pull.go

package buildah

import (
	"context"
	"io"
	"strings"
	"time"

	"github.com/containers/buildah/pkg/blobcache"
	"github.com/containers/buildah/util"
	"github.com/containers/image/v5/directory"
	"github.com/containers/image/v5/docker"
	dockerarchive "github.com/containers/image/v5/docker/archive"
	"github.com/containers/image/v5/docker/reference"
	tarfile "github.com/containers/image/v5/docker/tarfile"
	ociarchive "github.com/containers/image/v5/oci/archive"
	oci "github.com/containers/image/v5/oci/layout"
	"github.com/containers/image/v5/signature"
	is "github.com/containers/image/v5/storage"
	"github.com/containers/image/v5/transports"
	"github.com/containers/image/v5/types"
	"github.com/containers/storage"
	multierror "github.com/hashicorp/go-multierror"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

// PullOptions can be used to alter how an image is copied in from somewhere.
type PullOptions struct {
	// SignaturePolicyPath specifies an override location for the signature
	// policy which should be used for verifying the new image as it is
	// being written.  Except in specific circumstances, no value should be
	// specified, indicating that the shared, system-wide default policy
	// should be used.
	SignaturePolicyPath string
	// ReportWriter is an io.Writer which will be used to log the writing
	// of the new image.
	ReportWriter io.Writer
	// Store is the local storage store which holds the source image.
	Store storage.Store
	// github.com/containers/image/types SystemContext to hold credentials
	// and other authentication/authorization information.
	SystemContext *types.SystemContext
	// BlobDirectory is the name of a directory in which we'll attempt to
	// store copies of layer blobs that we pull down, if any.  It should
	// already exist.
	BlobDirectory string
	// AllTags is a boolean value that determines if all tagged images
	// will be downloaded from the repository. The default is false.
	AllTags bool
	// RemoveSignatures causes any existing signatures for the image to be
	// discarded when pulling it.
	RemoveSignatures bool
	// MaxRetries is the maximum number of attempts we'll make to pull any
	// one image from the external registry if the first attempt fails.
	MaxRetries int
	// RetryDelay is how long to wait before retrying a pull attempt.
	RetryDelay time.Duration
}

func localImageNameForReference(ctx context.Context, store storage.Store, srcRef types.ImageReference) (string, error) {
	if srcRef == nil {
		return "", errors.Errorf("reference to image is empty")
	}
	var name string
	switch srcRef.Transport().Name() {
	case dockerarchive.Transport.Name():
		file := srcRef.StringWithinTransport()
		tarSource, err := tarfile.NewSourceFromFile(file)
		if err != nil {
			return "", errors.Wrapf(err, "error opening tarfile %q as a source image", file)
		}
		defer tarSource.Close()
		manifest, err := tarSource.LoadTarManifest()
		if err != nil {
			return "", errors.Errorf("error retrieving manifest.json from tarfile %q: %v", file, err)
		}
		// to pull the first image stored in the tar file
		if len(manifest) == 0 {
			// use the hex of the digest if no manifest is found
			name, err = getImageDigest(ctx, srcRef, nil)
			if err != nil {
				return "", err
			}
		} else {
			if len(manifest[0].RepoTags) > 0 {
				name = manifest[0].RepoTags[0]
			} else {
				// If the input image has no repotags, we need to feed it a dest anyways
				name, err = getImageDigest(ctx, srcRef, nil)
				if err != nil {
					return "", err
				}
			}
		}
	case ociarchive.Transport.Name():
		// retrieve the manifest from index.json to access the image name
		manifest, err := ociarchive.LoadManifestDescriptor(srcRef)
		if err != nil {
			return "", errors.Wrapf(err, "error loading manifest for %q", transports.ImageName(srcRef))
		}
		// if index.json has no reference name, compute the image digest instead
		if manifest.Annotations == nil || manifest.Annotations["org.opencontainers.image.ref.name"] == "" {
			name, err = getImageDigest(ctx, srcRef, nil)
			if err != nil {
				return "", err
			}
		} else {
			name = manifest.Annotations["org.opencontainers.image.ref.name"]
		}
	case directory.Transport.Name():
		// supports pull from a directory
		name = toLocalImageName(srcRef.StringWithinTransport())
	case oci.Transport.Name():
		// supports pull from a directory
		split := strings.SplitN(srcRef.StringWithinTransport(), ":", 2)
		name = toLocalImageName(split[0])
	default:
		ref := srcRef.DockerReference()
		if ref == nil {
			name = srcRef.StringWithinTransport()
			_, err := is.Transport.ParseStoreReference(store, name)
			if err == nil {
				return name, nil
			}
			logrus.Debugf("error parsing local storage reference %q: %v", name, err)
			if strings.LastIndex(name, "/") != -1 {
				name = name[strings.LastIndex(name, "/")+1:]
				_, err = is.Transport.ParseStoreReference(store, name)
				if err == nil {
					return name, errors.Wrapf(err, "error parsing local storage reference %q", name)
				}
			}
			return "", errors.Errorf("reference to image %q is not a named reference", transports.ImageName(srcRef))
		}

