tapfreighter: validate proof courier address before commencing send

proof/courier.go

@@ -97,8 +97,8 @@ func ParseCourierAddrUrl(addr url.URL) (CourierAddr, error) {
 		return NewHashMailCourierAddr(addr)
 	}
 
-	return nil, fmt.Errorf("unknown courier address protocol: %v",
-		addr.Scheme)
+	return nil, fmt.Errorf("unknown courier address protocol "+
+		"(consider updating tapd): %v", addr.Scheme)
 }
 
 // HashMailCourierAddr is a hashmail protocol specific implementation of the

tapfreighter/chain_porter.go

@@ -795,6 +795,15 @@ func (p *ChainPorter) stateStep(currentPkg sendPackage) (*sendPackage, error) {
 			return nil, fmt.Errorf("unable to cast parcel to " +
 				"address parcel")
 		}
+
+		// Perform basic validation on the address parcel before we
+		// continue.
+		err := p.validateAddrParcel(*addrParcel)
+		if err != nil {
+			return nil, fmt.Errorf("failed to validate address "+
+				"parcel: %w", err)
+		}
+
 		fundSendRes, outputIdxToAddr, err :=
 			p.cfg.AssetWallet.FundAddressSend(
 				ctx, addrParcel.destAddrs...,
@@ -1030,6 +1039,28 @@ func (p *ChainPorter) stateStep(currentPkg sendPackage) (*sendPackage, error) {
 	}
 }
 
+// validateAddrParcel validates the given address parcel.
+func (p *ChainPorter) validateAddrParcel(addrParcel AddressParcel) error {
+	// We need at least one address to send to in an address parcel.
+	if len(addrParcel.destAddrs) < 1 {
+		return fmt.Errorf("at least one Tap address must be " +
+			"specified in address parcel")
+	}
+
+	for idx := range addrParcel.destAddrs {
+		tapAddr := addrParcel.destAddrs[idx]
+
+		// Validate proof courier addresses.
+		_, err := proof.ParseCourierAddrUrl(tapAddr.ProofCourierAddr)
+		if err != nil {
+			return fmt.Errorf("invalid proof courier address: %w",
+				err)
+		}
+	}
+
+	return nil
+}
+
 // RegisterSubscriber adds a new subscriber to the set of subscribers that will
 // be notified of any new events that are broadcast.
 //