allow psbt signature verification to be deferred

src/main/java/com/sparrowwallet/drongo/psbt/PSBT.java

@@ -16,7 +16,7 @@ import java.nio.ByteBuffer;
 import java.util.*;
 
 import static com.sparrowwallet.drongo.psbt.PSBTEntry.*;
-import static com.sparrowwallet.drongo.psbt.PSBTInput.PSBT_IN_BIP32_DERIVATION;
+import static com.sparrowwallet.drongo.psbt.PSBTInput.*;
 import static com.sparrowwallet.drongo.psbt.PSBTOutput.*;
 
 public class PSBT {
@@ -169,11 +169,15 @@ public class PSBT {
     }
 
     public PSBT(byte[] psbt) throws PSBTParseException {
-        this.psbtBytes = psbt;
+        this(psbt, true);
-        parse();
     }
 
-    private void parse() throws PSBTParseException {
+    public PSBT(byte[] psbt, boolean verifySignatures) throws PSBTParseException {
+        this.psbtBytes = psbt;
+        parse(verifySignatures);
+    }
+
+    private void parse(boolean verifySignatures) throws PSBTParseException {
         int seenInputs = 0;
         int seenOutputs = 0;
 
@@ -214,7 +218,7 @@ public class PSBT {
                         seenInputs++;
                         if (seenInputs == inputs) {
                             currentState = STATE_OUTPUTS;
-                            parseInputEntries(inputEntryLists);
+                            parseInputEntries(inputEntryLists, verifySignatures);
                         }
                         break;
                     case STATE_OUTPUTS:
@@ -315,7 +319,7 @@ public class PSBT {
         }
     }
 
-    private void parseInputEntries(List<List<PSBTEntry>> inputEntryLists) throws PSBTParseException {
+    private void parseInputEntries(List<List<PSBTEntry>> inputEntryLists, boolean verifySignatures) throws PSBTParseException {
         for(List<PSBTEntry> inputEntries : inputEntryLists) {
             PSBTEntry duplicate = findDuplicateKey(inputEntries);
             if(duplicate != null) {
@@ -325,9 +329,11 @@ public class PSBT {
             int inputIndex = this.psbtInputs.size();
             PSBTInput input = new PSBTInput(inputEntries, transaction, inputIndex);
 
+            if(verifySignatures) {
                 boolean verified = input.verifySignatures();
                 if(!verified && input.getPartialSignatures().size() > 0) {
-                throw new PSBTParseException("Unverifiable partial signatures provided");
+                    throw new PSBTSignatureException("Unverifiable partial signatures provided");
+                }
             }
 
             this.psbtInputs.add(input);
@@ -379,6 +385,19 @@ public class PSBT {
         return fee;
     }
 
+    public void verifySignatures() throws PSBTSignatureException {
+        for(PSBTInput input : getPsbtInputs()) {
+            boolean verified = input.verifySignatures();
+            if(!verified) {
+                if(input.getPartialSignatures().size() > 0) {
+                    throw new PSBTSignatureException("Unverifiable partial signatures provided");
+                }
+
+                throw new PSBTSignatureException("No UTXO data provided");
+            }
+        }
+    }
+
     public boolean hasSignatures() {
         for(PSBTInput psbtInput : getPsbtInputs()) {
             if(!psbtInput.getPartialSignatures().isEmpty() || psbtInput.getFinalScriptSig() != null || psbtInput.getFinalScriptWitness() != null) {
@@ -630,6 +649,10 @@ public class PSBT {
     }
 
     public static PSBT fromString(String strPSBT) throws PSBTParseException {
+        return fromString(strPSBT, true);
+    }
+
+    public static PSBT fromString(String strPSBT, boolean verifySignatures) throws PSBTParseException {
         if (!isPSBT(strPSBT)) {
             throw new PSBTParseException("Provided string is not a PSBT");
         }
@@ -639,6 +662,6 @@ public class PSBT {
         }
 
         byte[] psbtBytes = Utils.hexToBytes(strPSBT);
-        return new PSBT(psbtBytes);
+        return new PSBT(psbtBytes, verifySignatures);
     }
 }

src/main/java/com/sparrowwallet/drongo/psbt/PSBTInput.java

@@ -136,12 +136,16 @@ public class PSBTInput {
                             throw new PSBTParseException("Witness UTXO provided but redeem script is not P2WPKH or P2WSH");
                         }
                     }
-                    if(scriptPubKey == null || !P2SH.isScriptType(scriptPubKey)) {
+                    if(scriptPubKey == null) {
+                        log.warn("PSBT provided a redeem script for a transaction output that was not provided");
+                    } else {
+                        if(!P2SH.isScriptType(scriptPubKey)) {
                             throw new PSBTParseException("PSBT provided a redeem script for a transaction output that does not need one");
                         }
                         if(!Arrays.equals(Utils.sha256hash160(redeemScript.getProgram()), scriptPubKey.getPubKeyHash())) {
                             throw new PSBTParseException("Redeem script hash does not match transaction output script pubkey hash " + Utils.bytesToHex(scriptPubKey.getPubKeyHash()));
                         }
+                    }
 
                     this.redeemScript = redeemScript;
                     log.debug("Found input redeem script hex " + Utils.bytesToHex(redeemScript.getProgram()) + " script " + redeemScript);
@@ -156,7 +160,7 @@ public class PSBTInput {
                         pubKeyHash = this.witnessUtxo.getScript().getPubKeyHash();
                     }
                     if(pubKeyHash == null) {
-                        throw new PSBTParseException("Witness script provided without P2WSH witness utxo or P2SH redeem script");
+                        log.warn("Witness script provided without P2WSH witness utxo or P2SH redeem script");
                     } else if(!Arrays.equals(Sha256Hash.hash(witnessScript.getProgram()), pubKeyHash)) {
                         throw new PSBTParseException("Witness script hash does not match provided pay to script hash " + Utils.bytesToHex(pubKeyHash));
                     }
@@ -428,7 +432,7 @@ public class PSBTInput {
         return false;
     }
 
-    boolean verifySignatures() throws PSBTParseException {
+    boolean verifySignatures() throws PSBTSignatureException {
         SigHash localSigHash = getSigHash();
         if(localSigHash == null) {
             //Assume SigHash.ALL
@@ -443,7 +447,7 @@ public class PSBTInput {
                 for(ECKey sigPublicKey : getPartialSignatures().keySet()) {
                     TransactionSignature signature = getPartialSignature(sigPublicKey);
                     if(!sigPublicKey.verify(hash, signature)) {
-                        throw new PSBTParseException("Partial signature does not verify against provided public key");
+                        throw new PSBTSignatureException("Partial signature does not verify against provided public key");
                     }
                 }
 

src/main/java/com/sparrowwallet/drongo/psbt/PSBTSignatureException.java

@@ -0,0 +1,19 @@
+package com.sparrowwallet.drongo.psbt;
+
+public class PSBTSignatureException extends PSBTParseException {
+    public PSBTSignatureException() {
+        super();
+    }
+
+    public PSBTSignatureException(String message) {
+        super(message);
+    }
+
+    public PSBTSignatureException(Throwable cause) {
+        super(cause);
+    }
+
+    public PSBTSignatureException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}