From 6777071bc368c723c66501d287b3eaa38009123a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=84=E8=8B=8F=E7=A3=8A?= <466977183@qq.com>
Date: Thu, 15 Dec 2016 09:55:21 +0800
Subject: [PATCH] =?UTF-8?q?=E5=AE=8C=E6=88=90=E4=B8=BB=E4=BD=93=E9=80=BB?=
 =?UTF-8?q?=E8=BE=91?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md    |   3 +-
 outh.go      | 109 +++++++++++++++++++++++++++++++++++++++++++++++++++
 outh_test.go |   1 +
 3 files changed, 112 insertions(+), 1 deletion(-)
 create mode 100644 outh.go
 create mode 100644 outh_test.go

diff --git a/README.md b/README.md
index e212f70..d5e5681 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,2 @@
-# totp
\ No newline at end of file
+# TOTP-go
+使用`go`语言实现RFC6238。通过RFC6238中的java代码。用`go`实现一遍。
\ No newline at end of file
diff --git a/outh.go b/outh.go
new file mode 100644
index 0000000..5b804e2
--- /dev/null
+++ b/outh.go
@@ -0,0 +1,109 @@
+//实现outh算法
+package totp
+
+import (
+	"crypto/hmac"
+	"crypto/sha1"
+	"crypto/sha256"
+	"crypto/sha512"
+	"errors"
+	"hash"
+	"math/big"
+	"strconv"
+)
+
+const (
+	SHA1 uint8 = iota
+	SHA256
+	SHA512
+)
+
+//生成Hmac的值 (没有问题)
+func getHMACData(crypto uint8, keyBytes, textBytes []byte) ([]byte, error) {
+	var mac hash.Hash
+
+	switch crypto {
+	case SHA1:
+		mac = hmac.New(sha1.New, keyBytes)
+	case SHA256:
+		mac = hmac.New(sha256.New, keyBytes)
+	case SHA512:
+		mac = hmac.New(sha512.New, keyBytes)
+	}
+	//根据RFC6238中，对keyBytes没有做特殊的处理， 因此直接使用keyBytes中的原始数据
+
+	_, err := mac.Write(textBytes)
+	if err != nil {
+		return nil, err
+	}
+	return mac.Sum(nil), nil
+}
+
+func GeneratorTOTPSHA1(key, time string, returnNum int) (string, error) {
+	return generatorTOTP(SHA1, key, time, returnNum)
+}
+
+func GeneratorTOTPSHA256(key, time string, returnNum int) (string, error) {
+	return generatorTOTP(SHA256, key, time, returnNum)
+}
+
+func GeneratorTOTPSHA512(key, time string, returnNum int) (string, error) {
+	return generatorTOTP(SHA512, key, time, returnNum)
+}
+
+//把hex 转换成[]byte （）
+func hexStr2Bytes(hexstr string) ([]byte, bool) {
+	a := &big.Int{}
+	bInt, ok := a.SetString("10"+hexstr, 16)
+	if !ok {
+		return nil, false
+	}
+	bArray := bInt.Bytes()
+	ret := bArray[1:]
+	return ret, true
+}
+
+var DIGITS_POWER map[int]int
+
+func init() {
+	DIGITS_POWER = make(map[int]int, 9)
+	DIGITS_POWER[0] = 1
+	DIGITS_POWER[1] = 10
+	DIGITS_POWER[2] = 100
+	DIGITS_POWER[3] = 1000
+	DIGITS_POWER[4] = 10000
+	DIGITS_POWER[5] = 100000
+	DIGITS_POWER[6] = 1000000
+	DIGITS_POWER[7] = 10000000
+	DIGITS_POWER[8] = 100000000
+}
+
+//key私钥，time偏移时间，return 返回数量
+func generatorTOTP(crypto uint8, key, time string, returnNum int) (string, error) {
+	var result string
+	for len(time) < 16 {
+		time = "0" + time
+	}
+	msg, ok := hexStr2Bytes(time)
+	if !ok {
+		return "", errors.New("time 无法转化成byte数组")
+	}
+	k, ok := hexStr2Bytes(key)
+	if !ok {
+		return "", errors.New("key 无法转换成byte数组")
+	}
+
+	hash, err := getHMACData(crypto, k, msg)
+	if err != nil {
+		return "", err
+	}
+	offset := int(hash[len(hash)-1] & 0xf)
+
+	binary := (((int)(hash[offset]) & 0x7f) << 24) | (((int)(hash[offset+1]) & 0xff) << 16) | (((int)(hash[offset+2]) & 0xff) << 8) | ((int)(hash[offset+3]) & 0xff)
+	otp := binary % DIGITS_POWER[returnNum]
+	result = strconv.Itoa(otp)
+	for len(result) < returnNum {
+		result = "0" + result
+	}
+	return result, nil
+}
diff --git a/outh_test.go b/outh_test.go
new file mode 100644
index 0000000..90ccdb3
--- /dev/null
+++ b/outh_test.go
@@ -0,0 +1 @@
+package totp