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package continuity
import (
"bytes"
"fmt"
"io"
"log"
"os"
"path/filepath"
"strings"
"github.com/containerd/continuity/devices"
driverpkg "github.com/containerd/continuity/driver"
"github.com/containerd/continuity/pathdriver"
"github.com/opencontainers/go-digest"
)
var (
ErrNotFound = fmt.Errorf("not found")
ErrNotSupported = fmt.Errorf("not supported")
)
// Context represents a file system context for accessing resources. The
// responsibility of the context is to convert system specific resources to
// generic Resource objects. Most of this is safe path manipulation, as well
// as extraction of resource details.
type Context interface {
Apply(Resource) error
Verify(Resource) error
Resource(string, os.FileInfo) (Resource, error)
Walk(filepath.WalkFunc) error
}
// SymlinkPath is intended to give the symlink target value
// in a root context. Target and linkname are absolute paths
// not under the given root.
type SymlinkPath func(root, linkname, target string) (string, error)
type ContextOptions struct {
Digester Digester
Driver driverpkg.Driver
PathDriver pathdriver.PathDriver
Provider ContentProvider
}
// context represents a file system context for accessing resources.
// Generally, all path qualified access and system considerations should land
// here.
type context struct {
driver driverpkg.Driver
pathDriver pathdriver.PathDriver
root string
digester Digester
provider ContentProvider
}
// NewContext returns a Context associated with root. The default driver will
// be used, as returned by NewDriver.
func NewContext(root string) (Context, error) {
return NewContextWithOptions(root, ContextOptions{})
}
// NewContextWithOptions returns a Context associate with the root.
func NewContextWithOptions(root string, options ContextOptions) (Context, error) {
// normalize to absolute path
pathDriver := options.PathDriver
if pathDriver == nil {
pathDriver = pathdriver.LocalPathDriver
}
root = pathDriver.FromSlash(root)
root, err := pathDriver.Abs(pathDriver.Clean(root))
if err != nil {
return nil, err
}
driver := options.Driver
if driver == nil {
driver, err = driverpkg.NewSystemDriver()
if err != nil {
return nil, err
}
}
digester := options.Digester
if digester == nil {
digester = simpleDigester{digest.Canonical}
}
// Check the root directory. Need to be a little careful here. We are
// allowing a link for now, but this may have odd behavior when
// canonicalizing paths. As long as all files are opened through the link
// path, this should be okay.
fi, err := driver.Stat(root)
if err != nil {
return nil, err
}
if !fi.IsDir() {
return nil, &os.PathError{Op: "NewContext", Path: root, Err: os.ErrInvalid}
}
return &context{
root: root,
driver: driver,
pathDriver: pathDriver,
digester: digester,
provider: options.Provider,
}, nil
}
// Resource returns the resource as path p, populating the entry with info
// from fi. The path p should be the path of the resource in the context,
// typically obtained through Walk or from the value of Resource.Path(). If fi
// is nil, it will be resolved.
func (c *context) Resource(p string, fi os.FileInfo) (Resource, error) {
fp, err := c.fullpath(p)
if err != nil {
return nil, err
}
if fi == nil {
fi, err = c.driver.Lstat(fp)
if err != nil {
return nil, err
}
}
base, err := newBaseResource(p, fi)
if err != nil {
return nil, err
}
base.xattrs, err = c.resolveXAttrs(fp, fi, base)
if err == ErrNotSupported {
log.Printf("resolving xattrs on %s not supported", fp)
} else if err != nil {
return nil, err
}
// TODO(stevvooe): Handle windows alternate data streams.
if fi.Mode().IsRegular() {
dgst, err := c.digest(p)
if err != nil {
return nil, err
}
return newRegularFile(*base, base.paths, fi.Size(), dgst)
}
if fi.Mode().IsDir() {
return newDirectory(*base)
}
if fi.Mode()&os.ModeSymlink != 0 {
// We handle relative links vs absolute links by including a
// beginning slash for absolute links. Effectively, the bundle's
// root is treated as the absolute link anchor.
target, err := c.driver.Readlink(fp)
if err != nil {
return nil, err
}
return newSymLink(*base, target)
}
if fi.Mode()&os.ModeNamedPipe != 0 {
return newNamedPipe(*base, base.paths)
}
if fi.Mode()&os.ModeDevice != 0 {
deviceDriver, ok := c.driver.(driverpkg.DeviceInfoDriver)
if !ok {
log.Printf("device extraction not supported %s", fp)
return nil, ErrNotSupported
}
// character and block devices merely need to recover the
// major/minor device number.
