From 93e3fd925bd51981213a28c2ab8419ac289b77e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Vejpustek?= <ondrej.vejpustek@satoshilabs.com>
Date: Fri, 22 Nov 2024 17:54:51 +0100
Subject: [PATCH] refactor(legacy): introduce cryptoMultisigPubkeys

---
 legacy/firmware/crypto.c      | 19 +++++++++++++++++++
 legacy/firmware/crypto.h      |  5 +++++
 legacy/firmware/transaction.c | 20 ++++++++++++++------
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/legacy/firmware/crypto.c b/legacy/firmware/crypto.c
index 5d1f4ae907..60b1f69013 100644
--- a/legacy/firmware/crypto.c
+++ b/legacy/firmware/crypto.c
@@ -368,6 +368,25 @@ uint32_t cryptoMultisigPubkeyCount(const MultisigRedeemScriptType *multisig) {
                                : multisig->pubkeys_count;
 }
 
+uint32_t cryptoMultisigPubkeys(const CoinInfo *coin,
+                               const MultisigRedeemScriptType *multisig,
+                               uint8_t *pubkeys) {
+  const uint32_t n = cryptoMultisigPubkeyCount(multisig);
+  if (n < 1 || n > 15) {
+    return 0;
+  }
+
+  for (uint32_t i = 0; i < n; i++) {
+    const HDNode *pubnode = cryptoMultisigPubkey(coin, multisig, i);
+    if (!pubnode) {
+      return 0;
+    }
+    memcpy(pubkeys + i * 33, pubnode->public_key, 33);
+  }
+
+  return n;
+}
+
 int cryptoMultisigPubkeyIndex(const CoinInfo *coin,
                               const MultisigRedeemScriptType *multisig,
                               const uint8_t *pubkey) {
diff --git a/legacy/firmware/crypto.h b/legacy/firmware/crypto.h
index 8df938fc26..98c81fbd8e 100644
--- a/legacy/firmware/crypto.h
+++ b/legacy/firmware/crypto.h
@@ -88,6 +88,10 @@ int cryptoMultisigPubkeyIndex(const CoinInfo *coin,
                               const MultisigRedeemScriptType *multisig,
                               const uint8_t *pubkey);
 
+uint32_t cryptoMultisigPubkeys(const CoinInfo *coin,
+                               const MultisigRedeemScriptType *multisig,
+                               uint8_t *pubkeys);
+
 int cryptoMultisigFingerprint(const MultisigRedeemScriptType *multisig,
                               uint8_t *hash);
 
@@ -115,5 +119,6 @@ void slip21_from_seed(const uint8_t *seed, int seed_len, Slip21Node *out);
 void slip21_derive_path(Slip21Node *inout, const uint8_t *label,
                         size_t label_len);
 const uint8_t *slip21_key(const Slip21Node *node);
+bool multisig_uses_single_path(const MultisigRedeemScriptType *multisig);
 
 #endif
diff --git a/legacy/firmware/transaction.c b/legacy/firmware/transaction.c
index 8659dbf4b9..77ae1f7726 100644
--- a/legacy/firmware/transaction.c
+++ b/legacy/firmware/transaction.c
@@ -373,6 +373,12 @@ uint32_t compile_script_multisig(const CoinInfo *coin,
   const uint32_t n = cryptoMultisigPubkeyCount(multisig);
   if (m < 1 || m > 15) return 0;
   if (n < 1 || n > 15) return 0;
+
+  uint8_t pubkeys[33 * n];
+  if (!cryptoMultisigPubkeys(coin, multisig, pubkeys)) {
+    return 0;
+  }
+
   uint32_t r = 0;
   if (out) {
     out[r] = 0x50 + m;
@@ -380,9 +386,7 @@ uint32_t compile_script_multisig(const CoinInfo *coin,
     for (uint32_t i = 0; i < n; i++) {
       out[r] = 33;
       r++;  // OP_PUSH 33
-      const HDNode *pubnode = cryptoMultisigPubkey(coin, multisig, i);
-      if (!pubnode) return 0;
-      memcpy(out + r, pubnode->public_key, 33);
+      memcpy(out + r, pubkeys + 33 * i, 33);
       r += 33;
     }
     out[r] = 0x50 + n;
@@ -409,6 +413,12 @@ uint32_t compile_script_multisig_hash(const CoinInfo *coin,
   if (m < 1 || m > 15) return 0;
   if (n < 1 || n > 15) return 0;
 
+  // allocate on stack instead of heap
+  uint8_t pubkeys[33 * n];
+  if (!cryptoMultisigPubkeys(coin, multisig, pubkeys)) {
+    return 0;
+  }
+
   Hasher hasher = {0};
   hasher_Init(&hasher, coin->curve->hasher_script);
 
@@ -418,9 +428,7 @@ uint32_t compile_script_multisig_hash(const CoinInfo *coin,
   for (uint32_t i = 0; i < n; i++) {
     d[0] = 33;
     hasher_Update(&hasher, d, 1);  // OP_PUSH 33
-    const HDNode *pubnode = cryptoMultisigPubkey(coin, multisig, i);
-    if (!pubnode) return 0;
-    hasher_Update(&hasher, pubnode->public_key, 33);
+    hasher_Update(&hasher, pubkeys + 33 * i, 33);
   }
   d[0] = 0x50 + n;
   d[1] = 0xAE;