buildah/new.go

package buildah

import (
	"context"
	"fmt"
	"os"
	"strings"

	"github.com/containers/image/pkg/sysregistries"
	is "github.com/containers/image/storage"
	"github.com/containers/image/transports"
	"github.com/containers/image/transports/alltransports"
	"github.com/containers/image/types"
	"github.com/containers/storage"
	"github.com/opencontainers/selinux/go-selinux"
	"github.com/opencontainers/selinux/go-selinux/label"
	"github.com/openshift/imagebuilder"
	"github.com/pkg/errors"
	"github.com/projectatomic/buildah/util"
	"github.com/sirupsen/logrus"
)

const (
	// BaseImageFakeName is the "name" of a source image which we interpret
	// as "no image".
	BaseImageFakeName = imagebuilder.NoBaseImageSpecifier

	// DefaultTransport is a prefix that we apply to an image name if we
	// can't find one in the local Store, in order to generate a source
	// reference for the image that we can then copy to the local Store.
	DefaultTransport = "docker://"

	// minimumTruncatedIDLength is the minimum length of an identifier that
	// we'll accept as possibly being a truncated image ID.
	minimumTruncatedIDLength = 3
)

func reserveSELinuxLabels(store storage.Store, id string) error {
	if selinux.GetEnabled() {
		containers, err := store.Containers()
		if err != nil {
			return err
		}

		for _, c := range containers {
			if id == c.ID {
				continue
			} else {
				b, err := OpenBuilder(store, c.ID)
				if err != nil {
					if os.IsNotExist(err) {
						// Ignore not exist errors since containers probably created by other tool
						// TODO, we need to read other containers json data to reserve their SELinux labels
						continue
					}
					return err
				}
				// Prevent different containers from using same MCS label
				if err := label.ReserveLabel(b.ProcessLabel); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

func pullAndFindImage(ctx context.Context, store storage.Store, imageName string, options BuilderOptions, sc *types.SystemContext) (*storage.Image, types.ImageReference, error) {
	ref, err := pullImage(ctx, store, imageName, options, sc)
	if err != nil {
		logrus.Debugf("error pulling image %q: %v", imageName, err)
		return nil, nil, err
	}
	img, err := is.Transport.GetStoreImage(store, ref)
	if err != nil {
		logrus.Debugf("error reading pulled image %q: %v", imageName, err)
		return nil, nil, err
	}
	return img, ref, nil
}

func getImageName(name string, img *storage.Image) string {
	imageName := name
	if len(img.Names) > 0 {
		imageName = img.Names[0]
		// When the image used by the container is a tagged image
		// the container name might be set to the original image instead of
		// the image given in the "form" command line.
		// This loop is supposed to fix this.
		for _, n := range img.Names {
			if strings.Contains(n, name) {
				imageName = n
				break
			}
		}
	}
	return imageName
}

func imageNamePrefix(imageName string) string {
	prefix := imageName
	s := strings.Split(imageName, "/")
	if len(s) > 0 {
		prefix = s[len(s)-1]
	}
	s = strings.Split(prefix, ":")
	if len(s) > 0 {
		prefix = s[0]
	}
	s = strings.Split(prefix, "@")
	if len(s) > 0 {
		prefix = s[0]
	}
	return prefix
}

func newContainerIDMappingOptions(idmapOptions *IDMappingOptions) storage.IDMappingOptions {
	var options storage.IDMappingOptions
	if idmapOptions != nil {
		options.HostUIDMapping = idmapOptions.HostUIDMapping
		options.HostGIDMapping = idmapOptions.HostGIDMapping
		uidmap, gidmap := convertRuntimeIDMaps(idmapOptions.UIDMap, idmapOptions.GIDMap)
		if len(uidmap) > 0 && len(gidmap) > 0 {
			options.UIDMap = uidmap
			options.GIDMap = gidmap
		} else {
			options.HostUIDMapping = true
			options.HostGIDMapping = true
		}
	}
	return options
}

func resolveImage(ctx context.Context, systemContext *types.SystemContext, store storage.Store, options BuilderOptions) (types.ImageReference, *storage.Image, error) {
	var ref types.ImageReference
	var img *storage.Image
	for _, image := range util.ResolveName(options.FromImage, options.Registry, systemContext, store) {
		var err error
		if len(image) >= minimumTruncatedIDLength {
			if img, err = store.Image(image); err == nil && img != nil && strings.HasPrefix(img.ID, image) {
				if ref, err = is.Transport.ParseStoreReference(store, img.ID); err != nil {
					return nil, nil, errors.Wrapf(err, "error parsing reference to image %q", img.ID)
				}
				break
			}
		}

		if options.PullPolicy == PullAlways {
			pulledImg, pulledReference, err := pullAndFindImage(ctx, store, image, options, systemContext)
			if err != nil {
				logrus.Debugf("unable to pull and read image %q: %v", image, err)
				continue
			}
			ref = pulledReference
			img = pulledImg
			break
		}

		srcRef, err := alltransports.ParseImageName(image)
		if err != nil {
			if options.Transport == "" {
				logrus.Debugf("error parsing image name %q: %v", image, err)
				continue
			}
			transport := options.Transport
			if transport != DefaultTransport {
				transport = transport + ":"
			}
			srcRef2, err := alltransports.ParseImageName(transport + image)
			if err != nil {
				logrus.Debugf("error parsing image name %q: %v", image, err)
				continue
			}
			srcRef = srcRef2
		}

