OAuth2 作用域

FastAPI 无缝集成 OAuth2 作用域（Scopes），可以直接使用。

作用域是更精密的权限系统，遵循 OAuth2 标准，与 OpenAPI 应用（和 API 自动文档）集成。

OAuth2 也是脸书、谷歌、GitHub、微软、推特等第三方身份验证应用使用的机制。这些身份验证应用在用户登录应用时使用 OAuth2 提供指定权限。

脸书、谷歌、GitHub、微软、推特就是 OAuth2 作用域登录。

本章介绍如何在 FastAPI 应用中使用 OAuth2 作用域管理验证与授权。

警告

本章内容较难，刚接触 FastAPI 的新手可以跳过。

OAuth2 作用域不是必需的，没有它，您也可以处理身份验证与授权。

但 OAuth2 作用域与 API（通过 OpenAPI）及 API 文档集成地更好。

不管怎么说，FastAPI 支持在代码中使用作用域或其它安全/授权需求项。

很多情况下，OAuth2 作用域就像一把牛刀。

但如果您确定要使用作用域，或对它有兴趣，请继续阅读。

OAuth2 作用域与 OpenAPI

OAuth2 规范的作用域是由空格分割的字符串组成的列表。

这些字符串支持任何格式，但不能包含空格。

作用域表示的是权限。

OpenAPI 中（例如 API 文档）可以定义安全方案。

这些安全方案在使用 OAuth2 时，还可以声明和使用作用域。

作用域只是（不带空格的）字符串。

常用于声明特定安全权限，例如：

• 常见用例为，users:read 或 users:write
• 脸书和 Instagram 使用 instagram_basic
• 谷歌使用 https://www.googleapis.com/auth/drive

说明

OAuth2 中，作用域只是声明特定权限的字符串。

是否使用冒号 : 等符号，或是不是 URL 并不重要。

这些细节只是特定的实现方式。

对 OAuth2 来说，它们都只是字符串而已。

全局纵览

首先，快速浏览一下以下代码与用户指南中 OAuth2 实现密码哈希与 Bearer JWT 令牌验证一章中代码的区别。以下代码使用 OAuth2 作用域：

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

下面，我们逐步说明修改的代码内容。

OAuth2 安全方案

第一个修改的地方是，使用两个作用域 me 和 items 声明 OAuth2 安全方案。

scopes 参数接收字典，键是作用域、值是作用域的描述：

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

因为声明了作用域，所以登录或授权时会在 API 文档中显示。

此处，选择给予访问权限的作用域： me 和 items。

这也是使用脸书、谷歌、GitHub 登录时的授权机制。

JWT 令牌作用域

现在，修改令牌路径操作，返回请求的作用域。

此处仍然使用 OAuth2PasswordRequestForm。它包含类型为字符串列表的 scopes 属性，且scopes 属性中包含要在请求里接收的每个作用域。

这样，返回的 JWT 令牌中就包含了作用域。

危险

为了简明起见，本例把接收的作用域直接添加到了令牌里。

但在您的应用中，为了安全，应该只把作用域添加到确实需要作用域的用户，或预定义的用户。

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

在路径操作与依赖项中声明作用域

接下来，为路径操作 /users/me/items/ 声明作用域 items。

为此，要从 fastapi 中导入并使用 Security 。

Security 声明依赖项的方式和 Depends 一样，但 Security 还能接收作用域（字符串）列表类型的参数 scopes。

此处使用与 Depends 相同的方式，把依赖项函数 get_current_active_user 传递给 Security。

同时，还传递了作用域列表，本例中只传递了一个作用域：items（此处支持传递更多作用域）。

依赖项函数 get_current_active_user 还能声明子依赖项，不仅可以使用 Depends，也可以使用 Security。声明子依赖项函数（get_current_user）及更多作用域。

