Added option for node admin to create whitelist/blacklist of which co…

…lumns they want to allow to be requested

docs/v6-crosstab-py/privacy.rst

@@ -28,6 +28,27 @@ records:
   contains only unique values, the result would reveal which unique values are present
   in the column.
 
+- **Setting the allowed columns**: The node administrator can set on which
+  columns they want to allow or disallow the computation of the contingency table by
+  adding the following to the node configuration file:
+
+  .. code:: yaml
+
+    algorithm_env:
+      CROSSTAB_ALLOWED_COLUMNS: ["ageGroup", "isOverweight"]
+      CROSSTAB_DISALLOWED_COLUMNS: ["age", "weight"]
+
+  This configuration will ensure that only the columns `ageGroup` and `isOverweight`
+  are allowed to be used in the computation of the contingency table. The columns `age`
+  and `weight` are disallowed and will not be used in the computation. Usually, there
+  should either be an allowed or disallowed list, but not both: if there is an explicit
+  allowed list, all other columns are automatically disallowed.
+
+  We recommend to define these list to ensure that the contingency table can only be
+  computed for categorical tables, and not for numeric ones. The latter run a risk of
+  revealing that certain values are present in the data. We chose to let the node
+  administrator handle this as they know their own data best.
+
 - **Minimum number of data rows to participate**: A node will only participate if it
   contains at least `n` data rows. This is to prevent nodes with very little data from
   participating in the computation. By default, the minimum number of data rows is set

v6-crosstab-py/partial.py

@@ -45,14 +45,13 @@ def partial_crosstab(
     PRIVACY_THRESHOLD = _convert_envvar_to_int(
         "CROSSTAB_PRIVACY_THRESHOLD", DEFAULT_PRIVACY_THRESHOLD
     )
-    MINIMUM_ROWS_TOTAL = _convert_envvar_to_int(
-        "CROSSTAB_MINIMUM_ROWS_TOTAL", DEFAULT_MINIMUM_ROWS_TOTAL
-    )
     ALLOW_ZERO = _convert_envvar_to_bool("CROSSTAB_ALLOW_ZERO", DEFAULT_ALLOW_ZERO)
 
     # check if env var values are compatible
     info("Checking privacy settings before starting...")
-    _do_prestart_privacy_checks(df, PRIVACY_THRESHOLD, ALLOW_ZERO, MINIMUM_ROWS_TOTAL)
+    _do_prestart_privacy_checks(
+        df, group_cols + [results_col], PRIVACY_THRESHOLD, ALLOW_ZERO
+    )
 
     # Fill empty (categorical) values with "N/A"
     df = df.fillna("N/A")
@@ -112,7 +111,10 @@ def partial_crosstab(
 
 
 def _do_prestart_privacy_checks(
-    df: pd.DataFrame, privacy_threshold: int, allow_zero: bool, minimum_rows_total: int
+    df: pd.DataFrame,
+    requested_columns: list[str],
+    privacy_threshold: int,
+    allow_zero: bool,
 ) -> None:
     """
     Perform privacy checks before starting the computation.
@@ -121,13 +123,16 @@ def _do_prestart_privacy_checks(
     ----------
     df : pd.DataFrame
         The dataframe containing the data.
+    requested_columns : list[str]
+        The columns requested for the computation.
     privacy_threshold : int
         The privacy threshold value.
     allow_zero : bool
         The flag indicating whether zero values are allowed.
-    minimum_rows_total : int
-        The minimum number of rows to be found in the supplied dataframe.
     """
+    minimum_rows_total = _convert_envvar_to_int(
+        "CROSSTAB_MINIMUM_ROWS_TOTAL", DEFAULT_MINIMUM_ROWS_TOTAL
+    )
 
     if privacy_threshold == 0 and not allow_zero:
         raise ValueError(
@@ -142,6 +147,28 @@ def _do_prestart_privacy_checks(
             "handle this computation, as it may lead to privacy issues."
         )
 
+    # Check if requested columns are allowed
+    allowed_columns = get_env_var("CROSSTAB_ALLOWED_COLUMNS")
+    if allowed_columns:
+        allowed_columns = allowed_columns.split(",")
+        for col in requested_columns:
+            if col not in allowed_columns:
+                raise ValueError(
+                    f"The node administrator does not allow '{col}' to be requested in "
+                    "this algorithm computation. Please contact the node administrator "
+                    "for more information."
+                )
+    non_allowed_collumns = get_env_var("CROSSTAB_DISALLOWED_COLUMNS")
+    if non_allowed_collumns:
+        non_allowed_collumns = non_allowed_collumns.split(",")
+        for col in requested_columns:
+            if col in non_allowed_collumns:
+                raise ValueError(
+                    f"The node administrator does not allow '{col}' to be requested in "
+                    "this algorithm computation. Please contact the node administrator "
+                    "for more information."
+                )
+
 
 def _get_threshold_placeholder(privacy_threshold: int, allow_zero: bool) -> str:
     """