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DocsUnidad 3: usuarios

Cree una aplicación de notas con Nexy, parte 12: restablezca una contraseña olvidada por correo electrónico

La parte 12 envía un enlace por correo electrónico a un usuario que olvidó su contraseña. El enlace abre un formulario para una nueva contraseña, funciona durante una hora y solo una vez.

Antes de comenzar: la aplicación de la parte 11.

enviar un correo electrónico

smtplib, de la biblioteca estándar, se comunica con cualquier servidor de correo: el de su proveedor o un servicio como Postmark, Resend o Amazon SES, todos los cuales aceptan SMTP. Sin servidor, el correo electrónico se imprime en la terminal de nexy dev, que es todo lo que necesitas en tu computadora:

src/correo.py
import osimport smtplibfrom email.message import EmailMessage  def send_email(to: str, subject: str, body: str) -> None:    """Send through the SMTP server named in `.env`; without one, print the email instead."""    host = os.getenv("SMTP_HOST")    if not host:        print(f"To: {to}\nSubject: {subject}\n\n{body}", flush=True)        return    message = EmailMessage()    message["From"] = os.getenv("MAIL_FROM", "notes@localhost")    message["To"] = to    message["Subject"] = subject    message.set_content(body)    with smtplib.SMTP(host, int(os.getenv("SMTP_PORT", "587"))) as smtp:        smtp.starttls()        smtp.login(os.environ["SMTP_USER"], os.environ["SMTP_PASSWORD"])        smtp.send_message(message)

Para enviar de verdad, agregue el servidor a .env:

SMTP_HOST=smtp.example.comSMTP_PORT=587SMTP_USER=notes@example.comSMTP_PASSWORD=the-password-of-the-mailboxMAIL_FROM=notes@example.comAPP_URL=https://notes.example.com

starttls() cifra la conexión antes de enviar la contraseña.

Crea un enlace que funcione una vez, durante una hora

El enlace lleva un token firmado con el secreto de sesión, por lo que nadie puede crear uno a mano. itsdangerous escribe la hora en él y max_age la rechaza después de una hora. El token también contiene el final del hash de la contraseña: una vez que la contraseña cambia, el hash cambia y el enlace deja de funcionar.

src/contraseña_reset.py
import os from itsdangerous import BadSignature, URLSafeTimedSerializerfrom sqlmodel import Session, select from src.accounts import hash_passwordfrom src.configs.db import enginefrom src.models.user_model import User ONE_HOUR = 3600  def signer() -> URLSafeTimedSerializer:    return URLSafeTimedSerializer(os.environ["SESSION_SECRET"], salt="password-reset")  def find_by_email(email: str) -> User | None:    with Session(engine) as session:        return session.exec(select(User).where(User.email == email)).first()  def reset_token(user: User) -> str:    """A token that names the user and the end of their current password hash."""    return signer().dumps([user.id, user.password_hash[-16:]])  def user_of(token: str) -> User | None:    """The user of a token less than an hour old, whose password has not changed since."""    try:        user_id, fingerprint = signer().loads(token, max_age=ONE_HOUR)    except BadSignature:        return None    with Session(engine) as session:        user = session.get(User, user_id)    if user is None or user.password_hash[-16:] != fingerprint:        return None    return user  def set_password(user_id: int, password: str) -> None:    with Session(engine) as session:        user = session.get(User, user_id)        user.password_hash = hash_password(password)        session.commit()
src/contraseña_reset.py
import os from itsdangerous import BadSignature, URLSafeTimedSerializerfrom sqlmodel import Session, select from src.accounts import hash_passwordfrom src.apps.users.user_model import Userfrom src.configs.db import engine ONE_HOUR = 3600  def signer() -> URLSafeTimedSerializer:    return URLSafeTimedSerializer(os.environ["SESSION_SECRET"], salt="password-reset")  def find_by_email(email: str) -> User | None:    with Session(engine) as session:        return session.exec(select(User).where(User.email == email)).first()  def reset_token(user: User) -> str:    """A token that names the user and the end of their current password hash."""    return signer().dumps([user.id, user.password_hash[-16:]])  def user_of(token: str) -> User | None:    """The user of a token less than an hour old, whose password has not changed since."""    try:        user_id, fingerprint = signer().loads(token, max_age=ONE_HOUR)    except BadSignature:        return None    with Session(engine) as session:        user = session.get(User, user_id)    if user is None or user.password_hash[-16:] != fingerprint:        return None    return user  def set_password(user_id: int, password: str) -> None:    with Session(engine) as session:        user = session.get(User, user_id)        user.password_hash = hash_password(password)        session.commit()

