Nestjs Interceptor how to catch http 401 error and resubmit original request - nestjs

Question

I need to write an http header interceptor to add Authorization header, if there is a 401 error, submit another request for a new token, then resubmit the original request with the new token.
intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
const request = context.switchToHttp().getRequest();
const response = context.switchToHttp().getResponse();
return next.handle().pipe(
catchError(async error => {
if (error.response.status === 401) {
const originalRequest = error.config;
var authRes = await this.authenticationService.getAccessToken();
this.authenticationService.accessTokenSubject.next(authRes.access_token);
// I need to resubmit the original request with the new token from here
// but return next.handle(originalRequest) doesn't work
}
return throwError(error);
}),
);
}
But next.handle(originalRequest) doesn't work. How to resubmit the original request in the interceptor? Thank you very much in advance for your help.

Answer 1

I just encountered a similar problem, where I can catch the exception from exception filter but can't do so in interception layer.
So I looked up the manual and found it says:
Any exception thrown by a guard will be handled by the exceptions layer
(global exceptions filter and any exceptions filters that are applied to the current context).
So, if the exception is thrown from AuthGuard context(including the validate method in your AuthService), probably better to move the additional logic by extending the Authguard
like this:
export class CustomizedAuthGuard extends AuthGuard('strategy') {
handleRequest(err, user, info, context, status) {
if (err || !user) {
// your logic here
throw err || new UnauthorizedException();
}
return user;
}
}
or simply using customized exception filter.

Answer 2

It's been a while since the question but maybe it will help someone.
Ok, suppose that we need handle unauthorize exception out of route and guards, maybe service to service. So you can implement a interceptor like that and add some logic to get some data if needed, Ex: inject some Service in the interceptor.
So, throw an unauthorize exception and we are going to intercept it:
#Injectable()
export class UnauthorizedInterceptor implements NestInterceptor {
constructor(
private readonly authService: AuthService,
private readonly httpService: HttpService,
) {}
intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
return next.handle().pipe(
catchError((err) => {
const {
response: { status, config },
} = err;
// assuming we have a request body
const jsonData = JSON.parse(config.data);
if (status === HttpStatus.UNAUTHORIZED) {
// We can use some data in payload to find user data
// here for example the user email
if (jsonData?.email) {
return
from(this.authService.getByUserEmail(jsonData.email)).pipe(
switchMap((user: User) => {
if (user) {
// Ex: we can have stored token info in user entity.
// call function to refresh access token and update user data
// with new tokens
return from(this.authService.refreshToken(user)).pipe(
switchMap((updatedUser: User) => {
// now updatedUser have the new accessToken
const { accessToken } = updatedUser;
// set the new token to config (original request)
config.headers['Authorization'] = `Bearer ${accessToken}`;
// and use the underlying Axios instance created by #nestjs/axios
// to resubmit the original request
return of(this.httpService.axiosRef(config));
}),
);
}
}),
);
} else {
return throwError(() => new HttpException(err, Number(err.code)));
}
} else {
return throwError(() => new HttpException(err, Number(err.code)));
}
}),
);
}
}