Add function to allow hosts from environment variables (#287)

* Add allowed host option to handle CORS requests
* Update readme with new GRIST_ALLOWED_HOSTS environment variable

README.md

@@ -202,6 +202,7 @@ APP_STATIC_URL | url prefix for static resources
 APP_STATIC_INCLUDE_CUSTOM_CSS | set to "true" to include custom.css (from APP_STATIC_URL) in static pages
 APP_UNTRUSTED_URL   | URL at which to serve/expect plugin content.
 GRIST_ADAPT_DOMAIN  | set to "true" to support multiple base domains (careful, host header should be trustworthy)
+GRIST_ALLOWED_HOSTS | comma-separated list of permitted domains origin for requests (e.g. my.site,another.com)
 GRIST_APP_ROOT      | directory containing Grist sandbox and assets (specifically the sandbox and static subdirectories).
 GRIST_BACKUP_DELAY_SECS | wait this long after a doc change before making a backup
 GRIST_DATA_DIR      | directory in which to store document caches.

app/server/lib/Authorizer.ts

@@ -18,7 +18,7 @@ import {makeId} from 'app/server/lib/idUtils';
 import log from 'app/server/lib/log';
 import {IPermitStore, Permit} from 'app/server/lib/Permit';
 import {AccessTokenInfo} from 'app/server/lib/AccessTokens';
-import {allowHost, getOriginUrl, optStringParam} from 'app/server/lib/requestUtils';
+import {allowHost, isEnvironmentAllowedHost, getOriginUrl, optStringParam} from 'app/server/lib/requestUtils';
 import * as cookie from 'cookie';
 import {NextFunction, Request, RequestHandler, Response} from 'express';
 import {IncomingMessage} from 'http';
@@ -263,7 +263,7 @@ export async function addRequestUser(dbManager: HomeDBManager, permitStore: IPer
       // custom-domain owner could hijack such sessions.
       const allowedOrg = getAllowedOrgForSessionID(mreq.sessionID);
       if (allowedOrg) {
-        if (allowHost(req, allowedOrg.host)) {
+        if (allowHost(req, allowedOrg.host) || isEnvironmentAllowedHost(allowedOrg.host)) {
           customHostSession = ` custom-host-match ${allowedOrg.host}`;
         } else {
           // We need an exception for internal forwarding from home server to doc-workers. These use

app/server/lib/Triggers.ts

@@ -14,6 +14,7 @@ import {promisifyAll} from 'bluebird';
 import * as _ from 'lodash';
 import fetch from 'node-fetch';
 import {createClient, Multi, RedisClient} from 'redis';
+import {matchesBaseDomain} from 'app/server/lib/requestUtils';
 
 promisifyAll(RedisClient.prototype);
 
@@ -550,6 +551,6 @@ export function isUrlAllowed(urlString: string) {
   }
 
   return (process.env.ALLOWED_WEBHOOK_DOMAINS || "").split(",").some(domain =>
-    domain && url.host.endsWith(domain)
+    domain && matchesBaseDomain(url.host, domain)
   );
 }

app/server/lib/requestUtils.ts

@@ -9,6 +9,7 @@ import log from 'app/server/lib/log';
 import {Permit} from 'app/server/lib/Permit';
 import {Request, Response} from 'express';
 import {URL} from 'url';
+import _ from 'lodash';
 
 // log api details outside of dev environment (when GRIST_HOSTED_VERSION is set)
 const shouldLogApiDetails = Boolean(process.env.GRIST_HOSTED_VERSION);
@@ -85,7 +86,7 @@ export function trustOrigin(req: Request, resp: Response): boolean {
   const origin = req.get('origin');
   if (!origin) { return true; } // Not a CORS request.
   if (process.env.GRIST_HOST && req.hostname === process.env.GRIST_HOST) { return true; }
-  if (!allowHost(req, new URL(origin))) { return false; }
+  if (!allowHost(req, new URL(origin)) && !isEnvironmentAllowedHost(new URL(origin))) { return false; }
 
   // For a request to a custom domain, the full hostname must match.
   resp.header("Access-Control-Allow-Origin", origin);
@@ -107,10 +108,21 @@ export function allowHost(req: Request, allowedHost: string|URL) {
     // For requests to a native subdomains, only the base domain needs to match.
     const allowedDomain = parseSubdomain(allowedUrl.hostname);
     const actualDomain = parseSubdomain(actualUrl.hostname);
-    return (actualDomain.base === allowedDomain.base);
+    return (!_.isEmpty(actualDomain) ? actualDomain.base === allowedDomain.base : allowedUrl.hostname === actualUrl.hostname);
   }
 }
 
+export function matchesBaseDomain(domain: string, baseDomain: string) {
+  return domain === baseDomain || domain.endsWith("." + baseDomain);
+}
+
+export function isEnvironmentAllowedHost(url: string|URL) {
+  const urlHost = (typeof url === 'string') ? url : url.host;
+  return (process.env.GRIST_ALLOWED_HOSTS || "").split(",").some(domain =>
+    domain && matchesBaseDomain(urlHost, domain)
+  );
+}
+
 export function isParameterOn(parameter: any): boolean {
   return gutil.isAffirmative(parameter);
 }

test/server/lib/DocApi.ts

@@ -2773,6 +2773,23 @@ function testDocApi() {
     });
   });
 
+  describe("Allowed Origin", () => {
+    it('should allow only example.com',  async () => {
+      async function checkOrigin(origin: string, status: number, error?: string) {
+        const resp = await axios.get(`${serverUrl}/api/docs/${docIds.Timesheets}/`,
+        {...chimpy, headers: {...chimpy.headers, "Origin": origin}}
+        );
+        error && assert.deepEqual(resp.data, {error});
+        assert.equal(resp.status, status);
+      }
+      await checkOrigin("https://www.toto.com", 500, "Unrecognized origin");
+      await checkOrigin("https://badexample.com", 500, "Unrecognized origin");
+      await checkOrigin("https://bad.com/example.com/toto", 500, "Unrecognized origin");
+      await checkOrigin("https://example.com/path", 200);
+      await checkOrigin("https://good.example.com/toto", 200);
+    })
+  })
+
   // PLEASE ADD MORE TESTS HERE
 }
 
@@ -2866,6 +2883,7 @@ class TestServer {
       REDIS_URL: process.env.TEST_REDIS_URL,
       APP_HOME_URL: _homeUrl,
       ALLOWED_WEBHOOK_DOMAINS: `example.com,localhost:${webhooksTestPort}`,
+      GRIST_ALLOWED_HOSTS: `example.com,localhost:${webhooksTestPort}`,
       ...process.env
     };