common.go

// common package of CB-Spider's Cloud Drivers
// The CB-Spider is a sub-Framework of the Cloud-Barista Multi-Cloud Project.
// The CB-Spider Mission is to connect all the clouds with a single interface.
//
//      * Cloud-Barista: https://github.com/cloud-barista
//
// by CB-Spider Team, 2021.08.

package common

import (
	"bytes"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"io/ioutil"

	"golang.org/x/crypto/ssh"
)

// generate a KeyPair with 4KB length
// returns: privateKeyBytes, publicKeyBytes, error
func GenKeyPair() ([]byte, []byte, error) {

	// (1) Generate a private Key
	keyLength := 4096
	privateKey, err := rsa.GenerateKey(rand.Reader, keyLength)
	if err != nil {
		return nil, nil, err
	}

	err = privateKey.Validate()
	if err != nil {
		return nil, nil, err
	}

	// for ASN.1 DER format
	DERKey := x509.MarshalPKCS1PrivateKey(privateKey)
	keyBlock := pem.Block{
		Type:    "RSA PRIVATE KEY",
		Headers: nil,
		Bytes:   DERKey,
	}

	// for PEM format
	privateKeyBytes := pem.EncodeToMemory(&keyBlock)

	// (2) Generate a public key
	publicKey, err := ssh.NewPublicKey(&privateKey.PublicKey)
	if err != nil {
		return nil, nil, err
	}

	publicKeyBytes := ssh.MarshalAuthorizedKey(publicKey)

	return privateKeyBytes, publicKeyBytes, nil
}

// save a key to a file
func SaveKey(keyBytes []byte, targetFile string) error {
	err := ioutil.WriteFile(targetFile, keyBytes, 0600)
	if err != nil {
		return err
	}

	return nil
}

// ParseKey reads the given RSA private key and create a public one for it.
func MakePublicKeyFromPrivateKey(pem string) (string, error) {
	key, err := ssh.ParseRawPrivateKey([]byte(pem))
	if err != nil {
		return "", err
	}
	rsaKey, ok := key.(*rsa.PrivateKey)
	if !ok {
		return "", fmt.Errorf("%q is not a RSA key", pem)
	}
	pub, err := ssh.NewPublicKey(&rsaKey.PublicKey)
	if err != nil {
		return "", err
	}

	return string(bytes.TrimRight(ssh.MarshalAuthorizedKey(pub), "\n")), nil
}