文章

Flask - 角色與權限

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作者 Ned Hsu 7 分鐘閱讀

目標

  • 在用戶模型中添加角色字段
  • 實現權限檢查邏輯
  • 限制特定端點的操作

步驟

  1. 準備環境

    • 繼續使用 flask_api/ 項目結構，激活虛擬環境：
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      # Windows: flask_api_env\Scripts\activate
# macOS/Linux: source flask_api_env/bin/activate

  2. 更新模型

    • 修改 app/models.py，添加角色字段：

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      from . import db, bcrypt
from datetime import datetime

class User(db.Model):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(50), unique=True, nullable=False)
    password_hash = db.Column(db.String(128), nullable=False)
    role = db.Column(db.String(20), default='user')  # 新增角色字段：user 或 admin
    posts = db.relationship('Post', backref='user', lazy=True)

    def set_password(self, password):
        self.password_hash = bcrypt.generate_password_hash(password).decode('utf-8')

    def check_password(self, password):
        return bcrypt.check_password_hash(self.password_hash, password)

    @property
    def is_admin(self):
        return self.role == 'admin'

class Post(db.Model):
    __tablename__ = 'posts'
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100), nullable=False)
    content = db.Column(db.Text, nullable=False)
    created_at = db.Column(db.DateTime, default=datetime.utcnow)
    user_id = db.Column(db.Integer, db.ForeignKey('users.id'), nullable=False)
    category = db.Column(db.String(50), default='general')

    • 代碼解釋：

      • role：字符串字段，默認為 ‘user’，可設為 ‘admin’。
      • is_admin：屬性方法，方便檢查用戶是否為管理员。

  3. 更新序列化器

    • 修改 app/schemas.py，包含角色字段：

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      from . import ma
from .models import User, Post

class PostSchema(ma.SQLAlchemyAutoSchema):
    class Meta:
        model = Post
        include_fk = True
        fields = ('id', 'title', 'content', 'created_at', 'user_id', 'category')

class UserSchema(ma.SQLAlchemyAutoSchema):
    class Meta:
        model = User
        fields = ('id', 'username', 'role', 'posts')  # 添加 role
    posts = ma.Nested('PostSchema', many=True)

post_schema = PostSchema()
posts_schema = PostSchema(many=True)
user_schema = UserSchema()
users_schema = UserSchema(many=True)

  4. 實現權限檢查

    • 修改 app/init.py，添加權限裝飾器：

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      from flask import Flask, jsonify, g
from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow
from flask_bcrypt import Bcrypt
import jwt
from functools import wraps
from .routes.v1.todos import todos_bp as todos_v1_bp
from .routes.v1.users import users_bp as users_v1_bp
from .routes.v1.posts import posts_bp as posts_v1_bp
from .routes.v2.todos import todos_bp as todos_v2_bp
from .routes.v2.posts import posts_bp as posts_v2_bp
from .config import config_map
import os

db = SQLAlchemy()
ma = Marshmallow()
bcrypt = Bcrypt()

def create_app():
    app = Flask(__name__)
    env = os.getenv('FLASK_ENV', 'development')
    app.config.from_object(config_map[env])
    db.init_app(app)
    ma.init_app(app)
    bcrypt.init_app(app)

    app.register_blueprint(todos_v1_bp, url_prefix='/api/v1')
    app.register_blueprint(users_v1_bp, url_prefix='/api/v1')
    app.register_blueprint(posts_v1_bp, url_prefix='/api/v1')
    app.register_blueprint(todos_v2_bp, url_prefix='/api/v2')
    app.register_blueprint(posts_v2_bp, url_prefix='/api/v2')

    @app.errorhandler(404)
    def not_found(error):
        return jsonify({'error': 'Not Found', 'message': str(error)}), 404

    @app.errorhandler(400)
    def bad_request(error):
        return jsonify({'error': 'Bad Request', 'message': str(error)}), 400

    @app.errorhandler(500)
    def internal_error(error):
        return jsonify({'error': 'Internal Server Error', 'message': 'Something went wrong on our end'}), 500

    with app.app_context():
        db.create_all()

    return app

def login_required(f):
    @wraps(f)
    def decorated_function(*args, **kwargs):
        from .models import User
        token = request.headers.get('Authorization')
        if not token:
            abort(401, description='Missing token')
        try:
            if token.startswith('Bearer '):
                token = token[7:]
            data = jwt.decode(token, app.config['SECRET_KEY'], algorithms=['HS256'])
            user = User.query.get(data['user_id'])
            if not user:
                abort(401, description='Invalid token')
            g.current_user = user
        except jwt.ExpiredSignatureError:
            abort(401, description='Token has expired')
        except jwt.InvalidTokenError:
            abort(401, description='Invalid token')
        return f(*args, **kwargs)
    return decorated_function

def admin_required(f):
    @wraps(f)
    @login_required  # 先檢查登錄
    def decorated_function(*args, **kwargs):
        if not g.current_user.is_admin:
            abort(403, description='Admin access required')
        return f(*args, **kwargs)
    return decorated_function

  5. 更新路由

    • 修改 app/routes/v1/users.py，支持角色並限制管理操作：

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      from flask import Blueprint, jsonify, request, abort
from ...models import User
from ... import db, admin_required
from ...schemas import user_schema, users_schema
import jwt
import datetime

users_bp = Blueprint('users_v1', __name__)

@users_bp.route('/users', methods=['GET'])
def get_users():
    users = User.query.all()
    return jsonify({'users': users_schema.dump(users)})

