"Token inválido" no keycloak

Estas 3 etapas podem verificar o token

Step 1: Obtenha o certificado de chave pública do Keycloak para verificar a assinatura do token JWT.

Step 2: Converta o certificado em um formato de chave pública utilizável.

Step 3: Decodifique e verifique a assinatura do token JWT usando a chave pública, ignorando as verificações de público e emissor.

    # Step 1: Get public key for signature verification
    certs_url = f"{self.keycloak_url}/realms/{self.realm}/protocol/openid-connect/certs"
    certs_response = requests.get(certs_url)
    certs_response.raise_for_status()
    public_key_data = certs_response.json()
    certificate_pem = f"-----BEGIN CERTIFICATE-----\n{public_key_data['keys'][0]['x5c'][0]}\n-----END CERTIFICATE-----"

    # Step 2: Convert certificate to public key
    cert = x509.load_pem_x509_certificate(certificate_pem.encode('utf-8'), default_backend())
    public_key = cert.public_key().public_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PublicFormat.SubjectPublicKeyInfo
    )

    # Step 3: Use jwt.decode only for signature verification, disabling audience and issuer checks
    jwt.decode(
        token,
        public_key,
        algorithms=['RS256'],
        options={
            'verify_aud': False,
            'verify_iss': False
        }
    )

Iniciando o Key Cloak pelo Docker Compose

version: '3.8'

services:
  postgres:
    image: postgres:15.6
    container_name: postgres_db
    restart: always
    ports:
      - "5432:5432"
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      POSTGRES_DB: keycloak
      POSTGRES_USER: keycloak
      POSTGRES_PASSWORD: password

  keycloak_web:
    image: quay.io/keycloak/keycloak:26.0.5
    container_name: keycloak_web
    environment:
      KC_DB: postgres
      KC_DB_URL: jdbc:postgresql://postgres:5432/keycloak
      KC_DB_USERNAME: keycloak
      KC_DB_PASSWORD: password

      KC_HOSTNAME: localhost
      KC_HOSTNAME_STRICT: false
      KC_HOSTNAME_STRICT_HTTPS: false

      KC_LOG_LEVEL: info
      KC_METRICS_ENABLED: true
      KC_HEALTH_ENABLED: true
      KEYCLOAK_ADMIN: admin
      KEYCLOAK_ADMIN_PASSWORD: admin
    command: start-dev
    depends_on:
      - postgres
    ports:
      - 8080:8080

volumes:
  postgres_data:

Criar reino e usuário

realm

fastapi-realm

user

username: user1
password: 1234

Instalar dependência no Python 3.12 com conda

pip install fastapi uvicorn requests python-keycloak python-jose cryptography

Código do servidor FastAPI

api-server.py

from fastapi import FastAPI, HTTPException, Depends
from pydantic import BaseModel
from starlette.responses import JSONResponse
from keycloak import KeycloakOpenID
from jose import jwt, JWTError
from cryptography import x509
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization

import requests
import json

app = FastAPI()

# Configuration variables
KEYCLOAK_URL = 'http://localhost:8080'
REALM = 'fastapi-realm'
TOKEN_URL = f"{KEYCLOAK_URL}/realms/{REALM}/protocol/openid-connect/token"
KEYCLOAK_CLIENT_ID = 'admin-cli'

# Keycloak service class
class KeycloakService:
    def __init__(self):
        self.keycloak_url = KEYCLOAK_URL
        self.realm = REALM

    def decode_and_print_token(self, token):
        try:
            # Retrieve claims without verifying the signature or audience
            decoded_token = jwt.get_unverified_claims(token)
            print("Decoded JWT token:")
            print(json.dumps(decoded_token, indent=4))
            return decoded_token
        except JWTError as e:
            print(f"Error decoding token: {e}")
            return None
        
    def validate_token(self, token: str, client_id: str) -> bool:
        decoded_token = self.decode_and_print_token(token)
        if not decoded_token:
            print("Failed to decode token.")
            return False

        try:
            # Extract issuer, azp, and aud directly from decoded token
            issuer = decoded_token.get('iss')
            authorized_party = decoded_token.get('azp')
            audience = decoded_token.get('aud')

            print("Issuer (iss) in token:", issuer)
            print("Authorized party (azp) in token:", authorized_party)
            print("Audience (aud) in token:", audience)

            expected_issuer = f"{self.keycloak_url}/realms/{self.realm}"
            if issuer != expected_issuer:
                print(f"Invalid issuer. Expected: {expected_issuer}, Got: {issuer}")
                return False

            # Allow `aud` to be `None` for user tokens, or match "account" or the client_id for client tokens
            if audience is None:
                print("Audience is None, assuming this is a user token without an audience.")
            elif audience not in ["account", client_id]:
                print(f"Invalid audience. Expected: 'account' or '{client_id}', Got: {audience}")
                return False

            # Step 1: Get public key for signature verification
            certs_url = f"{self.keycloak_url}/realms/{self.realm}/protocol/openid-connect/certs"
            certs_response = requests.get(certs_url)
            certs_response.raise_for_status()
            public_key_data = certs_response.json()
            certificate_pem = f"-----BEGIN CERTIFICATE-----\n{public_key_data['keys'][0]['x5c'][0]}\n-----END CERTIFICATE-----"

            # Step 2: Convert certificate to public key
            cert = x509.load_pem_x509_certificate(certificate_pem.encode('utf-8'), default_backend())
            public_key = cert.public_key().public_bytes(
                encoding=serialization.Encoding.PEM,
                format=serialization.PublicFormat.SubjectPublicKeyInfo
            )

            # Step 3: Use jwt.decode only for signature verification, disabling audience and issuer checks
            jwt.decode(
                token,
                public_key,
                algorithms=['RS256'],
                options={
                    'verify_aud': False,
                    'verify_iss': False
                }
            )
            print("Token signature is valid.")
            return True
        except JWTError as e:
            print(f"Error validating token: {e}")
            return False
        except requests.RequestException as e:
            print(f"Error fetching public key: {e}")
            return False

keycloak_service = KeycloakService()

# Schemas
class Login(BaseModel):
    login: str
    password: str

class VerifyToken(BaseModel):
    token: str
    client_id: str

# Login endpoint
@app.post("/login")
def get_token(body: Login):
    data = {
        "grant_type": "password",
        "client_id": KEYCLOAK_CLIENT_ID,
        "username": body.login,
        "password": body.password
    }
    response = requests.post(TOKEN_URL, data=data, verify=False)
    if response.status_code == 200:
        return JSONResponse(status_code=200, content=response.json())
    else:
        raise HTTPException(status_code=response.status_code, detail=response.json())

# Verify endpoint
@app.post("/verify")
def verify_token(body: VerifyToken):
    is_valid = keycloak_service.validate_token(body.token, body.client_id)
    return {"valid": is_valid}

Iniciando o servidor FastAPI

uvicorn api-server:app --reload

API document URL

http://localhost:8000/docs#/

Obter Token pelo Carteiro

URL

POST http://localhost:8000/login

Input Body

{
  "login": "user1",
  "password": "1234"
}

Scriptpara atribuir variável user_token

var jsonData = JSON.parse(responseBody);

if (jsonData.access_token) {
    postman.setEnvironmentVariable("user_token", jsonData.access_token);
} else {
    console.error("access_token not found in the response");
}

Verificar Token pelo Postman

URL

POST http://localhost:8000/verify

Input Body

{
  "token": "{{user_token}}",
  "client_id": "admin-cli"
}

Então o token do usuário foi verificado com valor OK (verdadeiro).

Resultado válido do token

{
    "valid": true
}