google

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 Go to latest Published: Oct 1, 2018 License: BSD-3-Clause Imports: 22 Imported by: 0

Documentation

Overview

Package google provides support for making OAuth2 authorized and authenticated HTTP requests to Google APIs. It supports the Web server flow, client-side credentials, service accounts, Google Compute Engine service accounts, and Google App Engine service accounts.

A brief overview of the package follows. For more information, please read https://developers.google.com/accounts/docs/OAuth2 and https://developers.google.com/accounts/docs/application-default-credentials.

OAuth2 Configs

Two functions in this package return github.com/koofr/oauth2.Config values from Google credential data. Google supports two JSON formats for OAuth2 credentials: one is handled by ConfigFromJSON, the other by JWTConfigFromJSON. The returned Config can be used to obtain a TokenSource or create an http.Client.

Credentials

The Credentials type represents Google credentials, including Application Default Credentials.

Use FindDefaultCredentials to obtain Application Default Credentials. FindDefaultCredentials looks in some well-known places for a credentials file, and will call AppEngineTokenSource or ComputeTokenSource as needed.

DefaultClient and DefaultTokenSource are convenience methods. They first call FindDefaultCredentials, then use the credentials to construct an http.Client or an oauth2.TokenSource.

Use CredentialsFromJSON to obtain credentials from either of the two JSON formats described in OAuth2 Configs, above. The TokenSource in the returned value is the same as the one obtained from the oauth2.Config returned from ConfigFromJSON or JWTConfigFromJSON, but the Credentials may contain additional information that is useful is some circumstances.

Example (ServiceAccount) 
package main

import (
	"github.com/koofr/oauth2"
	"github.com/koofr/oauth2/google"
	"github.com/koofr/oauth2/jwt"
)

func main() {
	// Your credentials should be obtained from the Google
	// Developer Console (https://console.developers.google.com).
	conf := &jwt.Config{
		Email: "xxx@developer.gserviceaccount.com",
		// The contents of your RSA private key or your PEM file
		// that contains a private key.
		// If you have a p12 file instead, you
		// can use `openssl` to export the private key into a pem file.
		//
		//    $ openssl pkcs12 -in key.p12 -passin pass:notasecret -out key.pem -nodes
		//
		// The field only supports PEM containers with no passphrase.
		// The openssl command will convert p12 keys to passphrase-less PEM containers.
		PrivateKey: []byte("-----BEGIN RSA PRIVATE KEY-----..."),
		Scopes: []string{
			"https://www.googleapis.com/auth/bigquery",
			"https://www.googleapis.com/auth/blogger",
		},
		TokenURL: google.JWTTokenURL,
		// If you would like to impersonate a user, you can
		// create a transport with a subject. The following GET
		// request will be made on the behalf of user@example.com.
		// Optional.
		Subject: "user@example.com",
	}
	// Initiate an http.Client, the following GET request will be
	// authorized and authenticated on the behalf of user@example.com.
	client := conf.Client(oauth2.NoContext)
	client.Get("...")
}

Output:
Example (WebServer) 
package main

import (
	"fmt"
	"log"

	"github.com/koofr/oauth2"
	"github.com/koofr/oauth2/google"
)

func main() {
	// Your credentials should be obtained from the Google
	// Developer Console (https://console.developers.google.com).
	conf := &oauth2.Config{
		ClientID:     "YOUR_CLIENT_ID",
		ClientSecret: "YOUR_CLIENT_SECRET",
		RedirectURL:  "YOUR_REDIRECT_URL",
		Scopes: []string{
			"https://www.googleapis.com/auth/bigquery",
			"https://www.googleapis.com/auth/blogger",
		},
		Endpoint: google.Endpoint,
	}
	// Redirect user to Google's consent page to ask for permission
	// for the scopes specified above.
	url := conf.AuthCodeURL("state")
	fmt.Printf("Visit the URL for the auth dialog: %v", url)

	// Handle the exchange code to initiate a transport.
	tok, err := conf.Exchange(oauth2.NoContext, "authorization-code")
	if err != nil {
		log.Fatal(err)
	}
	client := conf.Client(oauth2.NoContext, tok)
	client.Get("...")
}

Output:

Index

Examples

Constants

View Source 
const JWTTokenURL = "https://accounts.google.com/o/oauth2/token"

JWTTokenURL is Google's OAuth 2.0 token URL to use with the JWT flow.

Variables

View Source 
var Endpoint = oauth2.Endpoint{
	AuthURL:  "https://accounts.google.com/o/oauth2/auth",
	TokenURL: "https://accounts.google.com/o/oauth2/token",
}

Endpoint is Google's OAuth 2.0 endpoint.

