allowlist.js

/**
 * Tests that only allowlisted stages are permitted to run in a $changeStream pipeline.
 */

import {assertErrorCode} from "jstests/aggregation/extras/utils.js";
import {assertDropAndRecreateCollection} from "jstests/libs/collection_drop_recreate.js";

const coll = assertDropAndRecreateCollection(db, "change_stream_allowlist");

// Bare-bones $changeStream pipeline which will be augmented during tests.
const changeStream = [{$changeStream: {}}];

// List of non-$changeStream stages which are explicitly allowlisted.
const allowlist = [
    {$match: {_id: {$exists: true}}},
    {$project: {_id: 1}},
    {$addFields: {newField: 1}},
    {$set: {newField: 1}},
    {$replaceRoot: {newRoot: {_id: "$_id"}}},
    {$replaceWith: {_id: "$_id"}},
    {$redact: "$$DESCEND"}
];

// List of stages which the allowlist mechanism will prevent from running in a $changeStream.
// Does not include stages which are denylisted but already implicitly prohibited, e.g. both
// $currentOp and $changeStream must be the first stage in a pipeline.
const denylist = [
        {$group: {_id: "$_id"}},
        {$sort: {_id: 1}},
        {$skip: 100},
        {$limit: 100},
        {$sample: {size: 100}},
        {$unwind: "$_id"},
        {$lookup: {from: "coll", as: "as", localField: "_id", foreignField: "_id"}},
        {
          $graphLookup: {
              from: "coll",
              as: "as",
              startWith: "$_id",
              connectFromField: "_id",
              connectToField: "_id"
          }
        },
        {$bucketAuto: {groupBy: "$_id", buckets: 2}},
        {$facet: {facetPipe: [{$match: {_id: {$exists: true}}}]}}
    ];

// Verify that each of the allowlisted stages are permitted to run in a $changeStream.
for (let allowedStage of allowlist) {
    assert.commandWorked(db.runCommand(
        {aggregate: coll.getName(), pipeline: changeStream.concat(allowedStage), cursor: {}}));
}

// Verify that all of the allowlisted stages are able to run in a $changeStream together.
assert.commandWorked(db.runCommand(
    {aggregate: coll.getName(), pipeline: changeStream.concat(allowlist), cursor: {}}));

// Verify that a $changeStream pipeline fails to validate if a denylisted stage is present.
for (let bannedStage of denylist) {
    assertErrorCode(coll, changeStream.concat(bannedStage), ErrorCodes.IllegalOperation);
}