dotcloud/docker

package containerd

import (
    "bytes"
    "context"
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "os"
    "runtime"
    "time"

    "github.com/containerd/containerd"
    "github.com/containerd/containerd/content"
    containerdimages "github.com/containerd/containerd/images"
    "github.com/containerd/containerd/leases"
    "github.com/containerd/containerd/mount"
    "github.com/containerd/containerd/platforms"
    "github.com/containerd/containerd/rootfs"
    cerrdefs "github.com/containerd/errdefs"
    "github.com/containerd/log"
    "github.com/distribution/reference"
    "github.com/docker/docker/api/types/backend"
    "github.com/docker/docker/api/types/container"
    "github.com/docker/docker/api/types/events"
    "github.com/docker/docker/api/types/registry"
    "github.com/docker/docker/builder"
    "github.com/docker/docker/errdefs"
    "github.com/docker/docker/image"
    dimage "github.com/docker/docker/image"
    "github.com/docker/docker/layer"
    "github.com/docker/docker/pkg/archive"
    "github.com/docker/docker/pkg/progress"
    "github.com/docker/docker/pkg/streamformatter"
    "github.com/docker/docker/pkg/stringid"
    registrypkg "github.com/docker/docker/registry"
    imagespec "github.com/moby/docker-image-spec/specs-go/v1"
    "github.com/opencontainers/go-digest"
    "github.com/opencontainers/image-spec/identity"
    "github.com/opencontainers/image-spec/specs-go"
    ocispec "github.com/opencontainers/image-spec/specs-go/v1"
)

const (
    // Digest of the image which was the base image of the committed container.
    imageLabelClassicBuilderParent = "org.mobyproject.image.parent"

    // "1" means that the image was created directly from the "FROM scratch".
    imageLabelClassicBuilderFromScratch = "org.mobyproject.image.fromscratch"

    // digest of the ContainerConfig stored in the content store.
    imageLabelClassicBuilderContainerConfig = "org.mobyproject.image.containerconfig"
)

const (
    // gc.ref label that associates the ContainerConfig content blob with the
    // corresponding Config content.
    contentLabelGcRefContainerConfig = "containerd.io/gc.ref.content.moby/container.config"

    // Digest of the image this ContainerConfig blobs describes.
    // Only ContainerConfig content should be labelled with it.
    contentLabelClassicBuilderImage = "org.mobyproject.content.image"
)

// GetImageAndReleasableLayer returns an image and releaseable layer for a
// reference or ID. Every call to GetImageAndReleasableLayer MUST call
// releasableLayer.Release() to prevent leaking of layers.
func (i *ImageService) GetImageAndReleasableLayer(ctx context.Context, refOrID string, opts backend.GetImageAndLayerOptions) (builder.Image, builder.ROLayer, error) {
    if refOrID == "" { // FROM scratch
        if runtime.GOOS == "windows" {
            return nil, nil, fmt.Errorf(`"FROM scratch" is not supported on Windows`)
        }
        if opts.Platform != nil {
            if err := dimage.CheckOS(opts.Platform.OS); err != nil {
                return nil, nil, err
            }
        }
        return nil, &rolayer{
            c:           i.client,
            snapshotter: i.snapshotter,
        }, nil
    }

    if opts.PullOption != backend.PullOptionForcePull {
        // TODO(laurazard): same as below
        img, err := i.GetImage(ctx, refOrID, backend.GetImageOpts{Platform: opts.Platform})
        if err != nil && opts.PullOption == backend.PullOptionNoPull {
            return nil, nil, err
        }
        imgDesc, err := i.resolveDescriptor(ctx, refOrID)
        if err != nil && !errdefs.IsNotFound(err) {
            return nil, nil, err
        }
        if img != nil {
            if err := dimage.CheckOS(img.OperatingSystem()); err != nil {
                return nil, nil, err
            }

            roLayer, err := newROLayerForImage(ctx, &imgDesc, i, opts.Platform)
            if err != nil {
                return nil, nil, err
            }

            return img, roLayer, nil
        }
    }

    ctx, _, err := i.client.WithLease(ctx, leases.WithRandomID(), leases.WithExpiration(1*time.Hour))
    if err != nil {
        return nil, nil, fmt.Errorf("failed to create lease for commit: %w", err)
    }

