Nestjs Passport-jwt better Unauthorized strategy - nestjs

Question

just going through docs on authentication in NestJS: docs.nestjs.com
Here is the code:
import { ExtractJwt, Strategy } from 'passport-jwt';
import { PassportStrategy } from '#nestjs/passport';
import { Injectable } from '#nestjs/common';
import { jwtConstants } from './constants';
#Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
constructor() {
super({
jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
ignoreExpiration: false,
secretOrKey: jwtConstants.secret,
});
}
async validate(payload: any) {
return { userId: payload.sub, username: payload.username };
}
}
According to docs validate method is called when request contains jwt and that jwt is valid.
I am wondering is there a callback method for the case when jwt is missing from request header, or jwt is invalid or expired. I would like to return response error with message to client that their token is expired or missing...
Thanks

Answer 1

You could implement a custom strategy and check headers or cookies how you like. This is a (shortened) exmaple I'am using on my app.
import { JwtService } from '#nestjs/jwt';
import { Strategy } from 'passport-custom';
#Injectable()
export class JwtStrategy extends PassportStrategy(Strategy, 'custom-jwt') {
constructor(private readonly jwtService: JwtService) {
super();
}
async validate(req: Request): Promise<any> {
const token = req.cookies.auth ?? req.headers.authorization;
if (!token) {
throw new UnauthorizedException();
}
const user = this.jwtService.decode(token, {
json: true
});
if (!user) {
throw new UnauthorizedException();
}
if (this.isExpired(user)) {
throw new UnauthorizedException();
}
return user;
}
private isExpired(user: JwtUserDto): boolean {
// ...
}
}
This code checks for a jwt token either in a "auth"-cookie or in "Authorization"-header and by returning user, it attaches the decoded user (if valid) to the request.
To use it: export class JwtAuthGuard extends AuthGuard('custom-jwt')
It's just an example, to see how it works. You might need to adapt it to fit your needs.