Multiple canActivate guards all run when first fails

Question

I have a route with two canActivate guards (AuthGuard and RoleGuard). The first (AuthGuard) checks to see if the user is logged in and, if not, redirects to the login page. The second checks to see if the user has a role defined that is allowed to view the page and, if not, redirects to the un-authorized page.

canActivate: [ AuthGuard, RoleGuard ]
...
export class AuthGuard implements CanActivate {
    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<boolean> {
        ...
        this.router.navigate(['/login']);
        resolve(false);
}

export class RoleGuard implements CanActivate {
    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<boolean> {
        ...
        this.router.navigate(['/unauthorized']);
        resolve(false);
}

The problem is that when I access the route and I am not logged in I hit the AuthGuard, which fails and tells the router to navigate to /login. However, even though the AuthGuard failed, the RoleGuard runs anyway which then navigates to /unauthorized.

In my opinion it is pointless to run the next guard if the first fails. Is there any way to enforce this behavior?

Answer 1

In the latest Angular version, even if both guards return false, both will still be executed.

You can however resolve this with your example by only using RoleGuard for urls where a certain Role is required, because I guess you need to be logged in to have a role. In that case you can change your RoleGuard to this:

@Injectable()
export class RoleGuard implements CanActivate {
  constructor(private _authGuard: AuthGuard) {}

  canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<boolean> {
    return this._authGuard.canActivate(route, state).then((auth: boolean) => {
      if(!auth) {
        return false;
      }
      //... your role guard check code goes here
    });
  }
}

Answer 2

As mentioned by @PierreDuc data property in Route Class along with a Master Guard can be used to solve this problem.

Problem

First of all, angular doesn't support the feature to call the guards in tandem. So if first guard is asynchronous and is trying to make ajax calls, all the remaining guards will get fired even before completion of the ajax request in guard 1.

I faced the similar problem and this is how I solved it -

---

Solution

The idea is to create a master guard and let the master guard handle the execution of other guards.

The routing configuration in this case, will contain master guard as the only guard.

To let master guard know about the guards to be triggered for specific routes, add a data property in Route.

The data property is a key value pair that allows us to attach data with the routes.

The data can then be accessed in the guards using ActivatedRouteSnapshot parameter of canActivate method in the guard.

The solution looks complicated but it will assure proper working of guards once it is integrated in the application.

Following example explains this approach -

---

Example

1. Constants Object to map all application guards -

export const GUARDS = {
    GUARD1: "GUARD1",
    GUARD2: "GUARD2",
    GUARD3: "GUARD3",
    GUARD4: "GUARD4",
}

2. Application Guard -

import { Injectable } from "@angular/core";
import { Guard4DependencyService } from "./guard4dependency";

@Injectable()
export class Guard4 implements CanActivate {
    //A  guard with dependency
    constructor(private _Guard4DependencyService:  Guard4DependencyService) {}

    canActivate(next: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<boolean> {
        return new Promise((resolve: Function, reject: Function) => {
            //logic of guard 4 here
            if (this._Guard4DependencyService.valid()) {
                resolve(true);
            } else {
                reject(false);
            }
        });
    }
}

3. Routing Configuration -

import { Route } from "@angular/router";
import { View1Component } from "./view1";
import { View2Component } from "./view2";
import { MasterGuard, GUARDS } from "./master-guard";
export const routes: Route[] = [
    {
        path: "view1",
        component: View1Component,
        //attach master guard here
        canActivate: [MasterGuard],
        //this is the data object which will be used by 
        //masteer guard to execute guard1 and guard 2
        data: {
            guards: [
                GUARDS.GUARD1,
                GUARDS.GUARD2
            ]
        }
    },
    {
        path: "view2",
        component: View2Component,
        //attach master guard here
        canActivate: [MasterGuard],
        //this is the data object which will be used by 
        //masteer guard to execute guard1, guard 2, guard 3 & guard 4
        data: {
            guards: [
                GUARDS.GUARD1,
                GUARDS.GUARD2,
                GUARDS.GUARD3,
                GUARDS.GUARD4
            ]
        }
    }
];

4. Master Guard -

import { Injectable } from "@angular/core";
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot, Router } from "@angular/router";

//import all the guards in the application
import { Guard1 } from "./guard1";
import { Guard2 } from "./guard2";
import { Guard3 } from "./guard3";
import { Guard4 } from "./guard4";

import { Guard4DependencyService } from "./guard4dependency";

@Injectable()
export class MasterGuard implements CanActivate {

    //you may need to include dependencies of individual guards if specified in guard constructor
    constructor(private _Guard4DependencyService:  Guard4DependencyService) {}

    private route: ActivatedRouteSnapshot;
    private state: RouterStateSnapshot;

    //This method gets triggered when the route is hit
    public canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<boolean> {

        this.route = route;
        this.state = state;

        if (!route.data) {
            Promise.resolve(true);
            return;
        }

        //this.route.data.guards is an array of strings set in routing configuration

        if (!this.route.data.guards || !this.route.data.guards.length) {
            Promise.resolve(true);
            return;
        }
        return this.executeGuards();
    }

