Refactor message hashing into a utility function

And add unit test for it.

The purpose of using a preamble or "magic" text as part of signing and
verifying a message was not given when the code was repeated in a few
locations. Make a test showing how it is used to prevent inadvertently
signing a transaction.

1 files changed, 20 insertions, 1 deletions

diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
index 8a2553617b..f86e713676 100644
--- a/src/test/util_tests.cpp
+++ b/src/test/util_tests.cpp
@@ -5,12 +5,14 @@
 #include <util/system.h>
 
 #include <clientversion.h>
+#include <hash.h> // For Hash()
 #include <key.h> // For CKey
 #include <optional.h>
 #include <sync.h>
 #include <test/util/setup_common.h>
 #include <test/util/str.h>
-#include <util/message.h> // For MessageSign(), MessageVerify()
+#include <uint256.h>
+#include <util/message.h> // For MessageSign(), MessageVerify(), MESSAGE_MAGIC
 #include <util/moneystr.h>
 #include <util/strencodings.h>
 #include <util/string.h>
@@ -2116,4 +2118,21 @@ BOOST_AUTO_TEST_CASE(message_verify)
         MessageVerificationResult::OK);
 }
 
+BOOST_AUTO_TEST_CASE(message_hash)
+{
+    const std::string unsigned_tx = "...";
+    const std::string prefixed_message =
+        std::string(1, (char)MESSAGE_MAGIC.length()) +
+        MESSAGE_MAGIC +
+        std::string(1, (char)unsigned_tx.length()) +
+        unsigned_tx;
+
+    const uint256 signature_hash = Hash(unsigned_tx.begin(), unsigned_tx.end());
+    const uint256 message_hash1 = Hash(prefixed_message.begin(), prefixed_message.end());
+    const uint256 message_hash2 = MessageHash(unsigned_tx);
+
+    BOOST_CHECK_EQUAL(message_hash1, message_hash2);
+    BOOST_CHECK_NE(message_hash1, signature_hash);
+}
+
 BOOST_AUTO_TEST_SUITE_END()