fix(tx_extra): enforce equal vector lengths in tx_extra_master_node_register

[raw391]

tx_extra_master_node_register at src/cryptonote_basic/tx_extra.h:317-334 carries three parallel vectors (m_public_spend_keys, m_public_view_keys, m_portions) that are intended to be index-aligned. The serializer reads each as an independent vector with no cross-field invariant, so a malformed field with desynchronized lengths deserializes successfully and exposes consumers to out-of-bounds reads.

Two consumers index by one vectors size and read another. The block-include path at master_node_list.cpp:305-309 (reg_tx_extract_fields):

for (size_t i = 0; i < registration.m_public_spend_keys.size(); i++) {
  contributor_args.addresses.back().m_view_public_key = registration.m_public_view_keys[i];
}

validate_contributor_args (line 333) catches the size mismatch only after the loop runs.

The RPC path at core_rpc_server.cpp:711-720 (extra_extractor::operator()(tx_extra_master_node_register&)) is reachable from any otherwise valid relayable transaction that carries a malformed tx_extra_master_node_register field. tx_pool::add_tx accepts arbitrary tx.extra content on standard transfer transactions, so the tx sits in mempool until a caller queries get_transactions or get_transaction_pool with tx_extra=true. The visitor then reads past the end of one of the key vectors; outcome depends on heap layout.

Patch enforces the equal-length invariant at deserialization (matching the tx_extra_padding pattern at tx_extra.h:195-210), and adds size-equality guards at both consumers so the call sites stay safe if the invariant ever drifts.

   struct tx_extra_master_node_register
   {
     ...
     BEGIN_SERIALIZE()
       FIELD(m_public_spend_keys)
       FIELD(m_public_view_keys)
       FIELD(m_portions_for_operator)
       FIELD(m_portions)
       FIELD(m_expiration_timestamp)
       FIELD(m_master_node_signature)
+      if (Archive::is_deserializer)
+      {
+        if (m_public_spend_keys.size() != m_public_view_keys.size())
+          throw std::invalid_argument{"tx_extra_master_node_register: spend/view key count mismatch"};
+        if (m_public_spend_keys.size() != m_portions.size())
+          throw std::invalid_argument{"tx_extra_master_node_register: spend/portions count mismatch"};
+      }
     END_SERIALIZE()
   };