# Pentesting gRPC-Web

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## **操纵 gRPC-Web 负载**
gRPC-Web 在请求中使用 Content-Type: `application/grpc-web-text`，这是一种以 base64 编码形式的 protobuf，您可以使用 [gprc-coder](https://github.com/nxenon/grpc-pentest-suite) 工具，也可以安装其 [Burp Suite 扩展](https://github.com/nxenon/grpc-pentest-suite)。

### **使用 gGRPC Coder 工具手动操作**
1. 首先解码负载：
```bash
echo "AAAAABYSC0FtaW4gTmFzaXJpGDY6BVhlbm9u" | python3 grpc-coder.py --decode --type grpc-web-text | protoscope > out.txt
```
2. 编辑解码负载的内容
```
nano out.txt
2: {"Amin Nasiri Xenon GRPC"}
3: 54
7: {"<script>alert(origin)</script>"}
```
3. 编码新的有效负载
```bash
protoscope -s out.txt | python3 grpc-coder.py --encode --type grpc-web-text
```
4. 在Burp拦截器中使用输出：
```
AAAAADoSFkFtaW4gTmFzaXJpIFhlbm9uIEdSUEMYNjoePHNjcmlwdD5hbGVydChvcmlnaW4pPC9zY3JpcHQ+
```
### **使用 gRPC-Web Coder Burp Suite 扩展的手册**
您可以在 [gRPC-Web Pentest Suite](https://github.com/nxenon/grpc-pentest-suite) 中使用 gRPC-Web Coder Burp Suite 扩展，这样更简单。您可以在其仓库中阅读安装和使用说明。

## **分析 gRPC-Web Javascript 文件**
每个 gRPC-Web 应用程序中至少有一个 Javascript 文件。您可以分析该文件以查找新的消息、端点和服务。尝试使用 [gRPC-Scan](https://github.com/nxenon/grpc-pentest-suite) 工具。
1. 下载 Javascript gRPC-Web 文件
2. 使用 grpc-scan.py 扫描它：
```bash
python3 grpc-scan.py --file main.js
```
3. 分析输出并测试新的端点和新服务：
```
Output:
Found Endpoints:
/grpc.gateway.testing.EchoService/Echo
/grpc.gateway.testing.EchoService/EchoAbort
/grpc.gateway.testing.EchoService/NoOp
/grpc.gateway.testing.EchoService/ServerStreamingEcho
/grpc.gateway.testing.EchoService/ServerStreamingEchoAbort

Found Messages:

grpc.gateway.testing.EchoRequest:
+------------+--------------------+--------------+
| Field Name |     Field Type     | Field Number |
+============+====================+==============+
| Message    | Proto3StringField  | 1            |
+------------+--------------------+--------------+
| Name       | Proto3StringField  | 2            |
+------------+--------------------+--------------+
| Age        | Proto3IntField     | 3            |
+------------+--------------------+--------------+
| IsAdmin    | Proto3BooleanField | 4            |
+------------+--------------------+--------------+
| Weight     | Proto3FloatField   | 5            |
+------------+--------------------+--------------+
| Test       | Proto3StringField  | 6            |
+------------+--------------------+--------------+
| Test2      | Proto3StringField  | 7            |
+------------+--------------------+--------------+
| Test3      | Proto3StringField  | 16           |
+------------+--------------------+--------------+
| Test4      | Proto3StringField  | 20           |
+------------+--------------------+--------------+

grpc.gateway.testing.EchoResponse:
+--------------+--------------------+--------------+
|  Field Name  |     Field Type     | Field Number |
+==============+====================+==============+
| Message      | Proto3StringField  | 1            |
+--------------+--------------------+--------------+
| Name         | Proto3StringField  | 2            |
+--------------+--------------------+--------------+
| Age          | Proto3IntField     | 3            |
+--------------+--------------------+--------------+
| IsAdmin      | Proto3BooleanField | 4            |
+--------------+--------------------+--------------+
| Weight       | Proto3FloatField   | 5            |
+--------------+--------------------+--------------+
| Test         | Proto3StringField  | 6            |
+--------------+--------------------+--------------+
| Test2        | Proto3StringField  | 7            |
+--------------+--------------------+--------------+
| Test3        | Proto3StringField  | 16           |
+--------------+--------------------+--------------+
| Test4        | Proto3StringField  | 20           |
+--------------+--------------------+--------------+
| MessageCount | Proto3IntField     | 8            |
+--------------+--------------------+--------------+

grpc.gateway.testing.ServerStreamingEchoRequest:
+-----------------+-------------------+--------------+
|   Field Name    |    Field Type     | Field Number |
+=================+===================+==============+
| Message         | Proto3StringField | 1            |
+-----------------+-------------------+--------------+
| MessageCount    | Proto3IntField    | 2            |
+-----------------+-------------------+--------------+
| MessageInterval | Proto3IntField    | 3            |
+-----------------+-------------------+--------------+

grpc.gateway.testing.ServerStreamingEchoResponse:
+------------+-------------------+--------------+
| Field Name |    Field Type     | Field Number |
+============+===================+==============+
| Message    | Proto3StringField | 1            |
+------------+-------------------+--------------+

grpc.gateway.testing.ClientStreamingEchoRequest:
+------------+-------------------+--------------+
| Field Name |    Field Type     | Field Number |
+============+===================+==============+
| Message    | Proto3StringField | 1            |
+------------+-------------------+--------------+

grpc.gateway.testing.ClientStreamingEchoResponse:
+--------------+----------------+--------------+
|  Field Name  |   Field Type   | Field Number |
+==============+================+==============+
| MessageCount | Proto3IntField | 1            |
+--------------+----------------+--------------+
```
## 参考文献

* [Amin Nasiri 的 gRPC-Web 黑客文章](https://infosecwriteups.com/hacking-into-grpc-web-a54053757a45)
* [gRPC-Web 渗透测试套件](https://github.com/nxenon/grpc-pentest-suite)

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