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]>

4 files changed, 89 insertions, 52 deletions

diff --git a/src/features/index.js b/src/features/index.js
index 8f3e5d1..70f8421 100644
--- a/src/features/index.js
+++ b/src/features/index.js
@@ -20,5 +20,5 @@ import { nwcFeature } from './nwc.js';
 // names sits between ark and zaps: a pasted user@domain resolves over DNS
 // (BIP-353) before the zaps feature treats it as a plain Lightning address.
 export function buildFeatures(ctx) {
-  return [giftsFeature(ctx), arkFeature(ctx), namesFeature(ctx), zapsFeature(ctx), nwcFeature(ctx), nostrLoginFeature(ctx), syncFeature(ctx)];
+  return [giftsFeature(ctx), arkFeature(ctx), nostrLoginFeature(ctx), namesFeature(ctx), zapsFeature(ctx), nwcFeature(ctx), syncFeature(ctx)];
 }
diff --git a/src/features/names.js b/src/features/names.js
index 970a690..33bddd7 100644
--- a/src/features/names.js
+++ b/src/features/names.js
@@ -12,6 +12,7 @@
 // record falls back to the Lightning-address flow (zaps feature).
 
 import { resolveBip353, parsePaymentName, parseBip21 } from '../bip353.js';
+import { nip98Header } from '../nostr-login.js';
 import { qrSvg } from '../qr.js';
 import { isArkAddress } from './ark.js';
 import { getNetwork } from '../api.js';
@@ -24,6 +25,25 @@ const AUTH_KIND = 21353;
 export function namesFeature(ctx) {
   const { h, ui, render, wallet, hook, toast, copyBtn } = ctx;
 
+  // The wallet's own key signs registrar requests: it's the one key that is
+  // always available — offline, in the background, with no signer attached.
+  const walletSigner = () => ({
+    pubkey: wallet.nostrPubkey && wallet.nostrPubkey(),
+    signEvent: async (e) => wallet.nostrSign(e),
+  });
+
+  async function post(path, method, payload, signer) {
+    const url = `${REGISTRAR}${path}`;
+    const body = JSON.stringify(payload);
+    const auth = await nip98Header(signer || walletSigner(), url, method, body);
+    const r = await fetch(url, {
+      method, headers: { 'content-type': 'application/json', authorization: auth }, body,
+    });
+    const j = await r.json().catch(() => ({}));
+    if (!r.ok || j.error) throw new Error(j.error || `registrar refused (${r.status})`);
+    return j;
+  }
+
   const load = () => wallet.loadFeatureState('names', {});
   const save = (st) => wallet.saveFeatureState('names', st);
 
@@ -35,31 +55,19 @@ export function namesFeature(ctx) {
     return addr ? `bitcoin:?ark=${encodeURIComponent(addr)}` : null;
   }
 
-  async function claim(name) {
+  async function claim(name, { signer, manager } = {}) {
     const uri = await currentUri();
     if (!uri) throw new Error(t('namesNeedArk'));
-    const auth = wallet.nostrSign({
-      kind: AUTH_KIND, created_at: Math.floor(Date.now() / 1000), tags: [],
-      content: JSON.stringify({ action: 'register', name, uri, domain: DOMAIN }),
-    });
-    if (!auth) throw new Error('wallet cannot sign');
-    const r = await fetch(`${REGISTRAR}/register`, {
-      method: 'POST', headers: { 'content-type': 'application/json' },
-      body: JSON.stringify({ auth }),
-    });
-    const j = await r.json();
-    if (!r.ok || j.error) throw new Error(j.error || `registrar refused (${r.status})`);
+    const j = await post('/register', 'POST', {
+      name, uri, domain: DOMAIN,
+      // when the login identity claims its own npub name, it nominates the
+      // wallet key to keep the record updated afterwards
+      ...(manager ? { manager } : {}),
+    }, signer);
     const prev = load().name;
     save({ name, domain: DOMAIN, uri, updated: Date.now() });
     if (prev && prev !== name) {
-      const bye = wallet.nostrSign({
-        kind: AUTH_KIND, created_at: Math.floor(Date.now() / 1000), tags: [],
-        content: JSON.stringify({ action: 'delete', name: prev, domain: DOMAIN }),
-      });
-      fetch(`${REGISTRAR}/register`, {
-        method: 'DELETE', headers: { 'content-type': 'application/json' },
-        body: JSON.stringify({ auth: bye }),
-      }).catch(() => {});
+      post('/register', 'DELETE', { name: prev, domain: DOMAIN }).catch(() => {});
     }
     return j;
   }
@@ -67,30 +75,10 @@ export function namesFeature(ctx) {
   async function release() {
     const st = load();
     if (!st.name) return;
-    const auth = wallet.nostrSign({
-      kind: AUTH_KIND, created_at: Math.floor(Date.now() / 1000), tags: [],
-      content: JSON.stringify({ action: 'delete', name: st.name, domain: st.domain || DOMAIN }),
-    });
-    await fetch(`${REGISTRAR}/register`, {
-      method: 'DELETE', headers: { 'content-type': 'application/json' },
-      body: JSON.stringify({ auth }),
-    }).catch(() => {});
+    await post('/register', 'DELETE', { name: st.name, domain: st.domain || DOMAIN }).catch(() => {});
     save({});
   }
 
