Integración del flujo de contraseña de OAuth2

Intro to OAuth2 Password Flow

Why Use Password Flow?

Key FastAPI Components

Setting up OAuth2PasswordBearer

from fastapi import FastAPI
from fastapi.security import OAuth2PasswordBearer

app = FastAPI()

# 'token' is the URL path where clients will log in
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

# We will create a @app.post("/token") endpoint next!

The Login Endpoint: /token

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordRequestForm

@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends()
):
    # 1. Authenticate user (verify username/password)
    # 2. If valid, create an access token
    # 3. Return the token
    pass # Details coming in the next scene!

Full Code: Login & Protected Endpoint

from fastapi import FastAPI, Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer, OAuth2PasswordRequestForm
from pydantic import BaseModel
from typing import Optional

app = FastAPI()

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

# --- Mock User & Token Logic (Simplified for this lesson) ---
class UserInDB(BaseModel):
    username: str
    hashed_password: str
    disabled: Optional[bool] = None

class CurrentUser(BaseModel):
    username: str
    email: Optional[str] = None
    full_name: Optional[str] = None
    disabled: Optional[bool] = None

fake_users_db = {
    "testuser": UserInDB(username="testuser", hashed_password="password123", disabled=False),
    "disableduser": UserInDB(username="disableduser", hashed_password="securepass", disabled=True)
}

def get_user_from_db(username: str):
    user_data = fake_users_db.get(username)
    if user_data:
        return CurrentUser(username=user_data.username, full_name=f"{user_data.username} Full", email=f"{user_data.username}@example.com", disabled=user_data.disabled)
    return None

def authenticate_user(username: str, password: str):
    user_in_db = fake_users_db.get(username)
    if not user_in_db or user_in_db.hashed_password != password: # In real app, use password hashing
        return None
    return get_user_from_db(username)

def create_access_token(data: dict):
    # In a real app, use `jwt.encode` with a secret key (from Lesson 1)
    return f"mock_jwt_for_{data['sub']}"
# --- End Mock Logic ---

@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends()
):
    user = authenticate_user(form_data.username, form_data.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username or password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    if user.disabled:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Inactive user"
        )
    access_token = create_access_token(data={"sub": user.username})
    return {"access_token": access_token, "token_type": "bearer"}

# Dependency to get the current user from the token
async def get_current_user(token: str = Depends(oauth2_scheme)):
    # In a real app, this would decode and validate the JWT (from Lesson 1)
    if not token.startswith("mock_jwt_for_"):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid authentication credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    username = token.replace("mock_jwt_for_", "")
    user = get_user_from_db(username)
    if user is None or user.disabled:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid authentication credentials or inactive user",
            headers={"WWW-Authenticate": "Bearer"},
        )
    return user

# A Protected Endpoint
@app.get("/users/me/", response_model=CurrentUser)
async def read_users_me(current_user: CurrentUser = Depends(get_current_user)):
    return current_user

Understanding get_current_user

How Clients Interact

Quick Check: OAuth2 Components

Recap: OAuth2 Password Flow