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Pentesting gRPC-Web
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Manipulating gRPC-Web Payloads
gRPC-Web uses Content-Type: application/grpc-web-text in requests which is kind of protobuf in base64 encoded form, you can use gprc-coder tool ,and you can also install its Burp Suite Extension.
Manual with gGRPC Coder Tool
- First decode the payload:
bash
echo "AAAAABYSC0FtaW4gTmFzaXJpGDY6BVhlbm9u" | python3 grpc-coder.py --decode --type grpc-web-text | protoscope > out.txt- Edit the content of decoded payload
nano out.txt
2: {"Amin Nasiri Xenon GRPC"}
3: 54
7: {"<script>alert(origin)</script>"}- Encode the new payload
bash
protoscope -s out.txt | python3 grpc-coder.py --encode --type grpc-web-text- Use output in Burp interceptor:
AAAAADoSFkFtaW4gTmFzaXJpIFhlbm9uIEdSUEMYNjoePHNjcmlwdD5hbGVydChvcmlnaW4pPC9zY3JpcHQ+Manual with gRPC-Web Coder Burp Suite Extension
You can use gRPC-Web Coder Burp Suite Extension in gRPC-Web Pentest Suite which is easier. You can read the installation and usage instruction in its repo.
Analysing gRPC-Web Javascript Files
There is at least one Javascript file in every gRPC-Web application. You can analyse the file to find new messages, endpoints and services. Try using gRPC-Scan tool.
- Download the Javascript gRPC-Web File
- Scan it with grpc-scan.py:
bash
python3 grpc-scan.py --file main.js- Analyse output and test the new endpoints and new services:
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 |
+--------------+----------------+--------------+References
Learn AWS hacking from zero to hero with htARTE (HackTricks AWS Red Team Expert)!
Other ways to support HackTricks:
- If you want to see your company advertised in HackTricks or download HackTricks in PDF Check the SUBSCRIPTION PLANS!
- Get the official PEASS & HackTricks swag
- Discover The PEASS Family, our collection of exclusive NFTs
- Join the 💬 Discord group or the telegram group or follow us on Twitter 🐦 @carlospolopm.
- Share your hacking tricks by submitting PRs to the HackTricks and HackTricks Cloud github repos.