xcore: more security for HDKeyRand and add EstimateNormalSize to pre-…

…computed P2PKH transaction size

xcore/bip32/hdkey.go

@@ -7,11 +7,10 @@ package bip32
 
 import (
 	"bytes"
+	"crypto/rand"
 	"fmt"
-	"math/rand"
 	"strconv"
 	"strings"
-	"time"
 
 	"crypto/hmac"
 	"crypto/sha512"
@@ -84,8 +83,7 @@ func NewHDKey(seed []byte) *HDKey {
 // NewHDKeyRand -- returns the HDKey with random seed.
 func NewHDKeyRand() (*HDKey, error) {
 	seed := make([]byte, 256)
-	random := rand.New(rand.NewSource(time.Now().UnixNano()))
-	if _, err := random.Read(seed); err != nil {
+	if _, err := rand.Read(seed); err != nil {
 		return nil, err
 	}
 	return NewHDKey(seed), nil

xcore/estimate.go

@@ -98,6 +98,33 @@ func EstimateSize(txins []*TxIn, txouts []*TxOut) int64 {
 	return int64((baseSize*(witnessScaleFactor-1) + (baseSize + witnessSize)) / witnessScaleFactor)
 }
 
+// EstimateNormalSize -- estimate the normal size by input and output count.
+func EstimateNormalSize(ins int, outs int) int64 {
+	baseSize := 0
+
+	// Core size.
+	{
+		// Version.
+		baseSize += 4
+		// Input size.
+		{
+			baseSize += xbase.VarIntSerializeSize(uint64(ins))
+			baseSize += inputP2PKHSize * ins
+		}
+
+		// Output size.
+		{
+			baseSize += xbase.VarIntSerializeSize(uint64(outs))
+			// 8 value size.
+			// 25 is the p2pkh script length.
+			baseSize += (8 + 25) * outs
+		}
+		// Locktime.
+		baseSize += 4
+	}
+	return int64(baseSize)
+}
+
 // EstimateFees -- estimate the fee.
 func EstimateFees(estimateSize int64, relayFeePerKb int64) int64 {
 	fees := 0.0

xcore/estimate_test.go

@@ -0,0 +1,17 @@
+// tokucore
+//
+// Copyright (c) 2019 TokuBlock
+// BSD License
+
+package xcore
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEstimateNormalSize(t *testing.T) {
+	size := EstimateNormalSize(2, 2)
+	assert.Equal(t, int64(374), size)
+}