From c83d888a7dae59b90507e377f688d341d4bfbdf6 Mon Sep 17 00:00:00 2001
From: catbref <misc-github@talk2dom.com>
Date: Thu, 30 May 2019 16:32:54 +0100
Subject: [PATCH] Demo HTML/JS page to show encrypted local storage of private
 key

---
 src/test/resources/local-key-storage.html | 192 ++++++++++++++++++++++
 1 file changed, 192 insertions(+)
 create mode 100644 src/test/resources/local-key-storage.html
diff --git a/src/test/resources/local-key-storage.html b/src/test/resources/local-key-storage.html
new file mode 100644
index 00000000..27172aa5
--- /dev/null
+++ b/src/test/resources/local-key-storage.html
@@ -0,0 +1,192 @@
+<!doctype html>
+<html>
+	<head>
+		<script src="Base58.js"></script>
+		<script src="nacl_factory.js"></script>
+		<script>
+			var cachedPrivateKey;
+
+			// Returns private key, or null if unable to decrypt or password is missing, etc.
+			function getPrivateKey() {
+				// If we have decrypted private key from local storage already then return it.
+				if (cachedPrivateKey != undefined)
+					return cachedPrivateKey;
+
+				var storedData = getLocallyStoredData();
+
+				// If there is nothing in local storage then we can't provide a private key.
+				// Prompt user for mnemonic phrase and new password so private key can be stored.
+				if (storedData == undefined)
+					return savePrivateKey();
+
+				// We need also password to decrypt private key.
+
+				// Prompting user for password and checking password isn't empty, etc. goes here
+				var password = document.getElementById('password').value;
+				if (password == "") {
+					document.getElementById('passwordContainer').style.display = "";
+					return null;
+				}
+
+				// Use password to create encryption key used to decrypt private key
+				var naclPromise = nacl_factory.instantiate(function (nacl) {
+					// Stored data is made up of salt(hex) + ':' + encrypted private key(hex)
+					var storedDataParts = storedData.split(':');
+
+					var salt = nacl.from_hex(storedDataParts[0]);
+					var encryptedPrivateKey = nacl.from_hex(storedDataParts[1]);
+
+					// Convert password to Uint8Array
+					var passwordArray = nacl.encode_utf8(password);
+				
+					// Use salt & password to calculate decryption key
+					var decryptionKey = deriveStorageKey(nacl, salt, passwordArray);
+
+					// Decrypt private key - throws exception on failure (e.g. wrong password)
+					var decryptedPrivateKey = nacl.crypto_secretbox_open(encryptedPrivateKey, salt, decryptionKey);
+
+					// Decryption worked so we can hide password input
+					document.getElementById('passwordContainer').style.display = "none";
+
+					// Convert decrypted private key to string
+					cachedPrivateKey = nacl.decode_utf8(decryptedPrivateKey);
+				});
+
+				return naclPromise;
+			}
+
+			function savePrivateKey() {
+				var phrase = document.getElementById('phrase').value;
+				var newPassword = document.getElementById('newPassword').value;
+
+				if (phrase == "" || newPassword == "") {
+					document.getElementById('setupContainer').style.display = "";
+					return null;
+				}
+
+				// Converting mnemonic phrase to private key goes here
+
+				// For demo we use fake private key
+				var privateKey = 'FakePrivateKey from mnemonic: ' + phrase;
+
+				// Use password to create encryption key used to encrypt private key
+				var naclPromise = nacl_factory.instantiate(function (nacl) {
+					// Generate "salt" used to protect encrypted key
+					var salt = nacl.crypto_secretbox_random_nonce();
+				
+					// Convert password to Uint8Array
+					var passwordArray = nacl.encode_utf8(newPassword);
+
+					// Use salt & password to calculate encryption key
