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package jwt
import (
"errors"
"crypto"
"crypto/ed25519"
"crypto/rand"
)
var (
ErrEd25519Verification = errors.New("ed25519: verification error")
)
// SigningMethodEd25519 implements the EdDSA family.
// Expects ed25519.PrivateKey for signing and ed25519.PublicKey for verification
type SigningMethodEd25519 struct{}
// Specific instance for EdDSA
var (
SigningMethodEdDSA *SigningMethodEd25519
)
func init() {
SigningMethodEdDSA = &SigningMethodEd25519{}
RegisterSigningMethod(SigningMethodEdDSA.Alg(), func() SigningMethod {
return SigningMethodEdDSA
})
}
func (m *SigningMethodEd25519) Alg() string {
return "EdDSA"
}
// Verify implements token verification for the SigningMethod.
// For this verify method, key must be an ed25519.PublicKey
func (m *SigningMethodEd25519) Verify(signingString, signature string, key interface{}) error {
var err error
var ed25519Key ed25519.PublicKey
var ok bool
if ed25519Key, ok = key.(ed25519.PublicKey); !ok {
return ErrInvalidKeyType
}
if len(ed25519Key) != ed25519.PublicKeySize {
return ErrInvalidKey
}
// Decode the signature
var sig []byte
if sig, err = DecodeSegment(signature); err != nil {
return err
}
// Verify the signature
if !ed25519.Verify(ed25519Key, []byte(signingString), sig) {
return ErrEd25519Verification
}
return nil
}
// Sign implements token signing for the SigningMethod.
// For this signing method, key must be an ed25519.PrivateKey
func (m *SigningMethodEd25519) Sign(signingString string, key interface{}) (string, error) {
var ed25519Key crypto.Signer
var ok bool
if ed25519Key, ok = key.(crypto.Signer); !ok {
return "", ErrInvalidKeyType
}
if _, ok := ed25519Key.Public().(ed25519.PublicKey); !ok {
return "", ErrInvalidKey
}
// Sign the string and return the encoded result
// ed25519 performs a two-pass hash as part of its algorithm. Therefore, we need to pass a non-prehashed message into the Sign function, as indicated by crypto.Hash(0)
sig, err := ed25519Key.Sign(rand.Reader, []byte(signingString), crypto.Hash(0))
if err != nil {
return "", err
}
return EncodeSegment(sig), nil
}
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