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

		ref, err = is.Transport.ParseStoreReference(store, destImage)
		if err != nil {
			return nil, nil, errors.Wrapf(err, "error parsing reference to image %q", destImage)
		}
		img, err = is.Transport.GetStoreImage(store, ref)
		if err != nil {
			if errors.Cause(err) == storage.ErrImageUnknown && options.PullPolicy != PullIfMissing {
				logrus.Debugf("no such image %q: %v", transports.ImageName(ref), err)
				continue
			}
			pulledImg, pulledReference, err := pullAndFindImage(ctx, store, image, options, systemContext)
			if err != nil {
				logrus.Debugf("unable to pull and read image %q: %v", image, err)
				continue
			}
			ref = pulledReference
			img = pulledImg
		}
		break
	}
	return ref, img, nil
}

func newBuilder(ctx context.Context, store storage.Store, options BuilderOptions) (*Builder, error) {
	var ref types.ImageReference
	var img *storage.Image
	var err error

	if options.FromImage == BaseImageFakeName {
		options.FromImage = ""
	}
	if options.Transport == "" {
		options.Transport = DefaultTransport
	}

	systemContext := getSystemContext(options.SystemContext, options.SignaturePolicyPath)

	if options.FromImage != "scratch" {
		ref, img, err = resolveImage(ctx, systemContext, store, options)
		if err != nil {
			return nil, err
		}
		if options.FromImage != "" && (ref == nil || img == nil) {
			// If options.FromImage is set but we ended up
			// with nil in ref or in img then there was an error that
			// we should return.
			return nil, errors.Wrapf(storage.ErrImageUnknown, "image %q not found in %s registries", options.FromImage, sysregistries.RegistriesConfPath(systemContext))
		}
	}
	image := options.FromImage
	imageID := ""
	topLayer := ""
	if img != nil {
		image = getImageName(imageNamePrefix(image), img)
		imageID = img.ID
		topLayer = img.TopLayer
	}
	var src types.ImageCloser
	if ref != nil {
		src, err = ref.NewImage(ctx, systemContext)
		if err != nil {
			return nil, errors.Wrapf(err, "error instantiating image for %q", transports.ImageName(ref))
		}
		defer src.Close()
	}

	// If the pull command was used, we only pull the image,
	// we don't create a container.
	if options.ImageOnly {
		imgBuilder := &Builder{
			FromImageID: imageID,
		}
		return imgBuilder, nil
	}

	name := "working-container"
	if options.Container != "" {
		name = options.Container
	} else {
		var err2 error
		if image != "" {
			name = imageNamePrefix(image) + "-" + name
		}
		suffix := 1
		tmpName := name
		for errors.Cause(err2) != storage.ErrContainerUnknown {
			_, err2 = store.Container(tmpName)
			if err2 == nil {
				suffix++
				tmpName = fmt.Sprintf("%s-%d", name, suffix)
			}
		}
		name = tmpName
	}

	coptions := storage.ContainerOptions{}
	coptions.IDMappingOptions = newContainerIDMappingOptions(options.IDMappingOptions)

	container, err := store.CreateContainer("", []string{name}, imageID, "", "", &coptions)
	if err != nil {
		return nil, errors.Wrapf(err, "error creating container")
	}

	defer func() {
		if err != nil {
			if err2 := store.DeleteContainer(container.ID); err != nil {
				logrus.Errorf("error deleting container %q: %v", container.ID, err2)
			}
		}
	}()

	if err = reserveSELinuxLabels(store, container.ID); err != nil {
		return nil, err
	}
	processLabel, mountLabel, err := label.InitLabels(options.CommonBuildOpts.LabelOpts)
	if err != nil {
		return nil, err
	}
	uidmap, gidmap := convertStorageIDMaps(container.UIDMap, container.GIDMap)

	defaultNamespaceOptions, err := DefaultNamespaceOptions()
	if err != nil {
		return nil, err
	}

	namespaceOptions := defaultNamespaceOptions
	namespaceOptions.AddOrReplace(options.NamespaceOptions...)

	builder := &Builder{
		store:                 store,
		Type:                  containerType,
		FromImage:             image,
		FromImageID:           imageID,
		Container:             name,
		ContainerID:           container.ID,
		ImageAnnotations:      map[string]string{},
		ImageCreatedBy:        "",
		ProcessLabel:          processLabel,
		MountLabel:            mountLabel,
		DefaultMountsFilePath: options.DefaultMountsFilePath,
		Isolation:             options.Isolation,
		NamespaceOptions:      namespaceOptions,
		ConfigureNetwork:      options.ConfigureNetwork,
		CNIPluginPath:         options.CNIPluginPath,
		CNIConfigDir:          options.CNIConfigDir,
		IDMappingOptions: IDMappingOptions{
			HostUIDMapping: len(uidmap) == 0,
			HostGIDMapping: len(uidmap) == 0,
			UIDMap:         uidmap,
			GIDMap:         gidmap,
		},
		AddCapabilities:  copyStringSlice(options.AddCapabilities),
		DropCapabilities: copyStringSlice(options.DropCapabilities),
		CommonBuildOpts:  options.CommonBuildOpts,
		TopLayer:         topLayer,
		Args:             options.Args,
	}

	if options.Mount {
		_, err = builder.Mount(mountLabel)
		if err != nil {
			return nil, errors.Wrapf(err, "error mounting build container")
		}
	}

	if err := builder.initConfig(ctx, src); err != nil {
		return nil, errors.Wrapf(err, "error preparing image configuration")
	}
	err = builder.Save()
	if err != nil {
		return nil, errors.Wrapf(err, "error saving builder state")
	}

	return builder, nil
}