> 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/authentication/broken-2fa-logic.md).

# 有缺陷的 2FA 逻辑

### 2FA 逻辑缺陷

该应用引入了双因素认证：/ 在登录名/密码之后，一个 **2FA 代码** 由……发送 **email**. / 我们有：

* 我们的凭据： `wiener:peter`
* 受害者的用户名： `carlos`

<figure><img src="/files/a468994a38c5572b8c961e0c80e2b9757208fdf0" alt=""><figcaption></figcaption></figure>

可访问 **邮件服务器** 以接收 2FA 代码

<figure><img src="/files/fe42b1f52ffd0f3a84d6d5c28ce3fefea9b78dd5" alt=""><figcaption></figcaption></figure>

#### 观察到的操作

1. 在第一步登录之后，应用会通过电子邮件发送一个 2FA 代码。
2. 第二步（`/login2`) 会检查该代码。
3. 2FA 对其有效的用户通过 **`验证`** Cookie。

第二步请求示例：

```http
GET /login2 HTTP/2
Host: 0a7500ab0376700f81a18e2c00f200a8.web-security-academy.net
Cookie: session=cNFHPofUz1wxXQpsZZN7yIiKQklG1Ygd; verify=carlos
```

在这里，我们强制将 `验证` cookie 设置为 `carlos` 以便在受害者的账户上执行 2FA 检查。

#### 暴力破解 2FA 代码

1. 2FA 验证请求发送到 **Intruder** （或等效项），方法是针对包含以下内容的请求：

```bash
mfa-code=XXXXX
```

<figure><img src="/files/0990cfe563baa5a1612ce09e2b2696911ce5132e" alt=""><figcaption></figcaption></figure>

* 该 **载荷** 被配置为测试所有可能的代码组合，从 `0000` 更改为 `9999` （即 10,000 个值）。

我们使用以下 cookie：

```bash
verify=carlos
```

* 以便所有代码测试都在 **carlos**.

<figure><img src="/files/49e1fe7499ba21c09574c9007a4bc9909c4efc93" alt=""><figcaption></figcaption></figure>

* 在设置中，向响应添加了一个 \*\*过滤条件\*\*，以忽略包含以下消息的响应：
* `安全码错误`

<figure><img src="/files/a45e43055dc59bfa2a79c2e420fc5826d2686df2" alt=""><figcaption></figcaption></figure>

1. 我们正在发起暴力破解攻击。
2. 在这些响应中，我们找到了不再包含错误消息并返回 \*\*HTTP 状态码 302\*\*（重定向）的那个。 / → 该响应对应于 **2FA 代码正确** 代表 **carlos**.

<figure><img src="/files/63e840a289eeec20a17f9591d1d9cc9e6d073378" alt=""><figcaption></figcaption></figure>


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