Support unknown psbt keypairs (#119)

* support unknown psbt keypairs

* rename testcase

* cleaning comment

* TxOpts: add allowUnknown flag

* run format

* remove "ESM is broken" lines

src/psbt.ts

@@ -458,7 +458,8 @@ export function mergeKeyMap<T extends PSBTKeyMap>(
   psbtEnum: T,
   val: PSBTKeyMapKeys<T>,
   cur?: PSBTKeyMapKeys<T>,
-  allowedFields?: (keyof PSBTKeyMapKeys<T>)[]
+  allowedFields?: (keyof PSBTKeyMapKeys<T>)[],
+  allowUnknown?: boolean
 ): PSBTKeyMapKeys<T> {
   const res: PSBTKeyMapKeys<T> = { ...cur, ...val };
   // All arguments can be provided as hex
@@ -517,8 +518,13 @@ export function mergeKeyMap<T extends PSBTKeyMap>(
         throw new Error(`Cannot change signed field=${k}`);
     }
   }
-  // Remove unknown keys
-  for (const k in res) if (!psbtEnum[k]) delete res[k];
+  // Remove unknown keys except the "unknown" array if allowUnknown is true
+  for (const k in res) {
+    if (!psbtEnum[k]) {
+      if (allowUnknown && k === 'unknown') continue;
+      delete res[k];
+    }
+  }
   return res;
 }
 

src/transaction.ts

@@ -61,7 +61,7 @@ export function cloneDeep<T>(obj: T): T {
 
 // Mostly security features, hardened defaults;
 // but you still can parse other people tx with unspendable outputs and stuff if you want
-export type TxOpts = {
+export interface TxOpts {
   version?: number;
   lockTime?: number;
   PSBTVersion?: number;
@@ -84,7 +84,9 @@ export type TxOpts = {
   allowLegacyWitnessUtxo?: boolean;
   lowR?: boolean; // Use lowR signatures
   customScripts?: CustomScript[]; // UNSAFE: Custom payment scripts
-};
+  // Allow to add additional unknown keys/values to the "unknown" array member
+  allowUnknown?: boolean;
+}
 
 /**
  * Internal, exported only for backwards-compat. Use `SigHash` instead.
@@ -520,7 +522,8 @@ export class Transaction {
       input,
       this.inputs[idx],
       allowedFields,
-      this.opts.disableScriptCheck
+      this.opts.disableScriptCheck,
+      this.opts.allowUnknown
     );
   }
   // Output stuff
@@ -556,7 +559,7 @@ export class Transaction {
     if (script === undefined) script = cur?.script;
     let res: psbt.PSBTKeyMapKeys<typeof psbt.PSBTOutput> = { ...cur, ...o, amount, script };
     if (res.amount === undefined) delete res.amount;
-    res = psbt.mergeKeyMap(psbt.PSBTOutput, res, cur, allowedFields);
+    res = psbt.mergeKeyMap(psbt.PSBTOutput, res, cur, allowedFields, this.opts.allowUnknown);
     psbt.PSBTOutputCoder.encode(res);
     if (
       res.script &&
@@ -1070,7 +1073,13 @@ export class Transaction {
       : P.EMPTY;
     if (!equalBytes(thisUnsigned, otherUnsigned))
       throw new Error(`Transaction/combine: different unsigned tx`);
-    this.global = psbt.mergeKeyMap(psbt.PSBTGlobal, this.global, other.global);
+    this.global = psbt.mergeKeyMap(
+      psbt.PSBTGlobal,
+      this.global,
+      other.global,
+      undefined,
+      this.opts.allowUnknown
+    );
     for (let i = 0; i < this.inputs.length; i++) this.updateInput(i, other.inputs[i], true);
     for (let i = 0; i < this.outputs.length; i++) this.updateOutput(i, other.outputs[i], true);
     return this;

src/utxo.ts

@@ -37,7 +37,8 @@ export function normalizeInput(
   i: psbt.TransactionInputUpdate,
   cur?: psbt.TransactionInput,
   allowedFields?: (keyof psbt.TransactionInput)[],
-  disableScriptCheck = false
+  disableScriptCheck = false,
+  allowUnknown = false
 ): psbt.TransactionInput {
   let { nonWitnessUtxo, txid } = i;
   // String support for common fields. We usually prefer Uint8Array to avoid errors
@@ -55,7 +56,7 @@ export function normalizeInput(
   if (!('nonWitnessUtxo' in i) && res.nonWitnessUtxo === undefined) delete res.nonWitnessUtxo;
   if (res.sequence === undefined) res.sequence = DEFAULT_SEQUENCE;
   if (res.tapMerkleRoot === null) delete res.tapMerkleRoot;
-  res = psbt.mergeKeyMap(psbt.PSBTInput, res, cur, allowedFields);
+  res = psbt.mergeKeyMap(psbt.PSBTInput, res, cur, allowedFields, allowUnknown);
   psbt.PSBTInputCoder.encode(res); // Validates that everything is correct at this point
 
   let prevOut;
@@ -410,7 +411,13 @@ export class _Estimator {
     }
     const inputKeys = new Set();
     this.normalizedInputs = allInputs.map((i) => {
-      const normalized = normalizeInput(i, undefined, undefined, opts.disableScriptCheck);
+      const normalized = normalizeInput(
+        i,
+        undefined,
+        undefined,
+        opts.disableScriptCheck,
+        opts.allowUnknown
+      );
       inputBeforeSign(normalized); // check fields
       const key = `${hex.encode(normalized.txid!)}:${normalized.index}`;
       if (!opts.allowSameUtxo && inputKeys.has(key))

test/bip174-psbt.test.js

@@ -248,4 +248,36 @@ should('bip174-psbt: PSBT garbage', () => {
   );
 });
 
+should('bip174-psbt: PSBT unknown keys', () => {
+  const tx =  hex.decode(
+    '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'
+  )
+
+  const psbtWithoutAllowUnknown = btc.Transaction.fromPSBT(tx);
+  const psbtWithAllowUnknown = btc.Transaction.fromPSBT(tx, { allowUnknown: true });
+
+  const unknown = [
+    [{ type: 0xff, key: new Uint8Array(Buffer.from('unknownKey1')) }, new Uint8Array(Buffer.from('unknownValue1'))],
+    [{ type: 0xff, key: new Uint8Array(Buffer.from('unknownKey2')) }, new Uint8Array(Buffer.from('unknownValue2'))],
+  ]
+
+  // input unknown key
+  psbtWithoutAllowUnknown.updateInput(0, { unknown });
+  psbtWithAllowUnknown.updateInput(0, { unknown });
+
+  // output unknown key
+  psbtWithoutAllowUnknown.updateOutput(0, { unknown });
+  psbtWithAllowUnknown.updateOutput(0, { unknown });
+  // verify the unknown key is preserved only if the flag is set
+  deepStrictEqual(psbtWithAllowUnknown.outputs[0].unknown, unknown);
+  deepStrictEqual(psbtWithAllowUnknown.inputs[0].unknown, unknown);
+  deepStrictEqual(psbtWithoutAllowUnknown.outputs[0].unknown, undefined);
+  deepStrictEqual(psbtWithoutAllowUnknown.inputs[0].unknown, undefined);
+
+  // verify the unknown key is preserved with serialization
+  const psbt2 = btc.Transaction.fromPSBT(psbtWithAllowUnknown.toPSBT());
+  deepStrictEqual(psbt2.outputs[0].unknown, unknown);
+  deepStrictEqual(psbt2.inputs[0].unknown, unknown);
+});
+
 should.runWhen(import.meta.url);