refactor: Move registry server to a subfolder

1 files changed, 492 insertions, 0 deletions

diff --git a/tools/nixery/server/main.go b/tools/nixery/server/main.go
new file mode 100644
index 0000000000..d20ede2eb5
--- /dev/null
+++ b/tools/nixery/server/main.go
@@ -0,0 +1,492 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+// Package main provides the implementation of a container registry that
+// transparently builds container images based on Nix derivations.
+//
+// The Nix derivation used for image creation is responsible for creating
+// objects that are compatible with the registry API. The targeted registry
+// protocol is currently Docker's.
+//
+// When an image is requested, the required contents are parsed out of the
+// request and a Nix-build is initiated that eventually responds with the
+// manifest as well as information linking each layer digest to a local
+// filesystem path.
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/storage"
+)
+
+// pkgSource represents the source from which the Nix package set used
+// by Nixery is imported. Users configure the source by setting one of
+// the supported environment variables.
+type pkgSource struct {
+	srcType string
+	args    string
+}
+
+// Convert the package source into the representation required by Nix.
+func (p *pkgSource) renderSource(tag string) string {
+	// The 'git' source requires a tag to be present.
+	if p.srcType == "git" {
+		if tag == "latest" || tag == "" {
+			tag = "master"
+		}
+
+		return fmt.Sprintf("git!%s!%s", p.args, tag)
+	}
+
+	return fmt.Sprintf("%s!%s", p.srcType, p.args)
+}
+
+// Retrieve a package source from the environment. If no source is
+// specified, the Nix code will default to a recent NixOS channel.
+func pkgSourceFromEnv() *pkgSource {
+	if channel := os.Getenv("NIXERY_CHANNEL"); channel != "" {
+		log.Printf("Using Nix package set from Nix channel %q\n", channel)
+		return &pkgSource{
+			srcType: "nixpkgs",
+			args:    channel,
+		}
+	}
+
+	if git := os.Getenv("NIXERY_PKGS_REPO"); git != "" {
+		log.Printf("Using Nix package set from git repository at %q\n", git)
+		return &pkgSource{
+			srcType: "git",
+			args:    git,
+		}
+	}
+
+	if path := os.Getenv("NIXERY_PKGS_PATH"); path != "" {
+		log.Printf("Using Nix package set from path %q\n", path)
+		return &pkgSource{
+			srcType: "path",
+			args:    path,
+		}
+	}
+
+	return nil
+}
+
+// Load (optional) GCS bucket signing data from the GCS_SIGNING_KEY and
+// GCS_SIGNING_ACCOUNT envvars.
+func signingOptsFromEnv() *storage.SignedURLOptions {
+	path := os.Getenv("GCS_SIGNING_KEY")
+	id := os.Getenv("GCS_SIGNING_ACCOUNT")
+
+	if path == "" || id == "" {
+		log.Println("GCS URL signing disabled")
+		return nil
+	}
+
+	log.Printf("GCS URL signing enabled with account %q\n", id)
+	k, err := ioutil.ReadFile(path)
+	if err != nil {
+		log.Fatalf("Failed to read GCS signing key: %s\n", err)
+	}
+
+	return &storage.SignedURLOptions{
+		GoogleAccessID: id,
+		PrivateKey:     k,
+		Method:         "GET",
+	}
+}
+
+// config holds the Nixery configuration options.
+type config struct {
+	bucket  string                    // GCS bucket to cache & serve layers
+	signing *storage.SignedURLOptions // Signing options to use for GCS URLs
+	builder string                    // Nix derivation for building images
+	port    string                    // Port on which to launch HTTP server
+	pkgs    *pkgSource                // Source for Nix package set
+}
+
+// ManifestMediaType is the Content-Type used for the manifest itself. This
+// corresponds to the "Image Manifest V2, Schema 2" described on this page:
+//
+// https://docs.docker.com/registry/spec/manifest-v2-2/
+const manifestMediaType string = "application/vnd.docker.distribution.manifest.v2+json"
+
+// Image represents the information necessary for building a container image.
