From cf5c58a89fcc3bf4917ab52de7b201ac81910372 Mon Sep 17 00:00:00 2001
From: Vincenzo Scamporlino <vincenzos@spotify.com>
Date: Wed, 1 Feb 2023 13:30:52 +0100
Subject: [PATCH] catalog-backend: validate cursor

Signed-off-by: Vincenzo Scamporlino <vincenzos@spotify.com>
---
 .../service/DefaultEntitiesCatalog.test.ts    | 20 +++++++++++
 .../src/service/DefaultEntitiesCatalog.ts     | 34 ++++++++++++++++---
 plugins/catalog-backend/src/service/util.ts   | 10 +++---
 3 files changed, 54 insertions(+), 10 deletions(-)

diff --git a/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.test.ts b/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.test.ts
index bde55ef9bb..a25cbf2240 100644
--- a/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.test.ts
+++ b/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.test.ts
@@ -1294,6 +1294,26 @@ describe('DefaultEntitiesCatalog', () => {
         expect(response5.totalItems).toBe(6);
       },
     );
+
+    it('should throw in case of malformed cursor', async () => {
+      const catalog = new DefaultEntitiesCatalog({
+        database: knex,
+        logger: getVoidLogger(),
+        stitcher,
+      });
+
+      const cursor = Buffer.from(
+        JSON.stringify({ filter: 'notavalidfilter' }),
+        'utf8',
+      ).toString('base64');
+      const request: PaginatedEntitiesCursorRequest = {
+        cursor,
+      };
+
+      await expect(catalog.paginatedEntities(request)).rejects.toThrow(
+        Error('Malformed cursor, could not be parsed'),
+      );
+    });
   });
 
   describe('removeEntityByUid', () => {
diff --git a/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.ts b/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.ts
index 0cc791e5de..67fe77cc8b 100644
--- a/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.ts
+++ b/plugins/catalog-backend/src/service/DefaultEntitiesCatalog.ts
@@ -23,6 +23,7 @@ import { InputError, NotFoundError } from '@backstage/errors';
 import { Knex } from 'knex';
 import { isEqual, chunk as lodashChunk } from 'lodash';
 import { Logger } from 'winston';
+import { z } from 'zod';
 import {
   EntitiesBatchRequest,
   EntitiesBatchResponse,
@@ -658,11 +659,39 @@ export class DefaultEntitiesCatalog implements EntitiesCatalog {
   }
 }
 
+const entityFilterParser: z.ZodSchema<EntityFilter> = z.lazy(() =>
+  z
+    .object({
+      key: z.string(),
+      values: z.array(z.string()).optional(),
+    })
+    .or(z.object({ not: entityFilterParser }))
+    .or(z.object({ anyOf: z.array(entityFilterParser) }))
+    .or(z.object({ allOf: z.array(entityFilterParser) })),
+);
+
+export const cursorParser: z.ZodSchema<Cursor> = z.object({
+  sortFields: z.array(
+    z.object({ field: z.string(), order: z.enum(['asc', 'desc']) }),
+  ),
+  sortFieldValues: z.array(z.string().or(z.null())),
+  filter: entityFilterParser.optional(),
+  isPrevious: z.boolean(),
+  query: z.string().optional(),
+  firstSortFieldValues: z.array(z.string().or(z.null())).optional(),
+  totalItems: z.number().optional(),
+});
+
 function encodeCursor(cursor: Cursor) {
   const json = JSON.stringify(cursor);
   return Buffer.from(json, 'utf8').toString('base64');
 }
 
+function decodeCursor(encodedCursor: string) {
+  const json = Buffer.from(encodedCursor, 'base64').toString('utf8');
+  return cursorParser.parse(JSON.parse(json));
+}
+
 function parseCursorFromRequest(
   request?: PaginatedEntitiesRequest,
 ): Partial<Cursor> {
@@ -672,10 +701,7 @@ function parseCursorFromRequest(
   }
   if (isPaginatedEntitiesCursorRequest(request)) {
     try {
-      const json = Buffer.from(request.cursor, 'base64').toString('utf8');
-      const cursor = JSON.parse(json);
-      // TODO(vinzscam): validate the shit
-      return cursor as unknown as Cursor;
+      return decodeCursor(request.cursor);
     } catch {
       throw new InputError('Malformed cursor, could not be parsed');
     }
diff --git a/plugins/catalog-backend/src/service/util.ts b/plugins/catalog-backend/src/service/util.ts
index bb86654565..958b4153f8 100644
--- a/plugins/catalog-backend/src/service/util.ts
+++ b/plugins/catalog-backend/src/service/util.ts
@@ -19,9 +19,9 @@ import { Request } from 'express';
 import lodash from 'lodash';
 import { z } from 'zod';
 import {
-  EntitiesRequest,
   PaginatedEntitiesCursorRequest,
   PaginatedEntitiesInitialRequest,
+  PaginatedEntitiesRequest,
 } from '../catalog/types';
 
 export async function requireRequestBody(req: Request): Promise<unknown> {
@@ -72,21 +72,19 @@ export function disallowReadonlyMode(readonly: boolean) {
 }
 
 export function isPaginatedEntitiesInitialRequest(
-  input: EntitiesRequest | undefined,
+  input: PaginatedEntitiesRequest | undefined,
 ): input is PaginatedEntitiesInitialRequest {
   if (!input) {
     return false;
   }
-  // TODO(vinzscam) expand this
   return !isPaginatedEntitiesCursorRequest(input);
 }
 
 export function isPaginatedEntitiesCursorRequest(
-  input: EntitiesRequest | undefined,
+  input: PaginatedEntitiesRequest | undefined,
 ): input is PaginatedEntitiesCursorRequest {
   if (!input) {
     return false;
   }
-  // TODO(vinzscam) expand this
-  return input?.hasOwnProperty('cursor') ?? false;
+  return !!(input as PaginatedEntitiesCursorRequest).cursor;
 }