本例要求使用作用域 me（还可以使用更多作用域）。

笔记

不必在不同位置添加不同的作用域。

本例使用的这种方式只是为了展示 FastAPI 如何处理在不同层级声明的作用域。

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

技术细节

Security 实际上是 Depends 的子类，而且只比 Depends 多一个参数。

但使用 Security 代替 Depends，FastAPI 可以声明安全作用域，并在内部使用这些作用域，同时，使用 OpenAPI 存档 API。

但实际上，从 fastapi 导入的 Query、Path、Depends、Security 等对象，只是返回特殊类的函数。

使用 SecurityScopes

修改依赖项 get_current_user。

这是上面的依赖项使用的依赖项。

这里使用的也是之前创建的 OAuth2 方案，并把它声明为依赖项：oauth2_scheme。

该依赖项函数本身不需要作用域，因此，可以使用 Depends 和 oauth2_scheme。不需要指定安全作用域时，不必使用 Security。

此处还声明了从 fastapin.security 导入的 SecurityScopes 类型的特殊参数。

SecuriScopes 类与 Request 类似（Request 用于直接提取请求对象）。

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

使用 scopes

参数 security_scopes 的类型是 SecurityScopes。

它的属性 scopes 是作用域列表，所有依赖项都把它作为子依赖项。也就是说所有依赖……这听起来有些绕，后文会有解释。

（类 SecurityScopes 的）security_scopes 对象还提供了单字符串类型的属性 scope_str，该属性是（要在本例中使用的）用空格分割的作用域。

此处还创建了后续代码中要复用（raise）的 HTTPException 。

该异常包含了作用域所需的（如有），以空格分割的字符串（使用 scope_str）。该字符串要放到包含作用域的 WWW-Authenticate 请求头中（这也是规范的要求）。

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

校验 username 与数据形状

我们可以校验是否获取了 username，并抽取作用域。

然后，使用 Pydantic 模型校验数据（捕获 ValidationError 异常），如果读取 JWT 令牌或使用 Pydantic 模型验证数据时出错，就会触发之前创建的 HTTPException 异常。

对此，要使用新的属性 scopes 更新 Pydantic 模型 TokenData。

使用 Pydantic 验证数据可以确保数据中含有由作用域组成的字符串列表，以及 username 字符串等内容。

反之，如果使用字典或其它数据结构，就有可能在后面某些位置破坏应用，形成安全隐患。

还可以使用用户名验证用户，如果没有用户，也会触发之前创建的异常。

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

校验 scopes

接下来，校验所有依赖项和依赖要素（包括路径操作）所需的作用域。这些作用域包含在令牌的 scopes 里，如果不在其中就会触发 HTTPException 异常。

为此，要使用包含所有作用域字符串列表的 security_scopes.scopes， 。

from datetime import datetime, timedelta, timezone
from typing import List, Union

from fastapi import Depends, FastAPI, HTTPException, Security, status
from fastapi.security import (
    OAuth2PasswordBearer,
    OAuth2PasswordRequestForm,
    SecurityScopes,
)
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel, ValidationError

# to get a string like this run:
# openssl rand -hex 32
SECRET_KEY = "09d25e094faa6ca2556c818166b7a9563b93f7099f6f0f4caa6cf63b88e8d3e7"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30


fake_users_db = {
    "johndoe": {
        "username": "johndoe",
        "full_name": "John Doe",
        "email": "johndoe@example.com",
        "hashed_password": "$2b$12$EixZaYVK1fsbw1ZfbX3OXePaWxn96p36WQoeG6Lruj3vjPGga31lW",
        "disabled": False,
    },
    "alice": {
        "username": "alice",
        "full_name": "Alice Chains",
        "email": "alicechains@example.com",
        "hashed_password": "$2b$12$gSvqqUPvlXP2tfVFaWK1Be7DlH.PKZbv5H8KnzzVgXXbVxpva.pFm",
        "disabled": True,
    },
}


class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None
    scopes: List[str] = []


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl="token",
    scopes={"me": "Read information about the current user.", "items": "Read items."},
)

app = FastAPI()


def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)


def get_password_hash(password):
    return pwd_context.hash(password)


def get_user(db, username: str):
    if username in db:
        user_dict = db[username]
        return UserInDB(**user_dict)


def authenticate_user(fake_db, username: str, password: str):
    user = get_user(fake_db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user


def create_access_token(data: dict, expires_delta: Union[timedelta, None] = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.now(timezone.utc) + expires_delta
    else:
        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt


async def get_current_user(
    security_scopes: SecurityScopes, token: str = Depends(oauth2_scheme)
):
    if security_scopes.scopes:
        authenticate_value = f'Bearer scope="{security_scopes.scope_str}"'
    else:
        authenticate_value = "Bearer"
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)
    except (JWTError, ValidationError):
        raise credentials_exception
    user = get_user(fake_users_db, username=token_data.username)
    if user is None:
        raise credentials_exception
    for scope in security_scopes.scopes:
        if scope not in token_data.scopes:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Not enough permissions",
                headers={"WWW-Authenticate": authenticate_value},
            )
    return user


async def get_current_active_user(
    current_user: User = Security(get_current_user, scopes=["me"]),
):
    if current_user.disabled:
        raise HTTPException(status_code=400, detail="Inactive user")
    return current_user