Functions

func AppEngineTokenSource 

func AppEngineTokenSource(ctx context.Context, scope ...string) oauth2.TokenSource

AppEngineTokenSource returns a token source that fetches tokens issued to the current App Engine application's service account. If you are implementing a 3-legged OAuth 2.0 flow on App Engine that involves user accounts, see oauth2.Config instead.

The provided context must have come from appengine.NewContext.

Example 
package main

import (
	"net/http"

	"github.com/koofr/oauth2"
	"github.com/koofr/oauth2/google"
	"google.golang.org/appengine"
	"google.golang.org/appengine/urlfetch"
)

func main() {
	var req *http.Request // from the ServeHTTP handler
	ctx := appengine.NewContext(req)
	client := &http.Client{
		Transport: &oauth2.Transport{
			Source: google.AppEngineTokenSource(ctx, "https://www.googleapis.com/auth/bigquery"),
			Base: &urlfetch.Transport{
				Context: ctx,
			},
		},
	}
	client.Get("...")
}

Output:

func ComputeTokenSource 

func ComputeTokenSource(account string) oauth2.TokenSource

ComputeTokenSource returns a token source that fetches access tokens from Google Compute Engine (GCE)'s metadata server. It's only valid to use this token source if your program is running on a GCE instance. If no account is specified, "default" is used. Further information about retrieving access tokens from the GCE metadata server can be found at https://cloud.google.com/compute/docs/authentication.

Example 
package main

import (
	"net/http"

	"github.com/koofr/oauth2"
	"github.com/koofr/oauth2/google"
)

func main() {
	client := &http.Client{
		Transport: &oauth2.Transport{
			// Fetch from Google Compute Engine's metadata server to retrieve
			// an access token for the provided account.
			// If no account is specified, "default" is used.
			Source: google.ComputeTokenSource(""),
		},
	}
	client.Get("...")
}

Output:

func ConfigFromJSON 

func ConfigFromJSON(jsonKey []byte, scope ...string) (*oauth2.Config, error)

ConfigFromJSON uses a Google Developers Console client_credentials.json file to construct a config. client_credentials.json can be downloaded from https://console.developers.google.com, under "Credentials". Download the Web application credentials in the JSON format and provide the contents of the file as jsonKey.

func DefaultClient 

func DefaultClient(ctx context.Context, scope ...string) (*http.Client, error)

DefaultClient returns an HTTP Client that uses the DefaultTokenSource to obtain authentication credentials.

Example 
package main

import (
	"log"

	"github.com/koofr/oauth2"
	"github.com/koofr/oauth2/google"
)

func main() {
	client, err := google.DefaultClient(oauth2.NoContext,
		"https://www.googleapis.com/auth/devstorage.full_control")
	if err != nil {
		log.Fatal(err)
	}
	client.Get("...")
}

Output:

func DefaultTokenSource 

func DefaultTokenSource(ctx context.Context, scope ...string) (oauth2.TokenSource, error)

DefaultTokenSource returns the token source for "Application Default Credentials". It is a shortcut for FindDefaultCredentials(ctx, scope).TokenSource.

func JWTAccessTokenSourceFromJSON 

func JWTAccessTokenSourceFromJSON(jsonKey []byte, audience string) (oauth2.TokenSource, error)

JWTAccessTokenSourceFromJSON uses a Google Developers service account JSON key file to read the credentials that authorize and authenticate the requests, and returns a TokenSource that does not use any OAuth2 flow but instead creates a JWT and sends that as the access token. The audience is typically a URL that specifies the scope of the credentials.

Note that this is not a standard OAuth flow, but rather an optimization supported by a few Google services. Unless you know otherwise, you should use JWTConfigFromJSON instead.

func JWTConfigFromJSON 

func JWTConfigFromJSON(jsonKey []byte, scope ...string) (*jwt.Config, error)

JWTConfigFromJSON uses a Google Developers service account JSON key file to read the credentials that authorize and authenticate the requests. Create a service account on "Credentials" for your project at https://console.developers.google.com to download a JSON key file.

