reuse HMAC hasher

Author: Snawoot

handler/handler.go

@@ -3,6 +3,8 @@ package handler
 import (
 	"bufio"
 	"bytes"
+	chmac "crypto/hmac"
+	"crypto/sha256"
 	"fmt"
 	"io"
 
@@ -28,6 +30,8 @@ func (a *BasicHMACAuthHandler) Run(input io.Reader, output io.Writer) error {
 	rd := bufio.NewReaderSize(input, bufSize)
 	scanner := proto.NewElasticLineScanner(rd, '\n')
 
+	mac := chmac.New(sha256.New, a.Secret)
+
 	for scanner.Scan() {
 		parts := bytes.SplitN(scanner.Bytes(), []byte{' '}, 4)
 		if len(parts) < 3 {
@@ -38,7 +42,7 @@ func (a *BasicHMACAuthHandler) Run(input io.Reader, output io.Writer) error {
 		username := proto.RFC1738Unescape(parts[1])
 		password := proto.RFC1738Unescape(parts[2])
 
-		if hmac.VerifyHMACLoginAndPassword(a.Secret, username, password) {
+		if hmac.VerifyHMACLoginAndPassword(mac, username, password) {
 			fmt.Fprintf(output, "%s OK\n", channelID)
 		} else {
 			fmt.Fprintf(output, "%s ERR\n", channelID)

hmac/hmac.go

@@ -3,9 +3,9 @@ package hmac
 import (
 	"bytes"
 	"crypto/hmac"
-	"crypto/sha256"
 	"encoding/base64"
 	"encoding/binary"
+	"hash"
 	"time"
 )
 
@@ -21,7 +21,7 @@ type HMACToken struct {
 	Signature [HMACSignatureSize]byte
 }
 
-func VerifyHMACLoginAndPassword(secret, login, password []byte) bool {
+func VerifyHMACLoginAndPassword(mac hash.Hash, login, password []byte) bool {
 	rd := base64.NewDecoder(base64.RawURLEncoding, bytes.NewReader(password))
 
 	var token HMACToken
@@ -33,12 +33,12 @@ func VerifyHMACLoginAndPassword(secret, login, password []byte) bool {
 		return false
 	}
 
-	expectedMAC := CalculateHMACSignature(secret, login, token.Expire)
+	expectedMAC := CalculateHMACSignature(mac, login, token.Expire)
 	return hmac.Equal(token.Signature[:], expectedMAC)
 }
 
-func CalculateHMACSignature(secret, username []byte, expire int64) []byte {
-	mac := hmac.New(sha256.New, secret)
+func CalculateHMACSignature(mac hash.Hash, username []byte, expire int64) []byte {
+	mac.Reset()
 	mac.Write(hmacSignaturePrefix)
 	mac.Write(username)
 	binary.Write(mac, binary.BigEndian, expire)