+// This can be either a list of package names (corresponding to keys in the
+// nixpkgs set) or a Nix expression that results in a *list* of derivations.
+type image struct {
+	name string
+	tag string
+
+	// Names of packages to include in the image. These must correspond
+	// directly to top-level names of Nix packages in the nixpkgs tree.
+	packages []string
+}
+
+// BuildResult represents the output of calling the Nix derivation responsible
+// for building registry images.
+//
+// The `layerLocations` field contains the local filesystem paths to each
+// individual image layer that will need to be served, while the `manifest`
+// field contains the JSON-representation of the manifest that needs to be
+// served to the client.
+//
+// The later field is simply treated as opaque JSON and passed through.
+type BuildResult struct {
+	Error string   `json:"error"`
+	Pkgs  []string `json:"pkgs"`
+
+	Manifest       json.RawMessage `json:"manifest"`
+	LayerLocations map[string]struct {
+		Path string `json:"path"`
+		Md5  []byte `json:"md5"`
+	} `json:"layerLocations"`
+}
+
+// imageFromName parses an image name into the corresponding structure which can
+// be used to invoke Nix.
+//
+// It will expand convenience names under the hood (see the `convenienceNames`
+// function below).
+func imageFromName(name string, tag string) image {
+	packages := strings.Split(name, "/")
+	return image{
+		name:     name,
+		tag:      tag,
+		packages: convenienceNames(packages),
+	}
+}
+
+// convenienceNames expands convenience package names defined by Nixery which
+// let users include commonly required sets of tools in a container quickly.
+//
+// Convenience names must be specified as the first package in an image.
+//
+// Currently defined convenience names are:
+//
+// * `shell`: Includes bash, coreutils and other common command-line tools
+// * `builder`: All of the above and the standard build environment
+func convenienceNames(packages []string) []string {
+	shellPackages := []string{"bashInteractive", "coreutils", "moreutils", "nano"}
+
+	if packages[0] == "shell" {
+		return append(packages[1:], shellPackages...)
+	}
+
+	return packages
+}
+
+// Call out to Nix and request that an image be built. Nix will, upon success,
+// return a manifest for the container image.
+func buildImage(ctx *context.Context, cfg *config, image *image, bucket *storage.BucketHandle) (*BuildResult, error) {
+	packages, err := json.Marshal(image.packages)
+	if err != nil {
+		return nil, err
+	}
+
+	args := []string{
+		"--no-out-link",
+		"--show-trace",
+		"--argstr", "name", image.name,
+		"--argstr", "packages", string(packages), cfg.builder,
+	}
+
+	if cfg.pkgs != nil {
+		args = append(args, "--argstr", "pkgSource", cfg.pkgs.renderSource(image.tag))
+	}
+	cmd := exec.Command("nix-build", args...)
+
+	outpipe, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+
+	errpipe, err := cmd.StderrPipe()
+	if err != nil {
+		return nil, err
+	}
+
+	if err = cmd.Start(); err != nil {
+		log.Println("Error starting nix-build:", err)
+		return nil, err
+	}
+	log.Printf("Started Nix image build for '%s'", image.name)
+
+	stdout, _ := ioutil.ReadAll(outpipe)
+	stderr, _ := ioutil.ReadAll(errpipe)
+
+	if err = cmd.Wait(); err != nil {
+		// TODO(tazjin): Propagate errors upwards in a usable format.
+		log.Printf("nix-build execution error: %s\nstdout: %s\nstderr: %s\n", err, stdout, stderr)
+		return nil, err
+	}
+
+	log.Println("Finished Nix image build")
+
+	buildOutput, err := ioutil.ReadFile(strings.TrimSpace(string(stdout)))
+	if err != nil {
+		return nil, err
+	}
+
+	// The build output returned by Nix is deserialised to add all
+	// contained layers to the bucket. Only the manifest itself is
+	// re-serialised to JSON and returned.
