How to refresh token in Nestjs

Question

import { ExtractJwt, Strategy } from 'passport-jwt';
import { AuthService } from './auth.service';
import { PassportStrategy } from '@nestjs/passport';
import { Injectable, UnauthorizedException } from '@nestjs/common';
import { JwtPayload } from './model/jwt-payload.model';

@Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
  constructor(private readonly authService: AuthService) {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      secretOrKey: 'secretKey',
    });
  }

  async validate(payload: JwtPayload) {
    const user = await this.authService.validateUser(payload);
    if (!user) {
      throw new UnauthorizedException();
    }
    return true;
  }
}

Token is extracted from the request by PassportStrategy. I don't know how to catch the error when the token expires or gets invalid. My purpose is if there is an error because the token expired, I need to refresh the token. Otherwise do something else.

Answer 1

Refresh token implementation could be handled in canActivate method in custom auth guard.

If the access token is expired, the refresh token will be used to obtain a new access token. In that process, refresh token is updated too.

If both tokens aren't valid, cookies will be cleared.

@Injectable()
export class CustomAuthGuard extends AuthGuard('jwt') {
  private logger = new Logger(CustomAuthGuard.name);

  constructor(
    private readonly authService: AuthService,
    private readonly userService: UserService,
  ) {
    super();
  }

  async canActivate(context: ExecutionContext): Promise<boolean> {
    const request = context.switchToHttp().getRequest();
    const response = context.switchToHttp().getResponse();

    try {
      const accessToken = ExtractJwt.fromExtractors([cookieExtractor])(request);
      if (!accessToken)
        throw new UnauthorizedException('Access token is not set');

      const isValidAccessToken = this.authService.validateToken(accessToken);
      if (isValidAccessToken) return this.activate(context);

      const refreshToken = request.cookies[REFRESH_TOKEN_COOKIE_NAME];
      if (!refreshToken)
        throw new UnauthorizedException('Refresh token is not set');
      const isValidRefreshToken = this.authService.validateToken(refreshToken);
      if (!isValidRefreshToken)
        throw new UnauthorizedException('Refresh token is not valid');

      const user = await this.userService.getByRefreshToken(refreshToken);
      const {
        accessToken: newAccessToken,
        refreshToken: newRefreshToken,
      } = this.authService.createTokens(user.id);

      await this.userService.updateRefreshToken(user.id, newRefreshToken);

      request.cookies[ACCESS_TOKEN_COOKIE_NAME] = newAccessToken;
      request.cookies[REFRESH_TOKEN_COOKIE_NAME] = newRefreshToken;

      response.cookie(ACCESS_TOKEN_COOKIE_NAME, newAccessToken, COOKIE_OPTIONS);
      response.cookie(
        REFRESH_TOKEN_COOKIE_NAME,
        newRefreshToken,
        COOKIE_OPTIONS,
      );

      return this.activate(context);
    } catch (err) {
      this.logger.error(err.message);
      response.clearCookie(ACCESS_TOKEN_COOKIE_NAME, COOKIE_OPTIONS);
      response.clearCookie(REFRESH_TOKEN_COOKIE_NAME, COOKIE_OPTIONS);
      return false;
    }
  }

  async activate(context: ExecutionContext): Promise<boolean> {
    return super.canActivate(context) as Promise<boolean>;
  }

  handleRequest(err, user) {
    if (err || !user) {
      throw new UnauthorizedException();
    }

    return user;
  }
}

Attaching user to the request is done in validate method in JwtStrategy class, it will be called if the access token is valid

@Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
  constructor(
    readonly configService: ConfigService,
    private readonly userService: UserService,
  ) {
    super({
      jwtFromRequest: cookieExtractor,
      ignoreExpiration: false,
      secretOrKey: configService.get('jwt.secret'),
    });
  }

  async validate({ id }): Promise<User> {
    const user = await this.userService.get(id);
    if (!user) {
      throw new UnauthorizedException();
    }

    return user;
  }
}

Example for custom cookie extractor

export const cookieExtractor = (request: Request): string | null => {
  let token = null;
  if (request && request.signedCookies) {
    token = request.signedCookies[ACCESS_TOKEN_COOKIE_NAME];
  }
  return token;
};

Answer 2

Instead of using the built-in AuthGuard you can create your own one and overwrite the request handler:

@Injectable()
export class MyAuthGuard extends AuthGuard('jwt') {

  handleRequest(err, user, info: Error) {
    if (info instanceof TokenExpiredError) {
      // do stuff when token is expired
      console.log('token expired');
    }
    return user;
  }

}

Depending on what you want to do, you can also overwrite the canActivate method where you have access to the request object. Have a look at the AuthGuard sourcecode.