New feature, support authentication via service account.

2 files changed, 31 insertions, 2 deletions

diff --git a/auth/file_source.go b/auth/file_source.go
index 5200203..11e7325 100644
--- a/auth/file_source.go
+++ b/auth/file_source.go
@@ -31,7 +31,7 @@ func (self *fileSource) Token() (*oauth2.Token, error) {
 	return token, nil
 }
 
-func ReadToken(path string) (*oauth2.Token, bool, error) {
+func ReadFile(path string) ([]byte, bool, error) {
 	if !fileExists(path) {
 		return nil, false, nil
 	}
@@ -40,8 +40,19 @@ func ReadToken(path string) (*oauth2.Token, bool, error) {
 	if err != nil {
 		return nil, true, err
 	}
+	return content, true, nil
+}
+
+
+func ReadToken(path string) (*oauth2.Token, bool, error) {
+
+	content, exists, err := ReadFile(path)
+	if err != nil {
+		return nil, exists, err
+	}
+
 	token := &oauth2.Token{}
-	return token, true, json.Unmarshal(content, token)
+	return token, exists, json.Unmarshal(content, token)
 }
 
 func SaveToken(path string, token *oauth2.Token) error {
diff --git a/auth/oauth.go b/auth/oauth.go
index 150642c..bc56738 100644
--- a/auth/oauth.go
+++ b/auth/oauth.go
@@ -3,6 +3,7 @@ package auth
 import (
 	"fmt"
 	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
 	"net/http"
 	"time"
 )
@@ -64,6 +65,23 @@ func NewAccessTokenClient(clientId, clientSecret, accessToken string) *http.Clie
 	)
 }
 
+func NewServiceAccountClient(serviceAccountFile string) (*http.Client, error) {
+	content, exists, err := ReadFile(serviceAccountFile)
+	if(!exists) {
+		return nil, fmt.Errorf("Service account filename %q not found", serviceAccountFile)
+	}
+
+	if(err != nil) {
+		return nil, err
+	}
+
+	conf, err := google.JWTConfigFromJSON(content, "https://www.googleapis.com/auth/drive")
+	if(err != nil) {
+		return nil, err
+	}
+	return conf.Client(oauth2.NoContext), nil
+}
+
 func getConfig(clientId, clientSecret string) *oauth2.Config {
 	return &oauth2.Config{
 		ClientID:     clientId,