+	var result BuildResult
+	err = json.Unmarshal(buildOutput, &result)
+	if err != nil {
+		return nil, err
+	}
+
+	for layer, meta := range result.LayerLocations {
+		err = uploadLayer(ctx, bucket, layer, meta.Path, meta.Md5)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return &result, nil
+}
+
+// uploadLayer uploads a single layer to Cloud Storage bucket. Before writing
+// any data the bucket is probed to see if the file already exists.
+//
+// If the file does exist, its MD5 hash is verified to ensure that the stored
+// file is not - for example - a fragment of a previous, incomplete upload.
+func uploadLayer(ctx *context.Context, bucket *storage.BucketHandle, layer string, path string, md5 []byte) error {
+	layerKey := fmt.Sprintf("layers/%s", layer)
+	obj := bucket.Object(layerKey)
+
+	// Before uploading a layer to the bucket, probe whether it already
+	// exists.
+	//
+	// If it does and the MD5 checksum matches the expected one, the layer
+	// upload can be skipped.
+	attrs, err := obj.Attrs(*ctx)
+
+	if err == nil && bytes.Equal(attrs.MD5, md5) {
+		log.Printf("Layer sha256:%s already exists in bucket, skipping upload", layer)
+	} else {
+		writer := obj.NewWriter(*ctx)
+		file, err := os.Open(path)
+
+		if err != nil {
+			return fmt.Errorf("failed to open layer %s from path %s: %v", layer, path, err)
+		}
+
+		size, err := io.Copy(writer, file)
+		if err != nil {
+			return fmt.Errorf("failed to write layer %s to Cloud Storage: %v", layer, err)
+		}
+
+		if err = writer.Close(); err != nil {
+			return fmt.Errorf("failed to write layer %s to Cloud Storage: %v", layer, err)
+		}
+
+		log.Printf("Uploaded layer sha256:%s (%v bytes written)\n", layer, size)
+	}
+
+	return 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 constructLayerUrl(cfg *config, digest string) (string, error) {
+	log.Printf("Redirecting layer '%s' request to bucket '%s'\n", digest, cfg.bucket)
+	object := "layers/" + digest
+
+	if cfg.signing != nil {
+		opts := *cfg.signing
+		opts.Expires = time.Now().Add(5 * time.Minute)
+		return storage.SignedURL(cfg.bucket, object, &opts)
+	} else {
+		return ("https://storage.googleapis.com/" + cfg.bucket + "/" + object), nil
+	}
+}
+
+// prepareBucket configures the handle to a Cloud Storage bucket in which
+// individual layers will be stored after Nix builds. Nixery does not directly
+// serve layers to registry clients, instead it redirects them to the public
+// URLs of the Cloud Storage bucket.
+//
+// The bucket is required for Nixery to function correctly, hence fatal errors
+// are generated in case it fails to be set up correctly.
+func prepareBucket(ctx *context.Context, cfg *config) *storage.BucketHandle {
+	client, err := storage.NewClient(*ctx)
+	if err != nil {
+		log.Fatalln("Failed to set up Cloud Storage client:", err)
+	}
+
+	bkt := client.Bucket(cfg.bucket)
+
+	if _, err := bkt.Attrs(*ctx); err != nil {
+		log.Fatalln("Could not access configured bucket", err)
+	}
+
+	return bkt
+}
+
+// Regexes matching the V2 Registry API routes. This only includes the
+// routes required for serving images, since pushing and other such
+// functionality is not available.
+var (
+	manifestRegex = regexp.MustCompile(`^/v2/([\w|\-|\.|\_|\/]+)/manifests/([\w|\-|\.|\_]+)$`)
+	layerRegex    = regexp.MustCompile(`^/v2/([\w|\-|\.|\_|\/]+)/blobs/sha256:(\w+)$`)
+)
+
+// Error format corresponding to the registry protocol V2 specification. This
+// allows feeding back errors to clients in a way that can be presented to
+// users.
