token-gas-relayer

Gas relayer mplementation for economic abstraction. This project consists of two elements:

• gas-relayer: nodejs service that listens to whisper on a symmetric key, with specific topics, and processes any transaction.
• test-dapp: DApp created for testing purposes. It allows the easy creation of the messages expected by the service.

Installation

• Install the latest develop version of embark: npm install -g https://github.com/embark-framework/embark.git@develop
• If running a development version of the gas relay

cd test-dapp
chmod a+x setup_dev_env.sh
embark blockchain

• Execute ./setup_dev_env.sh to create the test account

Node

Before executing this program, config/config.json must be setup and npm install needs to be executed. Important values to verify are related to the node configuration, just like:

• Host, port and protocol to connect to the geth node
• Host, port and protocol Ganache will use when forking the blockchain for gas estimations and other operations
• Wallet account used for processing the transactions
• Symmetric key used to receive the Whisper messages
• Symmetric key used to send the heartbeats that notify the tokens and prices accepted
• Accepted tokens information
• Contract configuration This program is configured with the default values for a embark installation run from 0

A geth node running whisper (via -shh option) is required. To execute the gas-relayer, you may use any of the following three methods.

npm start
node src/service.js
nodemon src/service.js

Test DApp

To run the test dapp, use embark run and then browse http://localhost:8000/dapp.html.

The gas relayer service needs to be running, and configured correctly to process the transactions. Things to take in account are: the account used in embark, and the contract addresses.

(TODO: update testnet configuration to guarantee the contract addresses don't change)

Additional notes

How to send a message to this service (all accounts and privatekeys should be replaced by your own test data)

shh.post({symKeyID: SYM_KEY, sig: WHISPER_KEY_ID, ttl: 1000, powTarget: 1, powTime: 20, topic: TOPIC_NAME, payload: PAYLOAD_BYTES});

• SYM_KEY must contain the whisper symmetric key used. It is shown on the console when running the service with node. With the provided configuration you can use the value:

0xd0d905c1c62b810b787141430417caf2b3f54cffadb395b7bb39fdeb8f17266b`

• WHISPER_KEY_ID represents a keypair registered on your node, that will be used to sign the message. Can be generated with web3W.shh.newKeyPair()
• TOPIC_NAME must contain one of the topic names generated based on converting the contract name to hex, and taking the first 8 bytes. For the provided configuration the following topics are available:
• • IdentityGasRelay: 0x4964656e
• • SNTController: 0x534e5443
• PAYLOAD_BYTES a hex string that contains the identity/contract address to invoke and the web3 encoded abi function invocation plus parameters. If we were to execute callGasRelayed(address,uint256,bytes,uint256,uint256,uint256,address,bytes) (part of the IdentityGasRelay) in contract 0x692a70d2e424a56d2c6c27aa97d1a86395877b3a, with these values: "0x11223344556677889900998877665544332211",100,"0x00",1,10,20,"0x1122334455112233445511223344551122334455", "0x1122334455", PAYLOAD_BYTES can be prepared as follows:

const whisperKeyPairID = await web3W.shh.newKeyPair();
const jsonAbi = ABIOfIdentityGasRelay.filter(x => x.name == "callGasRelayed")[0];

const funCall = web3.eth.abi.encodeFunctionCall(jsonAbi,
                [
                    "0x11223344556677889900998877665544332211", 
                    100, 
                    "0x00",
                    1,
                    10,
                    20,
                    "0x1122334455112233445511223344551122334455",
                    "0x1122334455"
                ]);

const msgObj = { 
    symKeyID: "0xd0d905c1c62b810b787141430417caf2b3f54cffadb395b7bb39fdeb8f17266b", 
    sig: whisperKeyPairID,
    ttl: 1000, 
    powTarget: 1, 
    powTime: 20, 
    topic: "0x4964656e", 
    payload: web3.utils.toHex({
        'address': "0x692a70d2e424a56d2c6c27aa97d1a86395877b3a",
        'encodedFunctionCall': funCall
    })
};

        
web3.shh.post(msgObj)
.then((err, result) => {
    console.log(result);
    console.log(err);
});