IdentityServer4授权码流程：令牌存储、选型与续期最佳实践咨询

Hey there! Let's break down your questions about IdentityServer4's authorization code flow one by one, based on real-world production best practices:

1. 将Access Token存储在Cookie中是否可行？ #

Absolutely, this is not just feasible—it's actually a recommended approach for server-side rendered apps like MVC, especially when you're making AJAX calls to APIs. But you need to lock down the cookie with strict security attributes to mitigate risks:

• Always set these cookie properties:
  • HttpOnly: Prevents client-side JavaScript from accessing the token, which blocks most XSS attacks from stealing it.
  • Secure: Ensures the cookie is only sent over HTTPS, never unencrypted HTTP.
  • SameSite: Use Strict or Lax (depending on your cross-domain needs) to reduce CSRF risks. For most MVC apps that don't need cross-domain cookie sharing, Strict is safer.
• Restrict the cookie's Path to your MVC app's root (e.g., /) to limit where it's sent.
• Remember: Unlike storing tokens in localStorage or sessionStorage, cookies with HttpOnly are immune to XSS theft. The main risk here is CSRF, so make sure your AJAX requests include a CSRF token (like ASP.NET Core's built-in anti-forgery tokens) to validate that the request comes from your app.

2. Self-contained令牌 vs Reference令牌：安全性角度怎么选？ #

The choice depends on your security requirements and infrastructure:

Self-contained Tokens (e.g., JWT) #

• Pros: The token itself contains all user claims and metadata. Your APIs can validate the token's signature locally without calling IdentityServer, which is faster and reduces network overhead.
• Cons: Once the token is stolen, it can be used until it expires (even if the user logs out or their permissions change). You can't revoke a self-contained token mid-lifecycle unless you implement a token blacklist (which adds complexity).
• Best for: Trusted internal APIs (same network as IdentityServer), or scenarios where token lifetimes are very short (e.g., 15-30 minutes) to minimize exposure risk.

Reference Tokens #

• Pros: The token is just a random string. Your APIs must call IdentityServer's introspection endpoint to validate the token and fetch claims. This means you can revoke tokens instantly (via IdentityServer's admin APIs or user logout), which is critical for sensitive systems.
• Cons: Adds a network round-trip between your API and IdentityServer for every authenticated request, which can impact performance (though caching introspection results can help).
• Best for: External APIs, systems that require immediate token revocation, or apps handling highly sensitive data.

Quick rule of thumb: If you need instant token revocation, go with reference tokens. If performance is a priority and you can tolerate short-lived tokens that can't be revoked mid-cycle, self-contained is the way to go.

3. 令牌过期后的最佳续期方案 #

The two most reliable approaches are Refresh Tokens and Silent Renew, and they often work together:

Refresh Tokens #

• This is the standard approach for long-lived sessions. When you request the offline_access scope during the authorization code flow, IdentityServer will return a refresh token alongside the access token.
• When your access token expires, your MVC app can send the refresh token to IdentityServer's token endpoint to get a new access token (and usually a new refresh token, if you enable sliding expiration).
• Critical security note: Store refresh tokens in an HttpOnly, Secure, SameSite cookie—never in client-side storage. Refresh tokens have longer lifetimes, so they're a bigger target for attackers.
• Configure IdentityServer's refresh token settings: Use sliding expiration to extend the session as long as the user is active, but set an absolute expiration limit to prevent infinite session extension.

Silent Renew #

• This is great for providing a seamless user experience. For MVC apps, you can implement it using an iframe that makes a silent authorization request to IdentityServer. Since the user is already authenticated (their IdentityServer session cookie exists), IdentityServer will return a new access token without prompting the user to log in.
• Make sure IdentityServer's CORS policy allows your MVC app's domain, and that your app's content security policy (CSP) allows loading the IdentityServer iframe.
• Pair this with short-lived access tokens (e.g., 15 minutes) and trigger silent renew a few minutes before the token expires to avoid interrupting the user.

Recommendation: Use refresh tokens as the primary renewal mechanism, and add silent renew to handle token expiration without user interaction. This balances security and user experience.

内容的提问来源于stack exchange，提问作者paranamix2