Solicite el enlace y luego úselo.

src/acciones/contraseña_reset.py
import osfrom urllib.parse import urlencode from nexy.decorators import Actionfrom nexy.http import RedirectResponsefrom src.mail import send_emailfrom src.password_reset import find_by_email, reset_token, set_password, user_of MIN_PASSWORD = 8  def go(path: str, **query: str) -> RedirectResponse:    return RedirectResponse(f"{path}?{urlencode(query)}" if query else path, status_code=303)  @Actionasync def request_reset(email: str) -> RedirectResponse:    user = find_by_email(email.strip().lower())    if user is not None:        link = f"{os.getenv('APP_URL', 'http://localhost:3000')}/reset?token={reset_token(user)}"        body = f"Open this link within an hour to choose a new password:\n\n{link}\n"        send_email(user.email, "Reset your password", body)    return go("/forgot", sent="1")  @Actionasync def reset_password(token: str, password: str) -> RedirectResponse:    user = user_of(token)    if user is None:        return go("/forgot", error="This link has expired or was used. Ask for a new one.")    if len(password) < MIN_PASSWORD:        return go("/reset", token=token, error=f"A password has at least {MIN_PASSWORD} characters.")    set_password(user.id, password)    return go("/signin", reset="1")

request_reset responde de la misma manera ya sea que el correo electrónico tenga una cuenta o no: la página dice que un enlace puede estar en camino, por lo que no le dice a nadie qué correos electrónicos están registrados.

Las dos páginas y un enlace a ellas.

