Unpad memos

firoorg · Dec 18, 2023 · 0fd2096 · 0fd2096
1 parent 5f86f62
commit 0fd2096
Show file tree

Hide file tree

Showing 3 changed files with 27 additions and 12 deletions.
diff --git a/src/libspark/coin.cpp b/src/libspark/coin.cpp
@@ -63,7 +63,8 @@ Coin::Coin(
 		MintCoinRecipientData r;
 		r.d = address.get_d();
 		r.k = k;
-		r.memo = std::string(padded_memo.begin(), padded_memo.end());
+		r.memo_length = (uint8_t) memo.size();
+		r.padded_memo = std::string(padded_memo.begin(), padded_memo.end());
 		CDataStream r_stream(SER_NETWORK, PROTOCOL_VERSION);
 		r_stream << r;
 		this->r_ = AEAD::encrypt(address.get_Q1()*SparkUtils::hash_k(k), "Mint coin data", r_stream);
@@ -73,7 +74,8 @@ Coin::Coin(
 		r.v = v;
 		r.d = address.get_d();
 		r.k = k;
-		r.memo = std::string(padded_memo.begin(), padded_memo.end());
+		r.memo_length = (uint8_t) memo.size();
+		r.padded_memo = std::string(padded_memo.begin(), padded_memo.end());
 		CDataStream r_stream(SER_NETWORK, PROTOCOL_VERSION);
 		r_stream << r;
 		this->r_ = AEAD::encrypt(address.get_Q1()*SparkUtils::hash_k(k), "Spend coin data", r_stream);
@@ -131,10 +133,15 @@ IdentifiedCoinData Coin::identify(const IncomingViewKey& incoming_view_key) {
 			throw std::runtime_error("Unable to identify coin");
 		}
 
+		// Check that the memo length is valid
+		if (r.memo_length > this->params->get_memo_bytes()) {
+			throw std::runtime_error("Unable to identify coin");
+		}
+
 		data.d = r.d;
 		data.v = this->v;
 		data.k = r.k;
-		data.memo = r.memo;
+		data.memo = std::string(r.padded_memo.begin(), r.padded_memo.begin() + r.memo_length);
 	} else {
 		SpendCoinRecipientData r;
 
@@ -146,10 +153,15 @@ IdentifiedCoinData Coin::identify(const IncomingViewKey& incoming_view_key) {
 			throw std::runtime_error("Unable to identify coin");
 		}
 
+		// Check that the memo length is valid
+		if (r.memo_length > this->params->get_memo_bytes()) {
+			throw std::runtime_error("Unable to identify coin");
+		}
+
 		data.d = r.d;
 		data.v = r.v;
 		data.k = r.k;
-		data.memo = r.memo;
+		data.memo = std::string(r.padded_memo.begin(), r.padded_memo.begin() + r.memo_length);
 	}
 
 	// Validate the coin

diff --git a/src/libspark/coin.h b/src/libspark/coin.h
@@ -33,15 +33,17 @@ struct RecoveredCoinData {
 struct MintCoinRecipientData {
 	std::vector<unsigned char> d; // encrypted diversifier
 	Scalar k; // nonce
-	std::string memo; // memo
+	uint8_t memo_length; // memo length
+	std::string padded_memo; // padded memo
 
 	ADD_SERIALIZE_METHODS;
 
 	template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action) {
         READWRITE(d);
 		READWRITE(k);
-		READWRITE(memo);
+		READWRITE(memo_length);
+		READWRITE(padded_memo);
     }
 };
 
@@ -50,7 +52,8 @@ struct SpendCoinRecipientData {
 	uint64_t v; // value
 	std::vector<unsigned char> d; // encrypted diversifier
 	Scalar k; // nonce
-	std::string memo; // memo
+	uint8_t memo_length; // memo length
+	std::string padded_memo; // padded memo
 
 	ADD_SERIALIZE_METHODS;
 
@@ -59,7 +62,8 @@ struct SpendCoinRecipientData {
         READWRITE(v);
         READWRITE(d);
 		READWRITE(k);
-		READWRITE(memo);
+		READWRITE(memo_length);
+		READWRITE(padded_memo);
     }
 };
 

diff --git a/src/libspark/test/coin_test.cpp b/src/libspark/test/coin_test.cpp
@@ -57,8 +57,8 @@ BOOST_AUTO_TEST_CASE(mint_identify_recover)
     BOOST_CHECK_EQUAL_COLLECTIONS(i_data.d.begin(), i_data.d.end(), address.get_d().begin(), address.get_d().end());
     BOOST_CHECK_EQUAL(i_data.v, v);
     BOOST_CHECK_EQUAL(i_data.k, k);
-    BOOST_CHECK_EQUAL(strcmp(memo.c_str(), i_data.memo.c_str()), 0); // compare strings in a lexicographical manner, as we pad the memo in the coin
-    BOOST_CHECK_EQUAL(i_data.memo.size(), params->get_memo_bytes()); // check that it is padded
+    BOOST_CHECK_EQUAL(i_data.memo, memo);
+
     // Recover coin
     RecoveredCoinData r_data = coin.recover(full_view_key, i_data);
     BOOST_CHECK_EQUAL(
@@ -105,8 +105,7 @@ BOOST_AUTO_TEST_CASE(spend_identify_recover)
     BOOST_CHECK_EQUAL_COLLECTIONS(i_data.d.begin(), i_data.d.end(), address.get_d().begin(), address.get_d().end());
     BOOST_CHECK_EQUAL(i_data.v, v);
     BOOST_CHECK_EQUAL(i_data.k, k);
-    BOOST_CHECK_EQUAL(strcmp(memo.c_str(), i_data.memo.c_str()), 0); // compare strings in a lexicographical manner, as we pad the memo in the coin
-    BOOST_CHECK_EQUAL(i_data.memo.size(), params->get_memo_bytes()); // check that it is padded
+    BOOST_CHECK_EQUAL(i_data.memo, memo);
 
     // Recover coin
     RecoveredCoinData r_data = coin.recover(full_view_key, i_data);