major, minor, err := deviceDriver.DeviceInfo(fi)
if err != nil {
return nil, err
}
return newDevice(*base, base.paths, major, minor)
}
log.Printf("%q (%v) is not supported", fp, fi.Mode())
return nil, ErrNotFound
}
func (c *context) verifyMetadata(resource, target Resource) error {
if target.Mode() != resource.Mode() {
return fmt.Errorf("resource %q has incorrect mode: %v != %v", target.Path(), target.Mode(), resource.Mode())
}
if target.UID() != resource.UID() {
return fmt.Errorf("unexpected uid for %q: %v != %v", target.Path(), target.UID(), resource.GID())
}
if target.GID() != resource.GID() {
return fmt.Errorf("unexpected gid for %q: %v != %v", target.Path(), target.GID(), target.GID())
}
if xattrer, ok := resource.(XAttrer); ok {
txattrer, tok := target.(XAttrer)
if !tok {
return fmt.Errorf("resource %q has xattrs but target does not support them", resource.Path())
}
// For xattrs, only ensure that we have those defined in the resource
// and their values match. We can ignore other xattrs. In other words,
// we only verify that target has the subset defined by resource.
txattrs := txattrer.XAttrs()
for attr, value := range xattrer.XAttrs() {
tvalue, ok := txattrs[attr]
if !ok {
return fmt.Errorf("resource %q target missing xattr %q", resource.Path(), attr)
}
if !bytes.Equal(value, tvalue) {
return fmt.Errorf("xattr %q value differs for resource %q", attr, resource.Path())
}
}
}
switch r := resource.(type) {
case RegularFile:
// TODO(stevvooe): Another reason to use a record-based approach. We
// have to do another type switch to get this to work. This could be
// fixed with an Equal function, but let's study this a little more to
// be sure.
t, ok := target.(RegularFile)
if !ok {
return fmt.Errorf("resource %q target not a regular file", r.Path())
}
if t.Size() != r.Size() {
return fmt.Errorf("resource %q target has incorrect size: %v != %v", t.Path(), t.Size(), r.Size())
}
case Directory:
t, ok := target.(Directory)
if !ok {
return fmt.Errorf("resource %q target not a directory", t.Path())
}
case SymLink:
t, ok := target.(SymLink)
if !ok {
return fmt.Errorf("resource %q target not a symlink", t.Path())
}
if t.Target() != r.Target() {
return fmt.Errorf("resource %q target has mismatched target: %q != %q", t.Path(), t.Target(), r.Target())
}
case Device:
t, ok := target.(Device)
if !ok {
return fmt.Errorf("resource %q is not a device", t.Path())
}
if t.Major() != r.Major() || t.Minor() != r.Minor() {
return fmt.Errorf("resource %q has mismatched major/minor numbers: %d,%d != %d,%d", t.Path(), t.Major(), t.Minor(), r.Major(), r.Minor())
}
case NamedPipe:
t, ok := target.(NamedPipe)
if !ok {
return fmt.Errorf("resource %q is not a named pipe", t.Path())
}
default:
return fmt.Errorf("cannot verify resource: %v", resource)
}
return nil
}
// Verify the resource in the context. An error will be returned a discrepancy
// is found.
func (c *context) Verify(resource Resource) error {
fp, err := c.fullpath(resource.Path())
if err != nil {
return err
}
fi, err := c.driver.Lstat(fp)
if err != nil {
return err
}
target, err := c.Resource(resource.Path(), fi)
if err != nil {
return err
}
if target.Path() != resource.Path() {
return fmt.Errorf("resource paths do not match: %q != %q", target.Path(), resource.Path())
}
if err := c.verifyMetadata(resource, target); err != nil {
return err
}
if h, isHardlinkable := resource.(Hardlinkable); isHardlinkable {
hardlinkKey, err := newHardlinkKey(fi)
if err == errNotAHardLink {
if len(h.Paths()) > 1 {
return fmt.Errorf("%q is not a hardlink to %q", h.Paths()[1], resource.Path())
}
} else if err != nil {
return err
}
for _, path := range h.Paths()[1:] {
fpLink, err := c.fullpath(path)
if err != nil {
return err
}
fiLink, err := c.driver.Lstat(fpLink)
if err != nil {
return err
}
targetLink, err := c.Resource(path, fiLink)
if err != nil {
return err
}
hardlinkKeyLink, err := newHardlinkKey(fiLink)
if err != nil {
return err
}
if hardlinkKeyLink != hardlinkKey {
return fmt.Errorf("%q is not a hardlink to %q", path, resource.Path())
}
if err := c.verifyMetadata(resource, targetLink); err != nil {
return err
}
}
}
switch r := resource.(type) {
case RegularFile:
t, ok := target.(RegularFile)
if !ok {
return fmt.Errorf("resource %q target not a regular file", r.Path())
}
// TODO(stevvooe): This may need to get a little more sophisticated
// for digest comparison. We may want to actually calculate the
// provided digests, rather than the implementations having an
// overlap.
