Log in with Nostr, and link a wallet to a Nostr account

Three ways in: a NIP-07 browser extension, a NIP-46 remote signer
(Amber, Amethyst — paste its bunker:// address), or a pasted
nsec/hex key that lives in memory for the session and is never stored.

How an account gets a wallet depends on what we can see, and the two
cases are genuinely different:

  * We hold the key (pasted nsec): the seed is DERIVED from it —
    sha256("coinos:wallet-seed:v1" | privkey) as BIP-39 entropy. The
    same Nostr key always opens the same wallet, on any device, with
    nothing stored anywhere.
  * We only have a signer: deriving is impossible (we never see the
    key, and neither signatures nor NIP-44 ciphertexts reproduce), so
    the seed is ASSOCIATED instead — generated once and published as a
    replaceable event encrypted to the user's own key, which only their
    signer can decrypt. Later logins find and decrypt it.

The second path means the Nostr key can recover the money; the UI says
so before publishing anything. Linking an already-open wallet uses the
same publish path and refuses to overwrite an account's existing wallet.

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

1 files changed, 163 insertions, 0 deletions

diff --git a/src/features/nostrlogin.js b/src/features/nostrlogin.js
new file mode 100644
index 0000000..60e3759
--- /dev/null
+++ b/src/features/nostrlogin.js
@@ -0,0 +1,163 @@
+// "Log in with Nostr" — open (or create) a wallet from a nostr identity, and
+// link an existing wallet to one after the fact.
+//
+// The mechanics and their tradeoffs live in ../nostr-login.js. In short: a
+// pasted key DERIVES its wallet deterministically; an extension or remote
+// signer ASSOCIATES one via a seed published encrypted to the user's own key.
+// The second is what makes "log in on a new device" work without the key
+// ever reaching us, and it is spelled out in the UI before anything is
+// published, because it means the nostr key can recover the money.
+
+import { newMnemonic } from '../wallet.js';
+import { npubOf } from '../nostr.js';
+import { t } from '../i18n.js';
+import {
+  extensionSigner, bunkerSigner, keySigner, parseNostrSecret,
+  walletForSigner, publishWalletBackup,
+} from '../nostr-login.js';
+
+export function nostrLoginFeature(ctx) {
+  const { h, ui, render, wallet, toast } = ctx;
+
+  const load = () => wallet.loadFeatureState('nostrlogin', {});
+  const save = (st) => wallet.saveFeatureState('nostrlogin', st);
+
+  const busy = (v) => { ui.nostrLoginBusy = v; render(); };
+  const fail = (e) => { ui.nostrLoginError = e.message || String(e); busy(false); };
+
+  // Open the wallet a signer identifies. New accounts confirm first, because
+  // publishing an encrypted seed to relays deserves an explicit yes.
+  async function loginWith(makeSigner) {
+    ui.nostrLoginError = '';
+    busy(true);
+    let signer;
+    try {
+      signer = await makeSigner();
+      const res = await walletForSigner(signer);
+      if (res.mode === 'new') {
+        // no wallet on this identity yet — ask before publishing one
+        ui.nostrLoginNew = { signer, npub: npubOf(signer.pubkey) };
+        busy(false);
+        return;
+      }
+      await ctx.hook('openMnemonic', res.mnemonic, res.passphrase || '', { nostrPubkey: signer.pubkey });
+      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() {
+    const st = ui.nostrLoginNew;
+    if (!st) return;
+    busy(true);
+    try {
+      const mnemonic = newMnemonic();
+      await publishWalletBackup(st.signer, { mnemonic });
+      ui.nostrLoginNew = null;
+      await ctx.hook('openMnemonic', mnemonic, '', { nostrPubkey: st.signer.pubkey });
+      toast(t('nlCreated'));
+      busy(false);
+    } catch (e) { fail(e); }
+  }
+
+  // Link the wallet that's already open to a nostr identity, so logging in
+  // with it on another device opens this same wallet.
+  async function linkOpenWallet(makeSigner) {
+    ui.nostrLoginError = '';
+    busy(true);
+    let signer;
+    try {
+      signer = await makeSigner();
+      if (!wallet.mnemonic) throw new Error(t('nlNeedSeed'));
