Merge pull request #5641 from BitGo/BTC-1826.test-tr1of3-tree.3

feat(utxo-core): add support for descriptors with plain keys

Author: OttoAllmendinger

modules/utxo-core/src/descriptor/psbt/findDescriptors.ts

@@ -14,6 +14,28 @@ import { Descriptor } from '@bitgo/wasm-miniscript';
 
 import { DescriptorMap } from '../DescriptorMap';
 
+type DescriptorWithoutIndex = { descriptor: Descriptor; index: undefined };
+
+/**
+ * Find a definite descriptor in the descriptor map that matches the given script.
+ * @param script
+ * @param descriptorMap
+ */
+function findDescriptorWithoutDerivation(
+  script: Buffer,
+  descriptorMap: DescriptorMap
+): DescriptorWithoutIndex | undefined {
+  for (const descriptor of descriptorMap.values()) {
+    if (!descriptor.hasWildcard()) {
+      if (Buffer.from(descriptor.scriptPubkey()).equals(script)) {
+        return { descriptor, index: undefined };
+      }
+    }
+  }
+
+  return undefined;
+}
+
 type DescriptorWithIndex = { descriptor: Descriptor; index: number };
 
 /**
@@ -29,7 +51,7 @@ function findDescriptorForDerivationIndex(
   descriptorMap: DescriptorMap
 ): DescriptorWithIndex | undefined {
   for (const descriptor of descriptorMap.values()) {
-    if (Buffer.from(descriptor.atDerivationIndex(index).scriptPubkey()).equals(script)) {
+    if (descriptor.hasWildcard() && Buffer.from(descriptor.atDerivationIndex(index).scriptPubkey()).equals(script)) {
       return { descriptor, index };
     }
   }
@@ -92,16 +114,16 @@ function getDerivationPaths(v: WithBip32Derivation | WithTapBip32Derivation): st
 export function findDescriptorForInput(
   input: PsbtInput,
   descriptorMap: DescriptorMap
-): DescriptorWithIndex | undefined {
+): DescriptorWithIndex | DescriptorWithoutIndex | undefined {
   const script = input.witnessUtxo?.script;
   if (!script) {
     throw new Error('Missing script');
   }
-  const derivationPaths = getDerivationPaths(input);
-  if (!derivationPaths) {
-    throw new Error('Missing derivation paths');
-  }
-  return findDescriptorForAnyDerivationPath(script, derivationPaths, descriptorMap);
+  const derivationPaths = getDerivationPaths(input) ?? [];
+  return (
+    findDescriptorWithoutDerivation(script, descriptorMap) ??
+    findDescriptorForAnyDerivationPath(script, derivationPaths, descriptorMap)
+  );
 }
 
 /**

modules/utxo-core/src/descriptor/psbt/parse.ts

@@ -7,7 +7,7 @@ import { getVirtualSize } from '../VirtualSize';
 import { findDescriptorForInput, findDescriptorForOutput } from './findDescriptors';
 import { assertSatisfiable } from './assertSatisfiable';
 
-export type ScriptId = { descriptor: Descriptor; index: number };
+export type ScriptId = { descriptor: Descriptor; index: number | undefined };
 
 export type ParsedInput = {
   address: string;
@@ -46,15 +46,15 @@ export function parse(
     if (!input.witnessUtxo.value) {
       throw new Error('invalid input: no value');
     }
-    const descriptorWithIndex = findDescriptorForInput(input, descriptorMap);
-    if (!descriptorWithIndex) {
+    const scriptId = findDescriptorForInput(input, descriptorMap);
+    if (!scriptId) {
       throw new Error('invalid input: no descriptor found');
     }
-    assertSatisfiable(psbt, inputIndex, descriptorWithIndex.descriptor);
+    assertSatisfiable(psbt, inputIndex, scriptId.descriptor);
     return {
       address: utxolib.address.fromOutputScript(input.witnessUtxo.script, network),
       value: input.witnessUtxo.value,
-      scriptId: descriptorWithIndex,
+      scriptId: scriptId,
     };
   });
   const outputs = psbt.txOutputs.map((output, i): ParsedOutput => {

modules/utxo-core/src/testutil/descriptor/descriptors.ts

@@ -1,7 +1,7 @@
 import assert from 'assert';
 
 import { Descriptor, ast } from '@bitgo/wasm-miniscript';
-import { BIP32Interface } from '@bitgo/utxo-lib';
+import { bip32, BIP32Interface } from '@bitgo/utxo-lib';
 
