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gRPC (Google Remote Procedure Call) is a high-performance, open-source framework for efficient communication between services. It uses Protocol Buffers (protobuf) as its interface definition language, enabling fast and obfuscated data exchange.
Key Benefits of gRPC:
- Fast: Uses HTTP/2 for multiplexing and low latency.
- Obfuscated: Binary format makes it harder to intercept.
- Language-Agnostic: Supports multiple programming languages.
Example gRPC Data Format:
Instead of JSON (`{“key”: “value”}`), gRPC may display:
403,,,null,null,null,null,,,0,0,0]
Useful gRPC Resources:
- gRPC Health Monitor
- gRPC End-to-End Communication Whitepaper
- Google API Authentication with gRPC
- Defining Network Operations with gRPC
You Should Know:
1. Inspecting gRPC Traffic in Chrome/Firefox
1. Open Developer Tools (`F12`).
2. Go to the Network tab.
3. Filter for gRPC requests (look for `application/grpc`).
4. Check responses for `.proto` files.
2. Decoding gRPC with `grpcurl` (Linux)
Install:
sudo apt install grpcurl
List gRPC services:
grpcurl -plaintext localhost:50051 list
Call a method:
grpcurl -plaintext localhost:50051 MyService.MyMethod
3. Analyzing Protobuf with `protoc`
Decode a `.proto` file:
protoc --decode_raw < binary_message.bin
Generate code from `.proto`:
protoc --python_out=. my_proto.proto
4. MITM gRPC Traffic (Ethical Hacking)
Intercept with Burp Suite:
1. Configure Proxy Listener on `:8080`.
2. Use gRPC over HTTP/2 in Burp.
3. Decode protobuf using Burp’s Protobuf Editor.
5. gRPC Security Testing Commands
Check for insecure gRPC endpoints:
nmap -p 50051 --script grpc-enum <target>
Test gRPC reflection:
grpcurl -reflect -plaintext <target>:50051 list
What Undercode Say:
gRPC is a powerful but often overlooked attack surface. Ethical hackers should master protobuf decoding, intercepting gRPC traffic, and testing for insecure configurations. Tools like grpcurl, protoc, and Burp Suite are essential for analyzing gRPC-based APIs.
Prediction:
As more companies adopt gRPC for microservices, vulnerabilities in misconfigured protobuf schemas and unauthenticated gRPC endpoints will become a prime target for attackers.
Expected Output:
- Decoded gRPC messages.
- Extracted `.proto` schemas.
- List of exposed gRPC methods.
- Security misconfigurations in gRPC services.
IT/Security Reporter URL:
Reported By: Activity 7335987087176880128 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
