x402 Rust Implementation

A high-performance, type-safe Rust implementation of the x402 HTTP-native micropayment protocol.

🎉 First public debut at EthGlobal Online 2025

📦 Installation

Add this to your Cargo.toml:

[dependencies]
rust-x402 = "0.2.2"

✨ Features

• 🚀 HTTP-native micropayments: Leverage the HTTP 402 status code for payment requirements
• ⛓️ Blockchain integration: Support for EIP-3009 token transfers with real wallet integration
• 🌐 Web framework support: Middleware for Axum, Actix Web, and Warp
• 💰 Facilitator integration: Built-in support for payment verification and settlement
• 📦 Standalone facilitator: Production-ready facilitator server as standalone binary
• 🗄️ Redis storage: Optional Redis backend for distributed nonce storage
• 🔒 Type safety: Strongly typed Rust implementation with comprehensive error handling
• 🧪 Comprehensive testing: 114 tests with 100% pass rate covering all real implementations
• 🏗️ Real implementations: Production-ready wallet, blockchain, and facilitator clients
• 🌊 Multipart & Streaming: Full support for large file uploads and streaming responses
• 📡 HTTP/3 Support: Optional HTTP/3 (QUIC) support for modern high-performance networking

🚀 Quick Start

Creating a Payment Server with Axum

use axum::{response::Json, routing::get};
use rust_x402::{
    axum::{create_payment_app, examples, AxumPaymentConfig},
    types::FacilitatorConfig,
};
use rust_decimal::Decimal;
use std::str::FromStr;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create facilitator config
    let facilitator_config = FacilitatorConfig::default();
    
    // Create payment configuration
    let payment_config = AxumPaymentConfig::new(
        Decimal::from_str("0.0001")?,
        "0x209693Bc6afc0C5328bA36FaF03C514EF312287C",
    )
    .with_description("Premium API access")
    .with_facilitator_config(facilitator_config)
    .with_testnet(true);

    // Create the application with payment middleware
    let app = create_payment_app(payment_config, |router| {
        router.route("/joke", get(examples::joke_handler))
    });

    // Start server
    let listener = tokio::net::TcpListener::bind("0.0.0.0:4021").await?;
    axum::serve(listener, app).await?;

    Ok(())
}

💳 Making Payments with a Client

use rust_x402::client::X402Client;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = X402Client::new()?;
    
    // Make a request to a protected resource
    let response = client.get("http://localhost:4021/joke").send().await?;
    
    if response.status() == 402 {
        println!("Payment required! Status: {}", response.status());
        // Handle payment required - parse PaymentRequirements and create signed payload
        // See examples/client.rs for complete implementation
    } else {
        let text = response.text().await?;
        println!("Response: {}", text);
    }
    
    Ok(())
}

🏭 Running the Standalone Facilitator Server

The facilitator can run as a standalone binary with optional Redis storage:

# In-memory storage (default)
cargo run --bin facilitator --features axum

# Redis storage backend
STORAGE_BACKEND=redis cargo run --bin facilitator --features axum,redis

# Custom configuration
BIND_ADDRESS=0.0.0.0:4020 \
REDIS_URL=redis://localhost:6379 \
REDIS_KEY_PREFIX=x402:nonce: \
cargo run --bin facilitator --features axum,redis

🏗️ Architecture

The Rust implementation is organized into several modules:

• 📦 types: Core data structures and type definitions
• 🌐 client: HTTP client with x402 payment support
• 💰 facilitator: Payment verification and settlement
• 🗄️ facilitator_storage: Nonce storage backends (in-memory and Redis)
• 🔧 middleware: Web framework middleware implementations
• 🔐 crypto: Cryptographic utilities for payment signing
• ❌ error: Comprehensive error handling
• 🏦 wallet: Real wallet integration with EIP-712 signing
• ⛓️ blockchain: Blockchain client for network interactions
• 🏭 blockchain_facilitator: Blockchain-based facilitator implementation
• 📡 http3: HTTP/3 (QUIC) support (feature-gated)
• 🔄 proxy: Reverse proxy with streaming support

