Sanity-check script sizes in bitcoin-tx

Summary:
"Sanity-check script sizes in bitcoin-tx (Matt Corallo)"

This is a backport from Core PR11554: bitcoin/bitcoin#11554

Test Plan:
  ninja check
  ./test/functional/test_runner.py

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix, Fabien

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D4666

src/bitcoin-tx.cpp

@@ -401,6 +401,11 @@ static void MutateTxAddOutMultiSig(CMutableTransaction &tx,
     CScript scriptPubKey = GetScriptForMultisig(required, pubkeys);
 
     if (bScriptHash) {
+        if (scriptPubKey.size() > MAX_SCRIPT_ELEMENT_SIZE) {
+            throw std::runtime_error(
+                strprintf("redeemScript exceeds size limit: %d > %d",
+                          scriptPubKey.size(), MAX_SCRIPT_ELEMENT_SIZE));
+        }
         // Get the ID for the script, and then construct a P2SH destination for
         // it.
         scriptPubKey = GetScriptForDestination(CScriptID(scriptPubKey));
@@ -462,7 +467,18 @@ static void MutateTxAddOutScript(CMutableTransaction &tx,
         bScriptHash = (flags.find('S') != std::string::npos);
     }
 
+    if (scriptPubKey.size() > MAX_SCRIPT_SIZE) {
+        throw std::runtime_error(strprintf("script exceeds size limit: %d > %d",
+                                           scriptPubKey.size(),
+                                           MAX_SCRIPT_SIZE));
+    }
+
     if (bScriptHash) {
+        if (scriptPubKey.size() > MAX_SCRIPT_ELEMENT_SIZE) {
+            throw std::runtime_error(
+                strprintf("redeemScript exceeds size limit: %d > %d",
+                          scriptPubKey.size(), MAX_SCRIPT_ELEMENT_SIZE));
+        }
         scriptPubKey = GetScriptForDestination(CScriptID(scriptPubKey));
     }