[API] Added klay_getProof and eth_getProof APIs

[hyunsooda]

Proposed changes

Added klay_getProof and eth_getProof APIs.

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[2dvorak]

Tried to test using eth-proof, successfully generated accountProof and storageProof, however verification won't work because eth-object fails to decode proof. @blukat29 noticed that it is due to Klaytn having different account struct (prefixed AccountType).

Ended up comparing the stateRoot and storageRoot calcuated from the proof with the known value using below test script:

const Caver = require('caver-js');
const fs = require('fs');

const { GetAndVerify, GetProof, VerifyProof } = require('eth-proof');

(async function main() {
    let getAndVerify = new GetAndVerify("http://localhost:8551")
    let getProof = new GetProof("http://localhost:8551")
    let verifyProof = new VerifyProof("http://localhost:8551")

    const key = "c26e4a47a7443384def9d7d2b405dfae0826c5142385f1a3fb142836f68407d9"
    const abi = JSON.parse(fs.readFileSync('./build/MyContract.abi', 'utf8'));
    const code = fs.readFileSync('./build/MyContract.bin', 'utf8');
    const caver = new Caver("http://localhost:8551");
    const senderAddr = caver.klay.accounts.wallet.add(key).address;

    const instance = new caver.klay.Contract(abi);
    let contract = await instance.deploy({data: code, arguments:[1]})
        .send({ from: senderAddr, gas: 100000000, value: 0 });

    const block = await caver.rpc.klay.getBlockByNumber("latest");

    let accountProof = await getProof.accountProof(contract._address, block.hash);

    let stateRoot = VerifyProof.getStateRootFromHeader(accountProof.header)
    let stateRootFromProof = VerifyProof.getRootFromProof(accountProof.accountProof)
    // These should match, see eth-proof/getAndVerifyProof.js:34
    console.log(stateRoot);
    console.log(stateRootFromProof);

    // Get storageRoot using RPC, because we cannot decode proof into eth-object Account
    let account = await caver.rpc.klay.getAccount(contract._address, block.hash);

    let storageProof = await getProof.storageProof(contract._address, "0x0", block.hash);
    let storageRootFromProof = VerifyProof.getRootFromProof(storageProof.storageProof)
    // These should match, see eth-proof/getAndVerifyProof.js:47
    console.log(account.account.storageRoot);
    console.log(storageRootFromProof);
})();

Output would be like:

<Buffer d9 9a 99 0c f1 5a 21 1a ef 49 aa 0d ff d9 2b 23 dc 57 60 3e de 79 c1 09 6b ce 41 9b 38 b2 fd 4d>
<Buffer d9 9a 99 0c f1 5a 21 1a ef 49 aa 0d ff d9 2b 23 dc 57 60 3e de 79 c1 09 6b ce 41 9b 38 b2 fd 4d>
0x821e2556a290c86405f8160a2d662042a431ba456b9db265c79bb837c04be5f0
<Buffer 82 1e 25 56 a2 90 c8 64 05 f8 16 0a 2d 66 20 42 a4 31 ba 45 6b 9d b2 65 c7 9b b8 37 c0 4b e5 f0>

Seems our getProof API is working fine.