Use a more specific exception class for note decryption failure

Closes #1545.

src/gtest/test_noteencryption.cpp

@@ -46,21 +46,25 @@ TEST(noteencryption, api)
             ASSERT_TRUE(plaintext == message);
 
             // Test wrong nonce
-            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), (i == 0) ? 1 : (i - 1)), std::runtime_error);
+            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), (i == 0) ? 1 : (i - 1)),
+                         libzcash::note_decryption_failed);
         
             // Test wrong ephemeral key
             {
                 ZCNoteEncryption c = ZCNoteEncryption(uint256());
 
-                ASSERT_THROW(decrypter.decrypt(ciphertext, c.get_epk(), uint256(), i), std::runtime_error);
+                ASSERT_THROW(decrypter.decrypt(ciphertext, c.get_epk(), uint256(), i),
+                             libzcash::note_decryption_failed);
             }
         
             // Test wrong seed
-            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256S("11035d60bc1983e37950ce4803418a8fb33ea68d5b937ca382ecbae7564d6a77"), i), std::runtime_error);
+            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256S("11035d60bc1983e37950ce4803418a8fb33ea68d5b937ca382ecbae7564d6a77"), i),
+                         libzcash::note_decryption_failed);
         
             // Test corrupted ciphertext
             ciphertext[10] ^= 0xff;
-            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), i), std::runtime_error);
+            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), i),
+                         libzcash::note_decryption_failed);
             ciphertext[10] ^= 0xff;
         }
 
@@ -69,7 +73,8 @@ TEST(noteencryption, api)
             uint256 sk_enc_2 = ZCNoteEncryption::generate_privkey(uint252());
             ZCNoteDecryption decrypter(sk_enc_2);
 
-            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), i), std::runtime_error);
+            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), i),
+                         libzcash::note_decryption_failed);
         }
 
         {
@@ -81,7 +86,8 @@ TEST(noteencryption, api)
 
             // Test wrong public key (test of KDF)
             decrypter.change_pk_enc(uint256());
-            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), i), std::runtime_error);
+            ASSERT_THROW(decrypter.decrypt(ciphertext, b.get_epk(), uint256(), i),
+                         libzcash::note_decryption_failed);
         }
     }
 

src/wallet/wallet.cpp

@@ -1275,12 +1275,7 @@ mapNoteData_t CWallet::FindMyNotes(const CTransaction& tx) const
                         noteData.insert(std::make_pair(jsoutpt, nd));
                     }
                     break;
-                } catch (const std::runtime_error &err) {
-                    if (memcmp("Could not decrypt message", err.what(), 25) != 0) {
-                        // Unexpected failure
-                        LogPrintf("FindMyNotes(): Unexpected runtime error while testing decrypt:\n");
-                        LogPrintf("%s\n", err.what());
-                    } // else
+                } catch (const note_decryption_failed &err) {
                     // Couldn't decrypt with this decryptor
                 } catch (const std::exception &exc) {
                     // Unexpected failure
@@ -3562,9 +3557,12 @@ void CWallet::GetFilteredNotes(std::vector<CNotePlaintextEntry> & outEntries, st
 
                 outEntries.push_back(CNotePlaintextEntry{jsop, plaintext});
 
-            } catch (const std::exception &) {
+            } catch (const note_decryption_failed &err) {
                 // Couldn't decrypt with this spending key
                 throw std::runtime_error(strprintf("Could not decrypt note for payment address %s", CZCPaymentAddress(pa).ToString()));
+            } catch (const std::exception &exc) {
+                // Unexpected failure
+                throw std::runtime_error(strprintf("Error while decrypting note for payment address %s: %s", CZCPaymentAddress(pa).ToString(), exc.what()));
             }
         }
     }

src/zcash/NoteEncryption.cpp

@@ -129,7 +129,7 @@ typename NoteDecryption<MLEN>::Plaintext NoteDecryption<MLEN>::decrypt
                                              NULL,
                                              0,
                                              cipher_nonce, K) != 0) {
-        throw std::runtime_error("Could not decrypt message");
+        throw note_decryption_failed();
     }
 
     return plaintext;

src/zcash/NoteEncryption.hpp

@@ -82,6 +82,11 @@ public:
 uint256 random_uint256();
 uint252 random_uint252();
 
+class note_decryption_failed : public std::runtime_error {
+public:
+    note_decryption_failed() : std::runtime_error("Could not decrypt message") { }
+};
+
 }
 
 typedef libzcash::NoteEncryption<ZC_NOTEPLAINTEXT_SIZE> ZCNoteEncryption;