+type registryError struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+type registryErrors struct {
+	Errors []registryError `json:"errors"`
+}
+
+func writeError(w http.ResponseWriter, status int, code, message string) {
+	err := registryErrors{
+		Errors: []registryError{
+			{code, message},
+		},
+	}
+	json, _ := json.Marshal(err)
+
+	w.WriteHeader(status)
+	w.Header().Add("Content-Type", "application/json")
+	w.Write(json)
+}
+
+type registryHandler struct {
+	cfg    *config
+	ctx    *context.Context
+	bucket *storage.BucketHandle
+}
+
+func (h *registryHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Acknowledge that we speak V2 with an empty response
+	if r.RequestURI == "/v2/" {
+		return
+	}
+
+	// Serve the manifest (straight from Nix)
+	manifestMatches := manifestRegex.FindStringSubmatch(r.RequestURI)
+	if len(manifestMatches) == 3 {
+		imageName := manifestMatches[1]
+		imageTag := manifestMatches[2]
+		log.Printf("Requesting manifest for image %q at tag %q", imageName, imageTag)
+		image := imageFromName(imageName, imageTag)
+		buildResult, err := buildImage(h.ctx, h.cfg, &image, h.bucket)
+
+		if err != nil {
+			writeError(w, 500, "UNKNOWN", "image build failure")
+			log.Println("Failed to build image manifest", err)
+			return
+		}
+
+		// Some error types have special handling, which is applied
+		// here.
+		if buildResult.Error == "not_found" {
+			s := fmt.Sprintf("Could not find Nix packages: %v", buildResult.Pkgs)
+			writeError(w, 404, "MANIFEST_UNKNOWN", s)
+			log.Println(s)
+			return
+		}
+
+		// This marshaling error is ignored because we know that this
+		// field represents valid JSON data.
+		manifest, _ := json.Marshal(buildResult.Manifest)
+		w.Header().Add("Content-Type", manifestMediaType)
+		w.Write(manifest)
+		return
+	}
+
+	// Serve an image layer. For this we need to first ask Nix for
+	// the manifest, then proceed to extract the correct layer from
+	// it.
+	layerMatches := layerRegex.FindStringSubmatch(r.RequestURI)
+	if len(layerMatches) == 3 {
+		digest := layerMatches[2]
+		url, err := constructLayerUrl(h.cfg, digest)
+
+		if err != nil {
+			log.Printf("Failed to sign GCS URL: %s\n", err)
+			writeError(w, 500, "UNKNOWN", "could not serve layer")
+			return
+		}
+
+		w.Header().Set("Location", url)
+		w.WriteHeader(303)
+		return
+	}
+
+	log.Printf("Unsupported registry route: %s\n", r.RequestURI)
+	w.WriteHeader(404)
+}
+
+func getConfig(key, desc string) string {
+	value := os.Getenv(key)
+	if value == "" {
+		log.Fatalln(desc + " must be specified")
+	}
+
+	return value
+}
+
+func main() {
+	cfg := &config{
+		bucket:  getConfig("BUCKET", "GCS bucket for layer storage"),
+		builder: getConfig("NIX_BUILDER", "Nix image builder code"),
+		port:    getConfig("PORT", "HTTP port"),
+		pkgs:    pkgSourceFromEnv(),
+		signing: signingOptsFromEnv(),
+	}
+
+	ctx := context.Background()
+	bucket := prepareBucket(&ctx, cfg)
+
+	log.Printf("Starting Kubernetes Nix controller on port %s\n", cfg.port)
+
+	// All /v2/ requests belong to the registry handler.
+	http.Handle("/v2/", &registryHandler{
+		cfg:    cfg,
+		ctx:    &ctx,
+		bucket: bucket,
+	})
+
+	// All other roots are served by the static file server.
+	webDir := http.Dir(getConfig("WEB_DIR", "Static web file dir"))
+	http.Handle("/", http.FileServer(webDir))
+
+	log.Fatal(http.ListenAndServe(":"+cfg.port, nil))
+}