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package crypto
import (
"bytes"
"crypto/ed25519"
"crypto/rand"
"crypto/x509"
"encoding/pem"
"fmt"
)
// Ed25519GenerateKey returns a random PEM encoded Ed25519 Private Key.
func Ed25519GenerateKey() ([]byte, error) {
_, secret, err := ed25519.GenerateKey(rand.Reader)
if err != nil {
return nil, fmt.Errorf("generateKey: %w", err)
}
return pemEncodeEdPrivateKey(secret)
}
// Ed25519GenerateKeyFromSeed returns a PEM encoded Ed25519 Private Key from
// `seed`. Returns error if len(seed) is not ed25519.SeedSize (32).
func Ed25519GenerateKeyFromSeed(seed []byte) ([]byte, error) {
if len(seed) != ed25519.SeedSize {
return nil, fmt.Errorf("generateKeyFromSeed: incorrect seed size - given: %d wanted %d", len(seed), ed25519.SeedSize)
}
return pemEncodeEdPrivateKey(ed25519.NewKeyFromSeed(seed))
}
// Ed25519DerivePublicKey returns an ed25519 Public Key from given PEM encoded
// `privatekey`.
func Ed25519DerivePublicKey(privatekey []byte) ([]byte, error) {
secret, err := ed25519DecodeFromPEM(privatekey)
if err != nil {
return nil, fmt.Errorf("ed25519DecodeFromPEM: could not decode private key: %w", err)
}
b, err := x509.MarshalPKIXPublicKey(secret.Public())
if err != nil {
return nil, fmt.Errorf("marshalPKIXPublicKey: failed to marshal PKIX public key: %w", err)
}
return pem.EncodeToMemory(&pem.Block{
Type: "PUBLIC KEY",
Bytes: b,
}), nil
}
// pemEncodeEdPrivateKey is a convenience function for PEM encoding `secret`.
func pemEncodeEdPrivateKey(secret ed25519.PrivateKey) ([]byte, error) {
der, err := x509.MarshalPKCS8PrivateKey(secret)
if err != nil {
return nil, fmt.Errorf("marshalPKCS8PrivateKey: failed to marshal ed25519 private key: %w", err)
}
block := &pem.Block{
Type: "PRIVATE KEY",
Bytes: der,
}
buf := &bytes.Buffer{}
err = pem.Encode(buf, block)
if err != nil {
return nil, fmt.Errorf("encode: PEM encoding: %w", err)
}
return buf.Bytes(), nil
}
// ed25519DecodeFromPEM returns an ed25519.PrivateKey from given PEM encoded
// `privatekey`.
func ed25519DecodeFromPEM(privatekey []byte) (ed25519.PrivateKey, error) {
block, _ := pem.Decode(privatekey)
if block == nil {
return nil, fmt.Errorf("decode: failed to read key")
}
priv, err := x509.ParsePKCS8PrivateKey(block.Bytes)
if err != nil {
return nil, fmt.Errorf("parsePKCS8PrivateKey: invalid private key: %w", err)
}
secret, ok := priv.(ed25519.PrivateKey)
if !ok {
return nil, fmt.Errorf("ed25519DecodeFromPEM: invalid ed25519 Private Key - given type: %T", priv)
}
return secret, nil
}
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