From 41c999ca2f71aefe799f645fd38e2581bb5a2c30 Mon Sep 17 00:00:00 2001
From: Amir Abrams <amirabrams@mail.com>
Date: Fri, 8 Nov 2019 15:37:21 -0600
Subject: [PATCH] [RPC] More user-friendly error message when partially signing
 - see Bitcoin pull request: https://github.com/bitcoin/bitcoin/pull/11288

---
 src/rpc/rawtransaction.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 9816db9fee..d4d2308876 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -841,14 +841,19 @@ UniValue signrawtransaction(const JSONRPCRequest& request)
             SignSignature(keystore, prevPubKey, mergedTx, i, nHashType);
 
         // ... and merge in other signatures:
-        BOOST_FOREACH (const CMutableTransaction& txv, txVariants) {
+        for (const CMutableTransaction& txv : txVariants) {
             if (txv.vin.size() > i) {
                 txin.scriptSig = CombineSignatures(prevPubKey, txConst, i, txin.scriptSig, txv.vin[i].scriptSig);
             }
         }
         ScriptError serror = SCRIPT_ERR_OK;
         if (!VerifyScript(txin.scriptSig, prevPubKey, STANDARD_SCRIPT_VERIFY_FLAGS, TransactionSignatureChecker(&txConst, i), &serror)) {
-            TxInErrorToJSON(txin, vErrors, ScriptErrorString(serror));
+            if (serror == SCRIPT_ERR_INVALID_STACK_OPERATION) {
+                // Unable to sign input and verification failed (possible attempt to partially sign).
+                TxInErrorToJSON(txin, vErrors, "Unable to sign input, invalid stack size (possibly missing key)");
+            } else {
+                TxInErrorToJSON(txin, vErrors, ScriptErrorString(serror));
+            }
         }
     }
     bool fComplete = vErrors.empty();