@users_bp.route('/users', methods=['POST'])
def create_user():
    if not request.is_json:
        abort(400, description='Request must be JSON')
    data = request.get_json()
    if 'username' not in data or 'password' not in data:
        abort(400, description='Missing username or password')
    if User.query.filter_by(username=data['username']).first():
        abort(400, description='Username already exists')
    user = User(username=data['username'])
    user.set_password(data['password'])
    if data.get('role') in ['user', 'admin']:  # 限制角色值
        user.role = data['role']
    db.session.add(user)
    db.session.commit()
    return jsonify(user_schema.dump(user)), 201

@users_bp.route('/login', methods=['POST'])
def login():
    if not request.is_json:
        abort(400, description='Request must be JSON')
    data = request.get_json()
    if 'username' not in data or 'password' not in data:
        abort(400, description='Missing username or password')
    user = User.query.filter_by(username=data['username']).first()
    if not user or not user.check_password(data['password']):
        abort(401, description='Invalid credentials')
    token = jwt.encode({
        'user_id': user.id,
        'exp': datetime.datetime.utcnow() + datetime.timedelta(hours=24)
    }, users_bp.app.config['SECRET_KEY'], algorithm='HS256')
    return jsonify({'token': token})

@users_bp.route('/users/<int:user_id>', methods=['DELETE'])
@admin_required  # 僅管理员可刪除用戶
def delete_user(user_id):
    user = User.query.get_or_404(user_id, description='User not found')
    db.session.delete(user)
    db.session.commit()
    return jsonify({'message': 'User deleted'}), 200

    • 修改 app/routes/v1/posts.py，允許管理员操作他人文章：

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      from flask import Blueprint, jsonify, request, abort, g
from ...models import Post, User
from ... import db, login_required, admin_required
from ...schemas import post_schema, posts_schema

posts_bp = Blueprint('posts_v1', __name__)

@posts_bp.route('/posts', methods=['GET'])
def get_posts():
    user_id = request.args.get('user_id', type=int)
    query = Post.query
    if user_id:
        query = query.filter_by(user_id=user_id)
    posts = query.all()
    return jsonify({'posts': posts_schema.dump(posts)})

@posts_bp.route('/posts/<int:post_id>', methods=['GET'])
def get_post(post_id):
    post = Post.query.get_or_404(post_id, description='Post not found')
    return jsonify(post_schema.dump(post))

@posts_bp.route('/posts', methods=['POST'])
@login_required
def create_post():
    if not request.is_json:
        abort(400, description='Request must be JSON')
    data = request.get_json()
    if 'title' not in data or 'content' not in data:
        abort(400, description='Missing title or content')
    post = Post(
        title=data['title'],
        content=data['content'],
        user_id=g.current_user.id
    )
    db.session.add(post)
    db.session.commit()
    return jsonify(post_schema.dump(post)), 201

@posts_bp.route('/posts/<int:post_id>', methods=['PUT'])
@login_required
def update_post(post_id):
    post = Post.query.get_or_404(post_id, description='Post not found')
    if post.user_id != g.current_user.id and not g.current_user.is_admin:
        abort(403, description='You can only edit your own posts unless you are an admin')
    if not request.is_json:
        abort(400, description='Request must be JSON')
    data = request.get_json()
    if 'title' in data:
        post.title = data['title']
    if 'content' in data:
        post.content = data['content']
    db.session.commit()
    return jsonify(post_schema.dump(post)), 200

@posts_bp.route('/posts/<int:post_id>', methods=['DELETE'])
@login_required
def delete_post(post_id):
    post = Post.query.get_or_404(post_id, description='Post not found')
    if post.user_id != g.current_user.id and not g.current_user.is_admin:
        abort(403, description='You can only delete your own posts unless you are an admin')
    db.session.delete(post)
    db.session.commit()
    return jsonify({'message': 'Post deleted'}), 200

@posts_bp.route('/posts/all', methods=['DELETE'])
@admin_required  # 僅管理员可批量刪除
def delete_all_posts():
    Post.query.delete()
    db.session.commit()
    return jsonify({'message': 'All posts deleted'}), 200

  6. 運行應用

    • 刪除舊的 blog.db（因表結構改變），運行：
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      python run.py

  7. 測試 API

    • 使用 Postman 測試：
      • POST /api/v1/users（普通用戶）：
        • Body：{"username": "alice", "password": "1234"}
      • POST /api/v1/users（管理员）：
        • Body：{"username": "admin", "password": "admin123", "role": "admin"}
      • POST /api/v1/login（普通用戶）：
        • Body：{"username": "alice", "password": "1234"}
        • 獲取 token1。
      • POST /api/v1/login（管理员）：
        • Body：{"username": "admin", "password": "admin123"}
        • 獲取 token2。
      • POST /api/v1/posts（用 token1）：
        • Headers：Authorization: Bearer <token1>
        • Body：{"title": "My Post", "content": "Hello"}
      • DELETE /api/v1/users/1（用 token1）：
        • 預期響應：403
      • DELETE /api/v1/users/1（用 token2）：
        • 預期響應：200
      • PUT /api/v1/posts/1（用 token2，修改他人文章）：
        • 預期響應：200

  8. 作業

    • 在 v2 的 posts 路由中實現相同的角色和權限邏輯。
    • 添加一個端點 GET /api/v1/users/<int:user_id>/role，允許管理员查看和更新用戶角色。

注意事項

  • 表結構改變後需重建數據庫。
  • 角色值應嚴格控制，避免無效輸入。
  • 實際應用中應限制誰能設置 role=admin。
Software, Python
Flask
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