-  // An imported seed doesn't know its username — the registrar does. Ask by
-  // the wallet's nostr pubkey and adopt what it says before deciding whether
-  // onboarding needs to prompt.
-  let checked = false; // lookup completed (gate stays closed until then)
-  async function lookupMine() {
-    try {
-      const pk = wallet.nostrPubkey && wallet.nostrPubkey();
-      if (!pk) return;
-      const r = await fetch(`${REGISTRAR}/pubkey/${pk}`).then((x) => x.json());
-      if (r && r.name) save({ ...load(), name: r.name, domain: r.domain || DOMAIN, uri: r.uri });
-    } catch {}
-  }
-
   // Everyone gets an address without being asked: the default username is a
   // prefix of the wallet's npub — unique, boring, and free. Custom names are
   // an optional change (and may cost something one day, to keep squatters
@@ -101,8 +89,18 @@ export function namesFeature(ctx) {
       let st = load();
       if (!st.name) { await lookupMine(); st = load(); }
       if (!st.name) {
-        const npub = wallet.nostrNpub && wallet.nostrNpub();
-        if (npub) { await claim(npub.slice(0, 20)); st = load(); }
+        // The address people see should be the identity they know the user
+        // by: their real npub when a nostr account is linked, else the
+        // wallet's own. Both are claimed the same way; the registrar checks
+        // that an npub-shaped name really belongs to its claimant.
+        const linked = hook('nostrLoginIdentity');
+        const npub = (linked && linked.npub) || (wallet.nostrNpub && wallet.nostrNpub());
+        if (npub) {
+          await claim(npub.slice(0, 20), linked
+            ? { signer: linked.signer, manager: wallet.nostrPubkey() }
+            : {});
+          st = load();
+        }
       }
       checked = true;
       render();
diff --git a/src/features/nostrlogin.js b/src/features/nostrlogin.js
index 60e3759..c5369e9 100644
--- a/src/features/nostrlogin.js
+++ b/src/features/nostrlogin.js
@@ -22,6 +22,11 @@ export function nostrLoginFeature(ctx) {
   const load = () => wallet.loadFeatureState('nostrlogin', {});
   const save = (st) => wallet.saveFeatureState('nostrlogin', st);
 
+  // The signer that opened this session, kept so the names feature can claim
+  // the user's real npub as their payment address (and nominate the wallet
+  // key as manager, so later updates work without the signer).
+  let live = null;
+
   const busy = (v) => { ui.nostrLoginBusy = v; render(); };
   const fail = (e) => { ui.nostrLoginError = e.message || String(e); busy(false); };
 
@@ -40,11 +45,16 @@ export function nostrLoginFeature(ctx) {
         busy(false);
         return;
       }
-      await ctx.hook('openMnemonic', res.mnemonic, res.passphrase || '', { nostrPubkey: signer.pubkey });
+      // Same wallet however you log in: a key-derived seed is published too,
+      // so an extension login later finds this wallet instead of making a new
+      // one. Costs nothing — anyone with the key could derive it anyway.
+      if (res.publish) await publishWalletBackup(signer, { mnemonic: res.mnemonic }).catch(() => {});
+      live = signer;
+      await ctx.openMnemonic(res.mnemonic, res.passphrase || '', { nostrPubkey: signer.pubkey });
+      save({ ...load(), pubkey: signer.pubkey, linked: Date.now() });
       toast(res.mode === 'derived' ? t('nlOpenedDerived') : t('nlOpenedRestored'));
       busy(false);
     } catch (e) { fail(e); }
-    finally { if (signer && signer.close && !ui.nostrLoginNew) signer.close(); }
   }
 
