Check actual sighash flags instead of psbtInput one

src/psbt.js

@@ -815,17 +815,15 @@ function checkTxEmpty(tx) {
 function checkInputsForPartialSig(inputs, action) {
   inputs.forEach(input => {
     let throws = false;
-    if ((input.partialSig || []).length > 0) {
-      if (input.sighashType !== undefined) {
+    if ((input.partialSig || []).length === 0) return;
+    input.partialSig.forEach(pSig => {
+      const { hashType } = bscript.signature.decode(pSig.signature);
       const whitelist = [];
       const isAnyoneCanPay =
-          input.sighashType & transaction_1.Transaction.SIGHASH_ANYONECANPAY;
+        hashType & transaction_1.Transaction.SIGHASH_ANYONECANPAY;
       if (isAnyoneCanPay) whitelist.push('addInput');
-        if (!isAnyoneCanPay && action === 'addInput') {
-          throws = true;
-        }
-        const hashType = input.sighashType & 0x1f;
-        switch (hashType) {
+      const hashMod = hashType & 0x1f;
+      switch (hashMod) {
         case transaction_1.Transaction.SIGHASH_ALL:
           break;
         case transaction_1.Transaction.SIGHASH_SINGLE:
@@ -837,10 +835,7 @@ function checkInputsForPartialSig(inputs, action) {
       if (whitelist.indexOf(action) === -1) {
         throws = true;
       }
-      } else {
-        throws = true;
-      }
-    }
+    });
     if (throws) {
       throw new Error('Can not modify transaction, signatures exist.');
     }

ts_src/psbt.ts

@@ -1028,17 +1028,14 @@ function checkTxEmpty(tx: Transaction): void {
 function checkInputsForPartialSig(inputs: PsbtInput[], action: string): void {
   inputs.forEach(input => {
     let throws = false;
-    if ((input.partialSig || []).length > 0) {
-      if (input.sighashType !== undefined) {
+    if ((input.partialSig || []).length === 0) return;
+    input.partialSig!.forEach(pSig => {
+      const { hashType } = bscript.signature.decode(pSig.signature);
       const whitelist: string[] = [];
-        const isAnyoneCanPay =
-          input.sighashType & Transaction.SIGHASH_ANYONECANPAY;
+      const isAnyoneCanPay = hashType & Transaction.SIGHASH_ANYONECANPAY;
       if (isAnyoneCanPay) whitelist.push('addInput');
-        if (!isAnyoneCanPay && action === 'addInput') {
-          throws = true;
-        }
-        const hashType = input.sighashType & 0x1f;
-        switch (hashType) {
+      const hashMod = hashType & 0x1f;
+      switch (hashMod) {
         case Transaction.SIGHASH_ALL:
           break;
         case Transaction.SIGHASH_SINGLE:
@@ -1050,10 +1047,7 @@ function checkInputsForPartialSig(inputs: PsbtInput[], action: string): void {
       if (whitelist.indexOf(action) === -1) {
         throws = true;
       }
-      } else {
-        throws = true;
-      }
-    }
+    });
     if (throws) {
       throw new Error('Can not modify transaction, signatures exist.');
     }