claude-code: the sealed hand-over, the credentials write with the lineage rule, the identity read (hq to-be 40 WP2, in progress)

The parts of the agent module that hold whichever way the console is registered: X25519 + HKDF + AES-GCM from Node's own library so the bundle carries no dependency; the predecessor's lineage rule (rotation only if newer, a re-issue adopted, a switch regardless) with its incidents as tests; an atomic 0600 write that strips any refresh token and keeps keys it does not know; the account read from the agent's own state file. Manifest and renderer follow.
2026-10-03 16:05:58 +02:00
parent 7c800705bf
commit fc78b743c9
6 changed files with 306 additions and 0 deletions
@@ -0,0 +1,77 @@
+// Sealing a token to one recipient (novox/hq ADR 0183): the manager seals what it hands a node to that
+// node's agent module key, and a node seals a waiting login to the key the manager names. X25519 for
+// the agreement, HKDF-SHA256 for the key, AES-256-GCM for the box — all from Node's own library, so a
+// bundle carries no dependency and no secret ever crosses the bus in the clear.
+//
+// A sealed box is `{ v: 1, eph, iv, tag, ct }`, every field base64. `eph` is a one-time public key, so
+// two boxes of one value to one recipient share nothing, and only the recipient's private key opens it.
+
+import {
+  createCipheriv, createDecipheriv, createPrivateKey, createPublicKey, diffieHellman,
+  generateKeyPairSync, hkdfSync, randomBytes, type KeyObject,
+} from "node:crypto";
+
+export interface SealedBox {
+  readonly v: 1;
+  readonly eph: string;
+  readonly iv: string;
+  readonly tag: string;
+  readonly ct: string;
+}
+
+/** A recipient's keypair, as the two PEM strings it is kept and published as. */
+export interface KeyPairPem {
+  readonly publicKey: string;
+  readonly privateKey: string;
+}
+
+const INFO = Buffer.from("novox-mesh sealed box v1");
+
+export function generateKeyPair(): KeyPairPem {
+  const { publicKey, privateKey } = generateKeyPairSync("x25519");
+  return {
+    publicKey: publicKey.export({ type: "spki", format: "pem" }).toString(),
+    privateKey: privateKey.export({ type: "pkcs8", format: "pem" }).toString(),
+  };
+}
+
+function keyFor(secret: Buffer, eph: Buffer, recipient: Buffer): Buffer {
+  // The ephemeral and the recipient's public halves are bound into the key, so a box cannot be
+  // re-addressed to another recipient by swapping its `eph`.
+  return Buffer.from(hkdfSync("sha256", secret, Buffer.concat([eph, recipient]), INFO, 32));
+}
+
+function rawPublic(key: KeyObject): Buffer {
+  return key.export({ type: "spki", format: "der" }).subarray(-32);
+}
+
+export function seal(plaintext: string, recipientPublicPem: string): SealedBox {
+  const recipient = createPublicKey(recipientPublicPem);
+  const eph = generateKeyPairSync("x25519");
+  const secret = diffieHellman({ privateKey: eph.privateKey, publicKey: recipient });
+  const ephRaw = eph.publicKey.export({ type: "spki", format: "der" });
+  const key = keyFor(secret, ephRaw, rawPublic(recipient));
+  const iv = randomBytes(12);
+  const cipher = createCipheriv("aes-256-gcm", key, iv);
+  const ct = Buffer.concat([cipher.update(plaintext, "utf8"), cipher.final()]);
+  return {
+    v: 1,
+    eph: ephRaw.toString("base64"),
+    iv: iv.toString("base64"),
+    tag: cipher.getAuthTag().toString("base64"),
+    ct: ct.toString("base64"),
+  };
+}
+
+/** Open a box with the recipient's private key. Throws on a box for another key or one tampered with. */
+export function open(box: SealedBox, privateKeyPem: string): string {
+  if (!box || box.v !== 1) throw new Error("not a sealed box this module can open");
+  const priv = createPrivateKey(privateKeyPem);
+  const ephRaw = Buffer.from(box.eph, "base64");
+  const eph = createPublicKey({ key: ephRaw, format: "der", type: "spki" });
+  const secret = diffieHellman({ privateKey: priv, publicKey: eph });
+  const key = keyFor(secret, ephRaw, rawPublic(createPublicKey(priv)));
+  const decipher = createDecipheriv("aes-256-gcm", key, Buffer.from(box.iv, "base64"));
+  decipher.setAuthTag(Buffer.from(box.tag, "base64"));
+  return Buffer.concat([decipher.update(Buffer.from(box.ct, "base64")), decipher.final()]).toString("utf8");
+}