src/rutas/olvidó.nexy
---from nexy import useSearchParams params = useSearchParams()sent = params.get("sent") == "1"error = params.get("error", "")---<section class="app-page">  <h1>Forgot your password?</h1>   {% if sent %}  <p role="status">If an account uses this email, a link to reset its password is on its way.</p>  {% endif %}  {% if error %}  <p class="note-error" role="alert">{{ error | e }}</p>  {% endif %}   <form method="post" action="{{ __actions_path['request_reset'] }}">    <label>Email <input type="email" name="email" autocomplete="email" required></label>    <button type="submit">Send the link</button>  </form></section>
src/rutas/reset.nexy
---from nexy import useSearchParams params = useSearchParams()token = params.get("token", "")error = params.get("error", "")---<section class="app-page">  <h1>Choose a new password</h1>   {% if error %}  <p class="note-error" role="alert">{{ error | e }}</p>  {% endif %}   <form method="post" action="{{ __actions_path['reset_password'] }}">    <input type="hidden" name="token" value="{{ token | e }}">    <label>New password <input type="password" name="password" autocomplete="new-password" minlength="8" required></label>    <button type="submit">Save the password</button>  </form></section>
src/rutas/signin.nexy
---from nexy import useSearchParams params = useSearchParams()error = params.get("error", "")reset = params.get("reset") == "1"---<section class="app-page">  <h1>Sign in</h1>   {% if reset %}  <p role="status">Your password is changed: sign in with the new one.</p>  {% endif %}  {% if error %}  <p class="note-error" role="alert">{{ error | e }}</p>  {% endif %}   <form method="post" action="{{ __actions_path['sign_in'] }}">    <label>Email <input type="email" name="email" autocomplete="email" required></label>    <label>Password <input type="password" name="password" autocomplete="current-password" required></label>    <button type="submit">Sign in</button>  </form>   <a href="/forgot">Forgot your password?</a>  <a href="/signup">Create an account</a></section>
src/apps/users/forgot_view.nexy
---from nexy import useSearchParams params = useSearchParams()sent = params.get("sent") == "1"error = params.get("error", "")---<section class="app-page">  <h1>Forgot your password?</h1>   {% if sent %}  <p role="status">If an account uses this email, a link to reset its password is on its way.</p>  {% endif %}  {% if error %}  <p class="note-error" role="alert">{{ error | e }}</p>  {% endif %}   <form method="post" action="{{ __actions_path['request_reset'] }}">    <label>Email <input type="email" name="email" autocomplete="email" required></label>    <button type="submit">Send the link</button>  </form></section>
src/apps/users/reset_view.nexy
---from nexy import useSearchParams params = useSearchParams()token = params.get("token", "")error = params.get("error", "")---<section class="app-page">  <h1>Choose a new password</h1>   {% if error %}  <p class="note-error" role="alert">{{ error | e }}</p>  {% endif %}   <form method="post" action="{{ __actions_path['reset_password'] }}">    <input type="hidden" name="token" value="{{ token | e }}">    <label>New password <input type="password" name="password" autocomplete="new-password" minlength="8" required></label>    <button type="submit">Save the password</button>  </form></section>
src/apps/users/signin_view.nexy
---from nexy import useSearchParams params = useSearchParams()error = params.get("error", "")reset = params.get("reset") == "1"---<section class="app-page">  <h1>Sign in</h1>   {% if reset %}  <p role="status">Your password is changed: sign in with the new one.</p>  {% endif %}  {% if error %}  <p class="note-error" role="alert">{{ error | e }}</p>  {% endif %}   <form method="post" action="{{ __actions_path['sign_in'] }}">    <label>Email <input type="email" name="email" autocomplete="email" required></label>    <label>Password <input type="password" name="password" autocomplete="current-password" required></label>    <button type="submit">Sign in</button>  </form>   <a href="/forgot">Forgot your password?</a>  <a href="/signup">Create an account</a></section>
src/apps/users/users_controller.py
from nexy.decorators import Controllerfrom nexy.hooks import useViews LAYOUT = "src/apps/layout.nexy"  def page(view: str):    return useViews(LAYOUT, context={"children": useViews(view)})  @Controller("/signup")class SignUpController:    async def get(self):        return page("src/apps/users/signup_view.nexy")  @Controller("/signin")class SignInController:    async def get(self):        return page("src/apps/users/signin_view.nexy")  @Controller("/forgot")class ForgotController:    async def get(self):        return page("src/apps/users/forgot_view.nexy")  @Controller("/reset")class ResetController:    async def get(self):        return page("src/apps/users/reset_view.nexy")
src/apps/app_module.py
from nexy.decorators import Module from .app_controller import AboutController, AppControllerfrom .notes.notes_controller import NoteController, NotesApiController, NotesControllerfrom .users.users_controller import (    ForgotController,    ResetController,    SignInController,    SignUpController,)  @Module()class AppModule:    controllers = [        AppController,        AboutController,        NotesController,        NoteController,        NotesApiController,        SignUpController,        SignInController,        ForgotController,        ResetController,    ]

role="status" hace que un lector de pantalla lea el mensaje sin interrumpir, donde role="alert" interrumpe: una confirmación no es un error.

Abra http://localhost:3000/forgot, escriba el correo electrónico de su cuenta y envíe. La terminal de nexy dev imprime el correo electrónico: abre su enlace, elige una nueva contraseña e inicia sesión con él. Abre el enlace por segunda vez: es rechazado.

lo que aprendiste

  • smtplib envía un correo electrónico a través de cualquier servidor SMTP; en desarrollo, imprimirlo es suficiente.
  • Un token firmado y cronometrado de itsdangerous crea un vínculo que nadie puede falsificar y es válido por una hora.
  • Poner parte del hash de la contraseña en el token hace que el enlace funcione solo una vez.

Próximos pasos

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