    // TODO(laurazard): do we really need a new method here to pull the image?
    imgDesc, err := i.pullForBuilder(ctx, refOrID, opts.AuthConfig, opts.Output, opts.Platform)
    if err != nil {
        return nil, nil, err
    }

    // TODO(laurazard): pullForBuilder should return whatever we
    // need here instead of having to go and get it again
    img, err := i.GetImage(ctx, refOrID, backend.GetImageOpts{
        Platform: opts.Platform,
    })
    if err != nil {
        return nil, nil, err
    }

    roLayer, err := newROLayerForImage(ctx, imgDesc, i, opts.Platform)
    if err != nil {
        return nil, nil, err
    }

    return img, roLayer, nil
}

func (i *ImageService) pullForBuilder(ctx context.Context, name string, authConfigs map[string]registry.AuthConfig, output io.Writer, platform *ocispec.Platform) (*ocispec.Descriptor, error) {
    ref, err := reference.ParseNormalizedNamed(name)
    if err != nil {
        return nil, err
    }

    pullRegistryAuth := &registry.AuthConfig{}
    if len(authConfigs) > 0 {
        // The request came with a full auth config, use it
        repoInfo, err := i.registryService.ResolveRepository(ref)
        if err != nil {
            return nil, err
        }

        resolvedConfig := registrypkg.ResolveAuthConfig(authConfigs, repoInfo.Index)
        pullRegistryAuth = &resolvedConfig
    }

    if err := i.PullImage(ctx, reference.TagNameOnly(ref), platform, nil, pullRegistryAuth, output); err != nil {
        return nil, err
    }

    img, err := i.GetImage(ctx, name, backend.GetImageOpts{Platform: platform})
    if err != nil {
        if errdefs.IsNotFound(err) && img != nil && platform != nil {
            imgPlat := ocispec.Platform{
                OS:           img.OS,
                Architecture: img.BaseImgArch(),
                Variant:      img.BaseImgVariant(),
            }

            p := *platform
            if !platforms.Only(p).Match(imgPlat) {
                po := streamformatter.NewJSONProgressOutput(output, false)
                progress.Messagef(po, "", `
WARNING: Pulled image with specified platform (%s), but the resulting image's configured platform (%s) does not match.
This is most likely caused by a bug in the build system that created the fetched image (%s).
Please notify the image author to correct the configuration.`,
                    platforms.Format(p), platforms.Format(imgPlat), name,
                )
                log.G(ctx).WithError(err).WithField("image", name).Warn("Ignoring error about platform mismatch where the manifest list points to an image whose configuration does not match the platform in the manifest.")
            }
        } else {
            return nil, err
        }
    }

    if err := dimage.CheckOS(img.OperatingSystem()); err != nil {
        return nil, err
    }

    imgDesc, err := i.resolveDescriptor(ctx, name)
    if err != nil {
        return nil, err
    }

    return &imgDesc, err
}

func newROLayerForImage(ctx context.Context, imgDesc *ocispec.Descriptor, i *ImageService, platform *ocispec.Platform) (builder.ROLayer, error) {
    if imgDesc == nil {
        return nil, fmt.Errorf("can't make an RO layer for a nil image :'(")
    }

    platMatcher := platforms.Default()
    if platform != nil {
        platMatcher = platforms.Only(*platform)
    }

    confDesc, err := containerdimages.Config(ctx, i.content, *imgDesc, platMatcher)
    if err != nil {
        return nil, err
    }

    diffIDs, err := containerdimages.RootFS(ctx, i.content, confDesc)
    if err != nil {
        return nil, err
    }

    // TODO(vvoland): Check if image is unpacked, and unpack it if it's not.
    imageSnapshotID := identity.ChainID(diffIDs).String()

    snapshotter := i.StorageDriver()
    _, lease, err := createLease(ctx, i.client.LeasesService())
    if err != nil {
        return nil, errdefs.System(fmt.Errorf("failed to lease image snapshot %s: %w", imageSnapshotID, err))
    }

    return &rolayer{
        key:                imageSnapshotID,
        c:                  i.client,
        snapshotter:        snapshotter,
        diffID:             "", // Image RO layer doesn't have a diff.
        contentStoreDigest: "",
        lease:              &lease,
    }, nil
}

func createLease(ctx context.Context, lm leases.Manager) (context.Context, leases.Lease, error) {
    lease, err := lm.Create(ctx,
        leases.WithExpiration(time.Hour*24),
        leases.WithLabels(map[string]string{
            "org.mobyproject.lease.classicbuilder": "true",
        }),
    )
    if err != nil {
        return nil, leases.Lease{}, fmt.Errorf("failed to create a lease for snapshot: %w", err)
    }

