Add descriptor support to createmultisig rpc

lib/descriptor/abstractdescriptor.js

@@ -241,7 +241,7 @@ class AbstractDescriptor {
    * @returns {Script[]}
    */
 
-  generateScripts(pos) {
+  generateScripts(pos = 0) {
     const pubkeys = [];
     const subscripts = [];
 
@@ -274,7 +274,7 @@ class AbstractDescriptor {
    * @returns {Address[]}
    */
 
-  getAddresses(pos) {
+  getAddresses(pos = 0) {
     const scripts = this.generateScripts(pos);
     const addresses = [];
 

lib/descriptor/common.js

@@ -58,6 +58,17 @@ common.scriptContext = {
   P2WSH: 'P2WSH'
 };
 
+/**
+ * output types for descriptor
+ * @const {Object}
+ */
+
+common.outputTypes = {
+  LEGACY: 'legacy',
+  BECH32: 'bech32',
+  P2SH_SEGWIT: 'p2sh-segwit'
+};
+
 /**
  * Allowed characters in descriptor expressions for checksum to work.
  * @see https://github.com/bitcoin/bips/blob/master/bip-0380.mediawiki#character-set

lib/node/rpc.js

@@ -35,10 +35,15 @@ const TX = require('../primitives/tx');
 const consensus = require('../protocol/consensus');
 const pkg = require('../pkg');
 const {filters} = require('../blockstore/common');
-const {createChecksum} = require('../descriptor/common');
+const MultisigDescriptor = require('../descriptor/type/multisig');
+const SHDescriptor = require('../descriptor/type/sh');
+const WSHDescriptor = require('../descriptor/type/wsh');
 const {parse} = require('../descriptor/parser');
 const RPCBase = bweb.RPC;
 const RPCError = bweb.RPCError;
+const {
+  createChecksum, outputTypes, scriptContext
+} = require('../descriptor/common');
 
 /*
  * Constants
@@ -2050,20 +2055,32 @@ class RPC extends RPCBase {
    */
 
   async createMultisig(args, help) {
-    if (help || args.length < 2 || args.length > 2) {
+    if (help || args.length < 2 || args.length > 3) {
       throw new RPCError(errs.MISC_ERROR,
-        'createmultisig nrequired ["key",...]');
+        'createmultisig nrequired ["key",...] (address_type)');
     }
 
     const valid = new Validator(args);
     const keys = valid.array(1, []);
+    let outputType = valid.str(2);
+
+    if (outputType === null) {
+      outputType = outputTypes.LEGACY;
+    }
+
+    assert(
+      Object.values(outputTypes).includes(outputType),
+      `Unknown address type '${outputType}'.`
+    );
+
     const m = valid.u32(0, 0);
     const n = keys.length;
 
-    if (m < 1 || n < m || n > 16)
+    if (m < 1 || n < m || n > 20)
       throw new RPCError(errs.INVALID_PARAMETER, 'Invalid m and n values.');
 
     const items = new Validator(keys);
+    let keyString = '';
 
     for (let i = 0; i < keys.length; i++) {
       const key = items.buf(i);
@@ -2074,21 +2091,46 @@ class RPC extends RPCBase {
       if (!secp256k1.publicKeyVerify(key))
         throw new RPCError(errs.INVALID_ADDRESS_OR_KEY, 'Invalid key.');
 
+      keyString += items.str(i) + ',';
       keys[i] = key;
     }
 
-    const script = Script.fromMultisig(m, n, keys, true, false);
+    keyString = keyString.slice(0, -1);
 
-    if (script.getSize() > consensus.MAX_SCRIPT_PUSH) {
-      throw new RPCError(errs.VERIFY_ERROR,
-        'Redeem script exceeds size limit.');
-    }
+    const isWitness = outputType !== outputTypes.LEGACY;
+    const script = Script.fromMultisig(m, n, keys, false, isWitness);
 
-    const addr = script.getAddress();
+    const {P2SH, P2WSH} = scriptContext;
+    const context = outputType === outputTypes.LEGACY ? P2SH : P2WSH;
+
+    const subdesc = MultisigDescriptor.fromString(
+      `multi(${m},${keyString})`, this.network, context
+    );
+
+    let descriptor;
+
+    const options = {
+      subdescriptors: [subdesc],
+      network: this.network
+    };
+
+    switch (outputType) {
+      case outputTypes.LEGACY:
+        descriptor = SHDescriptor.fromOptions(options);
+        break;
+      case outputTypes.BECH32:
+        descriptor = WSHDescriptor.fromOptions(options);
+        break;
+      case outputTypes.P2SH_SEGWIT: {
+        options.subdescriptors = [WSHDescriptor.fromOptions(options)];
+        descriptor = SHDescriptor.fromOptions(options);
+      }
+    }
 
     return {
-      address: addr.toString(this.network),
-      redeemScript: script.toJSON()
+      address: descriptor.getAddresses()[0],
+      redeemScript: script.toJSON(),
+      descriptor: descriptor.toString()
     };
   }