1 files changed, 92 insertions, 0 deletions
diff --git a/src/util/message.cpp b/src/util/message.cpp
new file mode 100644
index 0000000000..1e7128d225
--- /dev/null
+++ b/src/util/message.cpp
@@ -0,0 +1,92 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <hash.h>            // For CHashWriter
+#include <key.h>             // For CKey
+#include <key_io.h>          // For DecodeDestination()
+#include <pubkey.h>          // For CPubKey
+#include <script/standard.h> // For CTxDestination, IsValidDestination(), PKHash
+#include <serialize.h>       // For SER_GETHASH
+#include <util/message.h>
+#include <util/strencodings.h> // For DecodeBase64()
+
+#include <string>
+#include <vector>
+
+/**
+ * Text used to signify that a signed message follows and to prevent
+ * inadvertently signing a transaction.
+ */
+const std::string MESSAGE_MAGIC = "Bitcoin Signed Message:\n";
+
+MessageVerificationResult MessageVerify(
+    const std::string& address,
+    const std::string& signature,
+    const std::string& message)
+{
+    CTxDestination destination = DecodeDestination(address);
+    if (!IsValidDestination(destination)) {
+        return MessageVerificationResult::ERR_INVALID_ADDRESS;
+    }
+
+    if (boost::get<PKHash>(&destination) == nullptr) {
+        return MessageVerificationResult::ERR_ADDRESS_NO_KEY;
+    }
+
+    bool invalid = false;
+    std::vector<unsigned char> signature_bytes = DecodeBase64(signature.c_str(), &invalid);
+    if (invalid) {
+        return MessageVerificationResult::ERR_MALFORMED_SIGNATURE;
+    }
+
+    CPubKey pubkey;
+    if (!pubkey.RecoverCompact(MessageHash(message), signature_bytes)) {
+        return MessageVerificationResult::ERR_PUBKEY_NOT_RECOVERED;
+    }
+
+    if (!(CTxDestination(PKHash(pubkey)) == destination)) {
+        return MessageVerificationResult::ERR_NOT_SIGNED;
+    }
+
+    return MessageVerificationResult::OK;
+}
+
+bool MessageSign(
+    const CKey& privkey,
+    const std::string& message,
+    std::string& signature)
+{
+    std::vector<unsigned char> signature_bytes;
+
+    if (!privkey.SignCompact(MessageHash(message), signature_bytes)) {
+        return false;
+    }
+
+    signature = EncodeBase64(signature_bytes.data(), signature_bytes.size());
+
+    return true;
+}
+
+uint256 MessageHash(const std::string& message)
+{
+    CHashWriter hasher(SER_GETHASH, 0);
+    hasher << MESSAGE_MAGIC << message;
+
+    return hasher.GetHash();
+}
+
+std::string SigningResultString(const SigningResult res)
+{
+    switch (res) {
+        case SigningResult::OK:
+            return "No error";
+        case SigningResult::PRIVATE_KEY_NOT_AVAILABLE:
+            return "Private key not available";
+        case SigningResult::SIGNING_FAILED:
+            return "Sign failed";
+        // no default case, so the compiler can warn about missing cases
+    }
+    assert(false);
+}