Example 
package main

import (
	"io/ioutil"
	"log"

	"github.com/koofr/oauth2"
	"github.com/koofr/oauth2/google"
)

func main() {
	// Your credentials should be obtained from the Google
	// Developer Console (https://console.developers.google.com).
	// Navigate to your project, then see the "Credentials" page
	// under "APIs & Auth".
	// To create a service account client, click "Create new Client ID",
	// select "Service Account", and click "Create Client ID". A JSON
	// key file will then be downloaded to your computer.
	data, err := ioutil.ReadFile("/path/to/your-project-key.json")
	if err != nil {
		log.Fatal(err)
	}
	conf, err := google.JWTConfigFromJSON(data, "https://www.googleapis.com/auth/bigquery")
	if err != nil {
		log.Fatal(err)
	}
	// Initiate an http.Client. The following GET request will be
	// authorized and authenticated on the behalf of
	// your service account.
	client := conf.Client(oauth2.NoContext)
	client.Get("...")
}

Output:

Types

type Credentials 

type Credentials struct {
	ProjectID   string // may be empty
	TokenSource oauth2.TokenSource

	// JSON contains the raw bytes from a JSON credentials file.
	// This field may be nil if authentication is provided by the
	// environment and not with a credentials file, e.g. when code is
	// running on Google Cloud Platform.
	JSON []byte
}

Credentials holds Google credentials, including "Application Default Credentials". For more details, see: https://developers.google.com/accounts/docs/application-default-credentials

func CredentialsFromJSON 

func CredentialsFromJSON(ctx context.Context, jsonData []byte, scopes ...string) (*Credentials, error)

CredentialsFromJSON obtains Google credentials from a JSON value. The JSON can represent either a Google Developers Console client_credentials.json file (as in ConfigFromJSON) or a Google Developers service account key file (as in JWTConfigFromJSON).

Example 
package main

import (
	"io/ioutil"
	"log"

	"github.com/koofr/oauth2/google"
	"golang.org/x/net/context"
)

func main() {
	ctx := context.Background()
	data, err := ioutil.ReadFile("/path/to/key-file.json")
	if err != nil {
		log.Fatal(err)
	}
	creds, err := google.CredentialsFromJSON(ctx, data, "https://www.googleapis.com/auth/bigquery")
	if err != nil {
		log.Fatal(err)
	}
	_ = creds // TODO: Use creds.
}

Output:

func FindDefaultCredentials 

func FindDefaultCredentials(ctx context.Context, scopes ...string) (*Credentials, error)

FindDefaultCredentials searches for "Application Default Credentials".

It looks for credentials in the following places, preferring the first location found:

  1. A JSON file whose path is specified by the GOOGLE_APPLICATION_CREDENTIALS environment variable.
  2. A JSON file in a location known to the gcloud command-line tool. On Windows, this is %APPDATA%/gcloud/application_default_credentials.json. On other systems, $HOME/.config/gcloud/application_default_credentials.json.
  3. On Google App Engine it uses the appengine.AccessToken function.
  4. On Google Compute Engine and Google App Engine Managed VMs, it fetches credentials from the metadata server. (In this final case any provided scopes are ignored.)

type DefaultCredentials deprecated 

type DefaultCredentials = Credentials

DefaultCredentials is the old name of Credentials.

Deprecated: use Credentials instead.

type SDKConfig 

type SDKConfig struct {
	// contains filtered or unexported fields
}

An SDKConfig provides access to tokens from an account already authorized via the Google Cloud SDK.

Example 
package main

import (
	"log"

	"github.com/koofr/oauth2"
	"github.com/koofr/oauth2/google"
)

func main() {
	// The credentials will be obtained from the first account that
	// has been authorized with `gcloud auth login`.
	conf, err := google.NewSDKConfig("")
	if err != nil {
		log.Fatal(err)
	}
	// Initiate an http.Client. The following GET request will be
	// authorized and authenticated on the behalf of the SDK user.
	client := conf.Client(oauth2.NoContext)
	client.Get("...")
}

Output:

func NewSDKConfig 

func NewSDKConfig(account string) (*SDKConfig, error)

NewSDKConfig creates an SDKConfig for the given Google Cloud SDK account. If account is empty, the account currently active in Google Cloud SDK properties is used. Google Cloud SDK credentials must be created by running `gcloud auth` before using this function. The Google Cloud SDK is available at https://cloud.google.com/sdk/.

func (*SDKConfig) Client 

func (c *SDKConfig) Client(ctx context.Context) *http.Client

Client returns an HTTP client using Google Cloud SDK credentials to authorize requests. The token will auto-refresh as necessary. The underlying http.RoundTripper will be obtained using the provided context. The returned client and its Transport should not be modified.

func (*SDKConfig) Scopes 

func (c *SDKConfig) Scopes() []string

Scopes are the OAuth 2.0 scopes the current account is authorized for.

func (*SDKConfig) TokenSource 

func (c *SDKConfig) TokenSource(ctx context.Context) oauth2.TokenSource

TokenSource returns an oauth2.TokenSource that retrieve tokens from Google Cloud SDK credentials using the provided context. It will returns the current access token stored in the credentials, and refresh it when it expires, but it won't update the credentials with the new access token.

Source Files

View all Source files

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