Rainbow on Binance Smart Chain

[3alpha]

New BSC Feature

The new BSC feature allows Rainbow bridge to run on Binance Smart Chain.

Technical

When the Bridge is configured to use bsc mode, the first header has to be an epoch header (block_number%200==0). That is because the epoch header contains the validator set inside the extra_data field. After that, bridge starts to receive and validate the other blocks. If current block at the time of starting the bridge isn't the epoch block, bridge gets initialised at previous epoch block.
Every time Near client gets a new epoch header it saves it and uses the new validator set from it.

New Configurations:

The Bridge handles POW(ethash), POSA(bsc), or POA, by default the POW is used.

To use bsc:

    nearClientValidateHeader: 'true',
    nearClientValidateHeaderMode: 'bsc'

and to use ethash:

    nearClientValidateHeader: 'true',
    nearClientValidateHeaderMode: 'ethash'

here is an example of the new config file ~/.rainbow/config.json:

    {
        "nearNodeUrl": "http://localhost:3030",
        "nearNetworkId": "local",
        "nearMasterAccount": "node0",
        "nearMasterSk": "ed25519:3D4YudUQRE39Lc4JHghuB5WM8kbgDDa34mnrEP5DdTApVH81af7e2dWgNPEaiQfdJnZq1CNPp5im4Rg5b733oiMP",
        "ethNodeUrl": "https://data-seed-prebsc-1-s1.binance.org:8545",
        "ethMasterSk": "0x2bdd21761a483f71054e14f5b827213567971c676928d9a1808cbfa4b7501200",
        "nearClientValidateHeader": "true", 
        "nearClientValidateHeaderMode": "bsc",
        "nearClientSk": "ed25519:3D4YudUQRE39Lc4JHghuB5WM8kbgDDa34mnrEP5DdTApVH81af7e2dWgNPEaiQfdJnZq1CNPp5im4Rg5b733oiMP",
        "nearProverSk": "ed25519:3D4YudUQRE39Lc4JHghuB5WM8kbgDDa34mnrEP5DdTApVH81af7e2dWgNPEaiQfdJnZq1CNPp5im4Rg5b733oiMP",
        "ethEd25519Address": "0x62ff99964d1026bfd3fea2086b9d141917f1a793",
        "ethClientLockEthAmount": "1000",
        "ethClientLockDuration": "10",
        "ethClientAddress": "0x2cdaaa435937ae65705b97fbd01d28f4f6494545",
        "ethProverAddress": "0x5cdc96ce31bdf08ef39d5f65a9fd5e236ce2245f",
        "ethErc20Address": "0x7ef88a3901494435700ccc4c7615903b43ec2dbc",
        "ethLockerAddress": "0x24d718f7d8af7d7a4abaa2b1cb7abbb36a23a00d",
        "ethAdminAddress": "0xDf08F82De32B8d460adbE8D72043E3a7e25A3B39"
    }

Deploy the bridge locally with BSC Mode

To run the bridge locally with Binance Smart Chain, run the following cmd:

1. init yarn and generate Ethereum contracts:

make init

2. Start Near blockchain and connect with Binance testnet.

make start-bsc

3. Deploy Near and Ethereum contracts

make full-bsc-contracts

or use already deployed contracts (on BSC), first copy past the following parameters inside the ~/.rainbow/config.json file:

    "ethEd25519Address": "0x62ff99964d1026bfd3fea2086b9d141917f1a793",
    "ethClientLockEthAmount": "1000",
    "ethClientLockDuration": "10",
    "ethClientAddress": "0x2cdaaa435937ae65705b97fbd01d28f4f6494545",
    "ethProverAddress": "0x5cdc96ce31bdf08ef39d5f65a9fd5e236ce2245f",
    "ethErc20Address": "0x7ef88a3901494435700ccc4c7615903b43ec2dbc",
    "ethLockerAddress": "0x24d718f7d8af7d7a4abaa2b1cb7abbb36a23a00d",
    "ethAdminAddress": "0xDf08F82De32B8d460adbE8D72043E3a7e25A3B39"

then run the following command:

make light-bsc-contracts

4. Start the relayers:

make start-relayer

5. When you are done you can stop the bridge by running:

make stop-all

• The bridge uses pm2 tool so you can use it to check logs and list the processes

[mfornet]

For now only reviewed the code affecting the previous setup, will continue reviewing the code introducing the new feature next. I'm making this checkpoint to leave some comments.

[mfornet]

Let's use named ChainId here, to be clear what this number actually means. In this case since we are using ethash let's use chain_id 3, though it is not used anywhere so it makes no real difference.

Just as a note for other reviewing this PR I found a list of chain id from networks supporting EVM: Chainlist.

[mfornet]

Thanks for the Makefile, it is a really helpful addition. 🎉

[mfornet]

Contract LGTM.

For the BSC code in the client I think we should use rust feature flags so only the intended binary is compiled and deployed.

[mfornet]

Suggested change

	// check if the auther address is valid and is in the validator set.
	// check if the author address is valid and is in the validator set.

[mfornet]

Suggested change

	// Get validator offset postion.
	// Get validator offset position.

[mfornet]

Suggested change

	// verift basic header properties.
	// verify basic header properties.

[mfornet]

Merge conflicts needs to be solved before merging.

[idirall22]

Hello @mfornet @abacabadabacaba
The conflicts are solved the fork is ready to be merged.

[mfornet]

@sept-en could you take a look at this PR before merging.

[mfornet]

I discussed with @sept-en and agreed on merge it to bsc branch for now!