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Change SafeMakeDir to resolve symlinks in mounter implementation

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Kubelet should not resolve symlinks outside of mounter interface.
Only mounter interface knows, how to resolve them properly on the host.

As consequence, declaration of SafeMakeDir changes to simplify the
implementation:
from SafeMakeDir(fullPath string, base string, perm os.FileMode)
to   SafeMakeDir(subdirectoryInBase string, base string, perm os.FileMode)
This commit is contained in:
Jan Safranek 2018-05-22 12:56:25 +02:00
parent 74ba0878a1
commit 7e3fb502a8
5 changed files with 49 additions and 22 deletions
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13
pkg/kubelet/kubelet_pods.go
View File

@ -174,10 +174,7 @@ func makeMounts(pod *v1.Pod, podDir string, container *v1.Container, hostName, h
return nil, cleanupAction, fmt.Errorf("unable to provision SubPath `%s`: %v", mount.SubPath, err)
}
volumePath, err := filepath.EvalSymlinks(hostPath)
if err != nil {
return nil, cleanupAction, err
}
volumePath := hostPath
hostPath = filepath.Join(volumePath, mount.SubPath)
if subPathExists, err := mounter.ExistsPath(hostPath); err != nil {
@ -192,10 +189,10 @@ func makeMounts(pod *v1.Pod, podDir string, container *v1.Container, hostName, h
if err != nil {
return nil, cleanupAction, err
}
if err := mounter.SafeMakeDir(hostPath, volumePath, perm); err != nil {
glog.Errorf("failed to mkdir %q: %v", hostPath, err)
return nil, cleanupAction, err
if err := mounter.SafeMakeDir(mount.SubPath, volumePath, perm); err != nil {
// Don't pass detailed error back to the user because it could give information about host filesystem
glog.Errorf("failed to create subPath directory for volumeMount %q of container %q: %v", mount.Name, container.Name, err)
return nil, cleanupAction, fmt.Errorf("failed to create subPath directory for volumeMount %q of container %q", mount.Name, container.Name)
}
}
hostPath, cleanupAction, err = mounter.PrepareSafeSubpath(mountutil.Subpath{

16
pkg/util/mount/mount.go
View File

@ -84,13 +84,15 @@ type Interface interface {
// MakeDir creates a new directory.
// Will operate in the host mount namespace if kubelet is running in a container
MakeDir(pathname string) error
// SafeMakeDir makes sure that the created directory does not escape given
// base directory mis-using symlinks. The directory is created in the same
// mount namespace as where kubelet is running. Note that the function makes
// sure that it creates the directory somewhere under the base, nothing
// else. E.g. if the directory already exists, it may exists outside of the
// base due to symlinks.
SafeMakeDir(pathname string, base string, perm os.FileMode) error
// SafeMakeDir creates subdir within given base. It makes sure that the
// created directory does not escape given base directory mis-using
// symlinks. Note that the function makes sure that it creates the directory
// somewhere under the base, nothing else. E.g. if the directory already
// exists, it may exist outside of the base due to symlinks.
// This method should be used if the directory to create is inside volume
// that's under user control. User must not be able to use symlinks to
// escape the volume to create directories somewhere else.
SafeMakeDir(subdir string, base string, perm os.FileMode) error
// Will operate in the host mount namespace if kubelet is running in a container.
// Error is returned on any other error than "file not found".
ExistsPath(pathname string) (bool, error)

15
pkg/util/mount/mount_linux.go
View File

@ -955,8 +955,15 @@ func removeEmptyDirs(baseDir, endDir string) error {
return nil
}
func (mounter *Mounter) SafeMakeDir(pathname string, base string, perm os.FileMode) error {
return doSafeMakeDir(pathname, base, perm)
func (mounter *Mounter) SafeMakeDir(subdir string, base string, perm os.FileMode) error {
realBase, err := filepath.EvalSymlinks(base)
if err != nil {
return fmt.Errorf("error resolving symlinks in %s: %s", base, err)
}
realFullPath := filepath.Join(realBase, subdir)
return doSafeMakeDir(realFullPath, realBase, perm)
}
func (mounter *Mounter) GetMountRefs(pathname string) ([]string, error) {
@ -1001,7 +1008,9 @@ func getMode(pathname string) (os.FileMode, error) {
return info.Mode(), nil
}
// This implementation is shared between Linux and NsEnterMounter
// This implementation is shared between Linux and NsEnterMounter. Both pathname
// and base must be either already resolved symlinks or thet will be resolved in
// kubelet's mount namespace (in case it runs containerized).
func doSafeMakeDir(pathname string, base string, perm os.FileMode) error {
glog.V(4).Infof("Creating directory %q within base %q", pathname, base)

10
pkg/util/mount/mount_windows.go
View File

@ -472,8 +472,14 @@ func (mounter *Mounter) GetMode(pathname string) (os.FileMode, error) {
}
// SafeMakeDir makes sure that the created directory does not escape given base directory mis-using symlinks.
func (mounter *Mounter) SafeMakeDir(pathname string, base string, perm os.FileMode) error {
return doSafeMakeDir(pathname, base, perm)
func (mounter *Mounter) SafeMakeDir(subdir string, base string, perm os.FileMode) error {
realBase, err := filepath.EvalSymlinks(base)
if err != nil {
return fmt.Errorf("error resolving symlinks in %s: %s", base, err)
}
realFullPath := filepath.Join(realBase, subdir)
return doSafeMakeDir(realFullPath, realBase, perm)
}
func doSafeMakeDir(pathname string, base string, perm os.FileMode) error {

17
pkg/util/mount/nsenter_mount.go
View File

@ -327,8 +327,21 @@ func (mounter *NsenterMounter) PrepareSafeSubpath(subPath Subpath) (newHostPath
return newHostPath, cleanupAction, err
}
func (mounter *NsenterMounter) SafeMakeDir(pathname string, base string, perm os.FileMode) error {
return doSafeMakeDir(pathname, base, perm)
func (mounter *NsenterMounter) SafeMakeDir(subdir string, base string, perm os.FileMode) error {
fullSubdirPath := filepath.Join(base, subdir)
evaluatedSubdirPath, err := mounter.ne.EvalSymlinks(fullSubdirPath, false /* mustExist */)
if err != nil {
return fmt.Errorf("error resolving symlinks in %s: %s", fullSubdirPath, err)
}
kubeletSubdirPath := mounter.ne.KubeletPath(evaluatedSubdirPath)
evaluatedBase, err := mounter.ne.EvalSymlinks(base, true /* mustExist */)
if err != nil {
return fmt.Errorf("error resolving symlinks in %s: %s", base, err)
}
kubeletBase := mounter.ne.KubeletPath(evaluatedBase)
return doSafeMakeDir(kubeletSubdirPath, kubeletBase, perm)
}
func (mounter *NsenterMounter) GetMountRefs(pathname string) ([]string, error) {