PKCE 与公共客户端安全
了解 PKCE 扩展如何保护移动应用和单页应用中的 OAuth2 授权码流程，这些应用无法安全保存客户端密钥
PKCE 与公共客户端安全 是 CoddyKit 上的免费 Spring Security 6 & JWT Authentication 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Spring Security 6 & JWT Authentication 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Spring Security 6 & JWT Authentication 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
The Public Client Problem
Mobile apps and SPAs are public clients: their code ships to the user, so they cannot safely store a client secret. Without a secret, the plain Authorization Code flow is vulnerable to interception.
What PKCE Solves
PKCE (Proof Key for Code Exchange, pronounced 'pixy') adds a dynamic secret per authorization request. Even if the authorization code is stolen, it cannot be exchanged without the matching proof.
The Code Verifier
The client generates a random, high-entropy string called the code_verifier and keeps it in memory for this one flow.
const codeVerifier = base64url(randomBytes(32));The Code Challenge
The client hashes the verifier with SHA-256 to make the code_challenge. The hash is sent to the server, but the original verifier never leaves the device yet.
const codeChallenge = base64url(sha256(codeVerifier));Starting the Authorization Request
The client sends the challenge and the method (S256) to the authorization endpoint along with the usual parameters.
GET /authorize?response_type=code
&client_id=app123
&code_challenge=XYZ...
&code_challenge_method=S256Server Stores the Challenge
The authorization server remembers the code_challenge and links it to the authorization code it issues after the user logs in.
Exchanging the Code
When swapping the code for tokens, the client now reveals the original code_verifier.
POST /token
grant_type=authorization_code
&code=abc123
&code_verifier=ORIGINAL_RANDOMServer Verifies the Proof
The server hashes the received verifier and compares it to the stored challenge. If they match, the requester is the same party that started the flow; otherwise it rejects the exchange.
if (sha256(received_verifier) !== stored_challenge) {
reject('invalid_grant');
}Why It Stops Interception
An attacker who steals the authorization code (for example via a malicious app on the device) still cannot use it: they never saw the code_verifier, which existed only inside the legitimate client's memory.
PKCE Is Now Recommended for All
Originally for mobile, PKCE is now recommended for every Authorization Code flow, including confidential web clients. OAuth 2.1 makes it the default.
Library Support
You rarely implement PKCE by hand. Libraries like AppAuth, oidc-client-ts, and Spring Authorization Server handle verifier generation, hashing, and validation for you.
Quick Check
Test your understanding of PKCE.
Recap
You learned how PKCE secures public clients:
- Public clients cannot keep a secret, so the plain code flow is unsafe
- The client creates a
code_verifierand sends its hash as thecode_challenge - The verifier is revealed only at token exchange
- A stolen code is useless without the verifier
PKCE is now the default for all Authorization Code flows.
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常见问题解答
「PKCE 与公共客户端安全」课时是免费的吗？
是的 — 「PKCE 与公共客户端安全」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Spring Security 6 & JWT Authentication 课程的其余内容，请升级到 CoddyKit PRO。 Spring Security 6 & JWT Authentication 课程共包含 4 节课。
「PKCE 与公共客户端安全」这节课中我会学到什么？
了解 PKCE 扩展如何保护移动应用和单页应用中的 OAuth2 授权码流程，这些应用无法安全保存客户端密钥 你通过在浏览器中直接运行的动手代码来练习 Spring Security 6 & JWT Authentication，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Spring Security 6 & JWT Authentication 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Spring Security 6 & JWT Authentication 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「PKCE 与公共客户端安全」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Spring Security 6 & JWT Authentication 课中编写并运行代码吗？
能。每节 Spring Security 6 & JWT Authentication 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。
此课程中的所有课时
- OAuth2 协议概览
- OpenID Connect 简介
- 常见 OAuth2 授权类型
- PKCE 与公共客户端安全