feat: implement auth state management with RouteGuards

frontend/src/utils/crypto.ts

@@ -0,0 +1,82 @@
+/**
+ * 0 knowledge cryptography. No Server involved in encryption/decryption
+ */
+
+const ITERATIONS = 100000;
+const KEY_ALGO = { name: "AES-GCM", length: 256 };
+
+/**
+ * Derives a Master Encryption Key from a password and email (salt).
+ */
+export async function deriveMasterKey(
+  password: string,
+  email: string,
+): Promise<CryptoKey> {
+  const encoder = new TextEncoder();
+  const passwordKey = await crypto.subtle.importKey(
+    "raw",
+    encoder.encode(password),
+    "PBKDF2",
+    false,
+    ["deriveKey"],
+  );
+
+  return crypto.subtle.deriveKey(
+    {
+      name: "PBKDF2",
+      salt: encoder.encode(email.toLowerCase()),
+      iterations: ITERATIONS,
+      hash: "SHA-256",
+    },
+    passwordKey,
+    KEY_ALGO,
+    false,
+    ["encrypt", "decrypt", "wrapKey", "unwrapKey"],
+  );
+}
+
+/**
+ * Encrypts a letter using Envelope Encryption.
+ */
+export async function encryptLetter(plaintext: string, masterKey: CryptoKey) {
+  const encoder = new TextEncoder();
+
+  // Generate random Data Encryption Key (DEK)
+  const dek = await crypto.subtle.generateKey(KEY_ALGO, true, [
+    "encrypt",
+    "decrypt",
+  ]);
+
+  // Encrypt the content with the DEK
+  const iv = crypto.getRandomValues(new Uint8Array(12));
+  const ciphertext = await crypto.subtle.encrypt(
+    { name: "AES-GCM", iv },
+    dek,
+    encoder.encode(plaintext),
+  );
+
+  // encrpyt the DEK using the Master Key for the self access
+  const keyIv = crypto.getRandomValues(new Uint8Array(12));
+  const wrappedKey = await crypto.subtle.wrapKey("raw", dek, masterKey, {
+    name: "AES-GCM",
+    iv: keyIv,
+  });
+
+  // for recipients (link share), export DEK in raw format
+  const rawKey = await crypto.subtle.exportKey("raw", dek);
+
+  // conversion to base64 for transit
+  const toBase64 = (buffer: Uint8Array) => btoa(String.fromCharCode(...buffer));
+
+  return {
+    // This goes to the server
+    encryptedPayload: {
+      ciphertext: toBase64(new Uint8Array(ciphertext)),
+      iv: toBase64(new Uint8Array(iv)),
+      wrappedKey: toBase64(new Uint8Array(wrappedKey)),
+      keyIv: toBase64(new Uint8Array(keyIv)),
+    },
+    // This goes into the url for the recipient
+    sharingKey: toBase64(new Uint8Array(rawKey)),
+  };
+}