(core) add a login method based on headers

Summary:
This fleshes out header-based authentication a little more to
work with traefik-forward-auth.

Test Plan: manually tested

Reviewers: georgegevoian

Reviewed By: georgegevoian

Subscribers: alexmojaki

Differential Revision: https://phab.getgrist.com/D3348

app/server/lib/Authorizer.ts

@@ -94,10 +94,11 @@ export function isSingleUserMode(): boolean {
 /**
  * Returns a profile if it can be deduced from the request. This requires a
  * header to specify the users' email address. The header to set comes from the
- * environment variable GRIST_PROXY_AUTH_HEADER.
+ * environment variable GRIST_PROXY_AUTH_HEADER, or may be passed in.
  */
-export function getRequestProfile(req: Request|IncomingMessage): UserProfile|undefined {
-  const header = process.env.GRIST_PROXY_AUTH_HEADER;
+export function getRequestProfile(req: Request|IncomingMessage,
+                                  header?: string): UserProfile|undefined {
+  header = header || process.env.GRIST_PROXY_AUTH_HEADER;
   let profile: UserProfile|undefined;
 
   if (header) {

app/server/lib/FlexServer.ts

@@ -729,6 +729,11 @@ export class FlexServer implements GristServer {
             recordSignUpEvent: true,
           }});
 
+          if (process.env.GRIST_SINGLE_ORG) {
+            // Merged org is not meaningful in this case.
+            return res.redirect(this.getHomeUrl(req));
+          }
+
           // Redirect to teams page if users has access to more than one org. Otherwise, redirect to
           // personal org.
           const domain = mreq.org;

app/server/lib/ForwardAuthLogin.ts

@@ -0,0 +1,75 @@
+import { ApiError } from 'app/common/ApiError';
+import { getRequestProfile } from 'app/server/lib/Authorizer';
+import { expressWrap } from 'app/server/lib/expressWrap';
+import { GristLoginSystem, GristServer, setUserInSession } from 'app/server/lib/GristServer';
+import { optStringParam } from 'app/server/lib/requestUtils';
+import * as express from 'express';
+import trimEnd = require('lodash/trimEnd');
+import trimStart = require('lodash/trimStart');
+
+/**
+ * Return a login system that can work in concert with middleware that
+ * does authentication and then passes identity in a header. An example
+ * of such middleware is traefik-forward-auth:
+ *
+ *   https://github.com/thomseddon/traefik-forward-auth
+ *
+ * To make it function:
+ *   - Set GRIST_FORWARD_AUTH_HEADER to a header that will contain
+ *     authorized user emails, say "x-forwarded-user"
+ *   - Make sure /auth/login is processed by forward auth middleware
+ *   - Set GRIST_FORWARD_AUTH_LOGOUT_PATH to a path that will trigger
+ *     a logout (for traefik-forward-auth by default that is /_oauth/logout).
+ *   - Make sure that logout path is processed by forward auth middleware
+ *   - If you want to allow anonymous access in some cases, make sure all
+ *     other paths are free of the forward auth middleware - Grist will
+ *     trigger it as needed.
+ *   - Optionally, tell the middleware where to forward back to after logout.
+ *     (For traefik-forward-auth, you'd set LOGOUT_REDIRECT to .../signed-out)
+ *
+ * Redirection logic currently assumes a single-site installation.
+ */
+export async function getForwardAuthLoginSystem(): Promise<GristLoginSystem|undefined> {
+  const header = process.env.GRIST_FORWARD_AUTH_HEADER;
+  const logoutPath = process.env.GRIST_FORWARD_AUTH_LOGOUT_PATH || '';
+  if (!header) { return; }
+  return {
+    async getMiddleware(gristServer: GristServer) {
+      async function getLoginRedirectUrl(req: express.Request, url: URL)  {
+        const target = new URL(trimEnd(gristServer.getHomeUrl(req), '/') + "/auth/login");
+        // In lieu of sanatizing the next url, we include only the path
+        // component. This will only work for single-domain installations.
+        target.searchParams.append('next', url.pathname);
+        return target.href;
+      }
+      return {
+        getLoginRedirectUrl,
+        getSignUpRedirectUrl: getLoginRedirectUrl,
+        async getLogoutRedirectUrl(req: express.Request) {
+          return trimEnd(gristServer.getHomeUrl(req), '/') + '/' +
+            trimStart(logoutPath, '/');
+        },
+        async addEndpoints(app: express.Express) {
+          app.get('/auth/login', expressWrap(async (req, res) => {
+            const profile = getRequestProfile(req, header);
+            if (!profile) {
+              throw new ApiError('cannot find user', 401);
+            }
+            await setUserInSession(req, gristServer, profile);
+            const target = new URL(gristServer.getHomeUrl(req));
+            const next = optStringParam(req.query.next);
+            if (next) {
+              target.pathname = next;
+            }
+            res.redirect(target.href);
+          }));
+          return "forward-auth";
+        },
+      };
+    },
+    async deleteUser() {
+      // If we could delete the user account in the external
+      // authentication system, this is our chance - but we can't.
+    },
+  };
+}