		if named, ok := ref.(reference.Named); ok {
			name = named.Name()
			if namedTagged, ok := ref.(reference.NamedTagged); ok {
				name = name + ":" + namedTagged.Tag()
			}
			if canonical, ok := ref.(reference.Canonical); ok {
				name = name + "@" + canonical.Digest().String()
			}
		}
	}

	if _, err := is.Transport.ParseStoreReference(store, name); err != nil {
		return "", errors.Wrapf(err, "error parsing computed local image name %q", name)
	}
	return name, nil
}

// Pull copies the contents of the image from somewhere else to local storage.  Returns the
// ID of the local image or an error.
func Pull(ctx context.Context, imageName string, options PullOptions) (imageID string, err error) {
	systemContext := getSystemContext(options.Store, options.SystemContext, options.SignaturePolicyPath)

	boptions := BuilderOptions{
		FromImage:           imageName,
		SignaturePolicyPath: options.SignaturePolicyPath,
		SystemContext:       systemContext,
		BlobDirectory:       options.BlobDirectory,
		ReportWriter:        options.ReportWriter,
		MaxPullRetries:      options.MaxRetries,
		PullRetryDelay:      options.RetryDelay,
	}

	storageRef, transport, img, err := resolveImage(ctx, systemContext, options.Store, boptions)
	if err != nil {
		return "", err
	}

	var errs *multierror.Error
	if options.AllTags {
		if transport != util.DefaultTransport {
			return "", errors.New("Non-docker transport is not supported, for --all-tags pulling")
		}

		repo := reference.TrimNamed(storageRef.DockerReference())
		dockerRef, err := docker.NewReference(reference.TagNameOnly(storageRef.DockerReference()))
		if err != nil {
			return "", errors.Wrapf(err, "internal error creating docker.Transport reference for %s", storageRef.DockerReference().String())
		}
		tags, err := docker.GetRepositoryTags(ctx, systemContext, dockerRef)
		if err != nil {
			return "", errors.Wrapf(err, "error getting repository tags")
		}
		for _, tag := range tags {
			tagged, err := reference.WithTag(repo, tag)
			if err != nil {
				errs = multierror.Append(errs, err)
				continue
			}
			taggedRef, err := docker.NewReference(tagged)
			if err != nil {
				return "", errors.Wrapf(err, "internal error creating docker.Transport reference for %s", tagged.String())
			}
			if options.ReportWriter != nil {
				if _, err := options.ReportWriter.Write([]byte("Pulling " + tagged.String() + "\n")); err != nil {
					return "", errors.Wrapf(err, "error writing pull report")
				}
			}
			ref, err := pullImage(ctx, options.Store, taggedRef, options, systemContext)
			if err != nil {
				errs = multierror.Append(errs, err)
				continue
			}
			taggedImg, err := is.Transport.GetStoreImage(options.Store, ref)
			if err != nil {
				errs = multierror.Append(errs, err)
				continue
			}
			imageID = taggedImg.ID
		}
	} else {
		imageID = img.ID
	}

