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
|
// Copyright 2021 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 impersonate
import (
"bytes"
"context"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net/http"
"time"
"golang.org/x/oauth2"
"google.golang.org/api/option"
htransport "google.golang.org/api/transport/http"
)
// IDTokenConfig for generating an impersonated ID token.
type IDTokenConfig struct {
// Audience is the `aud` field for the token, such as an API endpoint the
// token will grant access to. Required.
Audience string
// TargetPrincipal is the email address of the service account to
// impersonate. Required.
TargetPrincipal string
// IncludeEmail includes the service account's email in the token. The
// resulting token will include both an `email` and `email_verified`
// claim.
IncludeEmail bool
// Delegates are the service account email addresses in a delegation chain.
// Each service account must be granted roles/iam.serviceAccountTokenCreator
// on the next service account in the chain. Optional.
Delegates []string
}
// IDTokenSource creates an impersonated TokenSource that returns ID tokens
// configured with the provided config and using credentials loaded from
// Application Default Credentials as the base credentials. The tokens provided
// by the source are valid for one hour and are automatically refreshed.
func IDTokenSource(ctx context.Context, config IDTokenConfig, opts ...option.ClientOption) (oauth2.TokenSource, error) {
if config.Audience == "" {
return nil, fmt.Errorf("impersonate: an audience must be provided")
}
if config.TargetPrincipal == "" {
return nil, fmt.Errorf("impersonate: a target service account must be provided")
}
clientOpts := append(defaultClientOptions(), opts...)
client, _, err := htransport.NewClient(ctx, clientOpts...)
if err != nil {
return nil, err
}
its := impersonatedIDTokenSource{
client: client,
targetPrincipal: config.TargetPrincipal,
audience: config.Audience,
includeEmail: config.IncludeEmail,
}
for _, v := range config.Delegates {
its.delegates = append(its.delegates, formatIAMServiceAccountName(v))
}
return oauth2.ReuseTokenSource(nil, its), nil
}
type generateIDTokenRequest struct {
Audience string `json:"audience"`
IncludeEmail bool `json:"includeEmail"`
Delegates []string `json:"delegates,omitempty"`
}
type generateIDTokenResponse struct {
Token string `json:"token"`
}
type impersonatedIDTokenSource struct {
client *http.Client
targetPrincipal string
audience string
includeEmail bool
delegates []string
}
func (i impersonatedIDTokenSource) Token() (*oauth2.Token, error) {
now := time.Now()
genIDTokenReq := generateIDTokenRequest{
Audience: i.audience,
IncludeEmail: i.includeEmail,
Delegates: i.delegates,
}
bodyBytes, err := json.Marshal(genIDTokenReq)
if err != nil {
return nil, fmt.Errorf("impersonate: unable to marshal request: %v", err)
}
url := fmt.Sprintf("%s/v1/%s:generateIdToken", iamCredentailsEndpoint, formatIAMServiceAccountName(i.targetPrincipal))
req, err := http.NewRequest("POST", url, bytes.NewReader(bodyBytes))
if err != nil {
return nil, fmt.Errorf("impersonate: unable to create request: %v", err)
}
req.Header.Set("Content-Type", "application/json")
resp, err := i.client.Do(req)
if err != nil {
return nil, fmt.Errorf("impersonate: unable to generate ID token: %v", err)
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
if err != nil {
return nil, fmt.Errorf("impersonate: unable to read body: %v", err)
}
if c := resp.StatusCode; c < 200 || c > 299 {
return nil, fmt.Errorf("impersonate: status code %d: %s", c, body)
}
var generateIDTokenResp generateIDTokenResponse
if err := json.Unmarshal(body, &generateIDTokenResp); err != nil {
return nil, fmt.Errorf("impersonate: unable to parse response: %v", err)
}
return &oauth2.Token{
AccessToken: generateIDTokenResp.Token,
// Generated ID tokens are good for one hour.
Expiry: now.Add(1 * time.Hour),
}, nil
}
|
