112 lines
2.7 KiB
Go
112 lines
2.7 KiB
Go
package main
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import (
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"crypto/ed25519"
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crand "crypto/rand"
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"encoding/pem"
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"math/rand"
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"os"
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"golang.org/x/crypto/ssh"
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)
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func generateSshKey(keyfile string) error {
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_, privateKey, err := ed25519.GenerateKey(crand.Reader)
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if err != nil {
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return err
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}
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privateKeyPEM := &pem.Block{
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Type: "OPENSSH PRIVATE KEY",
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Bytes: marshalED25519PrivateKey(privateKey),
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}
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privateKeyBytes := pem.EncodeToMemory(privateKeyPEM)
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return os.WriteFile(keyfile, privateKeyBytes, 0600)
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}
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// copy from https://github.com/mikesmitty/edkey/blob/master/edkey.go
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/*
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Writes ed25519 private keys into the new OpenSSH private key format.
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I have no idea why this isn't implemented anywhere yet, you can do seemingly
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everything except write it to disk in the OpenSSH private key format.
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*/
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func marshalED25519PrivateKey(key ed25519.PrivateKey) []byte {
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// Add our key header (followed by a null byte)
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magic := append([]byte("openssh-key-v1"), 0)
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var w struct {
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CipherName string
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KdfName string
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KdfOpts string
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NumKeys uint32
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PubKey []byte
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PrivKeyBlock []byte
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}
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// Fill out the private key fields
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pk1 := struct {
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Check1 uint32
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Check2 uint32
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Keytype string
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Pub []byte
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Priv []byte
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Comment string
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Pad []byte `ssh:"rest"`
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}{}
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// Set our check ints
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ci := rand.Uint32()
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pk1.Check1 = ci
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pk1.Check2 = ci
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// Set our key type
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pk1.Keytype = ssh.KeyAlgoED25519
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// Add the pubkey to the optionally-encrypted block
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pk, ok := key.Public().(ed25519.PublicKey)
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if !ok {
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//fmt.Fprintln(os.Stderr, "ed25519.PublicKey type assertion failed on an ed25519 public key. This should never ever happen.")
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return nil
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}
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pubKey := []byte(pk)
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pk1.Pub = pubKey
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// Add our private key
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pk1.Priv = []byte(key)
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// Might be useful to put something in here at some point
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pk1.Comment = ""
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// Add some padding to match the encryption block size within PrivKeyBlock (without Pad field)
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// 8 doesn't match the documentation, but that's what ssh-keygen uses for unencrypted keys. *shrug*
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bs := 8
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blockLen := len(ssh.Marshal(pk1))
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padLen := (bs - (blockLen % bs)) % bs
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pk1.Pad = make([]byte, padLen)
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// Padding is a sequence of bytes like: 1, 2, 3...
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for i := 0; i < padLen; i++ {
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pk1.Pad[i] = byte(i + 1)
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}
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// Generate the pubkey prefix "\0\0\0\nssh-ed25519\0\0\0 "
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prefix := []byte{0x0, 0x0, 0x0, 0x0b}
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prefix = append(prefix, []byte(ssh.KeyAlgoED25519)...)
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prefix = append(prefix, []byte{0x0, 0x0, 0x0, 0x20}...)
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// Only going to support unencrypted keys for now
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w.CipherName = "none"
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w.KdfName = "none"
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w.KdfOpts = ""
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w.NumKeys = 1
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w.PubKey = append(prefix, pubKey...)
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w.PrivKeyBlock = ssh.Marshal(pk1)
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magic = append(magic, ssh.Marshal(w)...)
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return magic
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}
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