    //Execute the guards sent in the route data 
    private executeGuards(guardIndex: number = 0): Promise<boolean> {
        return this.activateGuard(this.route.data.guards[guardIndex])
            .then(() => {
                if (guardIndex < this.route.data.guards.length - 1) {
                    return this.executeGuards(guardIndex + 1);
                } else {
                    return Promise.resolve(true);
                }
            })
            .catch(() => {
                return Promise.reject(false);
            });
    }

    //Create an instance of the guard and fire canActivate method returning a promise
    private activateGuard(guardKey: string): Promise<boolean> {

        let guard: Guard1 | Guard2 | Guard3 | Guard4;

        switch (guardKey) {
            case GUARDS.GUARD1:
                guard = new Guard1();
                break;
            case GUARDS.GUARD2:
                guard = new Guard2();
                break;
            case GUARDS.GUARD3:
                guard = new Guard3();
                break;
            case GUARDS.GUARD4:
                guard = new Guard4(this._Guard4DependencyService);
                break;
            default:
                break;
        }
        return guard.canActivate(this.route, this.state);
    }
}

Challenges

One of the challenges in this approach is refactoring of existing routing model. However, it can be done in parts as the changes are non-breaking.

I hope this helps.

Answer 3

As of Angular 8 I am able to do this. This solution was inspired by @planet_hunter's answer but with less code and uses observables for the heavy lifting which was a requirement for this project.

Create a guard with your name of choice that will handle running all guards in order.

@Injectable({
    providedIn: 'root'
})
export class SyncGuardHelper implements CanActivate {
    public constructor(public injector: Injector) {
    }
    canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<boolean | UrlTree> {
        return from(route.data.syncGuards).pipe(concatMap((value) => {
            const guard = this.injector.get(value);
            const result = guard.canActivate(route, state);
            if (result instanceof Observable) {
                return result;
            } else if (result instanceof Promise) {
                return from(result);
            } else {
                return of(result);
            }
        }), first((x) => x === false || x instanceof UrlTree, true));
    }
}

In your routes file use the data property to add the guards you want to run in order (synchronously):

const routes: Routes = [
    {
        path: '',
        component: MyComponent,
        canActivate: [SyncGuardHelper],
        data: {
            syncGuards: [
                Guard1,
                Guard2,
                Guard3
            ]
        }
    },
    // other routes
]

I had to come up with this solution today so if you have any feedback please leave a comment so I can improve this answer.

Answer 4

This issue is resolved in Angular 7.1 and above.

Guerds have now a sense of priority.
A detailed explanation on how it works can be found here in this great blog post.

I quote the following example from the blog post:

canActivate: [CanActivateRouteGuard, CanActivateRouteGuard2], 

Which will be working as follows:

All guards in a given canActivate array are executed in parallel, but the router will wait until any guards with a higher priority to finish before moving on. So in the above example:

• Even if CanActivateRouteGuard2 returns a UrlTree immediately:
  the router will still wait for CanActivateRouteGuard to resolve before initiating a new navigation.
• If CanActivateRouteGuard returns a UrlTree:
  that will win.
• If it returns false:
  the entire navigation fails (and no redirects happen).
• If it simply returns true:
  then the UrlTree returned by CanActivateRouteGuard2 will be navigated to.

Answer 5

Currently having multiple async guards(returning Promise or Observable) will run at the same time. I opened a issue for this: https://github.com/angular/angular/issues/21702

Another workaround to the described solution above is to use nested routes:

{
  path: '',
  canActivate: [
    AuthGuard,
  ],
  children: [
    {
      path: '',
      canActivate: [
        RoleGuard,
      ],
      component: YourComponent
      // or redirectTo
      // or children
      // or loadChildren
    }
  ]
}

Answer 6

I didn't find a better solution on the internet, but, using as guide the best answer I decide to use only one guard including both requests concatenated using Rxjs mergeMap, this to avoid duplicated calls to the same endpoint. Here my example, avoid the console.log if you want to, I was using it to be sure of what is been triggered first.

1 getCASUsername is called to authenticate the user (heres a console.log(1) that you can't see)
2 We have the userName
3 Here I'm doing a second request that will be triggered after the first one using the response (true)
4 Using the returned userName I get the roles for that user

With this I have the solution for call sequence and for avoiding duplicated calls. Maybe it could work for you.

@Injectable()
export class AuthGuard implements CanActivate {
  constructor(private AuthService  : AuthService,
              private AepApiService: AepApiService) {}

  canActivate(): Observable<boolean> {
    return this.AepApiService.getCASUsername(this.AuthService.token)
      .map(res => {
        console.log(2, 'userName');
        if (res.name) {
          this.AuthService.authenticateUser(res.name);
          return true
        }
      })
      .mergeMap( (res) => {
        console.log(3, 'authenticated: ' + res);
        if (res) {
          return this.AepApiService.getAuthorityRoles(this.AuthService.$userName)
            .map( res => {
              console.log(4, 'roles');
              const roles = res.roles;

              this.AuthService.$userRoles = roles;

              if (!roles.length) this.AuthService.goToAccessDenied();

              return true;
            })
            .catch(() => {
              return Observable.of(false);
            });
        } else {
          return Observable.of(false);
        }
      })
      .catch(():Observable<boolean> => {
        this.AuthService.goToCASLoginPage();
        return Observable.of(false);
      });
  }
}