    return leases.WithLease(ctx, lease.ID), lease, nil
}

type rolayer struct {
    key                string
    c                  *containerd.Client
    snapshotter        string
    diffID             layer.DiffID
    contentStoreDigest digest.Digest
    lease              *leases.Lease
}

func (rl *rolayer) ContentStoreDigest() digest.Digest {
    return rl.contentStoreDigest
}

func (rl *rolayer) DiffID() layer.DiffID {
    if rl.diffID == "" {
        return layer.DigestSHA256EmptyTar
    }
    return rl.diffID
}

func (rl *rolayer) Release() error {
    if rl.lease != nil {
        lm := rl.c.LeasesService()
        err := lm.Delete(context.TODO(), *rl.lease)
        if err != nil {
            return err
        }
        rl.lease = nil
    }
    return nil
}

// NewRWLayer creates a new read-write layer for the builder
func (rl *rolayer) NewRWLayer() (_ builder.RWLayer, outErr error) {
    snapshotter := rl.c.SnapshotService(rl.snapshotter)

    key := stringid.GenerateRandomID()

    ctx, lease, err := createLease(context.TODO(), rl.c.LeasesService())
    if err != nil {
        return nil, err
    }
    defer func() {
        if outErr != nil {
            if err := rl.c.LeasesService().Delete(ctx, lease); err != nil {
                log.G(ctx).WithError(err).Warn("failed to remove lease after NewRWLayer error")
            }
        }
    }()

    mounts, err := snapshotter.Prepare(ctx, key, rl.key)
    if err != nil {
        return nil, err
    }

    root, err := os.MkdirTemp(os.TempDir(), "rootfs-mount")
    if err != nil {
        return nil, err
    }
    if err := mount.All(mounts, root); err != nil {
        return nil, err
    }

    return &rwlayer{
        key:         key,
        parent:      rl.key,
        c:           rl.c,
        snapshotter: rl.snapshotter,
        root:        root,
        lease:       &lease,
    }, nil
}

type rwlayer struct {
    key         string
    parent      string
    c           *containerd.Client
    snapshotter string
    root        string
    lease       *leases.Lease
}

func (rw *rwlayer) Root() string {
    return rw.root
}

func (rw *rwlayer) Commit() (_ builder.ROLayer, outErr error) {
    snapshotter := rw.c.SnapshotService(rw.snapshotter)

    key := stringid.GenerateRandomID()

    lm := rw.c.LeasesService()
    ctx, lease, err := createLease(context.TODO(), lm)
    if err != nil {
        return nil, err
    }
    defer func() {
        if outErr != nil {
            if err := lm.Delete(ctx, lease); err != nil {
                log.G(ctx).WithError(err).Warn("failed to remove lease after NewRWLayer error")
            }
        }
    }()

    // Unmount the layer, required by the containerd windows snapshotter.
    // The windowsfilter graphdriver does this inside its own Diff method.
    //
    // The only place that calls this in-tree is (b *Builder) exportImage and
    // that is called from the end of (b *Builder) performCopy which has a
    // `defer rwLayer.Release()` pending.
    //
    // After the snapshotter.Commit the source snapshot is deleted anyway and
    // it shouldn't be accessed afterwards.
    if rw.root != "" {
        if err := mount.UnmountAll(rw.root, 0); err != nil && !errors.Is(err, os.ErrNotExist) {
            log.G(ctx).WithError(err).WithField("root", rw.root).Error("failed to unmount RWLayer")
            return nil, err
        }
    }

    err = snapshotter.Commit(ctx, key, rw.key)
    if err != nil && !cerrdefs.IsAlreadyExists(err) {
        return nil, err
    }

    differ := rw.c.DiffService()
    desc, err := rootfs.CreateDiff(ctx, key, snapshotter, differ)
    if err != nil {
        return nil, err
    }
    info, err := rw.c.ContentStore().Info(ctx, desc.Digest)
    if err != nil {
        return nil, err
    }
    diffIDStr, ok := info.Labels["containerd.io/uncompressed"]
    if !ok {
        return nil, fmt.Errorf("invalid differ response with no diffID")
    }
    diffID, err := digest.Parse(diffIDStr)
    if err != nil {
        return nil, err
    }