+      const existing = await walletForSigner(signer);
+      if (existing.mnemonic && existing.mnemonic !== wallet.mnemonic) {
+        throw new Error(t('nlAlreadyLinked'));
+      }
+      await publishWalletBackup(signer, { mnemonic: wallet.mnemonic, passphrase: wallet.passphrase || '' });
+      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 ---------------------------------------------------------------
+
+  // The three ways in, as buttons. `run` receives a signer factory.
+  function signerButtons(run) {
+    const hasExt = typeof window !== 'undefined' && !!window.nostr;
+    return h('div', { class: 'col', style: 'gap:8px' },
+      hasExt
+        ? h('button', { class: 'btn-block', disabled: ui.nostrLoginBusy,
+            onClick: () => run(() => extensionSigner()) }, t('nlExtension'))
+        : null,
+      h('div', { class: 'row gap6' },
+        h('input', {
+          type: 'password', placeholder: t('nlKeyOrBunker'), style: 'flex:1',
+          autocapitalize: 'none', autocomplete: 'off', spellcheck: 'false',
+          value: ui.nostrLoginInput || '',
+          onInput: (e) => { ui.nostrLoginInput = e.target.value.trim(); },
+        }),
+        h('button', { class: 'btn-sm', disabled: ui.nostrLoginBusy, onClick: () => {
+          const v = (ui.nostrLoginInput || '').trim();
+          const sk = parseNostrSecret(v);
+          if (sk) return run(() => keySigner(sk));
+          if (/^bunker:\/\//i.test(v)) {
+            return run(() => bunkerSigner(v, { onAuth: (url) => { ui.nostrLoginAuthUrl = url; render(); } }));
+          }
+          ui.nostrLoginError = t('nlUnrecognized');
+          render();
+        } }, ui.nostrLoginBusy ? h('span', { class: 'spinner' }) : t('nlGo'))),
+      h('div', { class: 'small faint' }, t('nlHint')),
+      ui.nostrLoginAuthUrl
+        ? h('a', { href: ui.nostrLoginAuthUrl, target: '_blank', class: 'small' }, t('nlApprove'))
+        : null,
+      ui.nostrLoginError ? h('div', { class: 'notice err' }, ui.nostrLoginError) : null);
+  }
+
+  // Shown under the create/import tabs on the unlock screen.
+  function unlockExtra() {
+    if (ui.nostrLoginNew) {
+      return h('div', { class: 'card col', style: 'gap:10px' },
+        h('h3', { style: 'margin:0' }, t('nlNewTitle')),
+        h('div', { class: 'small muted' }, ui.nostrLoginNew.npub || ''),
+        h('p', { class: 'small muted', style: 'margin:0' }, t('nlNewDesc')),
+        h('div', { class: 'notice info small' }, t('nlBackupWarning')),
+        ui.nostrLoginError ? h('div', { class: 'notice err' }, ui.nostrLoginError) : null,
+        h('div', { class: 'row gap6' },
+          h('button', { class: 'btn-ghost', onClick: () => {
+            if (ui.nostrLoginNew.signer.close) ui.nostrLoginNew.signer.close();
+            ui.nostrLoginNew = null; render();
+          } }, t('cancel')),
+          h('button', { class: 'btn-primary grow', disabled: ui.nostrLoginBusy, onClick: createForSigner },
+            ui.nostrLoginBusy ? h('span', { class: 'spinner' }) : t('nlCreateBtn'))));
+    }
+    return h('div', { class: 'card col', style: 'gap:10px' },
+      h('h3', { style: 'margin:0' }, t('nlTitle')),
+      h('p', { class: 'small muted', style: 'margin:0' }, t('nlDesc')),
+      signerButtons(loginWith));
+  }
+
+  function settingsCard() {
+    if (wallet.watchOnly || !wallet.mnemonic) return null;
+    const st = load();
+    if (st.pubkey) {
+      return h('div', { class: 'card col' },
+        h('h3', {}, t('nlLinkTitle')),
+        h('div', { class: 'small muted break' }, npubOf(st.pubkey) || st.pubkey),
+        h('p', { class: 'small faint', style: 'margin:0' }, t('nlLinkedDesc')));
+    }
+    return h('div', { class: 'card col' },
+      h('h3', {}, t('nlLinkTitle')),
+      h('p', { class: 'small muted', style: 'margin:0' }, t('nlLinkDesc')),
+      h('div', { class: 'notice info small' }, t('nlBackupWarning')),
+      signerButtons(linkOpenWallet));
+  }
+
+  return {
+    id: 'nostrlogin',
+    unlockExtra() { return unlockExtra(); },
+    settingsCards() { return [settingsCard()]; },
+  };
+}