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, 42 insertions, 36 deletions

diff --git a/src/qt/signverifymessagedialog.cpp b/src/qt/signverifymessagedialog.cpp
index 5f2836cc75..aa8e23f53b 100644
--- a/src/qt/signverifymessagedialog.cpp
+++ b/src/qt/signverifymessagedialog.cpp
@@ -11,7 +11,7 @@
 #include <qt/walletmodel.h>
 
 #include <key_io.h>
-#include <util/validation.h> // For strMessageMagic
+#include <util/message.h> // For strMessageMagic, MessageVerify()
 #include <wallet/wallet.h>
 
 #include <vector>
@@ -189,51 +189,57 @@ void SignVerifyMessageDialog::on_addressBookButton_VM_clicked()
 
 void SignVerifyMessageDialog::on_verifyMessageButton_VM_clicked()
 {
-    CTxDestination destination = DecodeDestination(ui->addressIn_VM->text().toStdString());
-    if (!IsValidDestination(destination)) {
+    const std::string& address = ui->addressIn_VM->text().toStdString();
+    const std::string& signature = ui->signatureIn_VM->text().toStdString();
+    const std::string& message = ui->messageIn_VM->document()->toPlainText().toStdString();
+
+    const auto result = MessageVerify(address, signature, message);
+
+    if (result == MessageVerificationResult::OK) {
+        ui->statusLabel_VM->setStyleSheet("QLabel { color: green; }");
+    } else {
         ui->statusLabel_VM->setStyleSheet("QLabel { color: red; }");
-        ui->statusLabel_VM->setText(tr("The entered address is invalid.") + QString(" ") + tr("Please check the address and try again."));
-        return;
     }
-    if (!boost::get<PKHash>(&destination)) {
+
+    switch (result) {
+    case MessageVerificationResult::OK:
+        ui->statusLabel_VM->setText(
+            QString("<nobr>") + tr("Message verified.") + QString("</nobr>")
+        );
+        return;
+    case MessageVerificationResult::ERR_INVALID_ADDRESS:
+        ui->statusLabel_VM->setText(
+            tr("The entered address is invalid.") + QString(" ") +
+            tr("Please check the address and try again.")
+        );
+        return;
+    case MessageVerificationResult::ERR_ADDRESS_NO_KEY:
         ui->addressIn_VM->setValid(false);
-        ui->statusLabel_VM->setStyleSheet("QLabel { color: red; }");
-        ui->statusLabel_VM->setText(tr("The entered address does not refer to a key.") + QString(" ") + tr("Please check the address and try again."));
+        ui->statusLabel_VM->setText(
+            tr("The entered address does not refer to a key.") + QString(" ") +
+            tr("Please check the address and try again.")
+        );
         return;
-    }
-
-    bool fInvalid = false;
-    std::vector<unsigned char> vchSig = DecodeBase64(ui->signatureIn_VM->text().toStdString().c_str(), &fInvalid);
-
-    if (fInvalid)
-    {
+    case MessageVerificationResult::ERR_MALFORMED_SIGNATURE:
         ui->signatureIn_VM->setValid(false);
-        ui->statusLabel_VM->setStyleSheet("QLabel { color: red; }");
-        ui->statusLabel_VM->setText(tr("The signature could not be decoded.") + QString(" ") + tr("Please check the signature and try again."));
+        ui->statusLabel_VM->setText(
+            tr("The signature could not be decoded.") + QString(" ") +
+            tr("Please check the signature and try again.")
+        );
         return;
-    }
-
-    CHashWriter ss(SER_GETHASH, 0);
-    ss << strMessageMagic;
-    ss << ui->messageIn_VM->document()->toPlainText().toStdString();
-
-    CPubKey pubkey;
-    if (!pubkey.RecoverCompact(ss.GetHash(), vchSig))
-    {
+    case MessageVerificationResult::ERR_PUBKEY_NOT_RECOVERED:
         ui->signatureIn_VM->setValid(false);
-        ui->statusLabel_VM->setStyleSheet("QLabel { color: red; }");
-        ui->statusLabel_VM->setText(tr("The signature did not match the message digest.") + QString(" ") + tr("Please check the signature and try again."));
+        ui->statusLabel_VM->setText(
+            tr("The signature did not match the message digest.") + QString(" ") +
+            tr("Please check the signature and try again.")
+        );
         return;
-    }
-
-    if (!(CTxDestination(PKHash(pubkey)) == destination)) {
-        ui->statusLabel_VM->setStyleSheet("QLabel { color: red; }");
-        ui->statusLabel_VM->setText(QString("<nobr>") + tr("Message verification failed.") + QString("</nobr>"));
+    case MessageVerificationResult::ERR_NOT_SIGNED:
+        ui->statusLabel_VM->setText(
+            QString("<nobr>") + tr("Message verification failed.") + QString("</nobr>")
+        );
         return;
     }
-
-    ui->statusLabel_VM->setStyleSheet("QLabel { color: green; }");
-    ui->statusLabel_VM->setText(QString("<nobr>") + tr("Message verified.") + QString("</nobr>"));
 }
 
 void SignVerifyMessageDialog::on_clearButton_VM_clicked()