mnemonics: add some logs to help debug failures

src/mnemonics/electrum-words.cpp

@@ -67,6 +67,9 @@
 #include "language_base.h"
 #include "singleton.h"
 
+#undef MONERO_DEFAULT_LOG_CATEGORY
+#define MONERO_DEFAULT_LOG_CATEGORY "mnemonic"
+
 namespace
 {
   uint32_t create_checksum_index(const std::vector<std::string> &word_list,
@@ -152,6 +155,7 @@ namespace
       if (full_match)
       {
         *language = *it1;
+        MINFO("Full match for language " << (*language)->get_english_language_name());
         return true;
       }
       // Some didn't match. Clear the index array.
@@ -164,9 +168,11 @@ namespace
     if (fallback)
     {
       *language = fallback;
+      MINFO("Fallback match for language " << (*language)->get_english_language_name());
       return true;
     }
 
+    MINFO("No match found");
     return false;
   }
 
@@ -217,7 +223,9 @@ namespace
       checksum;
     std::string trimmed_last_word = last_word.length() > unique_prefix_length ? Language::utf8prefix(last_word, unique_prefix_length) :
       last_word;
-    return trimmed_checksum == trimmed_last_word;
+    bool ret = trimmed_checksum == trimmed_last_word;
+    MINFO("Checksum is %s" << (ret ? "valid" : "invalid"));
+    return ret;
   }
 }
 
@@ -253,7 +261,10 @@ namespace crypto
       boost::split(seed, words, boost::is_any_of(" "), boost::token_compress_on);
 
       if (len % 4)
+      {
+        MERROR("Invalid seed: not a multiple of 4");
         return false;
+      }
 
       bool has_checksum = true;
       if (len)
@@ -263,6 +274,7 @@ namespace crypto
         if (seed.size() != expected/2 && seed.size() != expected &&
           seed.size() != expected + 1)
         {
+          MERROR("Invalid seed: unexpected number of words");
           return false;
         }
 
@@ -274,6 +286,7 @@ namespace crypto
       Language::Base *language;
       if (!find_seed_language(seed, has_checksum, matched_indices, &language))
       {
+        MERROR("Invalid seed: language not found");
         return false;
       }
       language_name = language->get_language_name();
@@ -284,6 +297,7 @@ namespace crypto
         if (!checksum_test(seed, language->get_unique_prefix_length()))
         {
           // Checksum fail
+          MERROR("Invalid seed: invalid checksum");
           return false;
         }
         seed.pop_back();
@@ -300,7 +314,11 @@ namespace crypto
         val = w1 + word_list_length * (((word_list_length - w1) + w2) % word_list_length) +
           word_list_length * word_list_length * (((word_list_length - w2) + w3) % word_list_length);
 
-        if (!(val % word_list_length == w1)) return false;
+        if (!(val % word_list_length == w1))
+        {
+          MERROR("Invalid seed: mumble mumble");
+          return false;
+        }
 
         dst.append((const char*)&val, 4);  // copy 4 bytes to position
       }
@@ -332,9 +350,15 @@ namespace crypto
     {
       std::string s;
       if (!words_to_bytes(words, s, sizeof(dst), true, language_name))
+      {
+        MERROR("Invalid seed: failed to convert words to bytes");
         return false;
+      }
       if (s.size() != sizeof(dst))
+      {
+        MERROR("Invalid seed: wrong output size");
         return false;
+      }
       dst = *(const crypto::secret_key*)s.data();
       return true;
     }