One wallet per Nostr identity, NIP-98 auth, npub payment addresses

Consistency fix with teeth: logging in with a pasted key derived one
wallet while an extension login for the SAME identity found no backup
and generated a different one. Now every signer kind runs one flow —
look for the published association first (that's where the money is),
then derive (key in hand) or generate (signer only) — and a derived
seed is published too. That costs nothing, since the derivation is
public and anyone holding the key could compute it anyway, and it makes
the identity open the same wallet however you log in.

Registrar auth is now NIP-98 (HTTP Auth, kind 27235) instead of a
homemade envelope: the signature binds the URL, method and body hash,
so a captured header can't be replayed elsewhere. NIP-78 already
covered the encrypted association; NIP-26 delegation is deprecated, so
owner→manager nomination lives in the registrar's own model: an
npub-shaped name may only be claimed by that identity, which nominates
the wallet key to keep the record updated afterwards (the wallet key is
the only one always available — offline, in the worker).

Payment addresses therefore default to the user's REAL npub in all
three login methods, falling back to the wallet's own identity when no
Nostr account is linked.

Co-Authored-By: Claude Fable 5 <[email protected]>

1 files changed, 58 insertions, 24 deletions

diff --git a/names/server.js b/names/server.js
index a43191e..bd693b2 100644
--- a/names/server.js
+++ b/names/server.js
@@ -1,6 +1,8 @@
 // BIP-353 name registrar for halwallet.app — gives every hal user a
 // ₿[email protected] payment address.
 //
+// Auth on every write is NIP-98 (HTTP Auth, kind 27235).
+//
 // A name is a DNSSEC-signed TXT record at
 //   <name>.user._bitcoin-payment.halwallet.app
 // whose content is a BIP-21 `bitcoin:` URI (for hal users: an ark address,
@@ -16,6 +18,8 @@
 import { readFileSync, writeFileSync, renameSync, mkdirSync } from 'node:fs';
 import { dirname, join } from 'node:path';
 import { verifyEvent } from 'nostr-tools/pure';
+import { npubEncode } from 'nostr-tools/nip19';
+import { createHash } from 'node:crypto';
 import { HDKey } from '@scure/bip32';
 import { mnemonicToSeedSync } from '@scure/bip39';
 import { lnBackend } from '../bridge/ln.js';
@@ -31,8 +35,6 @@ const CFG = JSON.parse(readFileSync(process.env.NAMES_CONFIG
 const DOMAIN = CFG.domain || 'coinos.io'; // the default domain for claims
 const DOMAINS = CFG.domains || { [DOMAIN]: { zoneId: CFG.zoneId } };
 const STATE = CFG.stateFile || join(import.meta.dir, 'data', 'names.json');
-const AUTH_KIND = 21353;         // arbitrary custom kind for signed claims
-const MAX_SKEW_SEC = 600;        // claim events must be fresh
 const TTL = 300;                 // record TTL: BIP-353 wallets cache by this
 
 const log = (...a) => console.log(new Date().toISOString(), ...a);
@@ -182,15 +184,35 @@ setInterval(async () => {
 // claims
 // ---------------------------------------------------------------------------
 
-// The claim is a signed nostr event: proof the caller controls the wallet's
-// nostr key, which becomes (or must match) the name's owner.
-function checkAuth(auth) {
-  if (!auth || auth.kind !== AUTH_KIND) return 'bad auth kind';
-  if (Math.abs(Date.now() / 1000 - (auth.created_at || 0)) > MAX_SKEW_SEC) return 'auth event too old';
-  if (!verifyEvent(auth)) return 'bad signature';
-  return null;
+// NIP-98 HTTP Auth (kind 27235). The signature covers this exact URL, method
+// and body hash, so a captured header is useless anywhere else.
+async function checkNip98(req, url, bodyText) {
+  const h = req.headers.get('authorization') || '';
+  const m = h.match(/^Nostr\s+(.+)$/i);
+  if (!m) return { error: 'missing Nostr authorization' };
+  let evt;
+  try { evt = JSON.parse(Buffer.from(m[1], 'base64').toString('utf8')); } catch { return { error: 'bad auth encoding' }; }
+  if (evt.kind !== 27235) return { error: 'auth must be kind 27235' };
+  if (Math.abs(Date.now() / 1000 - (evt.created_at || 0)) > 60) return { error: 'auth event expired' };
+  if (!verifyEvent(evt)) return { error: 'bad signature' };
+  const tag = (k) => (evt.tags.find((x) => x[0] === k) || [])[1];
+  if ((tag('method') || '').toUpperCase() !== req.method) return { error: 'method mismatch' };
+  let got;
+  try { got = new URL(tag('u') || ''); } catch { return { error: 'bad url tag' }; }
+  if (got.pathname !== url.pathname) return { error: 'url mismatch' };
+  if (bodyText) {
+    const want = createHash('sha256').update(bodyText).digest('hex');
+    if (tag('payload') !== want) return { error: 'payload hash mismatch' };
+  }
+  return { pubkey: evt.pubkey };
 }
 
