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/*
* Copyright 2018-2019 The NATS Authors
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jwt
import (
"encoding/json"
"fmt"
"strings"
)
const (
// Version is semantic version.
Version = "1.2.2"
// TokenTypeJwt is the JWT token type supported JWT tokens
// encoded and decoded by this library
TokenTypeJwt = "jwt"
// AlgorithmNkey is the algorithm supported by JWT tokens
// encoded and decoded by this library
AlgorithmNkey = "ed25519"
)
// Header is a JWT Jose Header
type Header struct {
Type string `json:"typ"`
Algorithm string `json:"alg"`
}
// Parses a header JWT token
func parseHeaders(s string) (*Header, error) {
h, err := decodeString(s)
if err != nil {
return nil, err
}
header := Header{}
if err := json.Unmarshal(h, &header); err != nil {
return nil, err
}
if err := header.Valid(); err != nil {
return nil, err
}
return &header, nil
}
// Valid validates the Header. It returns nil if the Header is
// a JWT header, and the algorithm used is the NKEY algorithm.
func (h *Header) Valid() error {
if TokenTypeJwt != strings.ToLower(h.Type) {
return fmt.Errorf("not supported type %q", h.Type)
}
if alg := strings.ToLower(h.Algorithm); alg != AlgorithmNkey {
if alg == "ed25519-nkey" {
return fmt.Errorf("more recent jwt version")
}
return fmt.Errorf("unexpected %q algorithm", h.Algorithm)
}
return nil
}
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