dotcloud/docker

package distribution // import "github.com/docker/docker/distribution"

import (
    "context"
    "errors"
    "fmt"
    "io"
    "net/http"
    "runtime"
    "sort"
    "strconv"
    "strings"

    "github.com/Microsoft/hcsshim/osversion"
    "github.com/containerd/log"
    "github.com/containerd/platforms"
    "github.com/docker/distribution"
    "github.com/docker/distribution/manifest/manifestlist"
    "github.com/docker/distribution/manifest/schema2"
    "github.com/docker/distribution/registry/client/transport"
    "github.com/docker/docker/image"
    ocispec "github.com/opencontainers/image-spec/specs-go/v1"
)

var _ distribution.Describable = &layerDescriptor{}

func (ld *layerDescriptor) Descriptor() distribution.Descriptor {
    if ld.src.MediaType == schema2.MediaTypeForeignLayer && len(ld.src.URLs) > 0 {
        return ld.src
    }
    return distribution.Descriptor{}
}

func (ld *layerDescriptor) open(ctx context.Context) (distribution.ReadSeekCloser, error) {
    blobs := ld.repo.Blobs(ctx)
    rsc, err := blobs.Open(ctx, ld.digest)

    if len(ld.src.URLs) == 0 {
        return rsc, err
    }

    // We're done if the registry has this blob.
    if err == nil {
        // Seek does an HTTP GET.  If it succeeds, the blob really is accessible.
        if _, err = rsc.Seek(0, io.SeekStart); err == nil {
            return rsc, nil
        }
        rsc.Close()
    }

    // Find the first URL that results in a 200 result code.
    for _, url := range ld.src.URLs {
        log.G(ctx).Debugf("Pulling %v from foreign URL %v", ld.digest, url)
        rsc = transport.NewHTTPReadSeeker(http.DefaultClient, url, nil)

        // Seek does an HTTP GET.  If it succeeds, the blob really is accessible.
        _, err = rsc.Seek(0, io.SeekStart)
        if err == nil {
            break
        }
        log.G(ctx).Debugf("Download for %v failed: %v", ld.digest, err)
        rsc.Close()
        rsc = nil
    }
    return rsc, err
}

func filterManifests(manifests []manifestlist.ManifestDescriptor, p ocispec.Platform) []manifestlist.ManifestDescriptor {
    version := osversion.Get()
    osVersion := fmt.Sprintf("%d.%d.%d", version.MajorVersion, version.MinorVersion, version.Build)
    log.G(context.TODO()).Debugf("will prefer Windows entries with version %s", osVersion)

    var matches []manifestlist.ManifestDescriptor
    foundWindowsMatch := false
    for _, manifestDescriptor := range manifests {
        skip := func() {
            log.G(context.TODO()).Debugf("ignoring %s/%s %s with media type %s, digest %s", manifestDescriptor.Platform.OS, manifestDescriptor.Platform.Architecture, manifestDescriptor.Platform.OSVersion, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())
        }
        // TODO(thaJeztah): should we also check for the user-provided architecture (if any)?
        if manifestDescriptor.Platform.Architecture != runtime.GOARCH {
            skip()
            continue
        }
        os := manifestDescriptor.Platform.OS
        if p.OS != "" {
            // Explicit user request for an OS
            os = p.OS
        }
        if err := image.CheckOS(os); err != nil {
            skip()
            continue
        }
        // TODO(thaJeztah): should we also take the user-provided platform into account (if any)?
        if strings.EqualFold("windows", manifestDescriptor.Platform.OS) {
            if err := checkImageCompatibility("windows", manifestDescriptor.Platform.OSVersion); err != nil {
                skip()
                continue
            }
            foundWindowsMatch = true
        }
        matches = append(matches, manifestDescriptor)
        log.G(context.TODO()).Debugf("found match %s/%s %s with media type %s, digest %s", manifestDescriptor.Platform.OS, runtime.GOARCH, manifestDescriptor.Platform.OSVersion, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())
    }
    if foundWindowsMatch {
        sort.Stable(manifestsByVersion{osVersion, matches})
    }
    return matches
}

func versionMatch(actual, expected string) bool {
    // Check whether the version matches up to the build, ignoring UBR
    return strings.HasPrefix(actual, expected+".")
}

type manifestsByVersion struct {
    version string
    list    []manifestlist.ManifestDescriptor
}

func (mbv manifestsByVersion) Less(i, j int) bool {
    // TODO: Split version by parts and compare
    // TODO: Prefer versions which have a greater version number
    // Move compatible versions to the top, with no other ordering changes
    return (strings.EqualFold("windows", mbv.list[i].Platform.OS) && !strings.EqualFold("windows", mbv.list[j].Platform.OS)) ||
        (versionMatch(mbv.list[i].Platform.OSVersion, mbv.version) && !versionMatch(mbv.list[j].Platform.OSVersion, mbv.version))
}

func (mbv manifestsByVersion) Len() int {
    return len(mbv.list)
}

func (mbv manifestsByVersion) Swap(i, j int) {
    mbv.list[i], mbv.list[j] = mbv.list[j], mbv.list[i]
}

// checkImageCompatibility blocks pulling incompatible images based on a later OS build
// Fixes https://github.com/moby/moby/issues/36184.
func checkImageCompatibility(imageOS, imageOSVersion string) error {
    if imageOS == "windows" {
        hostOSV := osversion.Get()
        splitImageOSVersion := strings.Split(imageOSVersion, ".") // eg 10.0.16299.nnnn
        if len(splitImageOSVersion) >= 3 {
            if imageOSBuild, err := strconv.Atoi(splitImageOSVersion[2]); err == nil {
                if imageOSBuild > int(hostOSV.Build) {
                    errMsg := fmt.Sprintf("a Windows version %s.%s.%s-based image is incompatible with a %s host", splitImageOSVersion[0], splitImageOSVersion[1], splitImageOSVersion[2], hostOSV.ToString())
                    log.G(context.TODO()).Debugf(errMsg)
                    return errors.New(errMsg)
                }
            }
        }
    }
    return nil
}

func formatPlatform(platform ocispec.Platform) string {
    if platform.OS == "" {
        platform = platforms.DefaultSpec()
    }
    return fmt.Sprintf("%s %s", platforms.Format(platform), osversion.Get().ToString())
}