1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153
|
// 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/ecdsa"
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
_ "crypto/sha512" // need for EC keys
"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 crypto.Signer, nonce string) ([]byte, error) {
jwk, err := jwkEncode(key.Public())
if err != nil {
return nil, err
}
alg, sha := jwsHasher(key)
if alg == "" || !sha.Available() {
return nil, ErrUnsupportedKey
}
phead := fmt.Sprintf(`{"alg":%q,"jwk":%s,"nonce":%q}`, alg, jwk, nonce)
phead = base64.RawURLEncoding.EncodeToString([]byte(phead))
cs, err := json.Marshal(claimset)
if err != nil {
return nil, err
}
payload := base64.RawURLEncoding.EncodeToString(cs)
hash := sha.New()
hash.Write([]byte(phead + "." + payload))
sig, err := jwsSign(key, sha, hash.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 or ECDSA key into a JWK.
// The result is also suitable for creating a JWK thumbprint.
// https://tools.ietf.org/html/rfc7517
func jwkEncode(pub crypto.PublicKey) (string, error) {
switch pub := pub.(type) {
case *rsa.PublicKey:
// https://tools.ietf.org/html/rfc7518#section-6.3.1
n := pub.N
e := big.NewInt(int64(pub.E))
// Field 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()),
), nil
case *ecdsa.PublicKey:
// https://tools.ietf.org/html/rfc7518#section-6.2.1
p := pub.Curve.Params()
n := p.BitSize / 8
if p.BitSize%8 != 0 {
n++
}
x := pub.X.Bytes()
if n > len(x) {
x = append(make([]byte, n-len(x)), x...)
}
y := pub.Y.Bytes()
if n > len(y) {
y = append(make([]byte, n-len(y)), y...)
}
// Field order is important.
// See https://tools.ietf.org/html/rfc7638#section-3.3 for details.
return fmt.Sprintf(`{"crv":"%s","kty":"EC","x":"%s","y":"%s"}`,
p.Name,
base64.RawURLEncoding.EncodeToString(x),
base64.RawURLEncoding.EncodeToString(y),
), nil
}
return "", ErrUnsupportedKey
}
// jwsSign signs the digest using the given key.
// It returns ErrUnsupportedKey if the key type is unknown.
// The hash is used only for RSA keys.
func jwsSign(key crypto.Signer, hash crypto.Hash, digest []byte) ([]byte, error) {
switch key := key.(type) {
case *rsa.PrivateKey:
return key.Sign(rand.Reader, digest, hash)
case *ecdsa.PrivateKey:
r, s, err := ecdsa.Sign(rand.Reader, key, digest)
if err != nil {
return nil, err
}
rb, sb := r.Bytes(), s.Bytes()
size := key.Params().BitSize / 8
if size%8 > 0 {
size++
}
sig := make([]byte, size*2)
copy(sig[size-len(rb):], rb)
copy(sig[size*2-len(sb):], sb)
return sig, nil
}
return nil, ErrUnsupportedKey
}
// jwsHasher indicates suitable JWS algorithm name and a hash function
// to use for signing a digest with the provided key.
// It returns ("", 0) if the key is not supported.
func jwsHasher(key crypto.Signer) (string, crypto.Hash) {
switch key := key.(type) {
case *rsa.PrivateKey:
return "RS256", crypto.SHA256
case *ecdsa.PrivateKey:
switch key.Params().Name {
case "P-256":
return "ES256", crypto.SHA256
case "P-384":
return "ES384", crypto.SHA384
case "P-512":
return "ES512", crypto.SHA512
}
}
return "", 0
}
// JWKThumbprint creates a JWK thumbprint out of pub
// as specified in https://tools.ietf.org/html/rfc7638.
func JWKThumbprint(pub crypto.PublicKey) (string, error) {
jwk, err := jwkEncode(pub)
if err != nil {
return "", err
}
b := sha256.Sum256([]byte(jwk))
return base64.RawURLEncoding.EncodeToString(b[:]), nil
}
|