KC-APP-Server/src/auth/token-verification.service.ts

import { Injectable, UnauthorizedException } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { JwtService } from '@nestjs/jwt';
import * as jwt from 'jsonwebtoken';
import * as jwksRsa from 'jwks-rsa';
import { PrismaClient } from '../prisma/prisma.module';
import { SyncService } from '../sync/sync.service';
import { AuthenticatedUser } from './authenticated-request';
import { GuestJwtPayload } from './guest-auth.service';
import { TeamAuthService } from './team-auth.service';
import {
  AuthentikClaims,
  authentikEmail,
  resolveOrProvisionAuthentikUser,
  toAuthenticatedUser,
} from './provision-user';

/// Verifies raw bearer tokens outside the HTTP/passport pipeline, needed for
/// the WebSocket handshake where AuthGuard('authentik'|'guest') don't apply.
@Injectable()
export class TokenVerificationService {
  private readonly issuerUrl: string;
  private readonly jwks: jwksRsa.JwksClient;
  private readonly leitungsteamGroup: string;

  constructor(
    private readonly config: ConfigService,
    private readonly prisma: PrismaClient,
    private readonly guestJwt: JwtService,
    private readonly teamAuth: TeamAuthService,
    private readonly sync: SyncService,
  ) {
    // See AuthentikStrategy: normalise the trailing slash, accept both forms.
    this.issuerUrl = config.getOrThrow<string>('AUTHENTIK_ISSUER_URL').replace(/\/+$/, '');
    this.jwks = jwksRsa({ jwksUri: `${this.issuerUrl}/jwks/`, cache: true, rateLimit: true });
    this.leitungsteamGroup = config.get<string>('AUTHENTIK_LEITUNGSTEAM_GROUP', 'Leitungsteam');
  }

  /// Verifies an Authentik token's signature and returns its identity claims
  /// plus whether the caller is in the Leitungsteam group, without requiring
  /// a local User to exist yet (used by the onboarding self-registration
  /// path, which provisions that User).
  async verifyAuthentikClaims(
    token: string,
  ): Promise<AuthentikClaims & { isLeitungsteam: boolean }> {
    const decoded = jwt.decode(token, { complete: true });
    const kid = decoded?.header.kid;
    if (!kid) {
      throw new UnauthorizedException('Malformed Authentik token');
    }
    const key = await this.jwks.getSigningKey(kid);
    const payload = jwt.verify(token, key.getPublicKey(), {
      issuer: [this.issuerUrl, `${this.issuerUrl}/`],
      algorithms: ['RS256'],
    }) as jwt.JwtPayload & {
      email?: string;
      given_name?: string;
      family_name?: string;
      preferred_username?: string;
      name?: string;
      groups?: string[];
    };
    const sub = payload.sub;
    if (!sub) {
      throw new UnauthorizedException('Authentik token missing subject');
    }
    return {
      sub,
      email: authentikEmail({
        email: payload.email,
        preferred_username: payload.preferred_username,
        sub,
      }),
      firstName: payload.given_name ?? payload.preferred_username ?? payload.name ?? '',
      lastName: payload.family_name ?? '',
      isLeitungsteam: (payload.groups ?? []).includes(this.leitungsteamGroup),
    };
  }

  async verifyAuthentik(token: string): Promise<AuthenticatedUser> {
    const { isLeitungsteam, ...claims } = await this.verifyAuthentikClaims(token);
    const user = await resolveOrProvisionAuthentikUser(
      this.prisma,
      this.sync,
      claims,
      isLeitungsteam,
    );
    return toAuthenticatedUser(user);
  }

  async verifyGuest(token: string): Promise<GuestJwtPayload> {
    return this.guestJwt.verifyAsync<GuestJwtPayload>(token);
  }

  /// Tries Authentik, then a local team (Teamer) token, then a guest token.
  async verifyEither(token: string): Promise<
    { kind: 'user'; user: AuthenticatedUser } | { kind: 'guest'; guest: GuestJwtPayload }
  > {
    try {
      return { kind: 'user', user: await this.verifyAuthentik(token) };
    } catch {
      // not an Authentik token
    }
    try {
      return { kind: 'user', user: await this.teamAuth.verify(token) };
    } catch {
      return { kind: 'guest', guest: await this.verifyGuest(token) };
    }
  }
}