    return &rolayer{
        key:                key,
        c:                  rw.c,
        snapshotter:        rw.snapshotter,
        diffID:             layer.DiffID(diffID),
        contentStoreDigest: desc.Digest,
        lease:              &lease,
    }, nil
}

func (rw *rwlayer) Release() (outErr error) {
    if rw.root == "" { // nothing to release
        return nil
    }

    if err := mount.UnmountAll(rw.root, 0); err != nil && !errors.Is(err, os.ErrNotExist) {
        log.G(context.TODO()).WithError(err).WithField("root", rw.root).Error("failed to unmount RWLayer")
        return err
    }
    if err := os.Remove(rw.root); err != nil && !errors.Is(err, os.ErrNotExist) {
        log.G(context.TODO()).WithError(err).WithField("dir", rw.root).Error("failed to remove mount temp dir")
        return err
    }
    rw.root = ""

    if rw.lease != nil {
        lm := rw.c.LeasesService()
        err := lm.Delete(context.TODO(), *rw.lease)
        if err != nil {
            log.G(context.TODO()).WithError(err).Warn("failed to delete lease when releasing RWLayer")
        } else {
            rw.lease = nil
        }
    }

    return nil
}

// CreateImage creates a new image by adding a config and ID to the image store.
// This is similar to LoadImage() except that it receives JSON encoded bytes of
// an image instead of a tar archive.
func (i *ImageService) CreateImage(ctx context.Context, config []byte, parent string, layerDigest digest.Digest) (builder.Image, error) {
    imgToCreate, err := dimage.NewFromJSON(config)
    if err != nil {
        return nil, err
    }

    ociImgToCreate := dockerImageToDockerOCIImage(*imgToCreate)

    var layers []ocispec.Descriptor

    var parentDigest digest.Digest
    // if the image has a parent, we need to start with the parents layers descriptors
    if parent != "" {
        parentDesc, err := i.resolveDescriptor(ctx, parent)
        if err != nil {
            return nil, err
        }
        parentImageManifest, err := containerdimages.Manifest(ctx, i.content, parentDesc, platforms.Default())
        if err != nil {
            return nil, err
        }

        layers = parentImageManifest.Layers
        parentDigest = parentDesc.Digest
    }

    cs := i.content

    ra, err := cs.ReaderAt(ctx, ocispec.Descriptor{Digest: layerDigest})
    if err != nil {
        return nil, fmt.Errorf("failed to read diff archive: %w", err)
    }
    defer ra.Close()

    empty, err := archive.IsEmpty(content.NewReader(ra))
    if err != nil {
        return nil, fmt.Errorf("failed to check if archive is empty: %w", err)
    }
    if !empty {
        info, err := cs.Info(ctx, layerDigest)
        if err != nil {
            return nil, err
        }

        layers = append(layers, ocispec.Descriptor{
            MediaType: containerdimages.MediaTypeDockerSchema2LayerGzip,
            Digest:    layerDigest,
            Size:      info.Size,
        })
    }

    createdImageId, err := i.createImageOCI(ctx, ociImgToCreate, parentDigest, layers, imgToCreate.ContainerConfig)
    if err != nil {
        return nil, err
    }

    return dimage.Clone(imgToCreate, createdImageId), nil
}

func (i *ImageService) createImageOCI(ctx context.Context, imgToCreate imagespec.DockerOCIImage,
    parentDigest digest.Digest, layers []ocispec.Descriptor,
    containerConfig container.Config,
) (dimage.ID, error) {
    // Necessary to prevent the contents from being GC'd
    // between writing them here and creating an image
    ctx, release, err := i.client.WithLease(ctx, leases.WithRandomID(), leases.WithExpiration(1*time.Hour))
    if err != nil {
        return "", err
    }
    defer func() {
        if err := release(context.WithoutCancel(ctx)); err != nil {
            log.G(ctx).WithError(err).Warn("failed to release lease created for create")
        }
    }()

    manifestDesc, ccDesc, err := writeContentsForImage(ctx, i.snapshotter, i.content, imgToCreate, layers, containerConfig)
    if err != nil {
        return "", err
    }

    img := containerdimages.Image{
        Name:      danglingImageName(manifestDesc.Digest),
        Target:    manifestDesc,
        CreatedAt: time.Now(),
        Labels: map[string]string{
            imageLabelClassicBuilderParent:          parentDigest.String(),
            imageLabelClassicBuilderContainerConfig: ccDesc.Digest.String(),
        },
    }

