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141 lines
6.0 KiB
Markdown
141 lines
6.0 KiB
Markdown
# Pentesting gRPC-Web
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{{#include ../banners/hacktricks-training.md}}
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## **Manipulación de Cargas Útiles de gRPC-Web**
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gRPC-Web utiliza Content-Type: `application/grpc-web-text` en las solicitudes, que es una especie de protobuf en forma codificada en base64. Puedes usar la herramienta [gprc-coder](https://github.com/nxenon/grpc-pentest-suite) y también puedes instalar su [Extensión de Burp Suite](https://github.com/nxenon/grpc-pentest-suite).
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### **Manual con la Herramienta gGRPC Coder**
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1. Primero decodifica la carga útil:
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```bash
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echo "AAAAABYSC0FtaW4gTmFzaXJpGDY6BVhlbm9u" | python3 grpc-coder.py --decode --type grpc-web-text | protoscope > out.txt
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```
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2. Editar el contenido de la carga útil decodificada
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```
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nano out.txt
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2: {"Amin Nasiri Xenon GRPC"}
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3: 54
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7: {"<script>alert(origin)</script>"}
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```
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3. Codificar la nueva carga útil
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```bash
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protoscope -s out.txt | python3 grpc-coder.py --encode --type grpc-web-text
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```
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4. Utiliza la salida en el interceptor de Burp:
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```
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AAAAADoSFkFtaW4gTmFzaXJpIFhlbm9uIEdSUEMYNjoePHNjcmlwdD5hbGVydChvcmlnaW4pPC9zY3JpcHQ+
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```
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### **Manual con la extensión gRPC-Web Coder de Burp Suite**
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Puedes usar la extensión gRPC-Web Coder de Burp Suite en [gRPC-Web Pentest Suite](https://github.com/nxenon/grpc-pentest-suite) que es más fácil. Puedes leer las instrucciones de instalación y uso en su repositorio.
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## **Analizando archivos Javascript de gRPC-Web**
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Hay al menos un archivo Javascript en cada aplicación gRPC-Web. Puedes analizar el archivo para encontrar nuevos mensajes, endpoints y servicios. Intenta usar la herramienta [gRPC-Scan](https://github.com/nxenon/grpc-pentest-suite).
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1. Descarga el archivo Javascript gRPC-Web
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2. Escanéalo con grpc-scan.py:
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```bash
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python3 grpc-scan.py --file main.js
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```
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3. Analiza la salida y prueba los nuevos endpoints y nuevos servicios:
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```
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Output:
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Found Endpoints:
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/grpc.gateway.testing.EchoService/Echo
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/grpc.gateway.testing.EchoService/EchoAbort
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/grpc.gateway.testing.EchoService/NoOp
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/grpc.gateway.testing.EchoService/ServerStreamingEcho
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/grpc.gateway.testing.EchoService/ServerStreamingEchoAbort
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Found Messages:
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grpc.gateway.testing.EchoRequest:
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+------------+--------------------+--------------+
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| Field Name | Field Type | Field Number |
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+============+====================+==============+
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| Message | Proto3StringField | 1 |
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+------------+--------------------+--------------+
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| Name | Proto3StringField | 2 |
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+------------+--------------------+--------------+
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| Age | Proto3IntField | 3 |
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+------------+--------------------+--------------+
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| IsAdmin | Proto3BooleanField | 4 |
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+------------+--------------------+--------------+
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| Weight | Proto3FloatField | 5 |
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+------------+--------------------+--------------+
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| Test | Proto3StringField | 6 |
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+------------+--------------------+--------------+
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| Test2 | Proto3StringField | 7 |
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+------------+--------------------+--------------+
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| Test3 | Proto3StringField | 16 |
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+------------+--------------------+--------------+
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| Test4 | Proto3StringField | 20 |
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+------------+--------------------+--------------+
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grpc.gateway.testing.EchoResponse:
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+--------------+--------------------+--------------+
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| Field Name | Field Type | Field Number |
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+==============+====================+==============+
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| Message | Proto3StringField | 1 |
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+--------------+--------------------+--------------+
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| Name | Proto3StringField | 2 |
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+--------------+--------------------+--------------+
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| Age | Proto3IntField | 3 |
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+--------------+--------------------+--------------+
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| IsAdmin | Proto3BooleanField | 4 |
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+--------------+--------------------+--------------+
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| Weight | Proto3FloatField | 5 |
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+--------------+--------------------+--------------+
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| Test | Proto3StringField | 6 |
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+--------------+--------------------+--------------+
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| Test2 | Proto3StringField | 7 |
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+--------------+--------------------+--------------+
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| Test3 | Proto3StringField | 16 |
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+--------------+--------------------+--------------+
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| Test4 | Proto3StringField | 20 |
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+--------------+--------------------+--------------+
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| MessageCount | Proto3IntField | 8 |
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+--------------+--------------------+--------------+
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grpc.gateway.testing.ServerStreamingEchoRequest:
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+-----------------+-------------------+--------------+
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| Field Name | Field Type | Field Number |
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+=================+===================+==============+
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| Message | Proto3StringField | 1 |
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+-----------------+-------------------+--------------+
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| MessageCount | Proto3IntField | 2 |
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+-----------------+-------------------+--------------+
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| MessageInterval | Proto3IntField | 3 |
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+-----------------+-------------------+--------------+
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grpc.gateway.testing.ServerStreamingEchoResponse:
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+------------+-------------------+--------------+
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| Field Name | Field Type | Field Number |
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+============+===================+==============+
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| Message | Proto3StringField | 1 |
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+------------+-------------------+--------------+
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grpc.gateway.testing.ClientStreamingEchoRequest:
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+------------+-------------------+--------------+
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| Field Name | Field Type | Field Number |
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+============+===================+==============+
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| Message | Proto3StringField | 1 |
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+------------+-------------------+--------------+
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grpc.gateway.testing.ClientStreamingEchoResponse:
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+--------------+----------------+--------------+
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| Field Name | Field Type | Field Number |
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+==============+================+==============+
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| MessageCount | Proto3IntField | 1 |
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+--------------+----------------+--------------+
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```
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## Referencias
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- [Hacking into gRPC-Web Article by Amin Nasiri](https://infosecwriteups.com/hacking-into-grpc-web-a54053757a45)
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- [gRPC-Web Pentest Suite](https://github.com/nxenon/grpc-pentest-suite)
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{{#include ../banners/hacktricks-training.md}}
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