fix(security): duckdb_query_readonly sandbox por defecto (enable_external_access=false)

CRÍTICO: read_only=True protege la base de datos pero NO el sistema de ficheros. Un
SELECT con read_csv/read_blob/glob/COPY...TO podía leer ficheros arbitrarios (claves SSH)
o escribirlos (camino a RCE). Añadido parámetro sandbox (default True) que abre la conexión
con enable_external_access=false, bloqueando todo acceso a FS/red desde la query. Los SELECT
normales sobre tablas siguen funcionando. Único consumidor (osint_db /api/query) queda
protegido sin cambios. Tests nuevos: sandbox bloquea read_csv; sandbox=False lo permite.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

python/functions/infra/duckdb_query_readonly_test.py

@@ -0,0 +1,119 @@
+"""Tests para duckdb_query_readonly."""
+
+import datetime
+import decimal
+
+import duckdb
+import pytest
+
+from .duckdb_query_readonly import duckdb_query_readonly
+
+
+@pytest.fixture
+def db(tmp_path):
+    """Crea una base DuckDB temporal con datos de ejemplo y devuelve su path."""
+    path = str(tmp_path / "test.duckdb")
+    con = duckdb.connect(path)
+    con.execute(
+        "CREATE TABLE ventas ("
+        "  id INTEGER,"
+        "  region VARCHAR,"
+        "  total DECIMAL(10,2),"
+        "  fecha DATE"
+        ")"
+    )
+    con.execute(
+        "INSERT INTO ventas VALUES "
+        "(1, 'norte', 120.50, DATE '2026-01-01'), "
+        "(2, 'sur',   80.00, DATE '2026-01-02'), "
+        "(3, 'norte', 45.25, DATE '2026-01-03')"
+    )
+    con.close()
+    return path
+
+
+def test_query_ok_devuelve_filas_como_dicts(db):
+    res = duckdb_query_readonly(db, "SELECT id, region FROM ventas ORDER BY id")
+    assert res["status"] == "ok"
+    assert res["columns"] == ["id", "region"]
+    assert res["row_count"] == 3
+    assert res["truncated"] is False
+    assert res["rows"][0] == {"id": 1, "region": "norte"}
+    assert res["rows"][1] == {"id": 2, "region": "sur"}
+
+
+def test_query_con_params_posicionales(db):
+    res = duckdb_query_readonly(
+        db,
+        "SELECT id FROM ventas WHERE region = ? ORDER BY id",
+        params=["norte"],
+    )
+    assert res["status"] == "ok"
+    assert res["row_count"] == 2
+    assert [row["id"] for row in res["rows"]] == [1, 3]
+
+
+def test_sql_invalido_devuelve_status_error(db):
+    res = duckdb_query_readonly(db, "SELECT * FROM tabla_que_no_existe")
+    assert res["status"] == "error"
+    assert "error" in res
+    assert isinstance(res["error"], str) and res["error"]
+
+
+def test_db_inexistente_devuelve_status_error(tmp_path):
+    missing = str(tmp_path / "no_existe.duckdb")
+    res = duckdb_query_readonly(missing, "SELECT 1")
+    assert res["status"] == "error"
+    assert "error" in res
+
+
+def test_truncado_a_max_rows(db):
+    res = duckdb_query_readonly(db, "SELECT id FROM ventas ORDER BY id", max_rows=2)
+    assert res["status"] == "ok"
+    assert res["row_count"] == 2
+    assert res["truncated"] is True
+    assert [row["id"] for row in res["rows"]] == [1, 2]
+
+
+def test_valores_no_serializables_se_convierten(db):
+    res = duckdb_query_readonly(
+        db,
+        "SELECT total, fecha FROM ventas WHERE id = ?",
+        params=[1],
+    )
+    assert res["status"] == "ok"
+    row = res["rows"][0]
+    # Decimal -> float
+    assert isinstance(row["total"], float)
+    assert row["total"] == pytest.approx(120.50)
+    # date -> isoformat str
+    assert isinstance(row["fecha"], str)
+    assert row["fecha"] == "2026-01-01"
+    # Verificamos que NO quedan tipos crudos no serializables.
+    assert not isinstance(row["total"], decimal.Decimal)
+    assert not isinstance(row["fecha"], datetime.date)
+
+
+def test_sandbox_por_defecto_bloquea_acceso_a_ficheros(db, tmp_path):
+    """Por defecto (sandbox=True) la query no puede tocar el sistema de ficheros."""
+    csv = tmp_path / "externo.csv"
+    csv.write_text("a\n1\n")
+    res = duckdb_query_readonly(db, f"SELECT * FROM read_csv_auto('{csv}')")
+    assert res["status"] == "error"
+    assert (
+        "access" in res["error"].lower() or "permission" in res["error"].lower()
+    )
+    # El SELECT normal sobre la propia base sigue funcionando con el sandbox.
+    ok = duckdb_query_readonly(db, "SELECT count(*) AS n FROM ventas")
+    assert ok["status"] == "ok" and ok["rows"][0]["n"] == 3
+
+
+def test_sandbox_off_permite_leer_csv_del_disco(db, tmp_path):
+    """Con sandbox=False (uso interno confiable) sí puede leer ficheros."""
+    csv = tmp_path / "externo.csv"
+    csv.write_text("a\n1\n2\n")
+    res = duckdb_query_readonly(
+        db, f"SELECT count(*) AS n FROM read_csv_auto('{csv}')", sandbox=False
+    )
+    assert res["status"] == "ok"
+    assert res["rows"][0]["n"] == 2