    if parentDigest == "" {
        img.Labels[imageLabelClassicBuilderFromScratch] = "1"
    }

    createdImage, err := i.images.Update(ctx, img)
    if err != nil {
        if !cerrdefs.IsNotFound(err) {
            return "", err
        }

        if createdImage, err = i.images.Create(ctx, img); err != nil {
            return "", fmt.Errorf("failed to create new image: %w", err)
        }
    }

    id := image.ID(createdImage.Target.Digest)
    i.LogImageEvent(id.String(), id.String(), events.ActionCreate)

    if err := i.unpackImage(ctx, i.StorageDriver(), img, manifestDesc); err != nil {
        return "", err
    }

    return id, nil
}

// writeContentsForImage will commit oci image config and manifest into containerd's content store.
func writeContentsForImage(ctx context.Context, snName string, cs content.Store,
    newConfig imagespec.DockerOCIImage, layers []ocispec.Descriptor,
    containerConfig container.Config,
) (
    manifestDesc ocispec.Descriptor,
    containerConfigDesc ocispec.Descriptor,
    _ error,
) {
    newConfigJSON, err := json.Marshal(newConfig)
    if err != nil {
        return ocispec.Descriptor{}, ocispec.Descriptor{}, err
    }

    configDesc := ocispec.Descriptor{
        MediaType: ocispec.MediaTypeImageConfig,
        Digest:    digest.FromBytes(newConfigJSON),
        Size:      int64(len(newConfigJSON)),
    }

    newMfst := struct {
        MediaType string `json:"mediaType,omitempty"`
        ocispec.Manifest
    }{
        MediaType: ocispec.MediaTypeImageManifest,
        Manifest: ocispec.Manifest{
            Versioned: specs.Versioned{
                SchemaVersion: 2,
            },
            Config: configDesc,
            Layers: layers,
        },
    }

    newMfstJSON, err := json.MarshalIndent(newMfst, "", "    ")
    if err != nil {
        return ocispec.Descriptor{}, ocispec.Descriptor{}, err
    }

    newMfstDesc := ocispec.Descriptor{
        MediaType: ocispec.MediaTypeImageManifest,
        Digest:    digest.FromBytes(newMfstJSON),
        Size:      int64(len(newMfstJSON)),
    }

    // new manifest should reference the layers and config content
    labels := map[string]string{
        "containerd.io/gc.ref.content.0": configDesc.Digest.String(),
    }
    for i, l := range layers {
        labels[fmt.Sprintf("containerd.io/gc.ref.content.%d", i+1)] = l.Digest.String()
    }

    err = content.WriteBlob(ctx, cs, newMfstDesc.Digest.String(), bytes.NewReader(newMfstJSON), newMfstDesc, content.WithLabels(labels))
    if err != nil {
        return ocispec.Descriptor{}, ocispec.Descriptor{}, err
    }

    ccDesc, err := saveContainerConfig(ctx, cs, newMfstDesc.Digest, containerConfig)
    if err != nil {
        return ocispec.Descriptor{}, ocispec.Descriptor{}, err
    }

    // config should reference to snapshotter and container config
    labelOpt := content.WithLabels(map[string]string{
        fmt.Sprintf("containerd.io/gc.ref.snapshot.%s", snName): identity.ChainID(newConfig.RootFS.DiffIDs).String(),
        contentLabelGcRefContainerConfig:                        ccDesc.Digest.String(),
    })
    err = content.WriteBlob(ctx, cs, configDesc.Digest.String(), bytes.NewReader(newConfigJSON), configDesc, labelOpt)
    if err != nil {
        return ocispec.Descriptor{}, ocispec.Descriptor{}, err
    }

    return newMfstDesc, ccDesc, nil
}

// saveContainerConfig serializes the given ContainerConfig into a json and
// stores it in the content store and returns its descriptor.
func saveContainerConfig(ctx context.Context, content content.Ingester, imgID digest.Digest, containerConfig container.Config) (ocispec.Descriptor, error) {
    containerConfigDesc, err := storeJson(ctx, content,
        "application/vnd.docker.container.image.v1+json", containerConfig,
        map[string]string{contentLabelClassicBuilderImage: imgID.String()},
    )
    if err != nil {
        return ocispec.Descriptor{}, err
    }

    return containerConfigDesc, nil
}