Merge #16026: Ensure that uncompressed public keys in a multisig always returns a legacy address

a49503402b6bc21e3878e151c07529941d36aed0 Make and get the multisig redeemscript and destination in one function instead of two (Andrew Chow)

Pull request description:

  `CreateMultisigRedeemscript()` is changed to `AddAndGetMultisigDestination()` so that the process of constructing the redeemScript and then getting the `CTxDestination` are done in the same function. This allows that function to see what the keys in the multisig are so that the correct address type is returned from `AddAndGetDestinationForScript()`.

  This only effects the `createmultisig` and `addmultisigaddress` RPCs and does not change signing logic as #16022 does.

  Alternative to #16022 and #16012

  Fixes #16011

ACKs for commit a49503:

Tree-SHA512: 5b0154a714deea3b2cc3a54beb420c95eeeacf4ca30c40ca80940d9d640f8b03611b0fc14c2f0710bfd8a79e8d27ad7d9ae380b4b83d52b40ab201624f2a63f0

3 files changed, 22 insertions, 9 deletions

diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index 2b29fd543b..7a1bdec7b9 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -122,9 +122,9 @@ static UniValue createmultisig(const JSONRPCRequest& request)
     }
 
     // Construct using pay-to-script-hash:
-    const CScript inner = CreateMultisigRedeemscript(required, pubkeys);
     CBasicKeyStore keystore;
-    const CTxDestination dest = AddAndGetDestinationForScript(keystore, inner, output_type);
+    CScript inner;
+    const CTxDestination dest = AddAndGetMultisigDestination(required, pubkeys, output_type, keystore, inner);
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("address", EncodeDestination(dest));
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index 9cdb22001f..4642cf16b1 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -4,6 +4,7 @@
 
 #include <key_io.h>
 #include <keystore.h>
+#include <outputtype.h>
 #include <rpc/util.h>
 #include <tinyformat.h>
 #include <util/strencodings.h>
@@ -150,8 +151,8 @@ CPubKey AddrToPubKey(CKeyStore* const keystore, const std::string& addr_in)
     return vchPubKey;
 }
 
-// Creates a multisig redeemscript from a given list of public keys and number required.
-CScript CreateMultisigRedeemscript(const int required, const std::vector<CPubKey>& pubkeys)
+// Creates a multisig address from a given list of public keys, number of signatures required, and the address type
+CTxDestination AddAndGetMultisigDestination(const int required, const std::vector<CPubKey>& pubkeys, OutputType type, CKeyStore& keystore, CScript& script_out)
 {
     // Gather public keys
     if (required < 1) {
@@ -164,13 +165,24 @@ CScript CreateMultisigRedeemscript(const int required, const std::vector<CPubKey
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Number of keys involved in the multisignature address creation > 16\nReduce the number");
     }
 
-    CScript result = GetScriptForMultisig(required, pubkeys);
+    script_out = GetScriptForMultisig(required, pubkeys);
 
-    if (result.size() > MAX_SCRIPT_ELEMENT_SIZE) {
-        throw JSONRPCError(RPC_INVALID_PARAMETER, (strprintf("redeemScript exceeds size limit: %d > %d", result.size(), MAX_SCRIPT_ELEMENT_SIZE)));
+    if (script_out.size() > MAX_SCRIPT_ELEMENT_SIZE) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, (strprintf("redeemScript exceeds size limit: %d > %d", script_out.size(), MAX_SCRIPT_ELEMENT_SIZE)));
     }
 
-    return result;
+    // Check if any keys are uncompressed. If so, the type is legacy
+    for (const CPubKey& pk : pubkeys) {
+        if (!pk.IsCompressed()) {
+            type = OutputType::LEGACY;
+            break;
+        }
+    }
+
+    // Make the address
+    CTxDestination dest = AddAndGetDestinationForScript(keystore, script_out, type);
+
+    return dest;
 }
 
 class DescribeAddressVisitor : public boost::static_visitor<UniValue>
diff --git a/src/rpc/util.h b/src/rpc/util.h
index e4fa8fc3d7..0eb2fef5c3 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -6,6 +6,7 @@
 #define BITCOIN_RPC_UTIL_H
 
 #include <node/transaction.h>
+#include <outputtype.h>
 #include <pubkey.h>
 #include <rpc/protocol.h>
 #include <script/standard.h>
@@ -70,7 +71,7 @@ extern std::string HelpExampleRpc(const std::string& methodname, const std::stri
 
 CPubKey HexToPubKey(const std::string& hex_in);
 CPubKey AddrToPubKey(CKeyStore* const keystore, const std::string& addr_in);
-CScript CreateMultisigRedeemscript(const int required, const std::vector<CPubKey>& pubkeys);
+CTxDestination AddAndGetMultisigDestination(const int required, const std::vector<CPubKey>& pubkeys, OutputType type, CKeyStore& keystore, CScript& script_out);
 
 UniValue DescribeAddress(const CTxDestination& dest);