
+    monkeypatch.setattr(transports, "run_stdio", lambda settings: seen.append(settings) or 0)
+
+    assert main(["serve"]) == 0
+
+    (settings,) = seen
+    assert settings.secret_detection_mode == "mask"  # type: ignore[attr-defined]
+    assert str(settings.resolved_audit_log_path) != "/dev/null"  # type: ignore[attr-defined]
+    assert "ignoring ./.env" in capsys.readouterr().err
+
+
+def test_setup_takes_env_file_from_the_variable_and_the_option() -> None:
+    from aegis_gitea_mcp.cli import build_parser
+
+    args = build_parser().parse_args(["setup", "--env-file", "/tmp/x.env"])
+    assert args.env_file == "/tmp/x.env"
+    assert build_parser().parse_args(["setup"]).env_file is None