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