Files
kubelogin/pkg/jwt/decode.go
2020-11-21 12:10:42 +09:00

72 lines
2.2 KiB
Go

// Package jwt provides JWT manipulations.
// See https://tools.ietf.org/html/rfc7519#section-4.1.3
package jwt
import (
"bytes"
"encoding/base64"
"encoding/json"
"fmt"
"strings"
"time"
)
// DecodeWithoutVerify decodes the JWT string and returns the claims.
// Note that this method does not verify the signature and always trust it.
func DecodeWithoutVerify(s string) (*Claims, error) {
payload, err := DecodePayloadAsRawJSON(s)
if err != nil {
return nil, fmt.Errorf("could not decode the payload: %w", err)
}
var claims struct {
Subject string `json:"sub,omitempty"`
ExpiresAt int64 `json:"exp,omitempty"`
}
if err := json.NewDecoder(bytes.NewReader(payload)).Decode(&claims); err != nil {
return nil, fmt.Errorf("could not decode the json of token: %w", err)
}
var prettyJson bytes.Buffer
if err := json.Indent(&prettyJson, payload, "", " "); err != nil {
return nil, fmt.Errorf("could not indent the json of token: %w", err)
}
return &Claims{
Subject: claims.Subject,
Expiry: time.Unix(claims.ExpiresAt, 0),
Pretty: prettyJson.String(),
}, nil
}
// DecodePayloadAsPrettyJSON decodes the JWT string and returns the pretty JSON string.
func DecodePayloadAsPrettyJSON(s string) (string, error) {
payload, err := DecodePayloadAsRawJSON(s)
if err != nil {
return "", fmt.Errorf("could not decode the payload: %w", err)
}
var prettyJson bytes.Buffer
if err := json.Indent(&prettyJson, payload, "", " "); err != nil {
return "", fmt.Errorf("could not indent the json of token: %w", err)
}
return prettyJson.String(), nil
}
// DecodePayloadAsRawJSON extracts the payload and returns the raw JSON.
func DecodePayloadAsRawJSON(s string) ([]byte, error) {
parts := strings.SplitN(s, ".", 3)
if len(parts) != 3 {
return nil, fmt.Errorf("wants %d segments but got %d segments", 3, len(parts))
}
payloadJSON, err := decodePayload(parts[1])
if err != nil {
return nil, fmt.Errorf("could not decode the payload: %w", err)
}
return payloadJSON, nil
}
func decodePayload(payload string) ([]byte, error) {
b, err := base64.URLEncoding.WithPadding(base64.NoPadding).DecodeString(payload)
if err != nil {
return nil, fmt.Errorf("invalid base64: %w", err)
}
return b, nil
}