4 files changed, 138 insertions(+), 2 deletions(-)

M content/_index.md
A content/chat.md
A layouts/shortcodes/chat.html
A static/js/chat.js

@@ 19,6 19,5 @@ for bi-annual research reports. Prior to joining Fors Marsh Group, he has
 worked for the Harris Poll in a similar role, and for Chris Harris & Associate
 as a political campaign finance intern.
 
-You can find my CV, code repositories, and other personal work here. Below are
-my most recent blog posts.
+You can find my CV, code repositories, and other personal work here.
 

@@ 0,0 1,9 @@
+---
+title: Live Chat
+chat: true
+---
+
+Here's a live chat app, with optional symmetric key encryption.
+
+{{< chat >}}
+

@@ 0,0 1,6 @@
+<input id="passwd-input" type="text">
+<button id="passwd-button">Update Key</button>
+<ul id="chat-room"></ul>
+<input id="chat-input" type="text">
+<button id="chat-button">Send</button>
+

@@ 0,0 1,122 @@
+const saltSize = 16;        // recommended size for salt used in password derivation functions
+const ivSize = 12;          // size for initial value array per AES GCM specification
+const iterationNum = 10000; // lowest recommendable number of iterations for password derivation
+
+// conversion functions
+function arrayBufferToArray(buf) {
+  return new Uint8Array(buf);
+}
+function arrayToBase64(arr) {
+  return btoa(String.fromCharCode.apply(null, arr));
+};
+function base64ToArray(b64) {
+  return Uint8Array.from(atob(b64), (c) => c.charCodeAt(null));
+};
+function stringToArray(str) {
+  return new TextEncoder().encode(str);
+};
+function arrayToString(arr) {
+  return new TextDecoder().decode(arr);
+};
+
+// cryptography
+async function password(passwd) {
+  return window.crypto.subtle.importKey("raw", stringToArray(passwd), "PBKDF2", false, ["deriveKey"]);
+};
+async function derive(key, salt) {
+  return window.crypto.subtle.deriveKey({ name: "PBKDF2", salt: salt, iterations: iterationNum, hash: "SHA-256" }, key, { name: "AES-GCM", length: 256 }, false, ["encrypt", "decrypt"]);
+};
+function buildMessage(salt, iv, arr) {
+  let msg = new Uint8Array(saltSize+ivSize+arr.byteLength);
+  msg.set(salt, 0);
+  msg.set(iv, saltSize);
+  msg.set(arr, saltSize+ivSize);
+  return arrayToBase64(msg);
+};
+async function encrypt(str) {
+  const salt = window.crypto.getRandomValues(new Uint8Array(saltSize));
+  const iv = window.crypto.getRandomValues(new Uint8Array(ivSize));
+
+  try {
+    const key = await derive(passkey, salt);
+    const buf = await window.crypto.subtle.encrypt({ name: "AES-GCM", iv: iv }, key, stringToArray(str));
+    return buildMessage(salt, iv, arrayBufferToArray(buf));
+  } catch (e) {
+    console.log("encryption failed");
+    return str;
+  }
+};
+async function decrypt(blob) {
+  const arr = base64ToArray(blob);
+  const salt = arr.slice(0, saltSize);
+  const iv = arr.slice(saltSize, saltSize+ivSize);
+  const msg = arr.slice(saltSize+ivSize);
+
+  try {
+    const key = await derive(passkey, salt);
+    const buf = await window.crypto.subtle.decrypt({ name: "AES-GCM", iv: iv }, key, msg);
+    return arrayToString(arrayBufferToArray(buf));
+  } catch (e) {
+    console.log("decryption failed");
+    return blob;
+  }
+};
+
+// initialize passkey to null
+var passkey;
+
+function connect() {
+  socket = new WebSocket('wss://api.dominic-ricottone.com/chat');
+
+  // On close, reconnect after 1s (=1000ms)
+  socket.onclose = () => {
+    setTimeout(connect, 1000);
+  };
+
+  socket.onmessage = async (m) => {
+    const el = document.createElement('li');
+    if (passkey == null) {
+      el.innerHTML = m.data;
+    } else {
+      const decrypted = await decrypt(m.data);
+      el.innerHTML = decrypted;
+    }
+    document.getElementById('chat-room').appendChild(el);
+  };
+};
+
+// try to initialize socket to a connection
+var socket;
+connect();
+
+document.addEventListener("DOMContentLoaded", () => {
+  // chat interface
+  const chatInput = document.getElementById('chat-input');
+  const chatButton = document.getElementById('chat-button');
+
+  chatButton.onclick = async () => {
+    if (passkey == null) {
+      socket.send(chatInput.value);
+    } else {
+      const encrypted = await encrypt(chatInput.value);
+      socket.send(encrypted);
+    }
+  };
+
+  chatInput.addEventListener('keyup', (event) => {
+    if (event.keyCode === 13) {
+      event.preventDefault();
+      chatButton.click();
+    }
+  });
+
+  // password interface
+  const passwdInput = document.getElementById('passwd-input');
+  const passwdButton = document.getElementById('passwd-button');
+
+  passwdButton.onclick = async () => {
+    const key = await password(passwdInput.value);
+    passkey = key
+  };
+});
+