+// npub-prefix names are the free default everyone gets, so they must not be
+// squattable: a name that looks like one may only be claimed by that very
+// identity — or by a key that identity nominated as its manager (the wallet
+// key, which is always available, even offline and in the service worker).
+const npubPrefixOwner = (name) => (/^npub1[a-z0-9]+$/.test(name) ? name : null);
+
 // coinos.io names that belong to existing coinos users are reserved for
 // them until the migration gives those users a way to claim their own.
 async function takenByCoinosUser(domain, name) {
@@ -271,24 +293,33 @@ Bun.serve({
 
     if (url.pathname === '/register' && req.method === 'POST') {
       if (!rateOk(ip)) return json({ error: 'rate limited' }, 429);
-      const body = await req.json().catch(() => null);
-      const auth = body?.auth;
-      const authErr = checkAuth(auth);
-      if (authErr) return json({ error: authErr }, 400);
+      const bodyText = await req.text();
+      const a = await checkNip98(req, url, bodyText);
+      if (a.error) return json({ error: a.error }, 401);
       let claim;
-      try { claim = JSON.parse(auth.content); } catch { return json({ error: 'bad claim content' }, 400); }
+      try { claim = JSON.parse(bodyText); } catch { return json({ error: 'bad body' }, 400); }
+      const auth = { pubkey: a.pubkey };
       const name = String(claim.name || '').toLowerCase();
       const domain = String(claim.domain || 'halwallet.app').toLowerCase();
       if (!DOMAINS[domain]) return json({ error: 'unknown domain' }, 400);
       if (!NAME_RE.test(name)) return json({ error: 'invalid name (a-z, 0-9, . _ -, max 30)' }, 400);
       if (RESERVED.has(name)) return json({ error: 'name is reserved' }, 400);
-      if (claim.action !== 'register') return json({ error: 'wrong action' }, 400);
       if (!validUri(claim.uri)) return json({ error: 'uri must be a bitcoin: URI' }, 400);
 
       const key = `${name}@${domain}`;
       const existing = state.names[key];
-      if (existing && existing.pubkey !== auth.pubkey) return json({ error: 'name is taken' }, 409);
+      // owner OR the manager key the owner nominated may update a record
+      if (existing && existing.pubkey !== auth.pubkey && existing.manager !== auth.pubkey) {
+        return json({ error: 'name is taken' }, 409);
+      }
       if (!existing && await takenByCoinosUser(domain, name)) return json({ error: 'name is taken' }, 409);
+      // an npub-shaped name belongs to that identity alone
+      if (npubPrefixOwner(name)) {
+        const managerOk = existing && existing.manager === auth.pubkey;
+        if (!npubEncode(auth.pubkey).startsWith(name) && !managerOk) {
+          return json({ error: 'that name belongs to another Nostr identity' }, 403);
+        }
+      }
       if (/[?&]lno=/.test(claim.uri)) return json({ error: 'lno is added by the registrar' }, 400);
 
       // Every name also gets a static Lightning offer on our node; payments
@@ -299,7 +330,11 @@ Bun.serve({
 
       const recordId = await cfWrite(name, domain, published, existing?.recordId);
       state.names[key] = {
-        pubkey: auth.pubkey, uri: published, recordId, updated: Date.now(), domain,
+        pubkey: existing?.pubkey || auth.pubkey,
+        // the owner may nominate a key that manages the record from here on
+        manager: (claim.manager && /^[0-9a-f]{64}$/.test(claim.manager) && auth.pubkey !== claim.manager)
+          ? claim.manager : existing?.manager,
+        uri: published, recordId, updated: Date.now(), domain,
         offerId: offer?.offerId, bolt12: offer?.bolt12,
       };
       persist();
@@ -309,19 +344,18 @@ Bun.serve({
 
     if (url.pathname === '/register' && req.method === 'DELETE') {
       if (!rateOk(ip)) return json({ error: 'rate limited' }, 429);
-      const body = await req.json().catch(() => null);
-      const auth = body?.auth;
-      const authErr = checkAuth(auth);
-      if (authErr) return json({ error: authErr }, 400);
+      const bodyText = await req.text();
+      const a = await checkNip98(req, url, bodyText);
+      if (a.error) return json({ error: a.error }, 401);
       let claim;
-      try { claim = JSON.parse(auth.content); } catch { return json({ error: 'bad claim content' }, 400); }
+      try { claim = JSON.parse(bodyText); } catch { return json({ error: 'bad body' }, 400); }
+      const auth = { pubkey: a.pubkey };
       const name = String(claim.name || '').toLowerCase();
       const domain = String(claim.domain || 'halwallet.app').toLowerCase();
-      if (claim.action !== 'delete') return json({ error: 'wrong action' }, 400);
       const key = `${name}@${domain}`;
       const existing = state.names[key];
       if (!existing) return json({ error: 'unknown name' }, 404);
-      if (existing.pubkey !== auth.pubkey) return json({ error: 'not your name' }, 403);
+      if (existing.pubkey !== auth.pubkey && existing.manager !== auth.pubkey) return json({ error: 'not your name' }, 403);
       await cfDelete(domain, existing.recordId).catch(() => {});
       if (existing.offerId && ln) await ln.call('disableoffer', { offer_id: existing.offerId }).catch(() => {});
       delete state.names[key];