+					var encryptionKey = deriveStorageKey(nacl, salt, passwordArray);
+
+					// Convert private key to Uint8Array
+					var privateKeyArray = nacl.encode_utf8(privateKey);
+
+					var encryptedPrivateKey = nacl.crypto_secretbox(privateKeyArray, salt, encryptionKey);
+
+					// Stored data is made up of salt(hex) + ':' + encrypted private key(hex)
+					var dataToStore = nacl.to_hex(salt) + ':' + nacl.to_hex(encryptedPrivateKey);
+
+					setLocallyStoredData(dataToStore);
+
+					// Save worked so we can hide inputs for mnemonic phrase and password
+					document.getElementById('setupContainer').style.display = "none";
+
+					cachedPrivateKey = privateKey;
+				});
+
+				return naclPromise;
+			}
+
+
+			function deriveStorageKey(nacl, salt, passwordArray) {
+				// First round
+				var toBeHashed = concatUint8Arrays(salt, passwordArray);
+
+				var hash = nacl.crypto_hash_sha256(toBeHashed);
+
+				// Many rounds of further hashing
+
+				// To be more efficient, we only need to do this once
+				toBeHashed = new Uint8Array(passwordArray.length + hash.length);
+				toBeHashed.set(passwordArray, 0);
+
+				for (var rounds = 0; rounds < 100; ++rounds) {
+					toBeHashed.set(hash, passwordArray.length);
+
+					hash = nacl.crypto_hash_sha256(toBeHashed);
+				}
+
+				return hash;
+			}
+
+			function clearPrivateKey() {
+				clearLocallyStoredData();
+
+				cachedPrivateKey = null;
+
+				document.getElementById('privateKey').innerHTML = "";
+
+				document.getElementById('passwordContainer').style.display = "none";
+				document.getElementById('setupContainer').style.display = "";
+			}
+
+			function concatUint8Arrays(array1, array2) {
+				var bigArray = new Uint8Array(array1.length + array2.length);
+				bigArray.set(array1, 0);
+				bigArray.set(array2, array1.length);
+				return bigArray;
+			}
+
+			function getLocallyStoredData() {
+				return window.localStorage.getItem("encryptedPrivateKey");
+			} 
+
+			function setLocallyStoredData(data) {
+				window.localStorage.setItem("encryptedPrivateKey", data);
+			}
+
+			function clearLocallyStoredData() {
+				window.localStorage.removeItem("encryptedPrivateKey");
+			}
+
+			window.addEventListener('load', getPrivateKey, false);
+		</script>
+		<style>
+			DIV {
+				margin-bottom: 40px;
+			}
+
+			#privateKey {
+				background: #eeeeee;
+				width: 600px;
+				display: inline-block;
+			}
+
+			#privateKey:empty:before {
+				content: "\200b"; /* Unicode zero-width space character to force span to have content */
+			}
+ 		</style>
+	</head>
+	<body>
+		<div id="activeContainer">
+			Decrypted private key: <span id="privateKey"></span><br>
+			<button onclick="clearPrivateKey(); return false">Clear Storage</button><br>
+			<button onclick="window.location = window.location; return false">Reload page</button><br>
+		</div>
+
+		<div id="passwordContainer" style="display: none">
+			For decrypting stored private key:<br>
+			Password: <input type="password" name="password" id="password"><br>
+			<button onclick="Promise.resolve(getPrivateKey()).then(function() { document.getElementById('privateKey').innerHTML = cachedPrivateKey; }).catch(function() { window.alert('wrong password'); }); return false">Decrypt</button>
+		</div>
+
+		<div id="setupContainer" style="display: none">
+			For storing private key:<br>
+			Mnemonic phrase: <input type="text" name="phrase" id="phrase"><br>
+			New password: <input type="password" name="newPassword" id="newPassword"><br>
+			<button onclick="Promise.resolve(savePrivateKey()).then(function() { document.getElementById('privateKey').innerHTML = cachedPrivateKey; }); return false">Save</button>
+		</div>
+	</body>
+</html>
\ No newline at end of file
