93 lines
2.7 KiB
Go
93 lines
2.7 KiB
Go
// Copyright 2017 Google LLC.
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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 internal
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import (
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"context"
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"encoding/json"
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"fmt"
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"io/ioutil"
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"golang.org/x/oauth2"
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"golang.org/x/oauth2/google"
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)
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// Creds returns credential information obtained from DialSettings, or if none, then
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// it returns default credential information.
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func Creds(ctx context.Context, ds *DialSettings) (*google.Credentials, error) {
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if ds.Credentials != nil {
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return ds.Credentials, nil
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}
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if ds.CredentialsJSON != nil {
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return credentialsFromJSON(ctx, ds.CredentialsJSON, ds.Endpoint, ds.Scopes, ds.Audiences)
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}
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if ds.CredentialsFile != "" {
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data, err := ioutil.ReadFile(ds.CredentialsFile)
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if err != nil {
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return nil, fmt.Errorf("cannot read credentials file: %v", err)
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}
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return credentialsFromJSON(ctx, data, ds.Endpoint, ds.Scopes, ds.Audiences)
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}
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if ds.TokenSource != nil {
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return &google.Credentials{TokenSource: ds.TokenSource}, nil
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}
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cred, err := google.FindDefaultCredentials(ctx, ds.Scopes...)
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if err != nil {
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return nil, err
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}
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if len(cred.JSON) > 0 {
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return credentialsFromJSON(ctx, cred.JSON, ds.Endpoint, ds.Scopes, ds.Audiences)
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}
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// For GAE and GCE, the JSON is empty so return the default credentials directly.
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return cred, nil
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}
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// JSON key file type.
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const (
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serviceAccountKey = "service_account"
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)
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// credentialsFromJSON returns a google.Credentials based on the input.
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//
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// - If the JSON is a service account and no scopes provided, returns self-signed JWT auth flow
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// - Otherwise, returns OAuth 2.0 flow.
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func credentialsFromJSON(ctx context.Context, data []byte, endpoint string, scopes []string, audiences []string) (*google.Credentials, error) {
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cred, err := google.CredentialsFromJSON(ctx, data, scopes...)
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if err != nil {
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return nil, err
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}
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if len(data) > 0 && len(scopes) == 0 {
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var f struct {
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Type string `json:"type"`
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// The rest JSON fields are omitted because they are not used.
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}
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if err := json.Unmarshal(cred.JSON, &f); err != nil {
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return nil, err
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}
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if f.Type == serviceAccountKey {
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ts, err := selfSignedJWTTokenSource(data, endpoint, audiences)
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if err != nil {
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return nil, err
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}
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cred.TokenSource = ts
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}
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}
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return cred, err
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}
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func selfSignedJWTTokenSource(data []byte, endpoint string, audiences []string) (oauth2.TokenSource, error) {
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// Use the API endpoint as the default audience
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audience := endpoint
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if len(audiences) > 0 {
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// TODO(shinfan): Update golang oauth to support multiple audiences.
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if len(audiences) > 1 {
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return nil, fmt.Errorf("multiple audiences support is not implemented")
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}
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audience = audiences[0]
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}
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return google.JWTAccessTokenSourceFromJSON(data, audience)
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}
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