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package cryptokit
import (
"crypto/ed25519"
"crypto/sha256"
"encoding/base64"
"encoding/hex"
"errors"
"fmt"
"strings"
)
func decodeKeyText(value string, expected ...int) ([]byte, error) {
value = strings.TrimSpace(value)
if value == "" {
return nil, errors.New("key material is required")
}
decoded, base64Err := base64.StdEncoding.DecodeString(value)
if base64Err != nil {
decoded, base64Err = base64.RawStdEncoding.DecodeString(value)
}
if base64Err != nil {
var hexErr error
decoded, hexErr = hex.DecodeString(value)
if hexErr != nil {
return nil, errors.New("key material is not valid base64 or hexadecimal")
}
}
for _, size := range expected {
if len(decoded) == size {
return decoded, nil
}
}
return nil, fmt.Errorf("unexpected key length %d bytes", len(decoded))
}
// SignEd25519 signs with a raw Ed25519 private key supplied as base64 or hex.
// Both the 32-byte seed and 64-byte private-key encodings are accepted.
func SignEd25519(message []byte, privateKey string) (string, error) {
key, err := decodeKeyText(privateKey, ed25519.SeedSize, ed25519.PrivateKeySize)
if err != nil {
return "", err
}
if len(key) == ed25519.SeedSize {
key = ed25519.NewKeyFromSeed(key)
}
signature := ed25519.Sign(ed25519.PrivateKey(key), message)
return base64.StdEncoding.EncodeToString(signature), nil
}
// Ed25519PublicKey derives the public key from a raw Ed25519 private key and
// returns it as standard base64. Both the 32-byte seed and 64-byte private-key
// encodings are accepted.
func Ed25519PublicKey(privateKey string) (string, error) {
key, err := decodeKeyText(privateKey, ed25519.SeedSize, ed25519.PrivateKeySize)
if err != nil {
return "", err
}
if len(key) == ed25519.SeedSize {
key = ed25519.NewKeyFromSeed(key)
}
publicKey := ed25519.PrivateKey(key).Public().(ed25519.PublicKey)
return base64.StdEncoding.EncodeToString(publicKey), nil
}
// Ed25519PublicKeyFingerprint returns a stable SHA-256 fingerprint for a
// base64 or hexadecimal Ed25519 public key.
func Ed25519PublicKeyFingerprint(publicKey string) (string, error) {
key, err := decodeKeyText(publicKey, ed25519.PublicKeySize)
if err != nil {
return "", err
}
digest := sha256.Sum256(key)
return "sha256:" + hex.EncodeToString(digest[:]), nil
}
// CanonicalEd25519PublicKey accepts a raw Ed25519 public key as base64 or
// hexadecimal and returns the protocol representation used by VFace.
func CanonicalEd25519PublicKey(publicKey string) (string, error) {
key, err := decodeKeyText(publicKey, ed25519.PublicKeySize)
if err != nil {
return "", fmt.Errorf("decode Ed25519 public key: %w", err)
}
return base64.StdEncoding.EncodeToString(key), nil
}
// VerifyEd25519 verifies a base64 or hexadecimal Ed25519 signature against a
// raw public key supplied as base64 or hex.
func VerifyEd25519(message []byte, signature, publicKey string) error {
sig, err := decodeKeyText(signature, ed25519.SignatureSize)
if err != nil {
return fmt.Errorf("decode Ed25519 signature: %w", err)
}
key, err := decodeKeyText(publicKey, ed25519.PublicKeySize)
if err != nil {
return fmt.Errorf("decode Ed25519 public key: %w", err)
}
if !ed25519.Verify(ed25519.PublicKey(key), message, sig) {
return errors.New("Ed25519 signature verification failed")
}
return nil
}
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