PipeGate Server Middleware Documentation

Overview

The pipegate middleware provides server-side verification and payment channel management for the PipeGate protocol. This guide covers the setup and configuration for API providers using the Rust implementation.

NOTE : Only live on Base sepolia ( rpc: "https://base-sepolia-rpc.publicnode.com" )

Installation

Add the following dependencies to your Cargo.toml:

[dependencies]
pipegate = { version = "0.1.0" }  # PipeGate server middleware
axum = "0.7"                               # Web framework
tokio = { version = "1.0", features = ["full"] }
alloy = { version = "0.1", features = ["full"] }

Basic Setup

Simple Server Implementation

use alloy::{primitives::U256};
use axum::{routing::get, Router};
use pipegate::{channel::ChannelState, middleware::PipegateMiddlewareLayer};

#[tokio::main]
async fn main() {
    // Configure RPC endpoint
    let rpc_url: alloy::transports::http::reqwest::Url =
        "https://base-sepolia-rpc.publicnode.com".parse().unwrap();

    // Configure payment amount per request ( not in decimals, parsed down )
    let payment_amount = U256::from(1000); // 0.001 USDC

    // Initialize channel state
    let state = ChannelState::new(rpc_url.clone());

    // Create router with middleware
    let app = Router::new()
        .route("/", get(root))
        .layer(PipegateMiddlewareLayer::new(state.clone(), payment_amount));

    // Start server
    let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
    axum::serve(listener, app).await.unwrap();
}

async fn root() -> &'static str {
    "Hello, World!"
}

Closing channel & withdraw

use pipegate::{
    channel::{close_channel, ChannelState},
    types::PaymentChannel,
};
pub async fn close_and_withdraw(_state: &ChannelState) {

    // Read the payment channel state
    // let payment_channel = state.get_channel(U256::from(1)).await.unwrap();
    //or
    // Define the payment channe
    let payment_channel = PaymentChannel {
        address: Address::from_str("0x4cf93d3b7cd9d50ecfba2082d92534e578fe46f6").unwrap(),
        sender: Address::from_str("0x898d0dbd5850e086e6c09d2c83a26bb5f1ff8c33").unwrap(),
        recipient: Address::from_str("0x62c43323447899acb61c18181e34168903e033bf").unwrap(),
        balance: U256::from(1000000),
        nonce: U256::from(0),
        expiration: U256::from(1734391330),
        channel_id: U256::from(1),
    };

    // Can be temporarily retrieved from the logs the latest one
    let signature : Signature = Signature::from_str("0x...").unwrap();

    // raw body of the same request
    let raw_body = Bytes::from("0x");

    let rpc_url: alloy::transports::http::reqwest::Url =
        "https://base-sepolia-rpc.publicnode.com".parse().unwrap();

    let private_key = env::var("PRIVATE_KEY").expect("PRIVATE_KEY must be set");

    let tx_hash = close_channel(
        rpc_url,
        private_key.as_str(),
        &payment_channel,
        &signature,
        raw_body,
    );
}

Verify one time payment tx

Use the verify_tx function to verify a one-time payment transaction. The function takes a SignedPaymentTx and OneTimePaymentConfig as input and returns a Result with the verification status or an error.

async fn verify_onetime_payment_tx() {
    let rpc_url = "https://base-sepolia-rpc.publicnode.com";

    // Payment config for one time payment set by server owner
    let onetime_payment_config = OneTimePaymentConfig {
        recipient: Address::from_str("0x62c43323447899acb61c18181e34168903e033bf").unwrap(),
        token_address: Address::from_str("0x036CbD53842c5426634e7929541eC2318f3dCF7e").unwrap(),
        amount: U256::from(1000000), // 1 USDC
        period: U256::from(0),
        rpc_url: rpc_url.to_string(),
    };

