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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package acme
import (
"crypto"
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"encoding/base64"
"encoding/json"
"fmt"
"math/big"
)
// jwsEncodeJSON signs claimset using provided key and a nonce.
// The result is serialized in JSON format.
// See https://tools.ietf.org/html/rfc7515#section-7.
func jwsEncodeJSON(claimset interface{}, key *rsa.PrivateKey, nonce string) ([]byte, error) {
jwk := jwkEncode(&key.PublicKey)
phead := fmt.Sprintf(`{"alg":"RS256","jwk":%s,"nonce":%q}`, jwk, nonce)
phead = base64.RawURLEncoding.EncodeToString([]byte(phead))
cs, err := json.Marshal(claimset)
if err != nil {
return nil, err
}
payload := base64.RawURLEncoding.EncodeToString(cs)
h := sha256.New()
h.Write([]byte(phead + "." + payload))
sig, err := rsa.SignPKCS1v15(rand.Reader, key, crypto.SHA256, h.Sum(nil))
if err != nil {
return nil, err
}
enc := struct {
Protected string `json:"protected"`
Payload string `json:"payload"`
Sig string `json:"signature"`
}{
Protected: phead,
Payload: payload,
Sig: base64.RawURLEncoding.EncodeToString(sig),
}
return json.Marshal(&enc)
}
// jwkEncode encodes public part of an RSA key into a JWK.
// The result is also suitable for creating a JWK thumbprint.
func jwkEncode(pub *rsa.PublicKey) string {
n := pub.N
e := big.NewInt(int64(pub.E))
// fields order is important
// see https://tools.ietf.org/html/rfc7638#section-3.3 for details
return fmt.Sprintf(`{"e":"%s","kty":"RSA","n":"%s"}`,
base64.RawURLEncoding.EncodeToString(e.Bytes()),
base64.RawURLEncoding.EncodeToString(n.Bytes()),
)
}
// JWKThumbprint creates a JWK thumbprint out of pub
// as specified in https://tools.ietf.org/html/rfc7638.
func JWKThumbprint(pub *rsa.PublicKey) string {
jwk := jwkEncode(pub)
b := sha256.Sum256([]byte(jwk))
return base64.RawURLEncoding.EncodeToString(b[:])
}
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