JS: Grant Active Permission

Full, runnable src of Grant Active Permission can be downloaded as part of: tutorials/javascript (or download just this tutorial: devportal-master-tutorials-javascript-31_grant_active_permission.zip).

This tutorial will take you through the process of checking a specific users’ data, altering the array pertaining to the active account_auths, and then broadcasting the changes to the blockchain. Demo account information has been provided to assist with the tutorial. This tutorial has been set up for the testnet but can be easily be changed for production.

Providing another user active permission for your account enables them to do fund transfers from your account. This can be usefull in setting up a secondary account(s) to manage funds for a main account or having a backup should you lose passwords for the main account.

One of the common practice nowadays is to lend/delegate HP to another account, above same technique can be used to create market around it with minimum 3rd party trust. All your funds stay in your account. You can use/create automated system where you can lease for certain period of time and system can take care of payments and release of delegations (notify clients). Even better, you can use multi-signature feature to establish 100% trust where clients will have to confirm, approve transactions.

Active permissions and authority should be used with utmost care, you don’t want to loose your funds. It is really not easy to hack Hive accounts, let alone take control over it. But without careful use (revealing private keys) loosing liquid funds are not that difficult and it takes only couple seconds to do that, keeping most value powered up always helps.

this article has more detail around active authorities

Intro

This tutorial uses the database API to gather account information for the user that is granting active permission to a secondary user. This information is used to check current permissions as well as to build the broadcast operation. Granting or revoking active permission works by changing the array of usernames containing this information and then pushing those changes to the blockchain. The parameters for this updateAccount function are:

1. account - The username of the main account
2. active - Optional parameter to denote changes to the active authority type. This is the parameter that we will be changing in this tutorial
3. jsonMetadata - This is a string value obtained from the current account info
4. memoKey - This is the public memoKey of the user
5. owner - Optional parameter to denote changes to the owner authority type
6. posting - Optional parameter to denote changes to the posting authority type
7. privateKey - The private active key of the user

The only other information required is the username of the account that the active permission is being granted to.

The tutorial is set up with three individual functions for each of the required operations - checking permission status, granting permission and revoking permission.

Also see:

• account_update_operation

Steps

1. Configure connection Configuration of dhive to communicate with a Hive blockchain
2. Input variables Collecting the required inputs via an HTML UI.
3. Database query Sending a query to the blockchain for the active permissions (status)
4. Object creation Create the array and subsequent data object for the broadcast operation
5. Broadcast operation Broadcasting the changes to the blockchain

1. Configure connection

As usual, we have a public/app.js file which holds the Javascript segment of the tutorial. In the first few lines we define the configured library and packages:

import { Client, PrivateKey } from '@hiveio/dhive';
import { Testnet as NetConfig } from '../../configuration'; //A Hive Testnet. Replace 'Testnet' with 'Mainnet' to connect to the main Hive blockchain.

let opts = { ...NetConfig.net };

//connect to a hive node, testnet in this case
const client = new Client(NetConfig.url, opts);

Above, we have dhive pointing to the testnet with the proper chainId, addressPrefix, and endpoint by importing it from the configuration.js file. Due to this tutorial altering the blockchain it is preferable to not work on production.

2. Input variables

The required parameters for the account status query is recorded via an HTML UI that can be found in the public/index.html file. Any active account information can be used for this tutorial but to make things easier we populate these fields once the UI loads.

window.onload = async () => {
    const account = NetConfig.accounts[0];
    const accountI = NetConfig.accounts[1];
    document.getElementById('username').value = account.address;
    document.getElementById('privateKey').value = account.privActive;
    document.getElementById('newAccount').value = accountI.address;
};

All of the functions use the same input variables. Once the function is activated via the UI the variables are allocated as seen below.

