golang实现google动态认证

网上论坛上看到的域外某大神实现的google 二次验证动态码。这个之间在其他应用上我也有应用过,包括本站在好多年前也已用上该技术,不过通过golang来实现一直没了解,刚好手头的一个小工具,想加上该功能,就先找到了如下代码:



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package main
import (
    "crypto/hmac"
    "crypto/sha1"
    "encoding/base32"
    "fmt"
    "os"
    "strings"
    "time"
)
func toBytes(value int64) []byte {
    var result []byte
    mask := int64(0xFF)
    shifts := [8]uint16{56, 48, 40, 32, 24, 16, 8, 0}
    for _, shift := range shifts {
        result = append(result, byte((value>>shift)&mask))
    }
    return result
}
func toUint32(bytes []byte) uint32 {
    return (uint32(bytes[0]) << 24) + (uint32(bytes[1]) << 16) +
        (uint32(bytes[2]) << 8) + uint32(bytes[3])
}
func oneTimePassword(key []byte, value []byte) uint32 {
    // sign the value using HMAC-SHA1
    hmacSha1 := hmac.New(sha1.New, key)
    hmacSha1.Write(value)
    hash := hmacSha1.Sum(nil)
    // We're going to use a subset of the generated hash.
    // Using the last nibble (half-byte) to choose the index to start from.
    // This number is always appropriate as it's maximum decimal 15, the hash will
    // have the maximum index 19 (20 bytes of SHA1) and we need 4 bytes.
    offset := hash[len(hash)-1] & 0x0F
    // get a 32-bit (4-byte) chunk from the hash starting at offset
    hashParts := hash[offset : offset+4]
    // ignore the most significant bit as per RFC 4226
    hashParts[0] = hashParts[0] & 0x7F
    number := toUint32(hashParts)
    // size to 6 digits
    // one million is the first number with 7 digits so the remainder
    // of the division will always return < 7 digits
    pwd := number % 1000000
    return pwd
}
// all []byte in this program are treated as Big Endian
func main() {
    if len(os.Args) < 2 {
        fmt.Fprintln(os.Stderr, "must specify key to use")
        os.Exit(1)
    }
    input := os.Args[1]
    // decode the key from the first argument
    inputNoSpaces := strings.Replace(input, " ", "", -1)
    inputNoSpacesUpper := strings.ToUpper(inputNoSpaces)
    key, err := base32.StdEncoding.DecodeString(inputNoSpacesUpper)
    if err != nil {
        fmt.Fprintln(os.Stderr, err.Error())
        os.Exit(1)
    }
    // generate a one-time password using the time at 30-second intervals
    epochSeconds := time.Now().Unix()
    pwd := oneTimePassword(key, toBytes(epochSeconds/30))
    secondsRemaining := 30 - (epochSeconds % 30)
    fmt.Printf("%06d (%d second(s) remaining)\n", pwd, secondsRemaining)
}
上面的代码虽然已经很经典了,但在使用时,可能还需要改动下oneTimePassword函数,因为其返回的默认是一个 uint32 类型的值。经常我们通过屏幕输入获取到的是字符串值,这就需要转化为同样类型的值才容易进行比较和调用。修改方式如下:



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func oneTimePassword(key []byte, value []byte) string {
    hmacSha1 := hmac.New(sha1.New, key)
    hmacSha1.Write(value)
    hash := hmacSha1.Sum(nil)
    offset := hash[len(hash)-1] & 0x0F
    hashParts := hash[offset : offset+4]
    hashParts[0] = hashParts[0] & 0x7F
    number := toUint32(hashParts)
    pwd := number % 1000000
    return strconv.Itoa(int(pwd))
具体效果如下:



<img src="https://www.361way.com/wp-content/uploads/2019/06/google-auth.png" alt="" />



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