Merge pull request #5289 from BitGo/BTC-1687.allow-wsh-2of3-cltv-drop

feat(abstract-utxo): permit Wsh2Of3CltvDrop in descriptor validation

Author: OttoAllmendinger

modules/abstract-utxo/src/descriptor/builder/builder.ts

@@ -11,11 +11,11 @@ export type DescriptorBuilder =
   | DescriptorWithKeys<'Wsh2Of2'>
   | DescriptorWithKeys<'Wsh2Of3'>
   /*
-   * This is a wrapped segwit 2of3 multisig that also uses a relative locktime with
-   * an OP_DROP (requiring a miniscript extension).
+   * This is a segwit (wrapped or native) 2of3 multisig that also uses a
+   * relative locktime with an OP_DROP (requiring a miniscript extension).
    * It is basically what is used in CoreDao staking transactions.
    */
-  | (DescriptorWithKeys<'ShWsh2Of3CltvDrop'> & { locktime: number });
+  | (DescriptorWithKeys<'ShWsh2Of3CltvDrop' | 'Wsh2Of3CltvDrop'> & { locktime: number });
 
 function toXPub(k: BIP32Interface | string): string {
   if (typeof k === 'string') {
@@ -41,8 +41,10 @@ function getDescriptorString(builder: DescriptorBuilder): string {
       return `wsh(${multi(2, 3, builder.keys, builder.path)})`;
     case 'Wsh2Of2':
       return `wsh(${multi(2, 2, builder.keys, builder.path)})`;
+    case 'Wsh2Of3CltvDrop':
+      return `wsh(and_v(r:after(${builder.locktime}),${multi(2, 3, builder.keys, builder.path)}))`;
     case 'ShWsh2Of3CltvDrop':
-      return `sh(wsh(and_v(r:after(${builder.locktime}),${multi(2, 3, builder.keys, builder.path)})))`;
+      return `sh(${getDescriptorString({ ...builder, name: 'Wsh2Of3CltvDrop' })})`;
   }
   throw new Error(`Unknown descriptor template: ${builder}`);
 }

modules/abstract-utxo/src/descriptor/builder/parse.ts

@@ -59,7 +59,7 @@ function parseMulti(node: unknown): {
   };
 }
 
-export function parseDescriptorNode(node: unknown): DescriptorBuilder {
+function parseWshMulti(node: unknown): DescriptorBuilder | undefined {
   const wshMsMulti = unwrapNode(node, ['Wsh', 'Ms', 'Multi']);
   if (wshMsMulti) {
     const { threshold, keys, path } = parseMulti(wshMsMulti);
@@ -77,31 +77,47 @@ export function parseDescriptorNode(node: unknown): DescriptorBuilder {
       path,
     };
   }
+}
 
-  const shWshMsAndV = unwrapNode(node, ['Sh', 'Wsh', 'Ms', 'AndV']);
-  if (shWshMsAndV) {
-    if (Array.isArray(shWshMsAndV) && shWshMsAndV.length === 2) {
-      const [a, b] = shWshMsAndV;
-      const dropAfterAbsLocktime = unwrapNode(a, ['Drop', 'After', 'absLockTime']);
-      if (typeof dropAfterAbsLocktime !== 'number') {
-        throw new Error('Expected absLockTime number');
-      }
-      if (!isUnaryNode(b, 'Multi')) {
-        throw new Error('Expected Multi node');
-      }
-      const multi = parseMulti(b.Multi);
-      if (multi.threshold === 2 && multi.keys.length === 3) {
-        return {
-          name: 'ShWsh2Of3CltvDrop',
-          locktime: dropAfterAbsLocktime,
-          keys: multi.keys,
-          path: multi.path,
-        };
-      }
+function parseCltvDrop(
+  node: unknown,
+  name: 'Wsh2Of3CltvDrop' | 'ShWsh2Of3CltvDrop',
+  wrapping: string[]
+): DescriptorBuilder | undefined {
+  const unwrapped = unwrapNode(node, wrapping);
+  if (!unwrapped) {
+    return;
+  }
+  if (Array.isArray(unwrapped) && unwrapped.length === 2) {
+    const [a, b] = unwrapped;
+    const dropAfterAbsLocktime = unwrapNode(a, ['Drop', 'After', 'absLockTime']);
+    if (typeof dropAfterAbsLocktime !== 'number') {
+      throw new Error('Expected absLockTime number');
+    }
+    if (!isUnaryNode(b, 'Multi')) {
+      throw new Error('Expected Multi node');
+    }
+    const multi = parseMulti(b.Multi);
+    if (multi.threshold === 2 && multi.keys.length === 3) {
+      return {
+        name,
+        locktime: dropAfterAbsLocktime,
+        keys: multi.keys,
+        path: multi.path,
+      };
     }
   }
+}
 
-  throw new Error('Not implemented');
+export function parseDescriptorNode(node: unknown): DescriptorBuilder {
+  const parsed =
+    parseWshMulti(node) ??
+    parseCltvDrop(node, 'ShWsh2Of3CltvDrop', ['Sh', 'Wsh', 'Ms', 'AndV']) ??
+    parseCltvDrop(node, 'Wsh2Of3CltvDrop', ['Wsh', 'Ms', 'AndV']);
+  if (!parsed) {
+    throw new Error('Failed to parse descriptor node');
+  }
+  return parsed;
 }
 
 export function parseDescriptor(descriptor: Descriptor): DescriptorBuilder {

modules/abstract-utxo/src/descriptor/validatePolicy.ts

@@ -61,7 +61,7 @@ export function getPolicyForEnv(env: EnvironmentName): DescriptorValidationPolic
     case 'adminProd':
     case 'prod':
       return {
-        allowedTemplates: ['Wsh2Of3', 'ShWsh2Of3CltvDrop'],
+        allowedTemplates: ['Wsh2Of3', 'Wsh2Of3CltvDrop', 'ShWsh2Of3CltvDrop'],
       };
     default:
       return 'allowAll';

modules/abstract-utxo/test/descriptor/builder.ts

@@ -13,6 +13,7 @@ function getDescriptorBuilderForType(name: DescriptorBuilder['name']): Descripto
         keys: keys.slice(0, name === 'Wsh2Of3' ? 3 : 2),
         path: '0/*',
       };
+    case 'Wsh2Of3CltvDrop':
     case 'ShWsh2Of3CltvDrop':
       return {
         name,
@@ -35,4 +36,5 @@ function describeForName(n: DescriptorBuilder['name']) {
 
 describeForName('Wsh2Of2');
 describeForName('Wsh2Of3');
+describeForName('Wsh2Of3CltvDrop');
 describeForName('ShWsh2Of3CltvDrop');