forked from dhaivat/apt-gcs
/
init.go
105 lines (92 loc) · 3.01 KB
/
init.go
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package gcs
import (
"io/ioutil"
"log"
"net/http"
"os"
"golang.org/x/net/context"
"golang.org/x/oauth2"
"golang.org/x/oauth2/google"
storage "google.golang.org/api/storage/v1"
)
const (
scope = storage.DevstorageReadOnlyScope
accessTokenPath = "/etc/apt/gcs_access_token"
serviceAccountJSONPath = "/etc/apt/gcs_sa_json"
)
var (
client *context.Context
service *storage.Service
oService *storage.ObjectsService
)
var ctx context.Context = context.Background()
// InitConfig creates the google storage client that is used from the apt package
func InitConfig() {
client, err := getClient()
if err != nil {
log.Fatalf("Unable to get client: %v", err)
}
service, err = storage.New(client)
if err != nil {
log.Fatalf("Unable to create storage service: %v", err)
}
oService = storage.NewObjectsService(service)
if err != nil {
log.Fatalf("Unable to create objects storage service: %v", err)
}
}
// getClient returns an authenticated http client based on a different set of GCP
// auth methods, cascading in the following order:
// if access_token (bearer) is present in /etc/apt/gcs_access_token use it,
// else if Service Account JSON key is present in /etc/apt/gcs_sa_json use it,
// else try to get Application Default credentials https://github.com/golang/oauth2/blob/master/google/default.go
func getClient() (client *http.Client, err error) {
switch {
case fileExists(accessTokenPath):
client, err = clientFromAccessToken(accessTokenPath)
if err != nil {
log.Fatalf("Unable to get client: %v", err)
}
case fileExists(serviceAccountJSONPath):
client, err = clientFromServiceAccount(serviceAccountJSONPath)
if err != nil {
log.Fatalf("Unable to get client: %v", err)
}
default:
client, err = google.DefaultClient(ctx, scope)
if err != nil {
log.Fatalf("Unable to get client: %v", err)
}
}
return client, err
}
// clientFromAccessToken creates an http client authenticated using a GCS access_token (gcloud auth print-access-token)
func clientFromAccessToken(accessTokenPath string) (client *http.Client, err error) {
tokenBytes, err := ioutil.ReadFile(accessTokenPath)
if err != nil {
log.Fatalf("Error while reading access_token file: %v", err)
}
token := oauth2.Token{
AccessToken: string(tokenBytes),
}
tokenSource := oauth2.StaticTokenSource(&token)
return oauth2.NewClient(ctx, tokenSource), err
}
// clientFromServiceAccount creates an http client authenticated using a GCS Service account JSON key
func clientFromServiceAccount(serviceAccountJSONPath string) (client *http.Client, err error) {
JSONBytes, err := ioutil.ReadFile(serviceAccountJSONPath)
if err != nil {
log.Fatalf("Error while reading SA json file: %v", err)
}
credentials, err := google.CredentialsFromJSON(ctx, JSONBytes, scope)
tokenSource := credentials.TokenSource
return oauth2.NewClient(ctx, tokenSource), err
}
// fileExists checks if a file exists
func fileExists(filename string) bool {
info, err := os.Stat(filename)
if os.IsNotExist(err) {
return false
}
return !info.IsDir()
}