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// Copyright 2017 Google LLC.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package internal
import (
"context"
"encoding/json"
"errors"
"fmt"
"io/ioutil"
"golang.org/x/oauth2"
"google.golang.org/api/internal/impersonate"
"golang.org/x/oauth2/google"
)
// Creds returns credential information obtained from DialSettings, or if none, then
// it returns default credential information.
func Creds(ctx context.Context, ds *DialSettings) (*google.Credentials, error) {
creds, err := baseCreds(ctx, ds)
if err != nil {
return nil, err
}
if ds.ImpersonationConfig != nil {
return impersonateCredentials(ctx, creds, ds)
}
return creds, nil
}
func baseCreds(ctx context.Context, ds *DialSettings) (*google.Credentials, error) {
if ds.InternalCredentials != nil {
return ds.InternalCredentials, nil
}
if ds.Credentials != nil {
return ds.Credentials, nil
}
if ds.CredentialsJSON != nil {
return credentialsFromJSON(ctx, ds.CredentialsJSON, ds)
}
if ds.CredentialsFile != "" {
data, err := ioutil.ReadFile(ds.CredentialsFile)
if err != nil {
return nil, fmt.Errorf("cannot read credentials file: %v", err)
}
return credentialsFromJSON(ctx, data, ds)
}
if ds.TokenSource != nil {
return &google.Credentials{TokenSource: ds.TokenSource}, nil
}
cred, err := google.FindDefaultCredentials(ctx, ds.GetScopes()...)
if err != nil {
return nil, err
}
if len(cred.JSON) > 0 {
return credentialsFromJSON(ctx, cred.JSON, ds)
}
// For GAE and GCE, the JSON is empty so return the default credentials directly.
return cred, nil
}
// JSON key file type.
const (
serviceAccountKey = "service_account"
)
// credentialsFromJSON returns a google.Credentials from the JSON data
//
// - A self-signed JWT flow will be executed if the following conditions are
// met:
// (1) At least one of the following is true:
// (a) No scope is provided
// (b) Scope for self-signed JWT flow is enabled
// (c) Audiences are explicitly provided by users
// (2) No service account impersontation
//
// - Otherwise, executes standard OAuth 2.0 flow
// More details: google.aip.dev/auth/4111
func credentialsFromJSON(ctx context.Context, data []byte, ds *DialSettings) (*google.Credentials, error) {
// By default, a standard OAuth 2.0 token source is created
cred, err := google.CredentialsFromJSON(ctx, data, ds.GetScopes()...)
if err != nil {
return nil, err
}
// Override the token source to use self-signed JWT if conditions are met
isJWTFlow, err := isSelfSignedJWTFlow(data, ds)
if err != nil {
return nil, err
}
if isJWTFlow {
ts, err := selfSignedJWTTokenSource(data, ds)
if err != nil {
return nil, err
}
cred.TokenSource = ts
}
return cred, err
}
func isSelfSignedJWTFlow(data []byte, ds *DialSettings) (bool, error) {
if (ds.EnableJwtWithScope || ds.HasCustomAudience()) &&
ds.ImpersonationConfig == nil {
// Check if JSON is a service account and if so create a self-signed JWT.
var f struct {
Type string `json:"type"`
// The rest JSON fields are omitted because they are not used.
}
if err := json.Unmarshal(data, &f); err != nil {
return false, err
}
return f.Type == serviceAccountKey, nil
}
return false, nil
}
func selfSignedJWTTokenSource(data []byte, ds *DialSettings) (oauth2.TokenSource, error) {
if len(ds.GetScopes()) > 0 && !ds.HasCustomAudience() {
// Scopes are preferred in self-signed JWT unless the scope is not available
// or a custom audience is used.
return google.JWTAccessTokenSourceWithScope(data, ds.GetScopes()...)
} else if ds.GetAudience() != "" {
// Fallback to audience if scope is not provided
return google.JWTAccessTokenSourceFromJSON(data, ds.GetAudience())
} else {
return nil, errors.New("neither scopes or audience are available for the self-signed JWT")
}
}
// QuotaProjectFromCreds returns the quota project from the JSON blob in the provided credentials.
//
// NOTE(cbro): consider promoting this to a field on google.Credentials.
func QuotaProjectFromCreds(cred *google.Credentials) string {
var v struct {
QuotaProject string `json:"quota_project_id"`
}
if err := json.Unmarshal(cred.JSON, &v); err != nil {
return ""
}
return v.QuotaProject
}
func impersonateCredentials(ctx context.Context, creds *google.Credentials, ds *DialSettings) (*google.Credentials, error) {
if len(ds.ImpersonationConfig.Scopes) == 0 {
ds.ImpersonationConfig.Scopes = ds.GetScopes()
}
ts, err := impersonate.TokenSource(ctx, creds.TokenSource, ds.ImpersonationConfig)
if err != nil {
return nil, err
}
return &google.Credentials{
TokenSource: ts,
ProjectID: creds.ProjectID,
}, nil
}
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