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buildpack.go
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buildpack.go
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package buildpack
import (
"archive/tar"
"fmt"
"io"
"os"
"path"
"path/filepath"
"strings"
"github.com/BurntSushi/toml"
"github.com/buildpacks/lifecycle/api"
"github.com/pkg/errors"
"github.com/buildpacks/pack/internal/style"
"github.com/buildpacks/pack/pkg/archive"
"github.com/buildpacks/pack/pkg/dist"
)
const (
KindBuildpack = "buildpack"
KindExtension = "extension"
)
//go:generate mockgen -package testmocks -destination ../testmocks/mock_build_module.go github.com/buildpacks/pack/pkg/buildpack BuildModule
type BuildModule interface {
// Open returns a reader to a tar with contents structured as per the distribution spec
// (currently '/cnb/buildpacks/{ID}/{version}/*', all entries with a zeroed-out
// timestamp and root UID/GID).
Open() (io.ReadCloser, error)
Descriptor() Descriptor
}
type Descriptor interface {
API() *api.Version
EnsureStackSupport(stackID string, providedMixins []string, validateRunStageMixins bool) error
EnsureTargetSupport(os, arch, distroName, distroVersion string) error
EscapedID() string
Info() dist.ModuleInfo
Kind() string
Order() dist.Order
Stacks() []dist.Stack
Targets() []dist.Target
}
type Blob interface {
// Open returns a io.ReadCloser for the contents of the Blob in tar format.
Open() (io.ReadCloser, error)
}
type buildModule struct {
descriptor Descriptor
Blob `toml:"-"`
}
func (b *buildModule) Descriptor() Descriptor {
return b.descriptor
}
// FromBlob constructs a buildpack or extension from a blob. It is assumed that the buildpack
// contents are structured as per the distribution spec (currently '/cnb/buildpacks/{ID}/{version}/*' or
// '/cnb/extensions/{ID}/{version}/*').
func FromBlob(descriptor Descriptor, blob Blob) BuildModule {
return &buildModule{
Blob: blob,
descriptor: descriptor,
}
}
// FromBuildpackRootBlob constructs a buildpack from a blob. It is assumed that the buildpack contents reside at the
// root of the blob. The constructed buildpack contents will be structured as per the distribution spec (currently
// a tar with contents under '/cnb/buildpacks/{ID}/{version}/*').
func FromBuildpackRootBlob(blob Blob, layerWriterFactory archive.TarWriterFactory, logger Logger) (BuildModule, error) {
descriptor := dist.BuildpackDescriptor{}
descriptor.WithAPI = api.MustParse(dist.AssumedBuildpackAPIVersion)
undecodedKeys, err := readDescriptor(KindBuildpack, &descriptor, blob)
if err != nil {
return nil, err
}
if len(undecodedKeys) > 0 {
logger.Warnf("Ignoring unexpected key(s) in descriptor for buildpack %s: %s", descriptor.EscapedID(), strings.Join(undecodedKeys, ", "))
}
if err := detectPlatformSpecificValues(&descriptor, blob); err != nil {
return nil, err
}
if err := validateBuildpackDescriptor(descriptor); err != nil {
return nil, err
}
return buildpackFrom(&descriptor, blob, layerWriterFactory)
}
// FromExtensionRootBlob constructs an extension from a blob. It is assumed that the extension contents reside at the
// root of the blob. The constructed extension contents will be structured as per the distribution spec (currently
// a tar with contents under '/cnb/extensions/{ID}/{version}/*').
func FromExtensionRootBlob(blob Blob, layerWriterFactory archive.TarWriterFactory, logger Logger) (BuildModule, error) {
descriptor := dist.ExtensionDescriptor{}
descriptor.WithAPI = api.MustParse(dist.AssumedBuildpackAPIVersion)
undecodedKeys, err := readDescriptor(KindExtension, &descriptor, blob)
if err != nil {
return nil, err
}
if len(undecodedKeys) > 0 {
logger.Warnf("Ignoring unexpected key(s) in descriptor for extension %s: %s", descriptor.EscapedID(), strings.Join(undecodedKeys, ", "))
}
if err := validateExtensionDescriptor(descriptor); err != nil {
return nil, err
}
return buildpackFrom(&descriptor, blob, layerWriterFactory)
}
func readDescriptor(kind string, descriptor interface{}, blob Blob) (undecodedKeys []string, err error) {
rc, err := blob.Open()
if err != nil {
return undecodedKeys, errors.Wrapf(err, "open %s", kind)
}
defer rc.Close()
descriptorFile := kind + ".toml"
_, buf, err := archive.ReadTarEntry(rc, descriptorFile)
if err != nil {
return undecodedKeys, errors.Wrapf(err, "reading %s", descriptorFile)
}
md, err := toml.Decode(string(buf), descriptor)
if err != nil {
return undecodedKeys, errors.Wrapf(err, "decoding %s", descriptorFile)
}
undecoded := md.Undecoded()
for _, k := range undecoded {
// FIXME: we should ideally update dist.ModuleInfo to expect sbom-formats, but this breaks other tests;
// it isn't possible to make [metadata] a decoded key because its type is undefined in the buildpack spec.