    // Example Signed Payment info from request headers
    let signed_payment_tx = SignedPaymentTx {
        signature: PrimitiveSignature::from_str("0xe3ebb83954309b86cc6d27e7e70b5dbcb0447cf79f8d74fc3806a6e814138fb573d3df3c1fcae6fd8fe1dca34ba8bb2748da3b68790df8ce45108016b601c12a1b").unwrap(),
        tx_hash: FixedBytes::<32>::from_str("0xe88140d4787b1305c24961dcef2f7f73d583bb862b3cbde4b7eec854f61a0248").unwrap(),
    };

    let result = verify_tx(signed_payment_tx, onetime_payment_config).await;
    println!("Result: {:?}", result);
}

Verification functions

1. Verify and Update Channel State: verify_and_update_channel - Verifies the signed request and updates the channel state. ChannelState is required to be persisted, better suited for serverful applications.

2. Verify Channel: verify_channel - Verifies the signed request and returns the updated channel. ChannelState is not required to be persisted, better suited for serverless applications, but would add latency due to extra RPC calls to verify the channel info on each call.

Helper functions

1. Parse headers for payment channel with axum: parse_headers_axum - Parsing and extracting signed request with payment channel from request headers in axum.

2. Modify headers for updated channel with axum: modify_headers_axum - Modifying response headers with updated channel state in axum.

3. Parse headers for payment channel with HTTP: parse_headers - Parsing and extracting signed request with payment channel from HTTP headers.

4. Modify headers for updated channel with HTTP: modify_headers - Modifying response headers with updated channel state in HTTP.

5. Parse headers for onetime payment tx: parse_tx_headers_axum - Parsing and extracting signed request with onetime payment tx from request headers in axum.

Error Handling

use pipegate::errors::AuthError;

async fn handle_request() -> Result<Response, AuthError> {
    match process_request().await {
        Ok(response) => Ok(response),
        Err(AuthError::InsufficientBalance) => {
            // Handle insufficient balance
        },
        Err(AuthError::InvalidSignature) => {
            // Handle invalid signature
        },
        Err(AuthError::ChannelExpired) => {
            // Handle expired channel
        },
        Err(e) => {
            // Handle other errors
        }
    }
}

WASM Compatibility

The PipeGate middleware can be compiled to WebAssembly (WASM) for use in browser-based applications. The middleware can be compiled using the wasm-pack tool and integrated into web applications using JavaScript. Only a subset of functions are exported currently with wasm-bindgen and can be found in wasm.rs. But other functions which are available can be easily exported as needed.

wasm-pack build --target web

Example usage can be found at tests/index.ts

Middleware Configuration Options

Environment Variables

# .env
RPC_URL=https://base-sepolia-rpc.publicnode.com
MIN_PAYMENT_AMOUNT=1000
CHANNEL_FACTORY_ADDRESS=0x...

Loading Configuration

use dotenv::dotenv;
use std::env;

async fn load_config() -> MiddlewareConfig {
    dotenv().ok();

    let rpc_url = env::var("RPC_URL")
        .expect("RPC_URL must be set");

    let min_payment = env::var("MIN_PAYMENT_AMOUNT")
        .map(|s| U256::from_dec_str(&s).unwrap())
        .expect("MIN_PAYMENT_AMOUNT must be set");

    // Return configuration
    MiddlewareConfig {
        rpc_url: rpc_url.parse().unwrap(),
        min_payment,
        // Other config options
    }
}

Best Practices

1. Security

   • Always verify signatures and nonces
   • Implement rate limiting
   • Monitor for suspicious activity
   • Keep RPC endpoint secure

2. Performance

   • Use connection pooling for RPC calls
   • Implement caching for channel states
   • Monitor middleware performance

3. Maintenance

   • Regularly update dependencies
   • Monitor channel states
   • Implement proper logging
   • Set up monitoring and alerts

4. Error Handling

   • Implement comprehensive error handling
   • Provide meaningful error messages
   • Log errors appropriately
   • Handle edge cases

Note: This middleware is part of the PipeGate protocol. Ensure you're using compatible versions of both client SDK and server middleware.

Credits & Refrences

• mahmudsudo/crypto_axum