   async function createForSigner() {
@@ -55,7 +65,9 @@ export function nostrLoginFeature(ctx) {
       const mnemonic = newMnemonic();
       await publishWalletBackup(st.signer, { mnemonic });
       ui.nostrLoginNew = null;
-      await ctx.hook('openMnemonic', mnemonic, '', { nostrPubkey: st.signer.pubkey });
+      live = st.signer;
+      await ctx.openMnemonic(mnemonic, '', { nostrPubkey: st.signer.pubkey });
+      save({ ...load(), pubkey: st.signer.pubkey, linked: Date.now() });
       toast(t('nlCreated'));
       busy(false);
     } catch (e) { fail(e); }
@@ -75,11 +87,11 @@ export function nostrLoginFeature(ctx) {
         throw new Error(t('nlAlreadyLinked'));
       }
       await publishWalletBackup(signer, { mnemonic: wallet.mnemonic, passphrase: wallet.passphrase || '' });
+      live = signer;
       save({ ...load(), pubkey: signer.pubkey, linked: Date.now() });
       toast(t('nlLinked'));
       busy(false);
     } catch (e) { fail(e); }
-    finally { if (signer && signer.close) signer.close(); }
   }
 
   // ---- UI ---------------------------------------------------------------
@@ -157,6 +169,13 @@ export function nostrLoginFeature(ctx) {
 
   return {
     id: 'nostrlogin',
+    // The nostr identity this session is logged in as, for features that
+    // should speak as the user (the payment address defaults to this npub).
+    nostrLoginIdentity() {
+      const st = load();
+      if (!st.pubkey) return null;
+      return { pubkey: st.pubkey, npub: npubOf(st.pubkey), signer: live };
+    },
     unlockExtra() { return unlockExtra(); },
     settingsCards() { return [settingsCard()]; },
   };
diff --git a/src/nostr-login.js b/src/nostr-login.js
index 6f23e2a..00106c4 100644
--- a/src/nostr-login.js
+++ b/src/nostr-login.js
@@ -150,12 +150,32 @@ export async function publishWalletBackup(signer, { mnemonic, passphrase }, rela
 
 // The whole login: given a signer, produce the wallet mnemonic to open.
 // `mode` reports what happened so the UI can be honest about it.
+//
+// ONE flow for all three signer kinds, because an identity must open the
+// SAME wallet however you log into it: look for the published association
+// FIRST (that's where the money already is), and only then fall back to
+// deriving (key in hand) or generating (signer only).
 export async function walletForSigner(signer) {
-  // A pasted key derives its wallet — no lookup, no storage, no exposure.
-  if (signer.secret) {
-    return { mnemonic: seedFromNostrKey(signer.secret), mode: 'derived' };
-  }
   const found = await fetchWalletBackup(signer);
   if (found) return { mnemonic: found.mnemonic, passphrase: found.passphrase, mode: 'restored' };
+  if (signer.secret) {
+    // Publishing the derived seed costs nothing: the derivation is public,
+    // so anyone holding this key could compute it anyway. It buys the thing
+    // that matters — an extension login later finds this same wallet.
+    return { mnemonic: seedFromNostrKey(signer.secret), mode: 'derived', publish: true };
+  }
   return { mnemonic: null, mode: 'new' }; // caller decides + confirms publishing
 }
+
+// NIP-98 HTTP Auth (kind 27235): the standard way to authenticate an HTTP
+// request with a nostr key. `u` and `method` bind the signature to this exact
+// request and `payload` to its body, so a captured header can't be replayed
+// against a different endpoint or a tampered body.
+export async function nip98Header(signer, url, method, bodyText) {
+  const tags = [['u', url], ['method', method.toUpperCase()]];
+  if (bodyText) tags.push(['payload', hex.encode(sha256(new TextEncoder().encode(bodyText)))]);
+  const evt = await signer.signEvent({
+    kind: 27235, created_at: Math.floor(Date.now() / 1000), tags, content: '',
+  });
+  return 'Nostr ' + btoa(JSON.stringify(evt));
+}