Initial commit

2025-11-29 18:34:03 +08:00
commit 0a77775e5d
11 changed files with 4474 additions and 0 deletions
--- a/skills/auth-implementation-patterns/SKILL.md
+++ b/skills/auth-implementation-patterns/SKILL.md
@@ -0,0 +1,634 @@
+---
+name: auth-implementation-patterns
+description: Master authentication and authorization patterns including JWT, OAuth2, session management, and RBAC to build secure, scalable access control systems. Use when implementing auth systems, securing APIs, or debugging security issues.
+---
+
+# Authentication & Authorization Implementation Patterns
+
+Build secure, scalable authentication and authorization systems using industry-standard patterns and modern best practices.
+
+## When to Use This Skill
+
+- Implementing user authentication systems
+- Securing REST or GraphQL APIs
+- Adding OAuth2/social login
+- Implementing role-based access control (RBAC)
+- Designing session management
+- Migrating authentication systems
+- Debugging auth issues
+- Implementing SSO or multi-tenancy
+
+## Core Concepts
+
+### 1. Authentication vs Authorization
+
+**Authentication (AuthN)**: Who are you?
+- Verifying identity (username/password, OAuth, biometrics)
+- Issuing credentials (sessions, tokens)
+- Managing login/logout
+
+**Authorization (AuthZ)**: What can you do?
+- Permission checking
+- Role-based access control (RBAC)
+- Resource ownership validation
+- Policy enforcement
+
+### 2. Authentication Strategies
+
+**Session-Based:**
+- Server stores session state
+- Session ID in cookie
+- Traditional, simple, stateful
+
+**Token-Based (JWT):**
+- Stateless, self-contained
+- Scales horizontally
+- Can store claims
+
+**OAuth2/OpenID Connect:**
+- Delegate authentication
+- Social login (Google, GitHub)
+- Enterprise SSO
+
+## JWT Authentication
+
+### Pattern 1: JWT Implementation
+
+```typescript
+// JWT structure: header.payload.signature
+import jwt from 'jsonwebtoken';
+import { Request, Response, NextFunction } from 'express';
+
+interface JWTPayload {
+    userId: string;
+    email: string;
+    role: string;
+    iat: number;
+    exp: number;
+}
+
+// Generate JWT
+function generateTokens(userId: string, email: string, role: string) {
+    const accessToken = jwt.sign(
+        { userId, email, role },
+        process.env.JWT_SECRET!,
+        { expiresIn: '15m' }  // Short-lived
+    );
+
+    const refreshToken = jwt.sign(
+        { userId },
+        process.env.JWT_REFRESH_SECRET!,
+        { expiresIn: '7d' }  // Long-lived
+    );
+
+    return { accessToken, refreshToken };
+}
+
+// Verify JWT
+function verifyToken(token: string): JWTPayload {
+    try {
+        return jwt.verify(token, process.env.JWT_SECRET!) as JWTPayload;
+    } catch (error) {
+        if (error instanceof jwt.TokenExpiredError) {
+            throw new Error('Token expired');
+        }
+        if (error instanceof jwt.JsonWebTokenError) {
+            throw new Error('Invalid token');
+        }
+        throw error;
+    }
+}
+
+// Middleware
+function authenticate(req: Request, res: Response, next: NextFunction) {
+    const authHeader = req.headers.authorization;
+    if (!authHeader?.startsWith('Bearer ')) {
+        return res.status(401).json({ error: 'No token provided' });
+    }
+
+    const token = authHeader.substring(7);
+    try {
+        const payload = verifyToken(token);
+        req.user = payload;  // Attach user to request
+        next();
+    } catch (error) {
+        return res.status(401).json({ error: 'Invalid token' });
+    }
+}
+
+// Usage
+app.get('/api/profile', authenticate, (req, res) => {
+    res.json({ user: req.user });
+});
+```
+
+### Pattern 2: Refresh Token Flow
+
+```typescript
+interface StoredRefreshToken {
+    token: string;
+    userId: string;
+    expiresAt: Date;
+    createdAt: Date;
+}
+
+class RefreshTokenService {
+    // Store refresh token in database
+    async storeRefreshToken(userId: string, refreshToken: string) {
+        const expiresAt = new Date(Date.now() + 7 * 24 * 60 * 60 * 1000);
+        await db.refreshTokens.create({
+            token: await hash(refreshToken),  // Hash before storing
+            userId,
+            expiresAt,
+        });
+    }
+
+    // Refresh access token
+    async refreshAccessToken(refreshToken: string) {
+        // Verify refresh token
+        let payload;
+        try {
+            payload = jwt.verify(
+                refreshToken,
+                process.env.JWT_REFRESH_SECRET!
