trezor: try empty passphrase first

- Try empty passphrase first when opening a wallet, as all Trezors will have passphrase enabled by default by Trezor Suite by default.
  This feature enables easier access to all users using disabled passphrase (or empty passhprase)
- If wallet address differs from device address with empty passphrase, another opening attempt is made, without passphrase suppression,
  so user can enter his passhprase if using some. In this scenario, nothing changes to user, wallet opening just consumes one more call
  to Trezor (get wallet address with empty passphrase)
- also change how m_passphrase is used. Previous version did not work well with recent passphrase entry mechanism change (made in Trezor),
  thus this commit fixes the behaviour).

4 files changed, 63 insertions, 10 deletions

diff --git a/src/device_trezor/device_trezor.cpp b/src/device_trezor/device_trezor.cpp
index c2070b0d1..03e8bbba4 100644
--- a/src/device_trezor/device_trezor.cpp
+++ b/src/device_trezor/device_trezor.cpp
@@ -178,6 +178,15 @@ namespace trezor {
       }
     }
 
+    bool device_trezor::get_public_address_with_no_passphrase(cryptonote::account_public_address &pubkey) {
+      m_reply_with_empty_passphrase = true;
+      const auto empty_passphrase_reverter = epee::misc_utils::create_scope_leave_handler([&]() {
+        m_reply_with_empty_passphrase = false;
+      });
+
+      return get_public_address(pubkey);
+    }
+
     bool device_trezor::get_secret_keys(crypto::secret_key &viewkey , crypto::secret_key &spendkey) {
       try {
         MDEBUG("Loading view-only key from the Trezor. Please check the Trezor for a confirmation.");
@@ -206,6 +215,18 @@ namespace trezor {
       get_address(index, payment_id, true);
     }
 
+    void device_trezor::reset_session() {
+      m_device_session_id.clear();
+    }
+
+    bool device_trezor::seen_passphrase_entry_prompt() {
+      return m_seen_passphrase_entry_message;
+    }
+
+    void device_trezor::set_use_empty_passphrase(bool always_use_empty_passphrase) {
+      m_always_use_empty_passphrase = always_use_empty_passphrase;
+    }
+
     /* ======================================================================= */
     /*  Helpers                                                                */
     /* ======================================================================= */
diff --git a/src/device_trezor/device_trezor.hpp b/src/device_trezor/device_trezor.hpp
index d91d1de3f..15337d2b4 100644
--- a/src/device_trezor/device_trezor.hpp
+++ b/src/device_trezor/device_trezor.hpp
@@ -205,6 +205,26 @@ namespace trezor {
                    const ::tools::wallet2::unsigned_tx_set & unsigned_tx,
                    ::tools::wallet2::signed_tx_set & signed_tx,
                    hw::tx_aux_data & aux_data) override;
+
+      /**
+      * Requests public address, uses empty passphrase if asked for.
+      */
+      bool get_public_address_with_no_passphrase(cryptonote::account_public_address &pubkey) override;
+
+      /**
+       * Reset session ID, restart with a new session.
+       */
+      virtual void reset_session() override;
+
+      /**
+       * Returns true if device already asked for passphrase entry before (i.e., obviously supports passphrase entry)
+       */
+      bool seen_passphrase_entry_prompt() override;
+
+      /**
+       * Uses empty passphrase for all passphrase queries.
+       */
+      void set_use_empty_passphrase(bool use_always_empty_passphrase) override;
     };
 
 #endif
diff --git a/src/device_trezor/device_trezor_base.cpp b/src/device_trezor/device_trezor_base.cpp
index b0b4342f5..016eb2816 100644
--- a/src/device_trezor/device_trezor_base.cpp
+++ b/src/device_trezor/device_trezor_base.cpp
@@ -45,7 +45,10 @@ namespace trezor {
 
     const uint32_t device_trezor_base::DEFAULT_BIP44_PATH[] = {0x8000002c, 0x80000080};
 
-    device_trezor_base::device_trezor_base(): m_callback(nullptr), m_last_msg_type(messages::MessageType_Success) {
+    device_trezor_base::device_trezor_base(): m_callback(nullptr), m_last_msg_type(messages::MessageType_Success),
+                                              m_reply_with_empty_passphrase(false),
+                                              m_always_use_empty_passphrase(false),
+                                              m_seen_passphrase_entry_message(false) {
 #ifdef WITH_TREZOR_DEBUGGING
       m_debug = false;
 #endif
@@ -155,6 +158,9 @@ namespace trezor {
       TREZOR_AUTO_LOCK_DEVICE();
       m_device_session_id.clear();
       m_features.reset();
+      m_seen_passphrase_entry_message = false;
+      m_reply_with_empty_passphrase = false;
+      m_always_use_empty_passphrase = false;
 
       if (m_transport){
         try {
@@ -476,6 +482,7 @@ namespace trezor {
         return;
       }
 
+      m_seen_passphrase_entry_message = true;
       bool on_device = true;
       if (msg->has__on_device() && !msg->_on_device()){
         on_device = false;  // do not enter on device, old devices.
@@ -491,19 +498,21 @@ namespace trezor {
       }
 
       boost::optional<epee::wipeable_string> passphrase;
-      TREZOR_CALLBACK_GET(passphrase, on_passphrase_request, on_device);
+      if (m_reply_with_empty_passphrase || m_always_use_empty_passphrase) {
+        MDEBUG("Answering passphrase prompt with an empty passphrase, always use empty: " << m_always_use_empty_passphrase);
+        on_device = false;
+        passphrase = epee::wipeable_string("");
+      } else if (m_passphrase){
+        MWARNING("Answering passphrase prompt with a stored passphrase (do not use; passphrase can be seen by a potential malware / attacker)");
+        on_device = false;
+        passphrase = epee::wipeable_string(m_passphrase.get());
+      } else {
+        TREZOR_CALLBACK_GET(passphrase, on_passphrase_request, on_device);
+      }
 
       messages::common::PassphraseAck m;
       m.set_on_device(on_device);
       if (!on_device) {
-        if (!passphrase && m_passphrase) {
-          passphrase = m_passphrase;
-        }
-
-        if (m_passphrase) {
-          m_passphrase = boost::none;
-        }
-
         if (passphrase) {
           m.set_allocated_passphrase(new std::string(passphrase->data(), passphrase->size()));
         }
diff --git a/src/device_trezor/device_trezor_base.hpp b/src/device_trezor/device_trezor_base.hpp
index 0162b23df..de49397d5 100644
--- a/src/device_trezor/device_trezor_base.hpp
+++ b/src/device_trezor/device_trezor_base.hpp
@@ -101,6 +101,9 @@ namespace trezor {
       messages::MessageType m_last_msg_type;
 
       cryptonote::network_type network_type;
+      bool m_reply_with_empty_passphrase;
+      bool m_always_use_empty_passphrase;
+      bool m_seen_passphrase_entry_message;
 
 #ifdef WITH_TREZOR_DEBUGGING
       std::shared_ptr<trezor_debug_callback> m_debug_callback;