From 20e0ca53cba796a67311360d7a21c0f7c8baf78a Mon Sep 17 00:00:00 2001 From: Vincent Ambo Date: Sun, 27 Oct 2019 17:59:30 +0100 Subject: feat(server): Implement GCS storage backend with new interface Logical implementation is mostly identical to the previous one, but adhering to the new storage.Backend interface. --- tools/nixery/server/storage/gcs.go | 206 +++++++++++++++++++++++++++++++++++++ 1 file changed, 206 insertions(+) create mode 100644 tools/nixery/server/storage/gcs.go diff --git a/tools/nixery/server/storage/gcs.go b/tools/nixery/server/storage/gcs.go new file mode 100644 index 000000000000..1b75722bbb77 --- /dev/null +++ b/tools/nixery/server/storage/gcs.go @@ -0,0 +1,206 @@ +// Google Cloud Storage backend for Nixery. +package storage + +import ( + "context" + "fmt" + "io" + "io/ioutil" + "net/http" + "net/url" + "os" + "time" + + "cloud.google.com/go/storage" + log "github.com/sirupsen/logrus" + "golang.org/x/oauth2/google" +) + +// HTTP client to use for direct calls to APIs that are not part of the SDK +var client = &http.Client{} + +// API scope needed for renaming objects in GCS +const gcsScope = "https://www.googleapis.com/auth/devstorage" + +type GCSBackend struct { + bucket string + handle *storage.BucketHandle + signing *storage.SignedURLOptions +} + +// Constructs a new GCS bucket backend based on the configured +// environment variables. +func New() (GCSBackend, error) { + bucket := os.Getenv("GCS_BUCKET") + if bucket == "" { + return GCSBackend{}, fmt.Errorf("GCS_BUCKET must be configured for GCS usage") + } + + ctx := context.Background() + client, err := storage.NewClient(ctx) + if err != nil { + log.WithError(err).Fatal("failed to set up Cloud Storage client") + } + + handle := client.Bucket(bucket) + + if _, err := handle.Attrs(ctx); err != nil { + log.WithError(err).WithField("bucket", bucket).Error("could not access configured bucket") + return GCSBackend{}, err + } + + signing, err := signingOptsFromEnv() + if err != nil { + log.WithError(err).Error("failed to configure GCS bucket signing") + return GCSBackend{}, err + } + + return GCSBackend{ + bucket: bucket, + handle: handle, + signing: signing, + }, nil +} + +func (b *GCSBackend) Name() string { + return "Google Cloud Storage (" + b.bucket + ")" +} + +func (b *GCSBackend) Persist(path string, f func(io.Writer) (string, int, error)) (string, int, error) { + ctx := context.Background() + obj := b.handle.Object(path) + w := obj.NewWriter(ctx) + + hash, size, err := f(w) + if err != nil { + log.WithError(err).WithField("path", path).Error("failed to upload to GCS") + return hash, size, err + } + + return hash, size, w.Close() +} + +func (b *GCSBackend) Fetch(path string) (io.ReadCloser, error) { + ctx := context.Background() + obj := b.handle.Object(path) + + // Probe whether the file exists before trying to fetch it + _, err := obj.Attrs(ctx) + if err != nil { + return nil, err + } + + return obj.NewReader(ctx) +} + +// renameObject renames an object in the specified Cloud Storage +// bucket. +// +// The Go API for Cloud Storage does not support renaming objects, but +// the HTTP API does. The code below makes the relevant call manually. +func (b *GCSBackend) Move(old, new string) error { + ctx := context.Background() + creds, err := google.FindDefaultCredentials(ctx, gcsScope) + if err != nil { + return err + } + + token, err := creds.TokenSource.Token() + if err != nil { + return err + } + + // as per https://cloud.google.com/storage/docs/renaming-copying-moving-objects#rename + url := fmt.Sprintf( + "https://www.googleapis.com/storage/v1/b/%s/o/%s/rewriteTo/b/%s/o/%s", + url.PathEscape(b.bucket), url.PathEscape(old), + url.PathEscape(b.bucket), url.PathEscape(new), + ) + + req, err := http.NewRequest("POST", url, nil) + req.Header.Add("Authorization", "Bearer "+token.AccessToken) + _, err = client.Do(req) + if err != nil { + return err + } + + // It seems that 'rewriteTo' copies objects instead of + // renaming/moving them, hence a deletion call afterwards is + // required. + if err = b.handle.Object(old).Delete(ctx); err != nil { + log.WithError(err).WithFields(log.Fields{ + "new": new, + "old": old, + }).Warn("failed to delete renamed object") + + // this error should not break renaming and is not returned + } + + return nil +} + +func (b *GCSBackend) Serve(digest string, w http.ResponseWriter) error { + url, err := b.constructLayerUrl(digest) + if err != nil { + log.WithError(err).WithFields(log.Fields{ + "layer": digest, + "bucket": b.bucket, + }).Error("failed to sign GCS URL") + + return err + } + + w.Header().Set("Location", url) + w.WriteHeader(303) + return nil +} + +// Configure GCS URL signing in the presence of a service account key +// (toggled if the user has set GOOGLE_APPLICATION_CREDENTIALS). +func signingOptsFromEnv() (*storage.SignedURLOptions, error) { + path := os.Getenv("GOOGLE_APPLICATION_CREDENTIALS") + if path == "" { + // No credentials configured -> no URL signing + return nil, nil + } + + key, err := ioutil.ReadFile(path) + if err != nil { + return nil, fmt.Errorf("failed to read service account key: %s", err) + } + + conf, err := google.JWTConfigFromJSON(key) + if err != nil { + return nil, fmt.Errorf("failed to parse service account key: %s", err) + } + + log.WithField("account", conf.Email).Info("GCS URL signing enabled") + + return &storage.SignedURLOptions{ + Scheme: storage.SigningSchemeV4, + GoogleAccessID: conf.Email, + PrivateKey: conf.PrivateKey, + Method: "GET", + }, nil +} + +// layerRedirect constructs the public URL of the layer object in the Cloud +// Storage bucket, signs it and redirects the user there. +// +// Signing the URL allows unauthenticated clients to retrieve objects from the +// bucket. +// +// The Docker client is known to follow redirects, but this might not be true +// for all other registry clients. +func (b *GCSBackend) constructLayerUrl(digest string) (string, error) { + log.WithField("layer", digest).Info("redirecting layer request to bucket") + object := "layers/" + digest + + if b.signing != nil { + opts := *b.signing + opts.Expires = time.Now().Add(5 * time.Minute) + return storage.SignedURL(b.bucket, object, &opts) + } else { + return ("https://storage.googleapis.com/" + b.bucket + "/" + object), nil + } +} -- cgit 1.4.1