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package edkey
import (
"math/rand"
"golang.org/x/crypto/ed25519"
"golang.org/x/crypto/ssh"
)
/* Writes ed25519 private keys into the new OpenSSH private key format.
I have no idea why this isn't implemented anywhere yet, you can do seemingly
everything except write it to disk in the OpenSSH private key format. */
func MarshalED25519PrivateKey(key ed25519.PrivateKey) []byte {
// Add our key header (followed by a null byte)
magic := append([]byte("openssh-key-v1"), 0)
var w struct {
CipherName string
KdfName string
KdfOpts string
NumKeys uint32
PubKey []byte
PrivKeyBlock []byte
}
// Fill out the private key fields
pk1 := struct {
Check1 uint32
Check2 uint32
Keytype string
Pub []byte
Priv []byte
Comment string
Pad []byte `ssh:"rest"`
}{}
// Set our check ints
ci := rand.Uint32()
pk1.Check1 = ci
pk1.Check2 = ci
// Set our key type
pk1.Keytype = ssh.KeyAlgoED25519
// Add the pubkey to the optionally-encrypted block
pk, ok := key.Public().(ed25519.PublicKey)
if !ok {
//fmt.Fprintln(os.Stderr, "ed25519.PublicKey type assertion failed on an ed25519 public key. This should never ever happen.")
return nil
}
pubKey := []byte(pk)
pk1.Pub = pubKey
// Add our private key
pk1.Priv = []byte(key)
// Might be useful to put something in here at some point
pk1.Comment = ""
// Add some padding to match the encryption block size within PrivKeyBlock (without Pad field)
// 8 doesn't match the documentation, but that's what ssh-keygen uses for unencrypted keys. *shrug*
bs := 8
blockLen := len(ssh.Marshal(pk1))
padLen := (bs - (blockLen % bs)) % bs
pk1.Pad = make([]byte, padLen)
// Padding is a sequence of bytes like: 1, 2, 3...
for i := 0; i < padLen; i++ {
pk1.Pad[i] = byte(i + 1)
}
// Generate the pubkey prefix "\0\0\0\nssh-ed25519\0\0\0 "
prefix := []byte{0x0, 0x0, 0x0, 0x0b}
prefix = append(prefix, []byte(ssh.KeyAlgoED25519)...)
prefix = append(prefix, []byte{0x0, 0x0, 0x0, 0x20}...)
// Only going to support unencrypted keys for now
w.CipherName = "none"
w.KdfName = "none"
w.KdfOpts = ""
w.NumKeys = 1
w.PubKey = append(prefix, pubKey...)
w.PrivKeyBlock = ssh.Marshal(pk1)
magic = append(magic, ssh.Marshal(w)...)
return magic
}
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