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ed25519.go
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ed25519.go
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package keys
import (
"bytes"
"crypto"
"crypto/ed25519"
"crypto/rand"
"crypto/subtle"
"encoding/json"
"errors"
"fmt"
"io"
"github.com/theupdateframework/go-tuf/data"
)
func init() {
SignerMap.Store(data.KeySchemeEd25519, NewEd25519Signer)
VerifierMap.Store(data.KeySchemeEd25519, NewEd25519Verifier)
}
func NewEd25519Signer() Signer {
return &ed25519Signer{}
}
func NewEd25519Verifier() Verifier {
return &ed25519Verifier{}
}
type ed25519Verifier struct {
PublicKey data.HexBytes `json:"public"`
key *data.PublicKey
}
func (e *ed25519Verifier) Public() string {
return string(e.PublicKey)
}
func (e *ed25519Verifier) Verify(msg, sig []byte) error {
if !ed25519.Verify([]byte(e.PublicKey), msg, sig) {
return errors.New("tuf: ed25519 signature verification failed")
}
return nil
}
func (e *ed25519Verifier) MarshalPublicKey() *data.PublicKey {
return e.key
}
func (e *ed25519Verifier) UnmarshalPublicKey(key *data.PublicKey) error {
e.key = key
// Prepare decoder limited to 512Kb
dec := json.NewDecoder(io.LimitReader(bytes.NewReader(key.Value), MaxJSONKeySize))
dec.DisallowUnknownFields()
// Unmarshal key value
if err := dec.Decode(e); err != nil {
switch {
case errors.Is(err, io.EOF), errors.Is(err, io.ErrUnexpectedEOF):
return fmt.Errorf("tuf: the public key is truncated or too large: %w", err)
default:
}
return err
}
if n := len(e.PublicKey); n != ed25519.PublicKeySize {
return fmt.Errorf("tuf: unexpected public key length for ed25519 key, expected %d, got %d", ed25519.PublicKeySize, n)
}
return nil
}
type Ed25519PrivateKeyValue struct {
Public data.HexBytes `json:"public"`
Private data.HexBytes `json:"private"`
}
type ed25519Signer struct {
ed25519.PrivateKey
keyType string
keyScheme string
keyAlgorithms []string
}
func GenerateEd25519Key() (*ed25519Signer, error) {
_, private, err := ed25519.GenerateKey(rand.Reader)
if err != nil {
return nil, err
}
if err != nil {
return nil, err
}
return &ed25519Signer{
PrivateKey: ed25519.PrivateKey(data.HexBytes(private)),
keyType: data.KeyTypeEd25519,
keyScheme: data.KeySchemeEd25519,
keyAlgorithms: data.HashAlgorithms,
}, nil
}
func NewEd25519SignerFromKey(keyValue Ed25519PrivateKeyValue) *ed25519Signer {
return &ed25519Signer{
PrivateKey: ed25519.PrivateKey(data.HexBytes(keyValue.Private)),
keyType: data.KeyTypeEd25519,
keyScheme: data.KeySchemeEd25519,
keyAlgorithms: data.HashAlgorithms,
}
}
func (e *ed25519Signer) SignMessage(message []byte) ([]byte, error) {
return e.Sign(rand.Reader, message, crypto.Hash(0))
}
func (e *ed25519Signer) MarshalPrivateKey() (*data.PrivateKey, error) {
valueBytes, err := json.Marshal(Ed25519PrivateKeyValue{
Public: data.HexBytes([]byte(e.PrivateKey.Public().(ed25519.PublicKey))),
Private: data.HexBytes(e.PrivateKey),
})
if err != nil {
return nil, err
}
return &data.PrivateKey{
Type: e.keyType,
Scheme: e.keyScheme,
Algorithms: e.keyAlgorithms,
Value: valueBytes,
}, nil
}
func (e *ed25519Signer) UnmarshalPrivateKey(key *data.PrivateKey) error {
keyValue := &Ed25519PrivateKeyValue{}
// Prepare decoder limited to 512Kb
dec := json.NewDecoder(io.LimitReader(bytes.NewReader(key.Value), MaxJSONKeySize))
dec.DisallowUnknownFields()
if err := dec.Decode(keyValue); err != nil {
switch {
case errors.Is(err, io.EOF), errors.Is(err, io.ErrUnexpectedEOF):
return fmt.Errorf("tuf: the private key is truncated or too large: %w", err)
default:
}
}
// Check private key length
if n := len(keyValue.Private); n != ed25519.PrivateKeySize {
return fmt.Errorf("tuf: invalid ed25519 private key length, expected %d, got %d", ed25519.PrivateKeySize, n)
}
// Generate public key from private key
pub, _, err := ed25519.GenerateKey(bytes.NewReader(keyValue.Private))
if err != nil {
return fmt.Errorf("tuf: unable to derive public key from private key: %w", err)
}
// Compare keys
if subtle.ConstantTimeCompare(keyValue.Public, pub) != 1 {
return errors.New("tuf: public and private keys don't match")
}
// Prepare signer
*e = ed25519Signer{
PrivateKey: ed25519.PrivateKey(data.HexBytes(keyValue.Private)),
keyType: key.Type,
keyScheme: key.Scheme,
keyAlgorithms: key.Algorithms,
}
return nil
}
func (e *ed25519Signer) PublicData() *data.PublicKey {
keyValBytes, _ := json.Marshal(ed25519Verifier{PublicKey: []byte(e.PrivateKey.Public().(ed25519.PublicKey))})
return &data.PublicKey{
Type: e.keyType,
Scheme: e.keyScheme,
Algorithms: e.keyAlgorithms,
Value: keyValBytes,
}
}