if k.String() == "metadata" || strings.HasPrefix(k.String(), "metadata.") ||
k.String() == "buildpack.sbom-formats" {
// buildpack.toml & extension.toml can contain [metadata] which is arbitrary
continue
}
undecodedKeys = append(undecodedKeys, k.String())
}
return undecodedKeys, nil
}
func detectPlatformSpecificValues(descriptor *dist.BuildpackDescriptor, blob Blob) error {
if val, err := hasFile(blob, path.Join("bin", "build")); val {
descriptor.WithLinuxBuild = true
} else if err != nil {
return err
}
if val, err := hasFile(blob, path.Join("bin", "build.bat")); val {
descriptor.WithWindowsBuild = true
} else if err != nil {
return err
}
if val, err := hasFile(blob, path.Join("bin", "build.exe")); val {
descriptor.WithWindowsBuild = true
} else if err != nil {
return err
}
return nil
}
func hasFile(blob Blob, file string) (bool, error) {
rc, err := blob.Open()
if err != nil {
return false, errors.Wrapf(err, "open %s", "buildpack bin/")
}
defer rc.Close()
_, _, err = archive.ReadTarEntry(rc, file)
return err == nil, nil
}
func buildpackFrom(descriptor Descriptor, blob Blob, layerWriterFactory archive.TarWriterFactory) (BuildModule, error) {
return &buildModule{
descriptor: descriptor,
Blob: &distBlob{
openFn: func() io.ReadCloser {
return archive.GenerateTarWithWriter(
func(tw archive.TarWriter) error {
return toDistTar(tw, descriptor, blob)
},
layerWriterFactory,
)
},
},
}, nil
}
type distBlob struct {
openFn func() io.ReadCloser
}
func (b *distBlob) Open() (io.ReadCloser, error) {
return b.openFn(), nil
}
func toDistTar(tw archive.TarWriter, descriptor Descriptor, blob Blob) error {
ts := archive.NormalizedDateTime
parentDir := dist.BuildpacksDir
if descriptor.Kind() == KindExtension {
parentDir = dist.ExtensionsDir
}
if err := tw.WriteHeader(&tar.Header{
Typeflag: tar.TypeDir,
Name: path.Join(parentDir, descriptor.EscapedID()),
Mode: 0755,
ModTime: ts,
}); err != nil {
return errors.Wrapf(err, "writing %s id dir header", descriptor.Kind())
}
baseTarDir := path.Join(parentDir, descriptor.EscapedID(), descriptor.Info().Version)
if err := tw.WriteHeader(&tar.Header{
Typeflag: tar.TypeDir,
Name: baseTarDir,
Mode: 0755,
ModTime: ts,
}); err != nil {
return errors.Wrapf(err, "writing %s version dir header", descriptor.Kind())
}
rc, err := blob.Open()
if err != nil {
return errors.Wrapf(err, "reading %s blob", descriptor.Kind())
}
defer rc.Close()
tr := tar.NewReader(rc)
for {
header, err := tr.Next()
if err == io.EOF {
break
}
if err != nil {
return errors.Wrap(err, "failed to get next tar entry")
}
archive.NormalizeHeader(header, true)
header.Name = path.Clean(header.Name)
if header.Name == "." || header.Name == "/" {
continue
}
header.Mode = calcFileMode(header)
header.Name = path.Join(baseTarDir, header.Name)
if header.Typeflag == tar.TypeLink {
header.Linkname = path.Join(baseTarDir, path.Clean(header.Linkname))
}
err = tw.WriteHeader(header)
if err != nil {
return errors.Wrapf(err, "failed to write header for '%s'", header.Name)
}
_, err = io.Copy(tw, tr)
if err != nil {
return errors.Wrapf(err, "failed to write contents to '%s'", header.Name)
}
}
return nil
}
func calcFileMode(header *tar.Header) int64 {
switch {
case header.Typeflag == tar.TypeDir:
return 0755
case nameOneOf(header.Name,
path.Join("bin", "build"),
path.Join("bin", "detect"),
path.Join("bin", "generate"),
):
return 0755
case anyExecBit(header.Mode):
return 0755
}
return 0644
}
func nameOneOf(name string, paths ...string) bool {
for _, p := range paths {
if name == p {
return true
}
}
return false
}
func anyExecBit(mode int64) bool {
return mode&0111 != 0
}
func validateBuildpackDescriptor(bpd dist.BuildpackDescriptor) error {
if bpd.Info().ID == "" {
return errors.Errorf("%s is required", style.Symbol("buildpack.id"))
}
if bpd.Info().Version == "" {
return errors.Errorf("%s is required", style.Symbol("buildpack.version"))
