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ctrl/nkey_from_ssh_ed25519_key.go

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package ctrl
import (
"bytes"
"crypto/ed25519"
"encoding/base32"
"encoding/binary"
"fmt"
"io"
"os"
"path/filepath"
"reflect"
"github.com/nats-io/nats.go"
"github.com/nats-io/nkeys"
"golang.org/x/crypto/ssh"
)
// nkeyOptFromSSHKey will read the ED25519 SSH private key file,
// then convert the content into a NKEY Seed file, and return
// the result as a nats.Option.
func (c *Configuration) nkeyOptFromSSHKey() (nats.Option, error) {
// --- Create key
p, err := c.CreateKeyPair(PrefixByteUser)
if err != nil {
return nil, fmt.Errorf("error: createpair failed: %v", err)
}
filepathSeed := filepath.Join(c.SocketFolder, "seed_from_ssh_key.txt")
filepathUser := filepath.Join(c.SocketFolder, "user_from_ssh_key.txt")
// Write the private key seed to file.
{
fh, err := os.OpenFile(filepathSeed, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0660)
if err != nil {
return nil, fmt.Errorf("error: open file for writing seed failed: %v", err)
}
defer fh.Close()
_, err = fh.Write(p.seed)
if err != nil {
return nil, fmt.Errorf("error: writing of seed file for ssh key failed: %v", err)
}
}
// Write the user key to file.
{
fh, err := os.OpenFile(filepathUser, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0660)
if err != nil {
return nil, fmt.Errorf("error: open file for writing user failed: %v", err)
}
defer fh.Close()
_, err = fh.Write([]byte(p.userKey))
if err != nil {
return nil, fmt.Errorf("error: writing of user file for ssh key failed: %v", err)
}
}
opt, err := nats.NkeyOptionFromSeed(filepathSeed)
if err != nil {
return nil, fmt.Errorf("error: creating option nkey from seed file failed: %v", err)
}
return opt, nil
}
// Convert the ed25519 public key to nkey user key.
func publicKeyToUserKey(signer ssh.Signer) (string, error) {
key := signer.PublicKey()
marshalled := key.Marshal()
seed := marshalled[len(marshalled)-32:]
encoded, err := nkeys.Encode(nkeys.PrefixByteUser, seed)
if err != nil {
return "", err
}
return string(encoded), nil
}
type PrefixByte byte
// PrefixByteUser is the version byte used for encoded NATS Users
const PrefixByteUser PrefixByte = 20 << 3 // Base32-encodes to 'U...'
type kp struct {
seed []byte
userKey string
}
// CreateKeyPair will create the key nkeys key pair.
// This is a slightly modified version of the function
// found in the nkeys package, just with less options.
func (c *Configuration) CreateKeyPair(prefix PrefixByte) (kp, error) {
fh, err := os.Open(c.NkeyFromED25519SSHKeyFile)
if err != nil {
return kp{}, fmt.Errorf("failed: open ssh private key file: %v", err)
}
defer fh.Close()
b, err := io.ReadAll(fh)
if err != nil {
return kp{}, fmt.Errorf("failed: read ssh private key file: %v", err)
}
signerRaw, err := ssh.ParseRawPrivateKey(b)
if err != nil {
return kp{}, fmt.Errorf("failed: parse raw private key: %v", err)
}
switch signerRaw.(type) {
case *ed25519.PrivateKey:
// ok, got correct type, just continue.
default:
t := reflect.TypeOf(signerRaw)
return kp{}, fmt.Errorf("failed: key is wrong type, want type ed25519 key, got: %v", t)
}
// ---
raw := signerRaw.(*ed25519.PrivateKey)
bytePrivAndPub := []byte(*raw)
seed, err := EncodeSeed(prefix, bytePrivAndPub[:32])
if err != nil {
return kp{}, err
}
signer, err := ssh.ParsePrivateKey(b)
if err != nil {
return kp{}, fmt.Errorf("failed: parse private key: %v", err)
}
pub, err := publicKeyToUserKey(signer)
if err != nil {
return kp{}, fmt.Errorf("failed: failed to get public key for signer: %v", err)
}
return kp{seed: seed, userKey: pub}, nil
}
// PrefixByteSeed is the version byte used for encoded NATS Seeds
const PrefixByteSeed PrefixByte = 18 << 3 // Base32-encodes to 'S...'
// EncodeSeed will encode a raw key with the prefix and then seed prefix and crc16 and then base32 encoded.
// This is a slightly modified version of the function
// found in the nkeys package, just with less options.
func EncodeSeed(public PrefixByte, src []byte) ([]byte, error) {
if len(src) != ed25519.SeedSize {
return nil, fmt.Errorf("invalid key length")
}
// In order to make this human printable for both bytes, we need to do a little
// bit manipulation to setup for base32 encoding which takes 5 bits at a time.
b1 := byte(PrefixByteSeed) | (byte(public) >> 5)
b2 := (byte(public) & 31) << 3 // 31 = 00011111
var raw bytes.Buffer
raw.WriteByte(b1)
raw.WriteByte(b2)
// write payload
if _, err := raw.Write(src); err != nil {
return nil, err
}
// Calculate and write crc16 checksum
err := binary.Write(&raw, binary.LittleEndian, crc16(raw.Bytes()))
if err != nil {
return nil, err
}
data := raw.Bytes()
buf := make([]byte, b32Enc.EncodedLen(len(data)))
b32Enc.Encode(buf, data)
return buf, nil
}
// Set our encoding to not include padding '=='
var b32Enc = base32.StdEncoding.WithPadding(base32.NoPadding)
// crc16 returns the 2-byte crc for the data provided.
// This is a slightly modified version of the function
// found in the nkeys package, just with less options.
func crc16(data []byte) uint16 {
var crc uint16
for _, b := range data {
crc = ((crc << 8) & 0xffff) ^ crc16tab[((crc>>8)^uint16(b))&0x00FF]
}
return crc
}
var crc16tab = [256]uint16{
0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
}