From 3f1b6097777183c81826c8e8b06000221cf4fd76 Mon Sep 17 00:00:00 2001
From: zy0n <zy0n@users.noreply.github.com>
Date: Fri, 24 Jul 2026 14:32:13 +0000
Subject: [PATCH] fix(transport): send P1=0x01 when fetching the spending
 public key

RAILGUN firmware 1.6.1 requires P1=0x01 (display + confirm) on the
spending-public-key command and rejects P1=0x00 with SW_WRONG_P1P2, so
the device now shows the account index and pubkey for on-device approval
before returning the key. Update buildGetPublicKey accordingly.

The viewing-private-key command keeps P1=0x00 (it is gated by its own
confirmation); document that so it is not changed by mistake. Lock both
P1 values in the public-API smoke test.
---
 src/core/transport/apdu.ts         | 14 ++++++++++++--
 test/unit/public-api-smoke.test.ts |  4 ++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/core/transport/apdu.ts b/src/core/transport/apdu.ts
index 7e42bc6..f3003b5 100644
--- a/src/core/transport/apdu.ts
+++ b/src/core/transport/apdu.ts
@@ -214,6 +214,11 @@ function assertBytes(value: Uint8Array, length: number, label: string): void {
 /**
  * Build GET_PUBLIC_KEY APDU.
  * Returns the BabyJubjub spending public key (x, y).
+ *
+ * P1 is `0x01` (display + confirm): the RAILGUN app shows the account index and
+ * pubkey hex and returns the 64-byte key only on Approve (Reject → `0x6985`).
+ * Production firmware rejects `P1 = 0x00` (`SW_WRONG_P1P2`), so this always
+ * requires an on-device tap.
  * @param account - Account index (default 0).
  * @param profile - APDU profile (default RAILGUN_PROFILE).
  */
@@ -224,7 +229,7 @@ export function buildGetPublicKey(
   return {
     cla: profile.cla,
     ins: profile.commands.getPublicKey.ins,
-    p1: 0,
+    p1: 0x01,
     p2: 0,
     data: encodeAccountIndex(account),
   };
@@ -262,9 +267,14 @@ export function buildSignHash(
 }
 
 /**
- * Build GET_VIEWING_KEY APDU.
+ * Build GET_VIEWING_KEY APDU (VIEWING_PRIVKEY, INS 0x13).
  * Returns the viewing private key — 32 bytes.
  * Device displays a confirmation prompt.
+ *
+ * P1 stays `0x00` here: unlike the *public* key commands (spending pubkey 0x01,
+ * viewing pubkey 0x10), the viewing-privkey export uses `P1 = 0x00` — the app
+ * already gates it behind an on-device confirmation. `P1 = 0x01` would return
+ * `SW_WRONG_P1P2`.
  * @param account - Account index (default 0).
  * @param profile - APDU profile (default RAILGUN_PROFILE).
  */
diff --git a/test/unit/public-api-smoke.test.ts b/test/unit/public-api-smoke.test.ts
index 6b21d33..abc0bff 100644
--- a/test/unit/public-api-smoke.test.ts
+++ b/test/unit/public-api-smoke.test.ts
@@ -57,6 +57,8 @@ describe('public API smoke tests', () => {
       const cmd = buildGetPublicKey();
       expect(cmd.cla).toBe(RAILGUN_CLA);
       expect(cmd.ins).toBe(RailgunAppINS.GET_PUBLIC_KEY);
+      // P1 = 0x01 (display + confirm); production firmware rejects P1 = 0x00.
+      expect(cmd.p1).toBe(0x01);
       // Default account 0 → 4 bytes big-endian
       expect(cmd.data).toEqual(new Uint8Array([0, 0, 0, 0]));
     });
@@ -77,6 +79,8 @@ describe('public API smoke tests', () => {
       const cmd = buildGetViewingKey();
       expect(cmd.cla).toBe(RAILGUN_CLA);
       expect(cmd.ins).toBe(RailgunAppINS.GET_VIEWING_KEY);
+      // Viewing-privkey export stays P1 = 0x00 (unlike the public-key commands).
+      expect(cmd.p1).toBe(0x00);
       expect(cmd.data).toEqual(new Uint8Array([0, 0, 0, 0]));
     });