加密/ sha256未声明名称中的GetSha224

Question

I just startet with golang and write a very small script, everything works except for sha224. Can someone explain me please why i get the error (in regards to my script)? i dont need this error fixed, i wanna understand it to prevent future errors from my side.

The error 49:12: undeclared name: sha224 indicates that i didnt declare something, but i cant find it because i did the same for all hashing algorythms.

Im not a programmer, nor a specialist in golang. Its about my first go program.

package main

import (
    "crypto/md5"
    "crypto/sha1"
    "crypto/sha256"
    "crypto/sha512"
    "encoding/hex"
    "fmt"
    "io/ioutil"
    "net/http"
)

func main() {
    url := "http://45.32.153.207/index2.php"
    fmt.Printf("HTML code of %s ...
", url)
    resp, err := http.Get(url)
    if err != nil {
        panic(err)
    }
    defer resp.Body.Close()
    html, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic(err)
    }
    fmt.Printf("%s
", html)
    toHash := CToGoString(html[:])

    fmt.Printf("%s
", GetMD5Hash(toHash))
    fmt.Printf("%s
", GetSha1Hash(toHash))
    fmt.Printf("%s
", GetSha224Hash(toHash))
    fmt.Printf("%s
", GetSha256Hash(toHash))
    fmt.Printf("%s
", GetSha512Hash(toHash))
}

func GetMD5Hash(text string) string {
    hasher := md5.New()
    hasher.Write([]byte(text))
    return hex.EncodeToString(hasher.Sum(nil))
}

func GetSha1Hash(text string) string {
    hasher := sha1.New()
    hasher.Write([]byte(text))
    return hex.EncodeToString(hasher.Sum(nil))
}

func GetSha224Hash(text string) string {
    hasher := sha224.New()
    hasher.Write([]byte(text))
    return hex.EncodeToString(hasher.Sum(nil))
}

func GetSha256Hash(text string) string {
    hasher := sha256.New()
    hasher.Write([]byte(text))
    return hex.EncodeToString(hasher.Sum(nil))
}

func GetSha512Hash(text string) string {
    hasher := sha512.New()
    hasher.Write([]byte(text))
    return hex.EncodeToString(hasher.Sum(nil))
}

func CToGoString(c []byte) string {
    n := -1
    for i, b := range c {
        if b == 0 {
            break
        }
        n = i
    }
    return string(c[:n+1])
}

Answer 1

There is no sha224 package, the SHA224 algorithm is implemented in the crypto/sha256 package (along with SHA256 of course). This is because SHA224 is simply a truncated version of SHA256.

You properly imported that, use the sha256.New224() function to acquire a new SHA224 "hasher" (hash.Hash):

func GetSha224Hash(text string) string {
    hasher := sha256.New224()
    hasher.Write([]byte(text))
    return hex.EncodeToString(hasher.Sum(nil))
}

Note: if you just want to hash some data, you don't need to create a hasher. Most packages provide a shortcut to do that, e.g. sha256.Sum224():

func GetSha224Hash(text string) string {
    s := sha256.Sum224([]byte(text))
    return hex.EncodeToString(s[:])
}

Or here's a one-liner:

func GetSha224Hash(text string) string {
    return fmt.Sprintf("%x", sha256.Sum224([]byte(text)))
}