🌐 Supported Web Frameworks

• 🚀 Axum: Modern, ergonomic web framework
• ⚡ Actix Web: High-performance actor-based framework
• 🪶 Warp: Lightweight, composable web server

🌐 HTTP Protocol Support

• ✅ HTTP/1.1: Full support with chunked transfer encoding
• ✅ HTTP/2: Full support with multiplexing
• ✅ Multipart: Support for multipart/form-data uploads (via multipart feature)
• ✅ Streaming: Chunked and streaming responses (via streaming feature)
• 🔜 HTTP/3 (optional): QUIC-based HTTP/3 via http3 feature flag

🎛️ Optional Features

x402 supports optional features for a modular build:

[dependencies]
rust-x402 = { version = "0.2.2", features = ["http3", "streaming", "multipart"] }

• http3: Enable HTTP/3 (QUIC) support
• streaming: Enable chunked and streaming responses
• multipart: Enable multipart/form-data upload support (requires streaming)
• redis: Enable Redis backend for facilitator storage
• axum: Enable Axum web framework integration (default)
• actix-web: Enable Actix Web framework integration
• warp: Enable Warp web framework integration

⛓️ Blockchain Support

Currently supports:

• 🏛️ Base: Base mainnet and testnet
• ❄️ Avalanche: Avalanche mainnet and Fuji testnet
• 📜 EIP-3009: Transfer with Authorization standard

📚 Examples

See the examples/ directory for complete working examples:

• 🚀 axum_server.rs: Payment server using Axum
• 💳 client.rs: Client making payments
• 💰 facilitator.rs: Custom facilitator implementation
• 🏦 real_implementation_demo.rs: Real wallet and blockchain integration
• 🔐 real_wallet_integration.rs: Production-ready wallet integration

🏗️ Module Structure

This project follows a clean, modular architecture for better maintainability:

src/
├── facilitator/        # Payment verification & settlement
│   ├── mod.rs         # Main client implementation
│   ├── coinbase.rs    # Coinbase CDP integration
│   └── tests.rs       # Comprehensive test suite
│
├── crypto/            # Cryptographic utilities
│   ├── mod.rs         # Module exports
│   ├── jwt.rs         # JWT authentication
│   ├── eip712.rs      # EIP-712 typed data hashing
│   ├── signature.rs   # ECDSA signature verification
│   └── tests.rs       # Crypto test suite
│
├── types/             # Core protocol types
│   ├── mod.rs         # Type exports
│   ├── network.rs     # Network configurations
│   ├── payment.rs     # Payment types
│   ├── facilitator.rs # Facilitator types
│   ├── discovery.rs   # Discovery API types
│   └── constants.rs   # Protocol constants
│
├── middleware/        # Web framework middleware
│   ├── mod.rs         # Module exports
│   ├── config.rs      # Middleware configuration
│   ├── payment.rs     # Payment processing logic
│   ├── service.rs     # Tower service layer
│   └── tests.rs       # Middleware tests
│
└── ...                # Other modules

Benefits:

• 📖 Clear Organization: Each module has a single, well-defined responsibility
• 🔍 Easy Navigation: Find code quickly in focused, smaller files
• 📚 Self-Documenting: Rich module-level documentation in each mod.rs
• 🧪 Better Testing: Isolated test suites per module
• 🤝 Team Friendly: Reduces merge conflicts

All module documentation is embedded in the code - run cargo doc --no-deps --open to view!

📊 Testing

• ✅ 114 tests with 100% pass rate
• 🧪 Comprehensive coverage of all real implementations
• 🔍 Integration tests for end-to-end workflows
• 🛡️ Error handling tests for robust error scenarios
• 🌊 Multipart & streaming tests for file upload/download scenarios
• 📡 HTTP/3 tests (with http3 feature)
• 🗄️ Redis storage tests with auto-skip when unavailable
• ⚙️ Feature-gated tests for modular builds

📄 License

Licensed under the Apache License, Version 2.0. See LICENSE for details.