replace some bespoke google auth code with code from golang's oauth2 library

builder/googlecompute/account.go

@@ -1,52 +1,34 @@
 package googlecompute
 
 import (
-	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"os"
-	"strings"
-)
-
-// accountFile represents the structure of the account file JSON file.
-type AccountFile struct {
-	PrivateKeyId string `json:"private_key_id"`
-	PrivateKey   string `json:"private_key"`
-	ClientEmail  string `json:"client_email"`
-	ClientId     string `json:"client_id"`
-}
 
-func parseJSON(result interface{}, text string) error {
+	"golang.org/x/oauth2/google"
-	r := strings.NewReader(text)
+	"golang.org/x/oauth2/jwt"
-	dec := json.NewDecoder(r)
+)
-	return dec.Decode(result)
-}
 
-func ProcessAccountFile(account_file *AccountFile, text string) error {
+func ProcessAccountFile(text string) (*jwt.Config, error) {
 	// Assume text is a JSON string
-	if err := parseJSON(account_file, text); err != nil {
+	conf, err := google.JWTConfigFromJSON([]byte(text), DriverScopes...)
+	if err != nil {
 		// If text was not JSON, assume it is a file path instead
 		if _, err := os.Stat(text); os.IsNotExist(err) {
-			return fmt.Errorf(
+			return nil, fmt.Errorf(
 				"account_file path does not exist: %s",
 				text)
 		}
-
+		data, err := ioutil.ReadFile(text)
-		b, err := ioutil.ReadFile(text)
 		if err != nil {
-			return fmt.Errorf(
+			return nil, fmt.Errorf(
 				"Error reading account_file from path '%s': %s",
 				text, err)
 		}
-
+		conf, err = google.JWTConfigFromJSON(data, DriverScopes...)
-		contents := string(b)
+		if err != nil {
-
+			return nil, fmt.Errorf("Error parsing account_file: %s", err)
-		if err := parseJSON(account_file, contents); err != nil {
-			return fmt.Errorf(
-				"Error parsing account file '%s': %s",
-				contents, err)
 		}
 	}
-
+	return conf, nil
-	return nil
 }

builder/googlecompute/builder.go

@@ -36,7 +36,7 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 // representing a GCE machine image.
 func (b *Builder) Run(ctx context.Context, ui packer.Ui, hook packer.Hook) (packer.Artifact, error) {
 	driver, err := NewDriverGCE(
-		ui, b.config.ProjectId, &b.config.Account)
+		ui, b.config.ProjectId, b.config.Account)
 	if err != nil {
 		return nil, err
 	}

builder/googlecompute/config.go

@@ -13,6 +13,7 @@ import (
 	"github.com/hashicorp/packer/helper/config"
 	"github.com/hashicorp/packer/packer"
 	"github.com/hashicorp/packer/template/interpolate"
+	"golang.org/x/oauth2/jwt"
 	compute "google.golang.org/api/compute/v1"
 )
 
@@ -65,7 +66,7 @@ type Config struct {
 	MetadataFiles                map[string]string              `mapstructure:"metadata_files"`
 	Zone                         string                         `mapstructure:"zone"`
 
-	Account            AccountFile
+	Account            *jwt.Config
 	stateTimeout       time.Duration
 	imageAlreadyExists bool
 	ctx                interpolate.Context
@@ -209,9 +210,11 @@ func NewConfig(raws ...interface{}) (*Config, []string, error) {
 	}
 
 	if c.AccountFile != "" {
-		if err := ProcessAccountFile(&c.Account, c.AccountFile); err != nil {
+		cfg, err := ProcessAccountFile(c.AccountFile)
+		if err != nil {
 			errs = packer.MultiErrorAppend(errs, err)
 		}
+		c.Account = cfg
 	}
 
 	if c.OmitExternalIP && c.Address != "" {

builder/googlecompute/driver_gce.go

@@ -35,24 +35,17 @@ type driverGCE struct {
 
 var DriverScopes = []string{"https://www.googleapis.com/auth/compute", "https://www.googleapis.com/auth/devstorage.full_control"}
 
-func NewClientGCE(a *AccountFile) (*http.Client, error) {
+func NewClientGCE(conf *jwt.Config) (*http.Client, error) {
 	var err error
 
 	var client *http.Client
 
 	// Auth with AccountFile first if provided
-	if a.PrivateKey != "" {
+	if len(conf.PrivateKey) > 0 {
-		log.Printf("[INFO] Requesting Google token via AccountFile...")
+		log.Printf("[INFO] Requesting Google token via account_file...")
-		log.Printf("[INFO]   -- Email: %s", a.ClientEmail)
+		log.Printf("[INFO]   -- Email: %s", conf.Email)
 		log.Printf("[INFO]   -- Scopes: %s", DriverScopes)
-		log.Printf("[INFO]   -- Private Key Length: %d", len(a.PrivateKey))
+		log.Printf("[INFO]   -- Private Key Length: %d", len(conf.PrivateKey))
-
-		conf := jwt.Config{
-			Email:      a.ClientEmail,
-			PrivateKey: []byte(a.PrivateKey),
-			Scopes:     DriverScopes,
-			TokenURL:   "https://accounts.google.com/o/oauth2/token",
-		}
 
