[image-builder] replace reference to aliases with actual repo for cross mount blobs

Author: Prince Rachit Sinha

components/image-builder-bob/pkg/proxy/proxy.go

@@ -52,7 +52,7 @@ type Repo struct {
 	Auth func() docker.Authorizer
 }
 
-func rewriteURL(u *url.URL, fromRepo, toRepo, host, tag string) {
+func (proxy *Proxy) rewriteURL(u *url.URL, fromRepo, toRepo, host, tag string) {
 	var (
 		from = "/v2/" + strings.Trim(fromRepo, "/") + "/"
 		to   = "/v2/" + strings.Trim(toRepo, "/") + "/"
@@ -76,6 +76,13 @@ func rewriteURL(u *url.URL, fromRepo, toRepo, host, tag string) {
 		}
 	}
 
+	if u.RawQuery != "" {
+		// As per OCI distribution spec this (from=) should be the only possible reference to a cross repo
+		// https://github.com/opencontainers/distribution-spec/blob/main/spec.md#push
+		for k, v := range proxy.Aliases {
+			u.RawQuery = strings.Replace(u.RawQuery, "from="+k, "from="+v.Repo, 1)
+		}
+	}
 	u.Host = host
 }
 
@@ -99,7 +106,7 @@ func (proxy *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	rewriteURL(r.URL, alias, repo.Repo, repo.Host, repo.Tag)
+	proxy.rewriteURL(r.URL, alias, repo.Repo, repo.Host, repo.Tag)
 	r.Host = r.URL.Host
 
 	auth := repo.Auth()
@@ -192,7 +199,7 @@ func (proxy *Proxy) reverse(alias string) *httputil.ReverseProxy {
 				return err
 			}
 
-			rewriteURL(lurl, repo.Repo, alias, proxy.Host.Host, "")
+			proxy.rewriteURL(lurl, repo.Repo, alias, proxy.Host.Host, "")
 			lurl.Host = proxy.Host.Host
 			// force scheme to http assuming this proxy never runs as https
 			lurl.Scheme = proxy.Host.Scheme

components/image-builder-bob/pkg/proxy/proxy_test.go

@@ -0,0 +1,94 @@
+// Copyright (c) 2022 Gitpod GmbH. All rights reserved.
+// Licensed under the GNU Affero General Public License (AGPL).
+// See License-AGPL.txt in the project root for license information.
+
+package proxy
+
+import (
+	"net/url"
+	"testing"
+)
+
+func TestRewriteURL(t *testing.T) {
+	type input struct {
+		proxy    *Proxy
+		u        url.URL
+		fromRepo string
+		toRepo   string
+		host     string
+		tag      string
+	}
+	tests := []struct {
+		Name string
+		in   input
+		u    url.URL
+	}{
+		{
+			Name: "updates alias reference when it is cross blob mount",
+			in: input{
+				proxy: &Proxy{
+					Host: url.URL{Host: "localhost:8080", Scheme: "http"},
+					Aliases: map[string]Repo{
+						"base": {
+							Repo: "/gitpod/base-images",
+						},
+						"target": {
+							Repo: "/gitpod/workspace-images",
+						},
+					},
+					proxies: nil,
+				},
+				fromRepo: "base",
+				toRepo:   "/gitpod/base-images",
+				host:     "registry.gitlab.com",
+				tag:      "tag12345",
+				u: url.URL{
+					Host:     "localhost.com",
+					RawQuery: "/mounts/uploads/?mount=sha:12345?from=base",
+				},
+			},
+			u: url.URL{
+				Host:     "registry.gitlab.com",
+				RawQuery: "/mounts/uploads/?mount=sha:12345?from=/gitpod/base-images",
+			},
+		},
+		{
+			Name: "does not update alias reference when it is not cross blob mount",
+			in: input{
+				proxy: &Proxy{
+					Host: url.URL{Host: "localhost:8080", Scheme: "http"},
+					Aliases: map[string]Repo{
+						"base": {
+							Repo: "/gitpod/base-images",
+						},
+						"target": {
+							Repo: "/gitpod/workspace-images",
+						},
+					},
+				},
+				fromRepo: "base",
+				toRepo:   "/gitpod/base-images",
+				host:     "registry.gitlab.com",
+				tag:      "tag12345",
+				u: url.URL{
+					Host:     "localhost.com",
+					RawQuery: "/blobs/sha:12345base",
+				},
+			},
+			u: url.URL{
+				Host:     "registry.gitlab.com",
+				RawQuery: "/blobs/sha:12345base",
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.Name, func(t *testing.T) {
+			test.in.proxy.rewriteURL(&test.in.u, test.in.fromRepo, test.in.toRepo, test.in.host, test.in.tag)
+			if test.in.u.RawQuery != test.u.RawQuery {
+				t.Errorf("expected raw query: %s but got %s", test.u.RawQuery, test.in.u.RawQuery)
+			}
+		})
+	}
+
+}