@app.post("/token")
async def login_for_access_token(
    form_data: OAuth2PasswordRequestForm = Depends(),
) -> Token:
    user = authenticate_user(fake_users_db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(status_code=400, detail="Incorrect username or password")
    access_token_expires = timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    access_token = create_access_token(
        data={"sub": user.username, "scopes": form_data.scopes},
        expires_delta=access_token_expires,
    )
    return Token(access_token=access_token, token_type="bearer")


@app.get("/users/me/", response_model=User)
async def read_users_me(current_user: User = Depends(get_current_active_user)):
    return current_user


@app.get("/users/me/items/")
async def read_own_items(
    current_user: User = Security(get_current_active_user, scopes=["items"]),
):
    return [{"item_id": "Foo", "owner": current_user.username}]


@app.get("/status/")
async def read_system_status(current_user: User = Depends(get_current_user)):
    return {"status": "ok"}

依赖项树与作用域

再次查看这个依赖项树与作用域。

get_current_active_user 依赖项包含子依赖项 get_current_user，并在 get_current_active_user中声明了作用域 "me" 包含所需作用域列表 ，在 security_scopes.scopes 中传递给 get_current_user。

路径操作自身也声明了作用域，"items"，这也是 security_scopes.scopes 列表传递给 get_current_user 的。

依赖项与作用域的层级架构如下：

• 路径操作 read_own_items 包含：
  • 依赖项所需的作用域 ["items"]：
  • get_current_active_user:
    • 依赖项函数 get_current_active_user 包含：
      • 所需的作用域 "me" 包含依赖项：
      • get_current_user:
        • 依赖项函数 get_current_user 包含：
          • 没有作用域需求其自身
          • 依赖项使用 oauth2_scheme
          • security_scopes 参数的类型是 SecurityScopes：
            • security_scopes 参数的属性 scopes 是包含上述声明的所有作用域的列表，因此：
              • security_scopes.scopes 包含用于路径操作的 ["me", "items"]
              • security_scopes.scopes 包含路径操作 read_users_me 的 ["me"]，因为它在依赖项里被声明
              • security_scopes.scopes 包含用于路径操作 read_system_status 的 []（空列表），并且它的依赖项 get_current_user 也没有声明任何 scope

提示

此处重要且神奇的事情是，get_current_user 检查每个路径操作时可以使用不同的 scopes 列表。

所有这些都依赖于在每个路径操作和指定路径操作的依赖树中的每个依赖项。

SecurityScopes 的更多细节

您可以任何位置或多个位置使用 SecurityScopes，不一定非得在根依赖项中使用。

它总是在当前 Security 依赖项中和所有依赖因子对于特定 路径操作和特定依赖树中安全作用域

因为 SecurityScopes 包含所有由依赖项声明的作用域，可以在核心依赖函数中用它验证所需作用域的令牌，然后再在不同的路径操作中声明不同作用域需求。

它们会为每个路径操作进行单独检查。

查看文档

打开 API 文档，进行身份验证，并指定要授权的作用域。

没有选择任何作用域，也可以进行身份验证，但访问 /uses/me 或 /users/me/items 时，会显示没有足够的权限。但仍可以访问 /status/。

如果选择了作用域 me，但没有选择作用域 items，则可以访问 /users/me/，但不能访问 /users/me/items。

这就是通过用户提供的令牌使用第三方应用访问这些路径操作时会发生的情况，具体怎样取决于用户授予第三方应用的权限。

关于第三方集成

本例使用 OAuth2 密码流。

这种方式适用于登录我们自己的应用，最好使用我们自己的前端。

因为我们能控制自己的前端应用，可以信任它接收 username 与 password。

但如果构建的是连接其它应用的 OAuth2 应用，比如具有与脸书、谷歌、GitHub 相同功能的第三方身份验证应用。那您就应该使用其它安全流。

最常用的是隐式流。

最安全的是代码流，但实现起来更复杂，而且需要更多步骤。因为它更复杂，很多第三方身份验证应用最终建议使用隐式流。

笔记

每个身份验证应用都会采用不同方式会命名流，以便融合入自己的品牌。

但归根结底，它们使用的都是 OAuth2 标准。

FastAPI 的 fastapi.security.oauth2 里包含了所有 OAuth2 身份验证流工具。

装饰器 dependencies 中的 Security

同样，您可以在装饰器的 dependencies 参数中定义 Depends 列表，（详见路径操作装饰器依赖项)），也可以把 scopes 与 Security 一起使用。