//get username
const username = document.getElementById('username').value;
//get private active key
const privateKey = PrivateKey.fromString(
    document.getElementById('privateKey').value
);
//get account to provide active auth
const newAccount = document.getElementById('newAccount').value;

3. Database query

The queries are sent through to the hive blockchain with the database API using the getAccounts function. The results of the query is used to check the status of the current active authorisations and parameters as per the intro.

//query database for active array
var _data = new Array
_data = await client.database.getAccounts([username]);
const activeAuth = _data[0].active;

//check for username duplication
const checkAuth = _data[0].active.account_auths;
var arrayindex = -1;
var checktext = " does not yet have active permission"
for (var i = 0,len = checkAuth.length; i<len; i++) {
    if (checkAuth[i][0]==newAccount) {
        arrayindex = i
        var checktext = " already has active permission"
    }
}

The result of this status query is then displayed on the UI along with the array on the console as a check.

document.getElementById('permCheckContainer').style.display = 'flex';
document.getElementById('permCheck').className = 'form-control-plaintext alert alert-success';
document.getElementById('permCheck').innerHTML = newAccount + checktext;
console.log(checkAuth);

4. Object creation

The database query is the same for all the functions and is required to create an updated array to broadcast to the blockchain. This is how we determine whether a user permission will be added or revoked. The actual operation is the same apart from the array variable as can be seen below. The difference is in that when creating a permission, an element is added to the account_auths array where revoking removes an element from it.

//add account permission
activeAuth.account_auths.push([
    newAccount,
    parseInt(activeAuth.weight_threshold)
]);
activeAuth.account_auths.sort();

//revoke permission
activeAuth.account_auths.splice(arrayindex, 1);

When adding to the array (creaing permission) it is required to sort the array before we can broadcast. The Hive blockchain does not accept the new fields in the array if it’s not alphabetically sorted. After the active array has been defined, the broadcast object can be created. This holds all the required information for a successful transaction to be sent to the blockchain. Where there is no change in the authority types, the parameter can be omitted or in the case of required parameters, allocated directly from the database query.

//object creation
const accObj = {
    account: username,
    json_metadata: _data[0].json_metadata,
    memo_key: _data[0].memo_key,
    active: activeAuth,
}

5. Broadcast operation

With all the parameters assigned, the transaction can be broadcast to the blockchain. As stated before, the actual broadcast operation for both new permissions and to revoke permissions use the same parameters.

//account update broadcast
client.broadcast.updateAccount(accObj, privateKey).then(
    function(result) {
        console.log(
            'included in block: ' + result.block_num,
            'expired: ' + result.expired
        );
        document.getElementById('permCheckContainer').style.display = 'flex';
        document.getElementById('permCheck').className = 'form-control-plaintext alert alert-success';
        document.getElementById('permCheck').innerHTML = "permission has been revoked for " + newAccount;
    },
    function(error) {
        console.error(error);
        document.getElementById('permCheckContainer').style.display = 'flex';
        document.getElementById('permCheck').className = 'form-control-plaintext alert alert-danger';
        document.getElementById('permCheck').innerHTML = error.jse_shortmsg;
    }
);

The results of the operation is displayed on the UI along with a block number in the console to confirm a successful operation. If you add permission to an account that already has permission, or if your private key has been entered incorrectly, an error of “Missing Active Authority” will be displayed.

Hiveconnect offers an alternative to revoking active permission with a “simple link” solution. Instead of running through a list of operations on your account, you can simply use a link similar to the one below. You will be prompted to enter your usename and password and the specified user will have their permissions removed instantly. https://v2.hivesigner.com/revoke/@username This is similar to the Hive Signer links that have been covered in previous tutorials. For a list of signing operations that work in this manner you can go to https://v2.hivesigner.com/sign

To run this tutorial

1. git clone https://gitlab.syncad.com/hive/devportal.git
2. cd devportal/tutorials/javascript/31_grant_active_permission
3. npm i
4. npm run dev-server or npm run start
5. After a few moments, the server should be running at http://localhost:3000/