}
if len(bpd.Order()) >= 1 && (len(bpd.Stacks()) >= 1 || len(bpd.Targets()) >= 1) {
return errors.Errorf(
"buildpack %s: cannot have both %s/%s and an %s defined",
style.Symbol(bpd.Info().FullName()),
style.Symbol("targets"),
style.Symbol("stacks"),
style.Symbol("order"),
)
}
return nil
}
func validateExtensionDescriptor(extd dist.ExtensionDescriptor) error {
if extd.Info().ID == "" {
return errors.Errorf("%s is required", style.Symbol("extension.id"))
}
if extd.Info().Version == "" {
return errors.Errorf("%s is required", style.Symbol("extension.version"))
}
return nil
}
func ToLayerTar(dest string, module BuildModule) (string, error) {
descriptor := module.Descriptor()
modReader, err := module.Open()
if err != nil {
return "", errors.Wrap(err, "opening blob")
}
defer modReader.Close()
layerTar := filepath.Join(dest, fmt.Sprintf("%s.%s.tar", descriptor.EscapedID(), descriptor.Info().Version))
fh, err := os.Create(layerTar)
if err != nil {
return "", errors.Wrap(err, "create file for tar")
}
defer fh.Close()
if _, err := io.Copy(fh, modReader); err != nil {
return "", errors.Wrap(err, "writing blob to tar")
}
return layerTar, nil
}
func ToNLayerTar(dest string, module BuildModule) ([]ModuleTar, error) {
modReader, err := module.Open()
if err != nil {
return nil, errors.Wrap(err, "opening blob")
}
defer modReader.Close()
tarCollection := newModuleTarCollection(dest)
tr := tar.NewReader(modReader)
var (
header *tar.Header
forWindows bool
)
for {
header, err = tr.Next()
if err != nil {
if err == io.EOF {
return handleEmptyModule(dest, module)
}
return nil, err
}
if _, err := sanitizePath(header.Name); err != nil {
return nil, err
}
if header.Name == "Files" {
forWindows = true
}
if strings.Contains(header.Name, `/cnb/buildpacks/`) || strings.Contains(header.Name, `\cnb\buildpacks\`) {
// Only for Windows, the first four headers are:
// - Files
// - Hives
// - Files/cnb
// - Files/cnb/buildpacks
// Skip over these until we find "Files/cnb/buildpacks/<buildpack-id>":
break
}
}
// The header should look like "/cnb/buildpacks/<buildpack-id>"
// The version should be blank because the first header is missing <buildpack-version>.
origID, origVersion := parseBpIDAndVersion(header)
if origVersion != "" {
return nil, fmt.Errorf("first header '%s' contained unexpected version", header.Name)
}
if err := toNLayerTar(origID, origVersion, header, tr, tarCollection, forWindows); err != nil {
return nil, err
}
errs := tarCollection.close()
if len(errs) > 0 {
return nil, errors.New("closing files")
}
return tarCollection.moduleTars(), nil
}
func toNLayerTar(origID, origVersion string, firstHeader *tar.Header, tr *tar.Reader, tc *moduleTarCollection, forWindows bool) error {
toWrite := []*tar.Header{firstHeader}
if origVersion == "" {
// the first header only contains the id - e.g., /cnb/buildpacks/<buildpack-id>,
// read the next header to get the version
secondHeader, err := tr.Next()
if err != nil {
return fmt.Errorf("getting second header: %w; first header was %s", err, firstHeader.Name)
}
if _, err := sanitizePath(secondHeader.Name); err != nil {
return err
}
nextID, nextVersion := parseBpIDAndVersion(secondHeader)
if nextID != origID || nextVersion == "" {
return fmt.Errorf("second header '%s' contained unexpected id or missing version", secondHeader.Name)
}
origVersion = nextVersion
toWrite = append(toWrite, secondHeader)
} else {
// the first header contains id and version - e.g., /cnb/buildpacks/<buildpack-id>/<buildpack-version>,
// we need to write the parent header - e.g., /cnb/buildpacks/<buildpack-id>
realFirstHeader := *firstHeader
realFirstHeader.Name = filepath.ToSlash(filepath.Dir(firstHeader.Name))
toWrite = append([]*tar.Header{&realFirstHeader}, toWrite...)
}
if forWindows {
toWrite = append(windowsPreamble(), toWrite...)