 import { DescriptorMap, PsbtParams } from '../../descriptor';
 import { getKeyTriple, Triple, KeyTriple } from '../key.utils';
@@ -41,6 +41,8 @@ function toDescriptorMap(v: Record<string, string>): DescriptorMap {
 export type DescriptorTemplate =
   | 'Wsh2Of3'
   | 'Tr1Of3-NoKeyPath-Tree'
+  // no xpubs, just plain keys
+  | 'Tr1Of3-NoKeyPath-Tree-Plain'
   | 'Tr2Of3-NoKeyPath'
   | 'Wsh2Of2'
   /*
@@ -57,6 +59,20 @@ function toXPub(k: BIP32Interface | string, path: string): string {
   return k.neutered().toBase58() + '/' + path;
 }
 
+function toPlain(k: BIP32Interface | string, { xonly = false } = {}): string {
+  if (typeof k === 'string') {
+    if (k.startsWith('xpub') || k.startsWith('xprv')) {
+      return toPlain(bip32.fromBase58(k), { xonly });
+    }
+    return k;
+  }
+  return k.publicKey.subarray(xonly ? 1 : 0).toString('hex');
+}
+
+function toXOnly(k: BIP32Interface | string): string {
+  return toPlain(k, { xonly: true });
+}
+
 function multiArgs(m: number, n: number, keys: BIP32Interface[] | string[], path: string): [number, ...string[]] {
   if (n < m) {
     throw new Error(`Cannot create ${m} of ${n} multisig`);
@@ -70,13 +86,10 @@ function multiArgs(m: number, n: number, keys: BIP32Interface[] | string[], path
 
 export function getPsbtParams(t: DescriptorTemplate): Partial<PsbtParams> {
   switch (t) {
-    case 'Wsh2Of3':
-    case 'Wsh2Of2':
-    case 'Tr1Of3-NoKeyPath-Tree':
-    case 'Tr2Of3-NoKeyPath':
-      return {};
     case 'Wsh2Of3CltvDrop':
       return { locktime: 1 };
+    default:
+      return {};
   }
 }
 
@@ -113,16 +126,29 @@ function getDescriptorNode(
           [{ pk: toXPub(keys[0], path) }, [{ pk: toXPub(keys[1], path) }, { pk: toXPub(keys[2], path) }]],
         ],
       };
+    case 'Tr1Of3-NoKeyPath-Tree-Plain':
+      return {
+        tr: [getUnspendableKey(), [{ pk: toXOnly(keys[0]) }, [{ pk: toXOnly(keys[1]) }, { pk: toXOnly(keys[2]) }]]],
+      };
   }
   throw new Error(`Unknown descriptor template: ${template}`);
 }
 
+function getDescriptorType(template: DescriptorTemplate): 'derivable' | 'definite' {
+  switch (template) {
+    case 'Tr1Of3-NoKeyPath-Tree-Plain':
+      return 'definite';
+    default:
+      return 'derivable';
+  }
+}
+
 export function getDescriptor(
   template: DescriptorTemplate,
   keys: KeyTriple | string[] = getDefaultXPubs(),
   path = '0/*'
 ): Descriptor {
-  return Descriptor.fromString(ast.formatNode(getDescriptorNode(template, keys, path)), 'derivable');
+  return Descriptor.fromString(ast.formatNode(getDescriptorNode(template, keys, path)), getDescriptorType(template));
 }
 
 export function getDescriptorMap(

modules/utxo-core/src/testutil/descriptor/mock.utils.ts

@@ -52,16 +52,20 @@ type MockOutput = {
   external?: boolean;
 };
 
+function tryDeriveAtIndex(descriptor: Descriptor, index: number): Descriptor {
+  return descriptor.hasWildcard() ? descriptor.atDerivationIndex(index) : descriptor;
+}
+
 export function mockPsbt(
   inputs: MockInput[],
   outputs: MockOutput[],
   params: Partial<PsbtParams> = {}
 ): utxolib.bitgo.UtxoPsbt {
   return createPsbt(
     { ...params, network: params.network ?? utxolib.networks.bitcoin },
-    inputs.map((i) => mockDerivedDescriptorWalletOutput(i.descriptor.atDerivationIndex(i.index), i)),
+    inputs.map((i) => mockDerivedDescriptorWalletOutput(tryDeriveAtIndex(i.descriptor, i.index), i)),
     outputs.map((o) => {
-      const derivedDescriptor = o.descriptor.atDerivationIndex(o.index);
+      const derivedDescriptor = tryDeriveAtIndex(o.descriptor, o.index);
       return {
         script: createScriptPubKeyFromDescriptor(derivedDescriptor),
         value: o.value,