Deduplicate the message verifying code

The logic of verifying a message was duplicated in 2 places:

src/qt/signverifymessagedialog.cpp
  SignVerifyMessageDialog::on_verifyMessageButton_VM_clicked()

src/rpc/misc.cpp
  verifymessage()

with the only difference being the result handling. Move the logic into
a dedicated

src/util/message.cpp
  MessageVerify()

which returns a set of result codes, call it from the 2 places and just
handle the results differently in the callers.

1 files changed, 11 insertions, 21 deletions

diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index f360cb7525..9686a111ed 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -11,9 +11,9 @@
 #include <rpc/util.h>
 #include <script/descriptor.h>
 #include <util/check.h>
+#include <util/message.h> // For strMessageMagic, MessageVerify()
 #include <util/strencodings.h>
 #include <util/system.h>
-#include <util/validation.h>
 
 #include <stdint.h>
 #include <tuple>
@@ -276,31 +276,21 @@ static UniValue verifymessage(const JSONRPCRequest& request)
     std::string strSign     = request.params[1].get_str();
     std::string strMessage  = request.params[2].get_str();
 
-    CTxDestination destination = DecodeDestination(strAddress);
-    if (!IsValidDestination(destination)) {
+    switch (MessageVerify(strAddress, strSign, strMessage)) {
+    case MessageVerificationResult::ERR_INVALID_ADDRESS:
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid address");
-    }
-
-    const PKHash *pkhash = boost::get<PKHash>(&destination);
-    if (!pkhash) {
+    case MessageVerificationResult::ERR_ADDRESS_NO_KEY:
         throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
-    }
-
-    bool fInvalid = false;
-    std::vector<unsigned char> vchSig = DecodeBase64(strSign.c_str(), &fInvalid);
-
-    if (fInvalid)
+    case MessageVerificationResult::ERR_MALFORMED_SIGNATURE:
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Malformed base64 encoding");
-
-    CHashWriter ss(SER_GETHASH, 0);
-    ss << strMessageMagic;
-    ss << strMessage;
-
-    CPubKey pubkey;
-    if (!pubkey.RecoverCompact(ss.GetHash(), vchSig))
+    case MessageVerificationResult::ERR_PUBKEY_NOT_RECOVERED:
+    case MessageVerificationResult::ERR_NOT_SIGNED:
         return false;
+    case MessageVerificationResult::OK:
+        return true;
+    }
 
-    return (pubkey.GetID() == *pkhash);
+    return false;
 }
 
 static UniValue signmessagewithprivkey(const JSONRPCRequest& request)