wallet: warn if not using the default ring size

src/simplewallet/simplewallet.cpp

@@ -1650,6 +1650,9 @@ bool simple_wallet::set_default_ring_size(const std::vector<std::string> &args/*
       return true;
     }
  
+    if (ring_size != 0 && ring_size != DEFAULT_MIX+1)
+      message_writer() << tr("WARNING: this is a non default ring size, which may harm your privacy. Default is recommended.");
+
     const auto pwd_container = get_and_verify_password();
     if (pwd_container)
     {
@@ -4581,6 +4584,23 @@ bool simple_wallet::transfer_main(int transfer_type, const std::vector<std::stri
           if (!print_ring_members(ptx_vector, prompt))
             return true;
         }
+        bool default_ring_size = true;
+        for (const auto &ptx: ptx_vector)
+        {
+          for (const auto &vin: ptx.tx.vin)
+          {
+            if (vin.type() == typeid(txin_to_key))
+            {
+              const txin_to_key& in_to_key = boost::get<txin_to_key>(vin);
+              if (in_to_key.key_offsets.size() != DEFAULT_MIX + 1)
+                default_ring_size = false;
+            }
+          }
+        }
+        if (m_wallet->confirm_non_default_ring_size() && !default_ring_size)
+        {
+          prompt << tr("WARNING: this is a non default ring size, which may harm your privacy. Default is recommended.");
+        }
         prompt << ENDL << tr("Is this okay?  (Y/Yes/N/No): ");
         
         std::string accepted = input_line(prompt.str());

src/wallet/wallet2.cpp

@@ -653,6 +653,7 @@ wallet2::wallet2(network_type nettype, bool restricted):
   m_refresh_from_block_height(0),
   m_explicit_refresh_from_block_height(true),
   m_confirm_missing_payment_id(true),
+  m_confirm_non_default_ring_size(true),
   m_ask_password(true),
   m_min_output_count(0),
   m_min_output_value(0),
@@ -2560,6 +2561,9 @@ bool wallet2::store_keys(const std::string& keys_file_name, const epee::wipeable
   value2.SetInt(m_confirm_missing_payment_id ? 1 :0);
   json.AddMember("confirm_missing_payment_id", value2, json.GetAllocator());
 
+  value2.SetInt(m_confirm_non_default_ring_size ? 1 :0);
+  json.AddMember("confirm_non_default_ring_size", value2, json.GetAllocator());
+
   value2.SetInt(m_ask_password ? 1 :0);
   json.AddMember("ask_password", value2, json.GetAllocator());
 
@@ -2661,6 +2665,7 @@ bool wallet2::load_keys(const std::string& keys_file_name, const epee::wipeable_
     m_auto_refresh = true;
     m_refresh_type = RefreshType::RefreshDefault;
     m_confirm_missing_payment_id = true;
+    m_confirm_non_default_ring_size = true;
     m_ask_password = true;
     m_min_output_count = 0;
     m_min_output_value = 0;
@@ -2761,6 +2766,8 @@ bool wallet2::load_keys(const std::string& keys_file_name, const epee::wipeable_
     m_refresh_from_block_height = field_refresh_height;
     GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, confirm_missing_payment_id, int, Int, false, true);
     m_confirm_missing_payment_id = field_confirm_missing_payment_id;
+    GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, confirm_non_default_ring_size, int, Int, false, true);
+    m_confirm_non_default_ring_size = field_confirm_non_default_ring_size;
     GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, ask_password, int, Int, false, true);
     m_ask_password = field_ask_password;
     GET_FIELD_FROM_JSON_RETURN_ON_ERROR(json, default_decimal_point, int, Int, false, CRYPTONOTE_DISPLAY_DECIMAL_POINT);

src/wallet/wallet2.h

@@ -874,6 +874,8 @@ namespace tools
     void key_reuse_mitigation2(bool value) { m_key_reuse_mitigation2 = value; }
     uint64_t segregation_height() const { return m_segregation_height; }
     void segregation_height(uint64_t height) { m_segregation_height = height; }
+    bool confirm_non_default_ring_size() const { return m_confirm_non_default_ring_size; }
+    void confirm_non_default_ring_size(bool always) { m_confirm_non_default_ring_size = always; }
 
     bool get_tx_key(const crypto::hash &txid, crypto::secret_key &tx_key, std::vector<crypto::secret_key> &additional_tx_keys) const;
     void check_tx_key(const crypto::hash &txid, const crypto::secret_key &tx_key, const std::vector<crypto::secret_key> &additional_tx_keys, const cryptonote::account_public_address &address, uint64_t &received, bool &in_pool, uint64_t &confirmations);
@@ -1194,6 +1196,7 @@ namespace tools
     // m_refresh_from_block_height was defaulted to zero.*/
     bool m_explicit_refresh_from_block_height;
     bool m_confirm_missing_payment_id;
+    bool m_confirm_non_default_ring_size;
     bool m_ask_password;
     uint32_t m_min_output_count;
     uint64_t m_min_output_value;