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util.go
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util.go
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package ssh
import (
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"encoding/pem"
"fmt"
"strings"
"golang.org/x/crypto/ed25519"
gossh "golang.org/x/crypto/ssh"
)
// KeyType is a type of SSH key
type KeyType string
// ED25519 is key of type ed25519
const ED25519 KeyType = "ed25519"
// ECDSA is key of type ecdsa
const ECDSA KeyType = "ecdsa"
// RSA is key of type rsa
const RSA KeyType = "rsa"
// RSAKeySize is a size of newly generated RSA key
const RSAKeySize = 2048
// GeneratePrivateKey creates RSA Private Key of specified byte size
func GeneratePrivateKey(keyType KeyType) ([]byte, error) {
var key crypto.Signer
var err error
switch keyType {
case ED25519:
_, key, err = ed25519.GenerateKey(rand.Reader)
case ECDSA:
key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
case RSA:
key, err = rsa.GenerateKey(rand.Reader, RSAKeySize)
default:
return nil, fmt.Errorf("unsupported key type %s", keyType)
}
if err != nil {
return nil, err
}
pemBytes, err := EncodePrivateKeyToPEM(key)
if err != nil {
return nil, err
}
return pemBytes, nil
}
// GeneratePublicKey returns the public part of the private key
func GeneratePublicKey(key []byte) ([]byte, error) {
signer, err := gossh.ParsePrivateKey(key)
if err != nil {
return nil, err
}
strKey := strings.TrimSpace(string(gossh.MarshalAuthorizedKey(signer.PublicKey())))
return []byte(strKey), nil
}
// EncodePrivateKeyToPEM encodes Private Key from RSA to PEM format
func EncodePrivateKeyToPEM(privateKey crypto.Signer) ([]byte, error) {
mk, err := x509.MarshalPKCS8PrivateKey(privateKey)
if err != nil {
return nil, err
}
// pem.Block
privBlock := pem.Block{
Type: "PRIVATE KEY",
Bytes: mk,
}
// Private key in PEM format
privatePEM := pem.EncodeToMemory(&privBlock)
return privatePEM, nil
}