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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

geth is required for installation
Install the latest develop version of embark: npm install -g https://github.com/embark-framework/embark.git
If running a development version of the gas relay

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

When Embark finishes loading, execute embark run && ./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/index.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);
});