 		// Initiate an http.Client. The following GET request will be
 		// authorized and authenticated on the behalf of
@@ -82,8 +75,8 @@ func NewClientGCE(a *AccountFile) (*http.Client, error) {
 	return client, nil
 }
 
-func NewDriverGCE(ui packer.Ui, p string, a *AccountFile) (Driver, error) {
+func NewDriverGCE(ui packer.Ui, p string, conf *jwt.Config) (Driver, error) {
-	client, err := NewClientGCE(a)
+	client, err := NewClientGCE(conf)
 	if err != nil {
 		return nil, err
 	}

builder/googlecompute/step_create_windows_password.go

@@ -60,7 +60,7 @@ func (s *StepCreateWindowsPassword) Run(ctx context.Context, state multistep.Sta
 		UserName: c.Comm.WinRMUser,
 		Modulus:  base64.StdEncoding.EncodeToString(priv.N.Bytes()),
 		Exponent: base64.StdEncoding.EncodeToString(buf[1:]),
-		Email:    c.Account.ClientEmail,
+		Email:    c.Account.Email,
 		ExpireOn: time.Now().Add(time.Minute * 5),
 	}
 

post-processor/googlecompute-export/post-processor.go

@@ -11,6 +11,7 @@ import (
 	"github.com/hashicorp/packer/helper/multistep"
 	"github.com/hashicorp/packer/packer"
 	"github.com/hashicorp/packer/template/interpolate"
+	"golang.org/x/oauth2/jwt"
 )
 
 type Config struct {
@@ -26,7 +27,7 @@ type Config struct {
 	Subnetwork  string   `mapstructure:"subnetwork"`
 	Zone        string   `mapstructure:"zone"`
 
-	Account googlecompute.AccountFile
+	Account *jwt.Config
 	ctx     interpolate.Context
 }
 
@@ -96,16 +97,18 @@ func (p *PostProcessor) PostProcess(ctx context.Context, ui packer.Ui, artifact
 
 	// Set up credentials for GCE driver.
 	if builderAccountFile != "" {
-		err := googlecompute.ProcessAccountFile(&p.config.Account, builderAccountFile)
+		cfg, err := googlecompute.ProcessAccountFile(builderAccountFile)
 		if err != nil {
 			return nil, false, false, err
 		}
+		p.config.Account = cfg
 	}
 	if p.config.AccountFile != "" {
-		err := googlecompute.ProcessAccountFile(&p.config.Account, p.config.AccountFile)
+		cfg, err := googlecompute.ProcessAccountFile(p.config.AccountFile)
 		if err != nil {
 			return nil, false, false, err
 		}
+		p.config.Account = cfg
 	}
 
 	// Set up exporter instance configuration.
@@ -139,7 +142,7 @@ func (p *PostProcessor) PostProcess(ctx context.Context, ui packer.Ui, artifact
 	}
 	exporterConfig.CalcTimeout()
 
-	driver, err := googlecompute.NewDriverGCE(ui, builderProjectId, &p.config.Account)
+	driver, err := googlecompute.NewDriverGCE(ui, builderProjectId, p.config.Account)
 	if err != nil {
 		return nil, false, false, err
 	}

post-processor/googlecompute-import/post-processor.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"time"
 
+	"golang.org/x/oauth2/jwt"
 	"google.golang.org/api/compute/v1"
 	"google.golang.org/api/storage/v1"
 
@@ -34,7 +35,7 @@ type Config struct {
 	ImageName            string            `mapstructure:"image_name"`
 	SkipClean            bool              `mapstructure:"skip_clean"`
 
-	Account googlecompute.AccountFile
+	Account *jwt.Config
 	ctx     interpolate.Context
 }
 
@@ -70,9 +71,11 @@ func (p *PostProcessor) Configure(raws ...interface{}) error {
 	}
 
 	if p.config.AccountFile != "" {
-		if err := googlecompute.ProcessAccountFile(&p.config.Account, p.config.AccountFile); err != nil {
+		cfg, err := googlecompute.ProcessAccountFile(p.config.AccountFile)
+		if err != nil {
 			errs = packer.MultiErrorAppend(errs, err)
 		}
+		p.config.Account = cfg
 	}
 
 	templates := map[string]*string{
@@ -95,7 +98,7 @@ func (p *PostProcessor) Configure(raws ...interface{}) error {
 }
 
 func (p *PostProcessor) PostProcess(ctx context.Context, ui packer.Ui, artifact packer.Artifact) (packer.Artifact, bool, bool, error) {
-	client, err := googlecompute.NewClientGCE(&p.config.Account)
+	client, err := googlecompute.NewClientGCE(p.config.Account)
 	if err != nil {
 		return nil, false, false, err
 	}