Golang: Storing and retrieving RSA encryption key

Question

I am trying to build an API, but to secure it properly I believe I need to go with RSA encryption for a private key stored on my server and a public key for the client. I have stored the generated private key into a JSON file, I plan to store on my server but to write to JSON, I needed to convert the type too

[]byte

. Now when I try to retrieve the private key to generate a public key, but it will not let me use type bytes for

*Publickey

The only other way I can think of to accomplish this goal is to seed the random number generator, so I can have the seed a secret on my server and then my private key should always generate to the same thing, any help this this would be great.

package main



import (

    "bytes"

    "crypto/rand"

    "crypto/rsa"

    "encoding/json"

    "fmt"

    "io/ioutil"

    "os"

)



func main() {

    mimicPrivateKey, err := rsa.GenerateKey(rand.Reader, 2048)

    if err != nil {

        fmt.Println(err)

        os.Exit(1)

    }

    buf := new(bytes.Buffer)

    json.NewEncoder(buf).Encode(mimicPrivateKey)

    secrets, _ := os.OpenFile("secrets.json",    os.O_RDWR|os.O_APPEND|os.O_CREATE, 0666)

    // Close the secrets file when the surrounding function exists



    secrets.WriteString(buf.String())

    secrets.Close()



    secrets, _ = os.OpenFile("secrets.json", os.O_RDWR, 0666)

    serverKey, _ := ioutil.ReadAll(secrets)

    if serverKey != nil {

        fmt.Println("can not open key")

    }



    serverKeyPublic := &serverKey.PublicKey

}

Answer 1

You need to Unmarshal it:

var data *rsa.PrivateKey
err = json.Unmarshal(serverKey, &data)
if err != nil {
    panic(err)
}

And you may use

err = ioutil.WriteFile("secrets.json", buf.Bytes(), 0666)

and

serverKey, err := ioutil.ReadFile("secrets.json")

See:

package main

import (
    "bytes"
    "crypto/rand"
    "crypto/rsa"
    "encoding/json"
    "fmt"
    "io/ioutil"
)

func main() {
    mimicPrivateKey, err := rsa.GenerateKey(rand.Reader, 2048)
    if err != nil {
        panic(err)
    }
    var buf bytes.Buffer
    err = json.NewEncoder(&buf).Encode(mimicPrivateKey)
    if err != nil {
        panic(err)
    }
    err = ioutil.WriteFile("secrets.json", buf.Bytes(), 0666)
    if err != nil {
        panic(err)
    }

    serverKey, err := ioutil.ReadFile("secrets.json")
    if err != nil {
        panic(err)
    }
    var data *rsa.PrivateKey
    err = json.Unmarshal(serverKey, &data)
    if err != nil {
        panic(err)
    }
    serverKeyPublic := data.PublicKey
    fmt.Println(serverKeyPublic)
}

Golang: Storing and retrieving RSA encryption key

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