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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
// Copyright 2014 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 jws provides encoding and decoding utilities for
// signed JWS messages.
package jws // import "golang.org/x/oauth2/jws"
import (
"bytes"
"crypto"
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"encoding/base64"
"encoding/json"
"errors"
"fmt"
"strings"
"time"
)
// ClaimSet contains information about the JWT signature including the
// permissions being requested (scopes), the target of the token, the issuer,
// the time the token was issued, and the lifetime of the token.
type ClaimSet struct {
Iss string `json:"iss"` // email address of the client_id of the application making the access token request
Scope string `json:"scope,omitempty"` // space-delimited list of the permissions the application requests
Aud string `json:"aud"` // descriptor of the intended target of the assertion (Optional).
Exp int64 `json:"exp"` // the expiration time of the assertion (seconds since Unix epoch)
Iat int64 `json:"iat"` // the time the assertion was issued (seconds since Unix epoch)
Typ string `json:"typ,omitempty"` // token type (Optional).
// Email for which the application is requesting delegated access (Optional).
Sub string `json:"sub,omitempty"`
// The old name of Sub. Client keeps setting Prn to be
// complaint with legacy OAuth 2.0 providers. (Optional)
Prn string `json:"prn,omitempty"`
// See http://tools.ietf.org/html/draft-jones-json-web-token-10#section-4.3
// This array is marshalled using custom code (see (c *ClaimSet) encode()).
PrivateClaims map[string]interface{} `json:"-"`
}
func (c *ClaimSet) encode() (string, error) {
// Reverting time back for machines whose time is not perfectly in sync.
// If client machine's time is in the future according
// to Google servers, an access token will not be issued.
now := time.Now().Add(-10 * time.Second)
if c.Iat == 0 {
c.Iat = now.Unix()
}
if c.Exp == 0 {
c.Exp = now.Add(time.Hour).Unix()
}
if c.Exp < c.Iat {
return "", fmt.Errorf("jws: invalid Exp = %v; must be later than Iat = %v", c.Exp, c.Iat)
}
b, err := json.Marshal(c)
if err != nil {
return "", err
}
if len(c.PrivateClaims) == 0 {
return base64Encode(b), nil
}
// Marshal private claim set and then append it to b.
prv, err := json.Marshal(c.PrivateClaims)
if err != nil {
return "", fmt.Errorf("jws: invalid map of private claims %v", c.PrivateClaims)
}
// Concatenate public and private claim JSON objects.
if !bytes.HasSuffix(b, []byte{'}'}) {
return "", fmt.Errorf("jws: invalid JSON %s", b)
}
if !bytes.HasPrefix(prv, []byte{'{'}) {
return "", fmt.Errorf("jws: invalid JSON %s", prv)
}
b[len(b)-1] = ',' // Replace closing curly brace with a comma.
b = append(b, prv[1:]...) // Append private claims.
return base64Encode(b), nil
}
// Header represents the header for the signed JWS payloads.
type Header struct {
// The algorithm used for signature.
Algorithm string `json:"alg"`
// Represents the token type.
Typ string `json:"typ"`
// The optional hint of which key is being used.
KeyID string `json:"kid,omitempty"`
}
func (h *Header) encode() (string, error) {
b, err := json.Marshal(h)
if err != nil {
return "", err
}
return base64Encode(b), nil
}
// Decode decodes a claim set from a JWS payload.
func Decode(payload string) (*ClaimSet, error) {
// decode returned id token to get expiry
s := strings.Split(payload, ".")
if len(s) < 2 {
// TODO(jbd): Provide more context about the error.
return nil, errors.New("jws: invalid token received")
}
decoded, err := base64Decode(s[1])
if err != nil {
return nil, err
}
c := &ClaimSet{}
err = json.NewDecoder(bytes.NewBuffer(decoded)).Decode(c)
return c, err
}
// Signer returns a signature for the given data.
type Signer func(data []byte) (sig []byte, err error)
// EncodeWithSigner encodes a header and claim set with the provided signer.
func EncodeWithSigner(header *Header, c *ClaimSet, sg Signer) (string, error) {
head, err := header.encode()
if err != nil {
return "", err
}
cs, err := c.encode()
if err != nil {
return "", err
}
ss := fmt.Sprintf("%s.%s", head, cs)
sig, err := sg([]byte(ss))
if err != nil {
return "", err
}
return fmt.Sprintf("%s.%s", ss, base64Encode(sig)), nil
}
// Encode encodes a signed JWS with provided header and claim set.
// This invokes EncodeWithSigner using crypto/rsa.SignPKCS1v15 with the given RSA private key.
func Encode(header *Header, c *ClaimSet, key *rsa.PrivateKey) (string, error) {
sg := func(data []byte) (sig []byte, err error) {
h := sha256.New()
h.Write(data)
return rsa.SignPKCS1v15(rand.Reader, key, crypto.SHA256, h.Sum(nil))
}
return EncodeWithSigner(header, c, sg)
}
// Verify tests whether the provided JWT token's signature was produced by the private key
// associated with the supplied public key.
func Verify(token string, key *rsa.PublicKey) error {
parts := strings.Split(token, ".")
if len(parts) != 3 {
return errors.New("jws: invalid token received, token must have 3 parts")
}
signedContent := parts[0] + "." + parts[1]
signatureString, err := base64Decode(parts[2])
if err != nil {
return err
}
h := sha256.New()
h.Write([]byte(signedContent))
return rsa.VerifyPKCS1v15(key, crypto.SHA256, h.Sum(nil), []byte(signatureString))
}
// base64Encode returns and Base64url encoded version of the input string with any
// trailing "=" stripped.
func base64Encode(b []byte) string {
return strings.TrimRight(base64.URLEncoding.EncodeToString(b), "=")
}
// base64Decode decodes the Base64url encoded string
func base64Decode(s string) ([]byte, error) {
// add back missing padding
switch len(s) % 4 {
case 1:
s += "==="
case 2:
s += "=="
case 3:
s += "="
}
return base64.URLEncoding.DecodeString(s)
}
|