if !digestsMatch(t.Digests(), r.Digests()) {
return fmt.Errorf("digests for resource %q do not match: %v != %v", t.Path(), t.Digests(), r.Digests())
}
}
return nil
}
func (c *context) checkoutFile(fp string, rf RegularFile) error {
if c.provider == nil {
return fmt.Errorf("no file provider")
}
var (
r io.ReadCloser
err error
)
for _, dgst := range rf.Digests() {
r, err = c.provider.Reader(dgst)
if err == nil {
break
}
}
if err != nil {
return fmt.Errorf("file content could not be provided: %v", err)
}
defer r.Close()
return atomicWriteFile(fp, r, rf)
}
// Apply the resource to the contexts. An error will be returned if the
// operation fails. Depending on the resource type, the resource may be
// created. For resource that cannot be resolved, an error will be returned.
func (c *context) Apply(resource Resource) error {
fp, err := c.fullpath(resource.Path())
if err != nil {
return err
}
if !strings.HasPrefix(fp, c.root) {
return fmt.Errorf("resource %v escapes root", resource)
}
var chmod = true
fi, err := c.driver.Lstat(fp)
if err != nil {
if !os.IsNotExist(err) {
return err
}
}
switch r := resource.(type) {
case RegularFile:
if fi == nil {
if err := c.checkoutFile(fp, r); err != nil {
return fmt.Errorf("error checking out file %q: %v", resource.Path(), err)
}
chmod = false
} else {
if !fi.Mode().IsRegular() {
return fmt.Errorf("file %q should be a regular file, but is not", resource.Path())
}
if fi.Size() != r.Size() {
if err := c.checkoutFile(fp, r); err != nil {
return fmt.Errorf("error checking out file %q: %v", resource.Path(), err)
}
} else {
for _, dgst := range r.Digests() {
f, err := os.Open(fp)
if err != nil {
return fmt.Errorf("failure opening file for read %q: %v", resource.Path(), err)
}
compared, err := dgst.Algorithm().FromReader(f)
if err == nil && dgst != compared {
if err := c.checkoutFile(fp, r); err != nil {
return fmt.Errorf("error checking out file %q: %v", resource.Path(), err)
}
break
}
if err1 := f.Close(); err == nil {
err = err1
}
if err != nil {
return fmt.Errorf("error checking digest for %q: %v", resource.Path(), err)
}
}
}
}
case Directory:
if fi == nil {
if err := c.driver.Mkdir(fp, resource.Mode()); err != nil {
return err
}
} else if !fi.Mode().IsDir() {
return fmt.Errorf("%q should be a directory, but is not", resource.Path())
}
case SymLink:
var target string // only possibly set if target resource is a symlink
if fi != nil {
if fi.Mode()&os.ModeSymlink != 0 {
target, err = c.driver.Readlink(fp)
if err != nil {
return err
}
}
}
if target != r.Target() {
if fi != nil {
if err := c.driver.Remove(fp); err != nil { // RemoveAll in case of directory?
return err
}
}
if err := c.driver.Symlink(r.Target(), fp); err != nil {
return err
}
}
// NOTE(stevvooe): Chmod on symlink is not supported on linux. We
// may want to maintain support for other platforms that have it.
