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package jose
import (
"bytes"
"crypto"
"crypto/hmac"
_ "crypto/sha256"
"errors"
"fmt"
)
type VerifierHMAC struct {
KeyID string
Hash crypto.Hash
Secret []byte
}
type SignerHMAC struct {
VerifierHMAC
}
func NewVerifierHMAC(jwk JWK) (*VerifierHMAC, error) {
if jwk.Alg != "" && jwk.Alg != "HS256" {
return nil, fmt.Errorf("unsupported key algorithm %q", jwk.Alg)
}
v := VerifierHMAC{
KeyID: jwk.ID,
Secret: jwk.Secret,
Hash: crypto.SHA256,
}
return &v, nil
}
func (v *VerifierHMAC) ID() string {
return v.KeyID
}
func (v *VerifierHMAC) Alg() string {
return "HS256"
}
func (v *VerifierHMAC) Verify(sig []byte, data []byte) error {
h := hmac.New(v.Hash.New, v.Secret)
h.Write(data)
if !bytes.Equal(sig, h.Sum(nil)) {
return errors.New("invalid hmac signature")
}
return nil
}
func NewSignerHMAC(kid string, secret []byte) *SignerHMAC {
return &SignerHMAC{
VerifierHMAC: VerifierHMAC{
KeyID: kid,
Secret: secret,
Hash: crypto.SHA256,
},
}
}
func (s *SignerHMAC) Sign(data []byte) ([]byte, error) {
h := hmac.New(s.Hash.New, s.Secret)
h.Write(data)
return h.Sum(nil), nil
}
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