From e5fe205c318f5f44dbcf70bc404fe26e27129eb3 Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@tailscale.com>
Date: Mon, 19 Dec 2022 17:37:08 -0800
Subject: [PATCH] cmd/sync-containers: program to sync tags between container
 registries.

Updates tailscale/corp#8461

Signed-off-by: David Anderson <danderson@tailscale.com>
---
 cmd/sync-containers/main.go | 174 ++++++++++++++++++++++++++++++++++++
 go.mod                      |   2 +-
 2 files changed, 175 insertions(+), 1 deletion(-)
 create mode 100644 cmd/sync-containers/main.go

diff --git a/cmd/sync-containers/main.go b/cmd/sync-containers/main.go
new file mode 100644
index 000000000..21210a926
--- /dev/null
+++ b/cmd/sync-containers/main.go
@@ -0,0 +1,174 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The sync-containers command synchronizes container image tags from one
+// registry to another.
+//
+// It is intended as a workaround for ghcr.io's lack of good push credentials:
+// you can either authorize "classic" Personal Access Tokens in your org (which
+// are a common vector of very bad compromise), or you can get a short-lived
+// credential in a Github action.
+//
+// Since we publish to both Docker Hub and ghcr.io, we use this program in a
+// Github action to effectively rsync from docker hub into ghcr.io, so that we
+// can continue to forbid dangerous Personal Access Tokens in the tailscale org.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"sort"
+	"strings"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+var (
+	src = flag.String("src", "", "Source image")
+	dst = flag.String("dst", "", "Destination image")
+	max = flag.Int("max", 0, "Maximum number of tags to sync (0 for all tags)")
+)
+
+func main() {
+	flag.Parse()
+
+	if *src == "" {
+		log.Fatalf("--src is required")
+	}
+	if *dst == "" {
+		log.Fatalf("--dst is required")
+	}
+
+	opts := []remote.Option{
+		remote.WithAuthFromKeychain(authn.DefaultKeychain),
+		remote.WithContext(context.Background()),
+	}
+
+	stags, err := listTags(*src, opts...)
+	if err != nil {
+		log.Fatalf("listing source tags: %v", err)
+	}
+	dtags, err := listTags(*dst, opts...)
+	if err != nil {
+		log.Fatalf("listing destination tags: %v", err)
+	}
+
+	add, remove := diffTags(stags, dtags)
+	if l := len(add); l > 0 {
+		log.Printf("%d tags to push: %s", len(add), strings.Join(add, ", "))
+		if *max > 0 && l > *max {
+			log.Printf("Limiting sync to %d tags", *max)
+			add = add[:*max]
+		}
+	}
+	for _, tag := range add {
+		log.Printf("Syncing tag %q", tag)
+		if err := copyTag(*src, *dst, tag, opts...); err != nil {
+			log.Printf("Syncing tag %q: progress error: %v", tag, err)
+		}
+	}
+
+	if len(remove) > 0 {
+		log.Printf("%d tags to remove: %s\n", len(remove), strings.Join(remove, ", "))
+		log.Printf("Not removing any tags for safety.\n")
+	}
+}
+
+func copyTag(srcStr, dstStr, tag string, opts ...remote.Option) error {
+	src, err := name.ParseReference(fmt.Sprintf("%s:%s", srcStr, tag))
+	if err != nil {
+		return err
+	}
+	dst, err := name.ParseReference(fmt.Sprintf("%s:%s", dstStr, tag))
+	if err != nil {
+		return err
+	}
+
+	desc, err := remote.Get(src)
+	if err != nil {
+		return err
+	}
+
+	ch := make(chan v1.Update, 10)
+	opts = append(opts, remote.WithProgress(ch))
+	progressDone := make(chan struct{})
+
+	go func() {
+		defer close(progressDone)
+		for p := range ch {
+			fmt.Printf("Syncing tag %q: %d%% (%d/%d)\n", tag, int(float64(p.Complete)/float64(p.Total)*100), p.Complete, p.Total)
+			if p.Error != nil {
+				fmt.Printf("error: %v\n", p.Error)
+			}
+		}
+	}()
+
+	switch desc.MediaType {
+	case types.OCIManifestSchema1, types.DockerManifestSchema2:
+		img, err := desc.Image()
+		if err != nil {
+			return err
+		}
+		if err := remote.Write(dst, img, opts...); err != nil {
+			return err
+		}
+	case types.OCIImageIndex, types.DockerManifestList:
+		idx, err := desc.ImageIndex()
+		if err != nil {
+			return err
+		}
+		if err := remote.WriteIndex(dst, idx, opts...); err != nil {
+			return err
+		}
+	}
+
+	<-progressDone
+	return nil
+}
+
+func listTags(repoStr string, opts ...remote.Option) ([]string, error) {
+	repo, err := name.NewRepository(repoStr)
+	if err != nil {
+		return nil, err
+	}
+
+	tags, err := remote.List(repo, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	sort.Strings(tags)
+	return tags, nil
+}
+
+func diffTags(src, dst []string) (add, remove []string) {
+	srcd := make(map[string]bool)
+	for _, tag := range src {
+		srcd[tag] = true
+	}
+	dstd := make(map[string]bool)
+	for _, tag := range dst {
+		dstd[tag] = true
+	}
+
+	for _, tag := range src {
+		if !dstd[tag] {
+			add = append(add, tag)
+		}
+	}
+	for _, tag := range dst {
+		if !srcd[tag] {
+			remove = append(remove, tag)
+		}
+	}
+	sort.Strings(add)
+	sort.Strings(remove)
+	return add, remove
+}
diff --git a/go.mod b/go.mod
index 967b3c88e..ed8c38bf6 100644
--- a/go.mod
+++ b/go.mod
@@ -29,6 +29,7 @@ require (
 	github.com/godbus/dbus/v5 v5.0.6
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da
 	github.com/google/go-cmp v0.5.8
+	github.com/google/go-containerregistry v0.9.0
 	github.com/google/uuid v1.3.0
 	github.com/goreleaser/nfpm v1.10.3
 	github.com/hdevalence/ed25519consensus v0.0.0-20220222234857-c00d1f31bab3
@@ -184,7 +185,6 @@ require (
 	github.com/golangci/unconvert v0.0.0-20180507085042-28b1c447d1f4 // indirect
 	github.com/google/btree v1.0.1 // indirect
 	github.com/google/gnostic v0.5.7-v3refs // indirect
-	github.com/google/go-containerregistry v0.9.0 // indirect
 	github.com/google/gofuzz v1.1.0 // indirect
 	github.com/google/goterm v0.0.0-20200907032337-555d40f16ae2 // indirect
 	github.com/google/rpmpack v0.0.0-20201206194719-59e495f2b7e1 // indirect