Merge branch 'wallet' into 'main'

Add an HD wallet

See merge request soapbox-pub/ditto!532

src/DittoWallet.ts

@@ -0,0 +1,51 @@
+import { HDKey } from '@scure/bip32';
+
+import { Conf } from '@/config.ts';
+
+/**
+ * HD wallet based on the `DITTO_NSEC`.
+ * The wallet is used to derive keys for various purposes.
+ * It is a singleton with static methods, and the keys are cached.
+ */
+export class DittoWallet {
+  static #root = HDKey.fromMasterSeed(Conf.seckey);
+  static #keys = new Map<string, HDKey>();
+
+  /** Derive the key cached. */
+  static derive(path: string): HDKey {
+    const existing = this.#keys.get(path);
+    if (existing) {
+      return existing;
+    } else {
+      const key = this.#root.derive(path);
+      this.#keys.set(path, key);
+      return key;
+    }
+  }
+
+  /** Derive the key and return the bytes. */
+  static deriveKey(path: string): Uint8Array {
+    const { privateKey } = this.derive(path);
+
+    if (!privateKey) {
+      throw new Error('Private key not available');
+    }
+
+    return privateKey;
+  }
+
+  /** Database encryption key for AES-GCM encryption of database columns. */
+  static get dbKey(): Uint8Array {
+    return this.deriveKey(Conf.wallet.dbKeyPath);
+  }
+
+  /** Captcha encryption key for encrypting answer data in AES-GCM. */
+  static get captchaKey(): Uint8Array {
+    return this.deriveKey(Conf.wallet.captchaKeyPath);
+  }
+
+  /** VAPID secret key, used for web push notifications. ES256. */
+  static get vapidKey(): Uint8Array {
+    return this.deriveKey(Conf.wallet.vapidKeyPath);
+  }
+}

src/config.ts

@@ -99,6 +99,25 @@ class Conf {
       },
     },
   };
+  /**
+   * BIP-32 derivation paths for different crypto use-cases.
+   * The `DITTO_NSEC` is used as the seed.
+   * Keys can be rotated by changing the derviation path.
+   */
+  static wallet = {
+    /** Private key for AES-GCM encryption in the Postgres database. */
+    get dbKeyPath(): string {
+      return Deno.env.get('WALLET_DB_KEY_PATH') || "m/0'/1'";
+    },
+    /** Private key for AES-GCM encryption of captcha answer data. */
+    get captchaKeyPath(): string {
+      return Deno.env.get('WALLET_CAPTCHA_KEY_PATH') || "m/0'/2'";
+    },
+    /** VAPID private key path. */
+    get vapidKeyPath(): string {
+      return Deno.env.get('WALLET_VAPID_KEY_PATH') || "m/0'/3'";
+    },
+  };
   /** Character limit to enforce for posts made through Mastodon API. */
   static get postCharLimit(): number {
     return Number(Deno.env.get('POST_CHAR_LIMIT') || 5000);