backup_decrypt.js

## backup_decrypt.js
const bitsharesjs = require('bitsharesjs');

const PrivateKey = bitsharesjs.PrivateKey;
const PublicKey = bitsharesjs.PublicKey;
const Aes = bitsharesjs.Aes;
const decompress = require('lzma').decompress;

if( process.argv.length != 4 ){
    console.error("usage: " + process.argv[1] + " <binfile> <password>");
    process.exit(1);
}

const binfilePath = process.argv[2];
const password = process.argv[3];

const fs = require('fs');

// copied from bitshares-ui/web/app/actions/WalletActions.js
function decryptWalletBackup(backup_wif, backup_buffer) {
    return new Promise( (resolve, reject) => {
        if( ! Buffer.isBuffer(backup_buffer))
            backup_buffer = new Buffer(backup_buffer, "binary");

        let private_key = PrivateKey.fromWif(backup_wif);
        let public_key;
        try {
            public_key = PublicKey.fromBuffer(backup_buffer.slice(0, 33));
        } catch(e) {
            console.error(e, e.stack);
            throw new Error("Invalid backup file");
        }

        backup_buffer = backup_buffer.slice(33);
        try {
            backup_buffer = Aes.decrypt_with_checksum(
                private_key, public_key, null/*nonce*/, backup_buffer);
        } catch(error) {
            console.error("Error decrypting wallet", error, error.stack);
            reject("invalid_decryption_key");
            return;
        }

        try {
            decompress(backup_buffer, wallet_string => {
                try {
                    let wallet_object = JSON.parse(wallet_string);
                    resolve(wallet_object);
                } catch(error) {
                    if( ! wallet_string) wallet_string = "";
                    console.error("Error parsing wallet json",
                        wallet_string.substring(0,10)+ "...");
                    reject("Error parsing wallet json");
                }
            });
        } catch(error) {
            console.error("Error decompressing wallet", error, error.stack);
            reject("Error decompressing wallet");
            return;
        }
    });
}


fs.readFile(binfilePath, function(err, buf){
    if( err ){
        console.error(`read file error, please ensure the file path
        is correct and you have access right.`);
        process.exit(1);
    }

    const privateKey = PrivateKey.fromSeed(password || '');
    console.log(privateKey.toWif());

    decryptWalletBackup(privateKey.toWif(), buf)
        .then( console.log)
        .catch( console.error);

});