+            ) as { userId: string };
+        } catch {
+            throw new Error('Invalid refresh token');
+        }
+
+        // Check if token exists in database
+        const storedToken = await db.refreshTokens.findOne({
+            where: {
+                token: await hash(refreshToken),
+                userId: payload.userId,
+                expiresAt: { $gt: new Date() },
+            },
+        });
+
+        if (!storedToken) {
+            throw new Error('Refresh token not found or expired');
+        }
+
+        // Get user
+        const user = await db.users.findById(payload.userId);
+        if (!user) {
+            throw new Error('User not found');
+        }
+
+        // Generate new access token
+        const accessToken = jwt.sign(
+            { userId: user.id, email: user.email, role: user.role },
+            process.env.JWT_SECRET!,
+            { expiresIn: '15m' }
+        );
+
+        return { accessToken };
+    }
+
+    // Revoke refresh token (logout)
+    async revokeRefreshToken(refreshToken: string) {
+        await db.refreshTokens.deleteOne({
+            token: await hash(refreshToken),
+        });
+    }
+
+    // Revoke all user tokens (logout all devices)
+    async revokeAllUserTokens(userId: string) {
+        await db.refreshTokens.deleteMany({ userId });
+    }
+}
+
+// API endpoints
+app.post('/api/auth/refresh', async (req, res) => {
+    const { refreshToken } = req.body;
+    try {
+        const { accessToken } = await refreshTokenService
+            .refreshAccessToken(refreshToken);
+        res.json({ accessToken });
+    } catch (error) {
+        res.status(401).json({ error: 'Invalid refresh token' });
+    }
+});
+
+app.post('/api/auth/logout', authenticate, async (req, res) => {
+    const { refreshToken } = req.body;
+    await refreshTokenService.revokeRefreshToken(refreshToken);
+    res.json({ message: 'Logged out successfully' });
+});
+```
+
+## Session-Based Authentication
+
+### Pattern 1: Express Session
+
+```typescript
+import session from 'express-session';
+import RedisStore from 'connect-redis';
+import { createClient } from 'redis';
+
+// Setup Redis for session storage
+const redisClient = createClient({
+    url: process.env.REDIS_URL,
+});
+await redisClient.connect();
+
+app.use(
+    session({
+        store: new RedisStore({ client: redisClient }),
+        secret: process.env.SESSION_SECRET!,
+        resave: false,
+        saveUninitialized: false,
+        cookie: {
+            secure: process.env.NODE_ENV === 'production',  // HTTPS only
+            httpOnly: true,  // No JavaScript access
+            maxAge: 24 * 60 * 60 * 1000,  // 24 hours
+            sameSite: 'strict',  // CSRF protection
+        },
+    })
+);
+
+// Login
+app.post('/api/auth/login', async (req, res) => {
+    const { email, password } = req.body;
+
+    const user = await db.users.findOne({ email });
+    if (!user || !(await verifyPassword(password, user.passwordHash))) {
+        return res.status(401).json({ error: 'Invalid credentials' });
+    }
+
+    // Store user in session
+    req.session.userId = user.id;
+    req.session.role = user.role;
+
+    res.json({ user: { id: user.id, email: user.email, role: user.role } });
+});
+
+// Session middleware
+function requireAuth(req: Request, res: Response, next: NextFunction) {
+    if (!req.session.userId) {
+        return res.status(401).json({ error: 'Not authenticated' });
+    }
+    next();
+}
+
+// Protected route
+app.get('/api/profile', requireAuth, async (req, res) => {
+    const user = await db.users.findById(req.session.userId);
+    res.json({ user });
+});
+
+// Logout
+app.post('/api/auth/logout', (req, res) => {
+    req.session.destroy((err) => {
+        if (err) {
+            return res.status(500).json({ error: 'Logout failed' });
+        }
+        res.clearCookie('connect.sid');
+        res.json({ message: 'Logged out successfully' });
+    });
+});
+```
+
+## OAuth2 / Social Login
+
+### Pattern 1: OAuth2 with Passport.js
+
+```typescript
+import passport from 'passport';
+import { Strategy as GoogleStrategy } from 'passport-google-oauth20';
+import { Strategy as GitHubStrategy } from 'passport-github2';
+
+// Google OAuth
+passport.use(
+    new GoogleStrategy(
+        {
+            clientID: process.env.GOOGLE_CLIENT_ID!,
+            clientSecret: process.env.GOOGLE_CLIENT_SECRET!,
+            callbackURL: '/api/auth/google/callback',
+        },
+        async (accessToken, refreshToken, profile, done) => {
+            try {
+                // Find or create user
+                let user = await db.users.findOne({
