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).

1 files changed, 19 insertions, 10 deletions

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()));
         }