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, 24 insertions, 4 deletions

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));
+}