parsing external signer master fingerprint string as bytes instead of caring for lower/upper case in ExternalSigner::SignTransaction

Author: avirgovi

src/external_signer.cpp

@@ -74,11 +74,12 @@ bool ExternalSigner::SignTransaction(PartiallySignedTransaction& psbtx, std::str
     // Serialize the PSBT
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
-
+    // parse ExternalSigner master fingerprint
+    std::vector<unsigned char> parsed_m_fingerprint = ParseHex(m_fingerprint);
     // Check if signer fingerprint matches any input master key fingerprint
     auto matches_signer_fingerprint = [&](const PSBTInput& input) {
         for (const auto& entry : input.hd_keypaths) {
-            if (m_fingerprint == strprintf("%08x", ReadBE32(entry.second.fingerprint))) return true;
+            if (parsed_m_fingerprint == MakeUCharSpan(entry.second.fingerprint)) return true;
         }
         return false;
     };