}
mt, err := tc.get(origID, origVersion)
if err != nil {
return fmt.Errorf("getting module from collection: %w", err)
}
for _, h := range toWrite {
if err := mt.writer.WriteHeader(h); err != nil {
return fmt.Errorf("failed to write header '%s': %w", h.Name, err)
}
}
// write the rest of the package
var header *tar.Header
for {
header, err = tr.Next()
if err != nil {
if err == io.EOF {
return nil
}
return fmt.Errorf("getting next header: %w", err)
}
if _, err := sanitizePath(header.Name); err != nil {
return err
}
nextID, nextVersion := parseBpIDAndVersion(header)
if nextID != origID || nextVersion != origVersion {
// we found a new module, recurse
return toNLayerTar(nextID, nextVersion, header, tr, tc, forWindows)
}
err = mt.writer.WriteHeader(header)
if err != nil {
return fmt.Errorf("failed to write header for '%s': %w", header.Name, err)
}
_, err = io.Copy(mt.writer, tr)
if err != nil {
return errors.Wrapf(err, "failed to write contents to '%s'", header.Name)
}
}
}
func sanitizePath(path string) (string, error) {
if strings.Contains(path, "..") {
return "", fmt.Errorf("path %s contains unexpected special elements", path)
}
return path, nil
}
func windowsPreamble() []*tar.Header {
return []*tar.Header{
{
Name: "Files",
Typeflag: tar.TypeDir,
},
{
Name: "Hives",
Typeflag: tar.TypeDir,
},
{
Name: "Files/cnb",
Typeflag: tar.TypeDir,
},
{
Name: "Files/cnb/buildpacks",
Typeflag: tar.TypeDir,
},
}
}
func parseBpIDAndVersion(hdr *tar.Header) (id, version string) {
// splitting "/cnb/buildpacks/{ID}/{version}/*" returns
// [0] = "" -> first element is empty or "Files" in windows
// [1] = "cnb"
// [2] = "buildpacks"
// [3] = "{ID}"
// [4] = "{version}"
// ...
parts := strings.Split(strings.ReplaceAll(filepath.Clean(hdr.Name), `\`, `/`), `/`)
size := len(parts)
switch {
case size < 4:
// error
case size == 4:
id = parts[3]
case size >= 5:
id = parts[3]
version = parts[4]
}
return id, version
}
func handleEmptyModule(dest string, module BuildModule) ([]ModuleTar, error) {
tarFile, err := ToLayerTar(dest, module)
if err != nil {
return nil, err
}
layerTar := &moduleTar{
info: module.Descriptor().Info(),
path: tarFile,
}
return []ModuleTar{layerTar}, nil
}
// Set returns a set of the given string slice.
func Set(exclude []string) map[string]struct{} {
type void struct{}
var member void
var excludedModules = make(map[string]struct{})
for _, fullName := range exclude {
excludedModules[fullName] = member
}
return excludedModules
}
type ModuleTar interface {
Info() dist.ModuleInfo
Path() string
}
type moduleTar struct {
info dist.ModuleInfo
path string
writer archive.TarWriter
}
func (t *moduleTar) Info() dist.ModuleInfo {
return t.info
}
func (t *moduleTar) Path() string {
return t.path
}
func newModuleTar(dest, id, version string) (moduleTar, error) {
layerTar := filepath.Join(dest, fmt.Sprintf("%s.%s.tar", id, version))
fh, err := os.Create(layerTar)
if err != nil {
return moduleTar{}, errors.Wrapf(err, "creating file at path %s", layerTar)
}
return moduleTar{
info: dist.ModuleInfo{
ID: id,
Version: version,
},
path: layerTar,
writer: tar.NewWriter(fh),
}, nil
}
type moduleTarCollection struct {
rootPath string
modules map[string]moduleTar
}
func newModuleTarCollection(rootPath string) *moduleTarCollection {
return &moduleTarCollection{
rootPath: rootPath,
modules: map[string]moduleTar{},
}
}
func (m *moduleTarCollection) get(id, version string) (moduleTar, error) {
key := fmt.Sprintf("%s@%s", id, version)
if _, ok := m.modules[key]; !ok {
module, err := newModuleTar(m.rootPath, id, version)
if err != nil {
return moduleTar{}, err
}
m.modules[key] = module
}
return m.modules[key], nil
}
func (m *moduleTarCollection) moduleTars() []ModuleTar {
var modulesTar []ModuleTar
for _, v := range m.modules {
v := v
vv := &v
modulesTar = append(modulesTar, vv)
}
return modulesTar
}
func (m *moduleTarCollection) close() []error {
var errors []error
for _, v := range m.modules {
err := v.writer.Close()
if err != nil {
errors = append(errors, err)
}
}
return errors
}