Move Build a Desktop Wallet code samples

content/_code-samples/build-a-desktop-wallet/js/library/5_helpers.js

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+const {prepareAccountData, prepareLedgerData} = require("./3_helpers");
+const {prepareTxData} = require("./4_helpers");
+const crypto = require("crypto");
+const fs = require("fs");
+const path = require("path");
+const fernet = require("fernet");
+
+/**
+ * Fetches some initial data to be displayed on application startup
+ *
+ * @param client
+ * @param wallet
+ * @param appWindow
+ * @returns {Promise<void>}
+ */
+const initialize = async (client, wallet, appWindow) => {
+    // Reference: https://xrpl.org/account_info.html
+    const accountInfoResponse = await client.request({
+        "command": "account_info",
+        "account": wallet.address,
+        "ledger_index": "current"
+    })
+    const accountData = prepareAccountData(accountInfoResponse.result.account_data)
+    appWindow.webContents.send('update-account-data', accountData)
+
+    // Reference: https://xrpl.org/account_tx.html
+    const txResponse = await client.request({
+        "command": "account_tx",
+        "account": wallet.address
+    })
+    const transactions = prepareTxData(txResponse.result.transactions)
+    appWindow.webContents.send('update-transaction-data', transactions)
+}
+
+/**
+ * Handles the subscriptions to ledger events and the internal routing of the responses
+ *
+ * @param client
+ * @param wallet
+ * @param appWindow
+ * @returns {Promise<void>}
+ */
+const subscribe = async (client, wallet, appWindow) => {
+
+    // Reference: https://xrpl.org/subscribe.html
+    await client.request({
+        "command": "subscribe",
+        "streams": ["ledger"],
+        "accounts": [wallet.address]
+    })
+
+    // Reference: https://xrpl.org/subscribe.html#ledger-stream
+    client.on("ledgerClosed", async (rawLedgerData) => {
+        const ledger = prepareLedgerData(rawLedgerData)
+        appWindow.webContents.send('update-ledger-data', ledger)
+    })
+
+    // Wait for transaction on subscribed account and re-request account data
+    client.on("transaction", async (transaction) => {
+        // Reference: https://xrpl.org/account_info.html
+        const accountInfoRequest = {
+            "command": "account_info",
+            "account": wallet.address,
+            "ledger_index": transaction.ledger_index
+        }
+
+        const accountInfoResponse = await client.request(accountInfoRequest)
+        const accountData = prepareAccountData(accountInfoResponse.result.account_data)
+        appWindow.webContents.send('update-account-data', accountData)
+
+        const transactions = prepareTxData([{tx: transaction.transaction}])
+        appWindow.webContents.send('update-transaction-data', transactions)
+    })
+}
+
+/**
+ * Saves the wallet seed using proper cryptographic functions
+ *
+ * @param WALLET_DIR
+ * @param seed
+ * @param password
+ */
+const saveSaltedSeed = (WALLET_DIR, seed, password)=> {
+    const salt = crypto.randomBytes(20).toString('hex')
+
+    fs.writeFileSync(path.join(__dirname, WALLET_DIR, 'salt.txt'), salt);
+
+    // Hashing salted password using Password-Based Key Derivation Function 2
+    const derivedKey = crypto.pbkdf2Sync(password, salt, 1000, 32, 'sha256')
+
+    // Generate a Fernet secret we can use for symmetric encryption
+    const secret = new fernet.Secret(derivedKey.toString('base64'));
+
+    // Generate encryption token with secret, time and initialization vector
+    // In a real-world use case we would have current time and a random IV,
+    // but for demo purposes being deterministic is just fine
+    const token = new fernet.Token({
+        secret: secret,
+        time: Date.parse(1),
+        iv: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
+    })
+
+    const privateKey = token.encode(seed)
+
+    fs.writeFileSync(path.join(__dirname, WALLET_DIR, 'seed.txt'), privateKey)
+}
+
+/**
+ * Loads the plaintext value of the encrypted seed
+ *
+ * @param WALLET_DIR
+ * @param password
+ * @returns {*}
+ */
+const loadSaltedSeed = (WALLET_DIR, password) => {
+    const salt = fs.readFileSync(path.join(__dirname, WALLET_DIR, 'salt.txt')).toString()
+
+    const encodedSeed = fs.readFileSync(path.join(__dirname, WALLET_DIR, 'seed.txt')).toString()
+
+    // Hashing salted password using Password-Based Key Derivation Function 2
+    const derivedKey = crypto.pbkdf2Sync(password, salt, 1000, 32, 'sha256')
+
+    // Generate a Fernet secret we can use for symmetric encryption
+    const secret = new fernet.Secret(derivedKey.toString('base64'));
+
+    // Generate decryption token
+    const token = new fernet.Token({
+        secret: secret,
+        token: encodedSeed,
+        ttl: 0
+    })
+
+    return token.decode();
+}
+
+module.exports = { initialize, subscribe, saveSaltedSeed, loadSaltedSeed }