+                    googleId: profile.id,
+                });
+
+                if (!user) {
+                    user = await db.users.create({
+                        googleId: profile.id,
+                        email: profile.emails?.[0]?.value,
+                        name: profile.displayName,
+                        avatar: profile.photos?.[0]?.value,
+                    });
+                }
+
+                return done(null, user);
+            } catch (error) {
+                return done(error, undefined);
+            }
+        }
+    )
+);
+
+// Routes
+app.get('/api/auth/google', passport.authenticate('google', {
+    scope: ['profile', 'email'],
+}));
+
+app.get(
+    '/api/auth/google/callback',
+    passport.authenticate('google', { session: false }),
+    (req, res) => {
+        // Generate JWT
+        const tokens = generateTokens(req.user.id, req.user.email, req.user.role);
+        // Redirect to frontend with token
+        res.redirect(`${process.env.FRONTEND_URL}/auth/callback?token=${tokens.accessToken}`);
+    }
+);
+```
+
+## Authorization Patterns
+
+### Pattern 1: Role-Based Access Control (RBAC)
+
+```typescript
+enum Role {
+    USER = 'user',
+    MODERATOR = 'moderator',
+    ADMIN = 'admin',
+}
+
+const roleHierarchy: Record<Role, Role[]> = {
+    [Role.ADMIN]: [Role.ADMIN, Role.MODERATOR, Role.USER],
+    [Role.MODERATOR]: [Role.MODERATOR, Role.USER],
+    [Role.USER]: [Role.USER],
+};
+
+function hasRole(userRole: Role, requiredRole: Role): boolean {
+    return roleHierarchy[userRole].includes(requiredRole);
+}
+
+// Middleware
+function requireRole(...roles: Role[]) {
+    return (req: Request, res: Response, next: NextFunction) => {
+        if (!req.user) {
+            return res.status(401).json({ error: 'Not authenticated' });
+        }
+
+        if (!roles.some(role => hasRole(req.user.role, role))) {
+            return res.status(403).json({ error: 'Insufficient permissions' });
+        }
+
+        next();
+    };
+}
+
+// Usage
+app.delete('/api/users/:id',
+    authenticate,
+    requireRole(Role.ADMIN),
+    async (req, res) => {
+        // Only admins can delete users
+        await db.users.delete(req.params.id);
+        res.json({ message: 'User deleted' });
+    }
+);
+```
+
+### Pattern 2: Permission-Based Access Control
+
+```typescript
+enum Permission {
+    READ_USERS = 'read:users',
+    WRITE_USERS = 'write:users',
+    DELETE_USERS = 'delete:users',
+    READ_POSTS = 'read:posts',
+    WRITE_POSTS = 'write:posts',
+}
+
+const rolePermissions: Record<Role, Permission[]> = {
+    [Role.USER]: [Permission.READ_POSTS, Permission.WRITE_POSTS],
+    [Role.MODERATOR]: [
+        Permission.READ_POSTS,
+        Permission.WRITE_POSTS,
+        Permission.READ_USERS,
+    ],
+    [Role.ADMIN]: Object.values(Permission),
+};
+
+function hasPermission(userRole: Role, permission: Permission): boolean {
+    return rolePermissions[userRole]?.includes(permission) ?? false;
+}
+
+function requirePermission(...permissions: Permission[]) {
+    return (req: Request, res: Response, next: NextFunction) => {
+        if (!req.user) {
+            return res.status(401).json({ error: 'Not authenticated' });
+        }
+
+        const hasAllPermissions = permissions.every(permission =>
+            hasPermission(req.user.role, permission)
+        );
+
+        if (!hasAllPermissions) {
+            return res.status(403).json({ error: 'Insufficient permissions' });
+        }
+
+        next();
+    };
+}
+
+// Usage
+app.get('/api/users',
+    authenticate,
+    requirePermission(Permission.READ_USERS),
+    async (req, res) => {
+        const users = await db.users.findAll();
+        res.json({ users });
+    }
+);
+```
+
+### Pattern 3: Resource Ownership
+
+```typescript
+// Check if user owns resource
+async function requireOwnership(
+    resourceType: 'post' | 'comment',
+    resourceIdParam: string = 'id'
+) {
+    return async (req: Request, res: Response, next: NextFunction) => {
+        if (!req.user) {
+            return res.status(401).json({ error: 'Not authenticated' });
+        }
+
+        const resourceId = req.params[resourceIdParam];
+
+        // Admins can access anything
+        if (req.user.role === Role.ADMIN) {
+            return next();
+        }
+
+        // Check ownership
+        let resource;
+        if (resourceType === 'post') {
+            resource = await db.posts.findById(resourceId);
+        } else if (resourceType === 'comment') {
+            resource = await db.comments.findById(resourceId);
+        }
+
+        if (!resource) {
+            return res.status(404).json({ error: 'Resource not found' });
