sal-modular/sigsocket_client/IMPLEMENTATION.md

SigSocket Client Implementation

Overview

This document describes the implementation of the sigsocket_client crate, a WebSocket client library designed for connecting to sigsocket servers with WASM-first support.

Architecture

Core Design Principles

1. WASM-First: Designed primarily for browser environments with native support as a secondary target
2. No Signing Logic: The client delegates all signing operations to the application
3. User Approval Flow: Applications are notified about incoming requests and handle user approval
4. Protocol Compatibility: Fully compatible with the sigsocket server protocol
5. Async/Await: Modern async Rust API throughout

Module Structure

sigsocket_client/
├── src/
│   ├── lib.rs           # Main library entry point
│   ├── error.rs         # Error types (native + WASM versions)
│   ├── protocol.rs      # Protocol message definitions
│   ├── client.rs        # Main client interface
│   ├── native.rs        # Native (tokio) implementation
│   └── wasm.rs          # WASM (web-sys) implementation
├── examples/
│   ├── basic_usage.rs   # Native usage example
│   └── wasm_usage.rs    # WASM usage example
├── tests/
│   └── integration_test.rs
└── README.md

Protocol Implementation

The sigsocket protocol is simple and consists of three message types:

1. Introduction Message

When connecting, the client sends its public key as a hex-encoded string:

02f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9

2. Sign Request (Server → Client)

{
  "id": "req_123",
  "message": "dGVzdCBtZXNzYWdl"  // base64-encoded message
}

3. Sign Response (Client → Server)

{
  "id": "req_123",
  "message": "dGVzdCBtZXNzYWdl",  // original message
  "signature": "c2lnbmF0dXJl"      // base64-encoded signature
}

Key Features Implemented

✅ Dual Platform Support

• Native: Uses tokio and tokio-tungstenite for async WebSocket communication
• WASM: Uses web-sys and wasm-bindgen for browser WebSocket API

✅ Type-Safe Protocol

• SignRequest and SignResponse structs with serde serialization
• Helper methods for base64 encoding/decoding
• Comprehensive error handling

✅ Flexible Sign Handler Interface

trait SignRequestHandler {
    fn handle_sign_request(&self, request: &SignRequest) -> Result<Vec<u8>>;
}

✅ Connection Management

• Automatic connection state tracking
• Clean disconnect handling
• Connection status queries

✅ Error Handling

• Comprehensive error types for different failure modes
• Platform-specific error conversions
• WASM-compatible error handling (no std::error::Error dependency)

Platform-Specific Implementations

Native Implementation (native.rs)

• Uses tokio-tungstenite for WebSocket communication
• Spawns separate tasks for reading and writing
• Thread-safe with Arc<RwLock<T>> for shared state
• Supports Send + Sync trait bounds

WASM Implementation (wasm.rs)

• Uses web-sys::WebSocket for browser WebSocket API
• Event-driven with JavaScript closures
• Single-threaded (no Send + Sync requirements)
• Browser console logging for debugging

Usage Patterns

Native Usage

#[tokio::main]
async fn main() -> Result<()> {
    let public_key = hex::decode("02f9308a...")?;
    let mut client = SigSocketClient::new("ws://localhost:8080/ws", public_key)?;
    
    client.set_sign_handler(MySignHandler);
    client.connect().await?;
    
    // Client handles requests automatically
    Ok(())
}

WASM Usage

#[wasm_bindgen]
pub async fn connect_to_sigsocket() -> Result<(), JsValue> {
    let public_key = get_user_public_key()?;
    let mut client = SigSocketClient::new("ws://localhost:8080/ws", public_key)?;
    
    client.set_sign_handler(WasmSignHandler);
    client.connect().await?;
    
    Ok(())
}

Testing

Unit Tests

• Protocol message serialization/deserialization
• Error handling and conversion
• Client creation and configuration

Integration Tests

• End-to-end usage patterns
• Sign request/response cycles
• Error scenarios

Documentation Tests

• Example code in documentation is verified to compile

Dependencies

Core Dependencies (Both Platforms)

• serde + serde_json - JSON serialization
• hex - Hex encoding/decoding
• base64 - Base64 encoding/decoding
• url - URL parsing and validation

Native-Only Dependencies

• tokio - Async runtime
• tokio-tungstenite - WebSocket client
• futures-util - Stream utilities
• thiserror - Error derive macros

WASM-Only Dependencies

• wasm-bindgen - Rust/JavaScript interop
• web-sys - Browser API bindings
• js-sys - JavaScript type bindings
• wasm-bindgen-futures - Async support

Build Targets

Native Build

cargo build --features native
cargo test --features native
cargo run --example basic_usage --features native

WASM Build

cargo check --target wasm32-unknown-unknown --features wasm
wasm-pack build --target web --features wasm

Future Enhancements

Potential Improvements

1. Reconnection Logic: Automatic reconnection with exponential backoff
2. Request Queuing: Queue multiple concurrent sign requests
3. Timeout Handling: Configurable timeouts for requests
4. Metrics: Connection and request metrics
5. Logging: Structured logging with configurable levels

WASM Enhancements

1. Better Callback System: More ergonomic callback handling in WASM
2. Browser Wallet Integration: Direct integration with MetaMask, etc.
3. Service Worker Support: Background request handling

Security Considerations

1. No Private Key Storage: The client never handles private keys
2. User Approval Required: All signing requires explicit user approval
3. Message Validation: All incoming messages are validated
4. Secure Transport: Requires WebSocket Secure (WSS) in production

Compatibility

• Rust Version: 1.70+
• WASM Target: wasm32-unknown-unknown
• Browser Support: Modern browsers with WebSocket support
• Server Compatibility: Compatible with sigsocket server protocol

This implementation provides a solid foundation for applications that need to connect to sigsocket servers while maintaining security and user control over signing operations.