app/server/lib/GristServer.ts

@@ -1,5 +1,5 @@
 import { GristLoadConfig } from 'app/common/gristUrls';
-import { FullUser } from 'app/common/UserAPI';
+import { FullUser, UserProfile } from 'app/common/UserAPI';
 import { Document } from 'app/gen-server/entity/Document';
 import { Organization } from 'app/gen-server/entity/Organization';
 import { Workspace } from 'app/gen-server/entity/Workspace';
@@ -12,6 +12,7 @@ import { IDocStorageManager } from 'app/server/lib/IDocStorageManager';
 import { INotifier } from 'app/server/lib/INotifier';
 import { IPermitStore } from 'app/server/lib/Permit';
 import { ISendAppPageOptions } from 'app/server/lib/sendAppPage';
+import { fromCallback } from 'app/server/lib/serverUtils';
 import { Sessions } from 'app/server/lib/Sessions';
 import * as express from 'express';
 
@@ -59,6 +60,20 @@ export interface GristLoginMiddleware {
   addEndpoints(app: express.Express): Promise<string>;
 }
 
+/**
+ * Set the user in the current session.
+ */
+export async function setUserInSession(req: express.Request, gristServer: GristServer, profile: UserProfile) {
+  const scopedSession = gristServer.getSessions().getOrCreateSessionFromRequest(req);
+  // Make sure session is up to date before operating on it.
+  // Behavior on a completely fresh session is a little awkward currently.
+  const reqSession = (req as any).session;
+  if (reqSession?.save) {
+    await fromCallback(cb => reqSession.save(cb));
+  }
+  await scopedSession.updateUserProfile(req, profile);
+}
+
 export interface RequestWithGrist extends express.Request {
   gristServer?: GristServer;
 }

app/server/lib/MinimalLogin.ts

@@ -1,6 +1,5 @@
 import { UserProfile } from 'app/common/UserAPI';
-import {GristLoginSystem, GristServer} from 'app/server/lib/GristServer';
-import {fromCallback} from 'app/server/lib/serverUtils';
+import { GristLoginSystem, GristServer, setUserInSession } from 'app/server/lib/GristServer';
 import { Request } from 'express';
 
 /**
@@ -11,18 +10,16 @@ export async function getMinimalLoginSystem(): Promise<GristLoginSystem> {
   // no nuance here.
   return {
     async getMiddleware(gristServer: GristServer) {
+      async function getLoginRedirectUrl(req: Request, url: URL)  {
+        await setUserInSession(req, gristServer, getDefaultProfile());
+        return url.href;
+    }
       return {
-        async getLoginRedirectUrl(req: Request, url: URL)  {
-          await setSingleUser(req, gristServer);
-          return url.href;
-        },
+        getLoginRedirectUrl,
+        getSignUpRedirectUrl: getLoginRedirectUrl,
         async getLogoutRedirectUrl(req: Request, url: URL) {
           return url.href;
         },
-        async getSignUpRedirectUrl(req: Request, url: URL) {
-          await setSingleUser(req, gristServer);
-          return url.href;
-        },
         async addEndpoints() {
           // If working without a login system, make sure default user exists.
           const dbManager = gristServer.getHomeDBManager();
@@ -43,22 +40,6 @@ export async function getMinimalLoginSystem(): Promise<GristLoginSystem> {
   };
 }
 
-/**
- * Set the user in the current session to the single hard-coded user.
- */
-async function setSingleUser(req: Request, gristServer: GristServer) {
-  const scopedSession = gristServer.getSessions().getOrCreateSessionFromRequest(req);
-  // Make sure session is up to date before operating on it.
-  // Behavior on a completely fresh session is a little awkward currently.
-  const reqSession = (req as any).session;
-  if (reqSession?.save) {
-    await fromCallback(cb => reqSession.save(cb));
-  }
-  await scopedSession.operateOnScopedSession(req, async (user) => Object.assign(user, {
-    profile: getDefaultProfile()
-  }));
-}
-
 function getDefaultProfile(): UserProfile {
   return {
     email: process.env.GRIST_DEFAULT_EMAIL || 'you@example.com',

stubs/app/server/lib/logins.ts

@@ -1,9 +1,10 @@
+import { getForwardAuthLoginSystem } from 'app/server/lib/ForwardAuthLogin';
 import { GristLoginSystem } from 'app/server/lib/GristServer';
 import { getMinimalLoginSystem } from 'app/server/lib/MinimalLogin';
 import { getSamlLoginSystem } from 'app/server/lib/SamlConfig';
 
 export async function getLoginSystem(): Promise<GristLoginSystem> {
-  const saml = await getSamlLoginSystem();
-  if (saml) { return saml; }
-  return getMinimalLoginSystem();
+  return await getSamlLoginSystem() ||
+    await getForwardAuthLoginSystem() ||
+    await getMinimalLoginSystem();
 }