+        }
+
+        if (resource.userId !== req.user.userId) {
+            return res.status(403).json({ error: 'Not authorized' });
+        }
+
+        next();
+    };
+}
+
+// Usage
+app.put('/api/posts/:id',
+    authenticate,
+    requireOwnership('post'),
+    async (req, res) => {
+        // User can only update their own posts
+        const post = await db.posts.update(req.params.id, req.body);
+        res.json({ post });
+    }
+);
+```
+
+## Security Best Practices
+
+### Pattern 1: Password Security
+
+```typescript
+import bcrypt from 'bcrypt';
+import { z } from 'zod';
+
+// Password validation schema
+const passwordSchema = z.string()
+    .min(12, 'Password must be at least 12 characters')
+    .regex(/[A-Z]/, 'Password must contain uppercase letter')
+    .regex(/[a-z]/, 'Password must contain lowercase letter')
+    .regex(/[0-9]/, 'Password must contain number')
+    .regex(/[^A-Za-z0-9]/, 'Password must contain special character');
+
+// Hash password
+async function hashPassword(password: string): Promise<string> {
+    const saltRounds = 12;  // 2^12 iterations
+    return bcrypt.hash(password, saltRounds);
+}
+
+// Verify password
+async function verifyPassword(
+    password: string,
+    hash: string
+): Promise<boolean> {
+    return bcrypt.compare(password, hash);
+}
+
+// Registration with password validation
+app.post('/api/auth/register', async (req, res) => {
+    try {
+        const { email, password } = req.body;
+
+        // Validate password
+        passwordSchema.parse(password);
+
+        // Check if user exists
+        const existingUser = await db.users.findOne({ email });
+        if (existingUser) {
+            return res.status(400).json({ error: 'Email already registered' });
+        }
+
+        // Hash password
+        const passwordHash = await hashPassword(password);
+
+        // Create user
+        const user = await db.users.create({
+            email,
+            passwordHash,
+        });
+
+        // Generate tokens
+        const tokens = generateTokens(user.id, user.email, user.role);
+
+        res.status(201).json({
+            user: { id: user.id, email: user.email },
+            ...tokens,
+        });
+    } catch (error) {
+        if (error instanceof z.ZodError) {
+            return res.status(400).json({ error: error.errors[0].message });
+        }
+        res.status(500).json({ error: 'Registration failed' });
+    }
+});
+```
+
+### Pattern 2: Rate Limiting
+
+```typescript
+import rateLimit from 'express-rate-limit';
+import RedisStore from 'rate-limit-redis';
+
+// Login rate limiter
+const loginLimiter = rateLimit({
+    store: new RedisStore({ client: redisClient }),
+    windowMs: 15 * 60 * 1000,  // 15 minutes
+    max: 5,  // 5 attempts
+    message: 'Too many login attempts, please try again later',
+    standardHeaders: true,
+    legacyHeaders: false,
+});
+
+// API rate limiter
+const apiLimiter = rateLimit({
+    windowMs: 60 * 1000,  // 1 minute
+    max: 100,  // 100 requests per minute
+    standardHeaders: true,
+});
+
+// Apply to routes
+app.post('/api/auth/login', loginLimiter, async (req, res) => {
+    // Login logic
+});
+
+app.use('/api/', apiLimiter);
+```
+
+## Best Practices
+
+1. **Never Store Plain Passwords**: Always hash with bcrypt/argon2
+2. **Use HTTPS**: Encrypt data in transit
+3. **Short-Lived Access Tokens**: 15-30 minutes max
+4. **Secure Cookies**: httpOnly, secure, sameSite flags
+5. **Validate All Input**: Email format, password strength
+6. **Rate Limit Auth Endpoints**: Prevent brute force attacks
+7. **Implement CSRF Protection**: For session-based auth
+8. **Rotate Secrets Regularly**: JWT secrets, session secrets
+9. **Log Security Events**: Login attempts, failed auth
+10. **Use MFA When Possible**: Extra security layer
+
+## Common Pitfalls
+
+- **Weak Passwords**: Enforce strong password policies
+- **JWT in localStorage**: Vulnerable to XSS, use httpOnly cookies
+- **No Token Expiration**: Tokens should expire
+- **Client-Side Auth Checks Only**: Always validate server-side
+- **Insecure Password Reset**: Use secure tokens with expiration
+- **No Rate Limiting**: Vulnerable to brute force
+- **Trusting Client Data**: Always validate on server
+
+## Resources
+
+- **references/jwt-best-practices.md**: JWT implementation guide
+- **references/oauth2-flows.md**: OAuth2 flow diagrams and examples
+- **references/session-security.md**: Secure session management
+- **assets/auth-security-checklist.md**: Security review checklist
+- **assets/password-policy-template.md**: Password requirements template
+- **scripts/token-validator.ts**: JWT validation utility