chmod = false
case Device:
if fi == nil {
if err := c.driver.Mknod(fp, resource.Mode(), int(r.Major()), int(r.Minor())); err != nil {
return err
}
} else if (fi.Mode() & os.ModeDevice) == 0 {
return fmt.Errorf("%q should be a device, but is not", resource.Path())
} else {
major, minor, err := devices.DeviceInfo(fi)
if err != nil {
return err
}
if major != r.Major() || minor != r.Minor() {
if err := c.driver.Remove(fp); err != nil {
return err
}
if err := c.driver.Mknod(fp, resource.Mode(), int(r.Major()), int(r.Minor())); err != nil {
return err
}
}
}
case NamedPipe:
if fi == nil {
if err := c.driver.Mkfifo(fp, resource.Mode()); err != nil {
return err
}
} else if (fi.Mode() & os.ModeNamedPipe) == 0 {
return fmt.Errorf("%q should be a named pipe, but is not", resource.Path())
}
}
if h, isHardlinkable := resource.(Hardlinkable); isHardlinkable {
for _, path := range h.Paths() {
if path == resource.Path() {
continue
}
lp, err := c.fullpath(path)
if err != nil {
return err
}
if _, fi := c.driver.Lstat(lp); fi == nil {
c.driver.Remove(lp)
}
if err := c.driver.Link(fp, lp); err != nil {
return err
}
}
}
// Update filemode if file was not created
if chmod {
if err := c.driver.Lchmod(fp, resource.Mode()); err != nil {
return err
}
}
if err := c.driver.Lchown(fp, resource.UID(), resource.GID()); err != nil {
return err
}
if xattrer, ok := resource.(XAttrer); ok {
// For xattrs, only ensure that we have those defined in the resource
// and their values are set. We can ignore other xattrs. In other words,
// we only set xattres defined by resource but never remove.
if _, ok := resource.(SymLink); ok {
lxattrDriver, ok := c.driver.(driverpkg.LXAttrDriver)
if !ok {
return fmt.Errorf("unsupported symlink xattr for resource %q", resource.Path())
}
if err := lxattrDriver.LSetxattr(fp, xattrer.XAttrs()); err != nil {
return err
}
} else {
xattrDriver, ok := c.driver.(driverpkg.XAttrDriver)
if !ok {
return fmt.Errorf("unsupported xattr for resource %q", resource.Path())
}
if err := xattrDriver.Setxattr(fp, xattrer.XAttrs()); err != nil {
return err
}
}
}
return nil
}
// Walk provides a convenience function to call filepath.Walk correctly for
// the context. Otherwise identical to filepath.Walk, the path argument is
// corrected to be contained within the context.
func (c *context) Walk(fn filepath.WalkFunc) error {
return c.pathDriver.Walk(c.root, func(p string, fi os.FileInfo, err error) error {
contained, err := c.contain(p)
return fn(contained, fi, err)
})
}
// fullpath returns the system path for the resource, joined with the context
// root. The path p must be a part of the context.
func (c *context) fullpath(p string) (string, error) {
p = c.pathDriver.Join(c.root, p)
if !strings.HasPrefix(p, c.root) {
return "", fmt.Errorf("invalid context path")
}
return p, nil
}
// contain cleans and santizes the filesystem path p to be an absolute path,
// effectively relative to the context root.
func (c *context) contain(p string) (string, error) {
sanitized, err := c.pathDriver.Rel(c.root, p)
if err != nil {
return "", err
}
// ZOMBIES(stevvooe): In certain cases, we may want to remap these to a
// "containment error", so the caller can decide what to do.
return c.pathDriver.Join("/", c.pathDriver.Clean(sanitized)), nil
}
// digest returns the digest of the file at path p, relative to the root.
func (c *context) digest(p string) (digest.Digest, error) {
f, err := c.driver.Open(c.pathDriver.Join(c.root, p))
if err != nil {
return "", err
}
defer f.Close()
return c.digester.Digest(f)
}
// resolveXAttrs attempts to resolve the extended attributes for the resource
// at the path fp, which is the full path to the resource. If the resource
// cannot have xattrs, nil will be returned.
func (c *context) resolveXAttrs(fp string, fi os.FileInfo, base *resource) (map[string][]byte, error) {
if fi.Mode().IsRegular() || fi.Mode().IsDir() {
xattrDriver, ok := c.driver.(driverpkg.XAttrDriver)
if !ok {
log.Println("xattr extraction not supported")
return nil, ErrNotSupported
}
return xattrDriver.Getxattr(fp)
}
if fi.Mode()&os.ModeSymlink != 0 {
lxattrDriver, ok := c.driver.(driverpkg.LXAttrDriver)
if !ok {
log.Println("xattr extraction for symlinks not supported")
return nil, ErrNotSupported
}
return lxattrDriver.LGetxattr(fp)
}
return nil, nil
}
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