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package jws
import (
"crypto"
"crypto/ed25519"
"crypto/rand"
"fmt"
"github.com/lestrrat-go/jwx/v2/internal/keyconv"
"github.com/lestrrat-go/jwx/v2/jwa"
)
type eddsaSigner struct{}
func newEdDSASigner() Signer {
return &eddsaSigner{}
}
func (s eddsaSigner) Algorithm() jwa.SignatureAlgorithm {
return jwa.EdDSA
}
func (s eddsaSigner) Sign(payload []byte, key interface{}) ([]byte, error) {
if key == nil {
return nil, fmt.Errorf(`missing private key while signing payload`)
}
// The ed25519.PrivateKey object implements crypto.Signer, so we should
// simply accept a crypto.Signer here.
signer, ok := key.(crypto.Signer)
if ok {
if !isValidEDDSAKey(key) {
return nil, fmt.Errorf(`cannot use key of type %T to generate EdDSA based signatures`, key)
}
} else {
// This fallback exists for cases when jwk.Key was passed, or
// users gave us a pointer instead of non-pointer, etc.
var privkey ed25519.PrivateKey
if err := keyconv.Ed25519PrivateKey(&privkey, key); err != nil {
return nil, fmt.Errorf(`failed to retrieve ed25519.PrivateKey out of %T: %w`, key, err)
}
signer = privkey
}
return signer.Sign(rand.Reader, payload, crypto.Hash(0))
}
type eddsaVerifier struct{}
func newEdDSAVerifier() Verifier {
return &eddsaVerifier{}
}
func (v eddsaVerifier) Verify(payload, signature []byte, key interface{}) (err error) {
if key == nil {
return fmt.Errorf(`missing public key while verifying payload`)
}
var pubkey ed25519.PublicKey
signer, ok := key.(crypto.Signer)
if ok {
v := signer.Public()
pubkey, ok = v.(ed25519.PublicKey)
if !ok {
return fmt.Errorf(`expected crypto.Signer.Public() to return ed25519.PublicKey, but got %T`, v)
}
} else {
if err := keyconv.Ed25519PublicKey(&pubkey, key); err != nil {
return fmt.Errorf(`failed to retrieve ed25519.PublicKey out of %T: %w`, key, err)
}
}
if !ed25519.Verify(pubkey, payload, signature) {
return fmt.Errorf(`failed to match EdDSA signature`)
}
return nil
}
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