	return imageID, errs.ErrorOrNil()
}

func pullImage(ctx context.Context, store storage.Store, srcRef types.ImageReference, options PullOptions, sc *types.SystemContext) (types.ImageReference, error) {
	blocked, err := isReferenceBlocked(srcRef, sc)
	if err != nil {
		return nil, errors.Wrapf(err, "error checking if pulling from registry for %q is blocked", transports.ImageName(srcRef))
	}
	if blocked {
		return nil, errors.Errorf("pull access to registry for %q is blocked by configuration", transports.ImageName(srcRef))
	}
	if err := checkRegistrySourcesAllows("pull from", srcRef); err != nil {
		return nil, err
	}

	destName, err := localImageNameForReference(ctx, store, srcRef)
	if err != nil {
		return nil, errors.Wrapf(err, "error computing local image name for %q", transports.ImageName(srcRef))
	}
	if destName == "" {
		return nil, errors.Errorf("error computing local image name for %q", transports.ImageName(srcRef))
	}

	destRef, err := is.Transport.ParseStoreReference(store, destName)
	if err != nil {
		return nil, errors.Wrapf(err, "error parsing image name %q", destName)
	}
	var maybeCachedDestRef = types.ImageReference(destRef)
	if options.BlobDirectory != "" {
		cachedRef, err := blobcache.NewBlobCache(destRef, options.BlobDirectory, types.PreserveOriginal)
		if err != nil {
			return nil, errors.Wrapf(err, "error wrapping image reference %q in blob cache at %q", transports.ImageName(destRef), options.BlobDirectory)
		}
		maybeCachedDestRef = cachedRef
	}

	policy, err := signature.DefaultPolicy(sc)
	if err != nil {
		return nil, errors.Wrapf(err, "error obtaining default signature policy")
	}

	policyContext, err := signature.NewPolicyContext(policy)
	if err != nil {
		return nil, errors.Wrapf(err, "error creating new signature policy context")
	}

	defer func() {
		if err2 := policyContext.Destroy(); err2 != nil {
			logrus.Debugf("error destroying signature policy context: %v", err2)
		}
	}()

	logrus.Debugf("copying %q to %q", transports.ImageName(srcRef), destName)
	if _, err := retryCopyImage(ctx, policyContext, maybeCachedDestRef, srcRef, srcRef, "pull", getCopyOptions(store, options.ReportWriter, sc, nil, "", options.RemoveSignatures, ""), options.MaxRetries, options.RetryDelay); err != nil {
		logrus.Debugf("error copying src image [%q] to dest image [%q] err: %v", transports.ImageName(srcRef), destName, err)
		return nil, err
	}
	return destRef, nil
}

// getImageDigest creates an image object and uses the hex value of the digest as the image ID
// for parsing the store reference
func getImageDigest(ctx context.Context, src types.ImageReference, sc *types.SystemContext) (string, error) {
	newImg, err := src.NewImage(ctx, sc)
	if err != nil {
		return "", errors.Wrapf(err, "error opening image %q for reading", transports.ImageName(src))
	}
	defer newImg.Close()

	digest := newImg.ConfigInfo().Digest
	if err = digest.Validate(); err != nil {
		return "", errors.Wrapf(err, "error getting config info from image %q", transports.ImageName(src))
	}
	return "@" + digest.Hex(), nil
}

// toLocalImageName converts an image name into a 'localhost/' prefixed one
func toLocalImageName(imageName string) string {
	return "localhost/" + strings.TrimLeft(imageName, "/")
}