basic registry pull subcommand

go.mod

@@ -32,6 +32,7 @@ require (
 	github.com/gocolly/colly/v2 v2.0.1
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/google/go-containerregistry v0.8.0
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/gorilla/websocket v1.4.2
 	github.com/gosuri/uilive v0.0.3 // indirect

pkg/app/master/commands/registry/cli.go

@@ -27,11 +27,13 @@ func fullCmdName(subCmdName string) string {
 }
 
 type PullCommandParams struct {
+	TargetRef    string
 	SaveToDocker bool
 }
 
 func PullCommandFlagValues(ctx *cli.Context) (*PullCommandParams, error) {
 	values := &PullCommandParams{
+		TargetRef:    ctx.String(commands.FlagTarget),
 		SaveToDocker: ctx.Bool(FlagSaveToDocker),
 	}
 
@@ -47,9 +49,12 @@ var CLI = &cli.Command{
 			Name:  PullCmdName,
 			Usage: PullCmdNameUsage,
 			Flags: []cli.Flag{
+				commands.Cflag(commands.FlagTarget),
 				cflag(FlagSaveToDocker),
 			},
 			Action: func(ctx *cli.Context) error {
+				xc := app.NewExecutionContext(fullCmdName(PullCmdName))
+
 				gcvalues, err := commands.GlobalFlagValues(ctx)
 				if err != nil {
 					return err
@@ -60,7 +65,16 @@ var CLI = &cli.Command{
 					return err
 				}
 
-				xc := app.NewExecutionContext(fullCmdName(PullCmdName))
+				if cparams.TargetRef == "" {
+					if ctx.Args().Len() < 1 {
+						xc.Out.Error("param.target", "missing target")
+						cli.ShowCommandHelp(ctx, Name)
+						return nil
+					} else {
+						cparams.TargetRef = ctx.Args().First()
+					}
+				}
+
 				OnPullCommand(xc, gcvalues, cparams)
 				return nil
 			},

pkg/app/master/commands/registry/handler.go

@@ -3,6 +3,12 @@ package registry
 import (
 	"fmt"
 
+	"github.com/google/go-containerregistry/pkg/crane"
+	"github.com/google/go-containerregistry/pkg/name"
+	gocrv1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/daemon"
+	log "github.com/sirupsen/logrus"
+
 	"github.com/docker-slim/docker-slim/pkg/app"
 	"github.com/docker-slim/docker-slim/pkg/app/master/commands"
 	"github.com/docker-slim/docker-slim/pkg/app/master/docker/dockerclient"
@@ -12,8 +18,6 @@ import (
 	"github.com/docker-slim/docker-slim/pkg/util/errutil"
 	"github.com/docker-slim/docker-slim/pkg/util/fsutil"
 	v "github.com/docker-slim/docker-slim/pkg/version"
-
-	log "github.com/sirupsen/logrus"
 )
 
 const appName = commands.AppName
@@ -33,8 +37,13 @@ func OnPullCommand(
 
 	cmdReport := report.NewRegistryCommand(gparams.ReportLocation, gparams.InContainer)
 	cmdReport.State = command.StateStarted
+	cmdReport.TargetReference = cparams.TargetRef
 
 	xc.Out.State("started")
+	xc.Out.Info("params",
+		ovars{
+			"cmd.params": fmt.Sprintf("%+v", cparams),
+		})
 
 	client, err := dockerclient.New(gparams.ClientConfig)
 	if err == dockerclient.ErrNoDockerInfo {
@@ -63,6 +72,24 @@ func OnPullCommand(
 		version.Print(prefix, logger, client, false, gparams.InContainer, gparams.IsDSImage)
 	}
 
+	//todo: pass a custom client to Pull (based on `client` above)
+	targetImage, err := crane.Pull(cparams.TargetRef)
+	errutil.FailOn(err)
+	outImageInfo(xc, targetImage)
+
+	if cparams.SaveToDocker {
+		xc.Out.State("save.docker.start")
+
+		tag, err := name.NewTag(cparams.TargetRef)
+		errutil.FailOn(err)
+
+		rawResponse, err := daemon.Write(tag, targetImage)
+		errutil.FailOn(err)
+		logger.Tracef("Image save to Docker response: %v", rawResponse)
+
+		xc.Out.State("save.docker.done")
+	}
+
 	xc.Out.State("completed")
 	cmdReport.State = command.StateCompleted
 	xc.Out.State("done")
@@ -194,3 +221,33 @@ func OnCopyCommand(
 			})
 	}
 }
+
+func outImageInfo(
+	xc *app.ExecutionContext,
+	targetImage gocrv1.Image) {
+	cn, err := targetImage.ConfigName()
+	errutil.FailOn(err)
+
+	d, err := targetImage.Digest()
+	errutil.FailOn(err)
+
+	cf, err := targetImage.ConfigFile()
+	errutil.FailOn(err)
+
+	m, err := targetImage.Manifest()
+	errutil.FailOn(err)
+
+	xc.Out.Info("image.info",
+		ovars{
+			"id":                         fmt.Sprintf("%s:%s", cn.Algorithm, cn.Hex),
+			"digest":                     fmt.Sprintf("%s:%s", d.Algorithm, d.Hex),
+			"architecture":               cf.Architecture,
+			"os":                         cf.OS,
+			"manifest.schema":            m.SchemaVersion,
+			"manifest.media_type":        m.MediaType,
+			"manifest.config.media_type": m.Config.MediaType,
+			"manifest.config.size":       fmt.Sprintf("%v", m.Config.Size),
+			"manifest.config.digest":     fmt.Sprintf("%s:%s", m.Config.Digest.Algorithm, m.Config.Digest.Hex),
+			"manifest.layers.count":      fmt.Sprintf("%v", len(m.Layers)),
+		})
+}