131 lines
4.2 KiB
Go
131 lines
4.2 KiB
Go
// Copyright 2015 The Go Authors. All rights reserved.
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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 google
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import (
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"encoding/json"
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"fmt"
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"io/ioutil"
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"net/http"
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"os"
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"path/filepath"
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"runtime"
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"cloud.google.com/go/compute/metadata"
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"golang.org/x/net/context"
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"golang.org/x/oauth2"
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)
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// DefaultCredentials holds "Application Default Credentials".
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// For more details, see:
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// https://developers.google.com/accounts/docs/application-default-credentials
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type DefaultCredentials struct {
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ProjectID string // may be empty
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TokenSource oauth2.TokenSource
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}
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// DefaultClient returns an HTTP Client that uses the
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// DefaultTokenSource to obtain authentication credentials.
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func DefaultClient(ctx context.Context, scope ...string) (*http.Client, error) {
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ts, err := DefaultTokenSource(ctx, scope...)
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if err != nil {
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return nil, err
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}
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return oauth2.NewClient(ctx, ts), nil
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}
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// DefaultTokenSource returns the token source for
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// "Application Default Credentials".
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// It is a shortcut for FindDefaultCredentials(ctx, scope).TokenSource.
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func DefaultTokenSource(ctx context.Context, scope ...string) (oauth2.TokenSource, error) {
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creds, err := FindDefaultCredentials(ctx, scope...)
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if err != nil {
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return nil, err
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}
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return creds.TokenSource, nil
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}
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// FindDefaultCredentials searches for "Application Default Credentials".
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//
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// It looks for credentials in the following places,
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// preferring the first location found:
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//
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// 1. A JSON file whose path is specified by the
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// GOOGLE_APPLICATION_CREDENTIALS environment variable.
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// 2. A JSON file in a location known to the gcloud command-line tool.
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// On Windows, this is %APPDATA%/gcloud/application_default_credentials.json.
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// On other systems, $HOME/.config/gcloud/application_default_credentials.json.
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// 3. On Google App Engine it uses the appengine.AccessToken function.
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// 4. On Google Compute Engine and Google App Engine Managed VMs, it fetches
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// credentials from the metadata server.
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// (In this final case any provided scopes are ignored.)
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func FindDefaultCredentials(ctx context.Context, scope ...string) (*DefaultCredentials, error) {
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// First, try the environment variable.
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const envVar = "GOOGLE_APPLICATION_CREDENTIALS"
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if filename := os.Getenv(envVar); filename != "" {
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creds, err := readCredentialsFile(ctx, filename, scope)
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if err != nil {
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return nil, fmt.Errorf("google: error getting credentials using %v environment variable: %v", envVar, err)
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}
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return creds, nil
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}
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// Second, try a well-known file.
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filename := wellKnownFile()
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if creds, err := readCredentialsFile(ctx, filename, scope); err == nil {
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return creds, nil
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} else if !os.IsNotExist(err) {
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return nil, fmt.Errorf("google: error getting credentials using well-known file (%v): %v", filename, err)
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}
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// Third, if we're on Google App Engine use those credentials.
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if appengineTokenFunc != nil && !appengineVM {
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return &DefaultCredentials{
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ProjectID: appengineAppIDFunc(ctx),
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TokenSource: AppEngineTokenSource(ctx, scope...),
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}, nil
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}
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// Fourth, if we're on Google Compute Engine use the metadata server.
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if metadata.OnGCE() {
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id, _ := metadata.ProjectID()
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return &DefaultCredentials{
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ProjectID: id,
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TokenSource: ComputeTokenSource(""),
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}, nil
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}
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// None are found; return helpful error.
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const url = "https://developers.google.com/accounts/docs/application-default-credentials"
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return nil, fmt.Errorf("google: could not find default credentials. See %v for more information.", url)
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}
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func wellKnownFile() string {
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const f = "application_default_credentials.json"
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if runtime.GOOS == "windows" {
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return filepath.Join(os.Getenv("APPDATA"), "gcloud", f)
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}
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return filepath.Join(guessUnixHomeDir(), ".config", "gcloud", f)
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}
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func readCredentialsFile(ctx context.Context, filename string, scopes []string) (*DefaultCredentials, error) {
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b, err := ioutil.ReadFile(filename)
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if err != nil {
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return nil, err
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}
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var f credentialsFile
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if err := json.Unmarshal(b, &f); err != nil {
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return nil, err
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}
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ts, err := f.tokenSource(ctx, append([]string(nil), scopes...))
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if err != nil {
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return nil, err
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}
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return &DefaultCredentials{
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ProjectID: f.ProjectID,
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TokenSource: ts,
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}, nil
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}
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