Output a descriptor in createmultisig and addmultisigaddress

Author: achow101

doc/descriptors.md

@@ -17,6 +17,7 @@ Supporting RPCs are:
   (`regtest` only, since v0.19).
 - `utxoupdatepsbt` takes as input descriptors to add information to the psbt
   (since v0.19).
+- `createmultisig` and `addmultisigaddress` return descriptors as well (since v0.20)
 
 This document describes the language. For the specifics on usage, see the RPC
 documentation for the functions mentioned above.

src/rpc/misc.cpp

@@ -83,6 +83,7 @@ static UniValue createmultisig(const JSONRPCRequest& request)
             "{\n"
             "  \"address\":\"multisigaddress\",  (string) The value of the new multisig address.\n"
             "  \"redeemScript\":\"script\"       (string) The string value of the hex-encoded redemption script.\n"
+            "  \"descriptor\":\"descriptor\"     (string) The descriptor for this multisig\n"
             "}\n"
                 },
                 RPCExamples{
@@ -119,9 +120,13 @@ static UniValue createmultisig(const JSONRPCRequest& request)
     CScript inner;
     const CTxDestination dest = AddAndGetMultisigDestination(required, pubkeys, output_type, keystore, inner);
 
+    // Make the descriptor
+    std::unique_ptr<Descriptor> descriptor = InferDescriptor(GetScriptForDestination(dest), keystore);
+
     UniValue result(UniValue::VOBJ);
     result.pushKV("address", EncodeDestination(dest));
     result.pushKV("redeemScript", HexStr(inner.begin(), inner.end()));
+    result.pushKV("descriptor", descriptor->ToString());
 
     return result;
 }

src/wallet/rpcwallet.cpp

@@ -974,6 +974,7 @@ static UniValue addmultisigaddress(const JSONRPCRequest& request)
             "{\n"
             "  \"address\":\"multisigaddress\",    (string) The value of the new multisig address.\n"
             "  \"redeemScript\":\"script\"         (string) The string value of the hex-encoded redemption script.\n"
+            "  \"descriptor\":\"descriptor\"     (string) The descriptor for this multisig\n"
             "}\n"
                 },
                 RPCExamples{
@@ -1018,9 +1019,13 @@ static UniValue addmultisigaddress(const JSONRPCRequest& request)
     CTxDestination dest = AddAndGetMultisigDestination(required, pubkeys, output_type, spk_man, inner);
     pwallet->SetAddressBook(dest, label, "send");
 
+    // Make the descriptor
+    std::unique_ptr<Descriptor> descriptor = InferDescriptor(GetScriptForDestination(dest), spk_man);
+
     UniValue result(UniValue::VOBJ);
     result.pushKV("address", EncodeDestination(dest));
     result.pushKV("redeemScript", HexStr(inner.begin(), inner.end()));
+    result.pushKV("descriptor", descriptor->ToString());
     return result;
 }
 

test/functional/rpc_createmultisig.py

@@ -4,7 +4,7 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test multisig RPCs"""
 
-from test_framework.descriptors import descsum_create
+from test_framework.descriptors import descsum_create, drop_origins
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_raises_rpc_error,
@@ -116,16 +116,28 @@ def checkbalances(self):
     def do_multisig(self):
         node0, node1, node2 = self.nodes
 
+        # Construct the expected descriptor
+        desc = 'multi({},{})'.format(self.nsigs, ','.join(self.pub))
+        if self.output_type == 'legacy':
+            desc = 'sh({})'.format(desc)
+        elif self.output_type == 'p2sh-segwit':
+            desc = 'sh(wsh({}))'.format(desc)
+        elif self.output_type == 'bech32':
+            desc = 'wsh({})'.format(desc)
+        desc = descsum_create(desc)
+
         msig = node2.createmultisig(self.nsigs, self.pub, self.output_type)
         madd = msig["address"]
         mredeem = msig["redeemScript"]
+        assert_equal(desc, msig['descriptor'])
         if self.output_type == 'bech32':
             assert madd[0:4] == "bcrt"  # actually a bech32 address
 
         # compare against addmultisigaddress
         msigw = node1.addmultisigaddress(self.nsigs, self.pub, None, self.output_type)
         maddw = msigw["address"]
         mredeemw = msigw["redeemScript"]
+        assert_equal(desc, drop_origins(msigw['descriptor']))
         # addmultisigiaddress and createmultisig work the same
         assert maddw == madd
         assert mredeemw == mredeem

test/functional/test_framework/descriptors.py

@@ -4,6 +4,8 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Utility functions related to output descriptors"""
 
+import re
+
 INPUT_CHARSET = "0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ "
 CHECKSUM_CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
 GENERATOR = [0xf5dee51989, 0xa9fdca3312, 0x1bab10e32d, 0x3706b1677a, 0x644d626ffd]
@@ -53,3 +55,10 @@ def descsum_check(s, require=True):
         return False
     symbols = descsum_expand(s[:-9]) + [CHECKSUM_CHARSET.find(x) for x in s[-8:]]
     return descsum_polymod(symbols) == 1
+
+def drop_origins(s):
+    '''Drop the key origins from a descriptor'''
+    desc = re.sub(r'\[.+?\]', '', s)
+    if '#' in s:
+        desc = desc[:desc.index('#')]
+    return descsum_create(desc)