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-rw-r--r--libpod/container_path_resolution.go127
1 files changed, 127 insertions, 0 deletions
diff --git a/libpod/container_path_resolution.go b/libpod/container_path_resolution.go
new file mode 100644
index 000000000..68f174278
--- /dev/null
+++ b/libpod/container_path_resolution.go
@@ -0,0 +1,127 @@
+package libpod
+
+import (
+ "path/filepath"
+ "strings"
+
+ securejoin "github.com/cyphar/filepath-securejoin"
+ "github.com/opencontainers/runtime-spec/specs-go"
+ "github.com/pkg/errors"
+ "github.com/sirupsen/logrus"
+)
+
+// resolveContainerPaths resolves the container's mount point and the container
+// path as specified by the user. Both may resolve to paths outside of the
+// container's mount point when the container path hits a volume or bind mount.
+func (container *Container) resolvePath(mountPoint string, containerPath string) (string, string, error) {
+ // Let's first make sure we have a path relative to the mount point.
+ pathRelativeToContainerMountPoint := containerPath
+ if !filepath.IsAbs(containerPath) {
+ // If the containerPath is not absolute, it's relative to the
+ // container's working dir. To be extra careful, let's first
+ // join the working dir with "/", and the add the containerPath
+ // to it.
+ pathRelativeToContainerMountPoint = filepath.Join(filepath.Join("/", container.WorkingDir()), containerPath)
+ }
+ resolvedPathOnTheContainerMountPoint := filepath.Join(mountPoint, pathRelativeToContainerMountPoint)
+ pathRelativeToContainerMountPoint = strings.TrimPrefix(pathRelativeToContainerMountPoint, mountPoint)
+ pathRelativeToContainerMountPoint = filepath.Join("/", pathRelativeToContainerMountPoint)
+
+ // Now we have an "absolute container Path" but not yet resolved on the
+ // host (e.g., "/foo/bar/file.txt"). As mentioned above, we need to
+ // check if "/foo/bar/file.txt" is on a volume or bind mount. To do
+ // that, we need to walk *down* the paths to the root. Assuming
+ // volume-1 is mounted to "/foo" and volume-2 is mounted to "/foo/bar",
+ // we must select "/foo/bar". Once selected, we need to rebase the
+ // remainder (i.e, "/file.txt") on the volume's mount point on the
+ // host. Same applies to bind mounts.
+
+ searchPath := pathRelativeToContainerMountPoint
+ for {
+ volume, err := findVolume(container, searchPath)
+ if err != nil {
+ return "", "", err
+ }
+ if volume != nil {
+ logrus.Debugf("Container path %q resolved to volume %q on path %q", containerPath, volume.Name(), searchPath)
+
+ // TODO: We really need to force the volume to mount
+ // before doing this, but that API is not exposed
+ // externally right now and doing so is beyond the scope
+ // of this commit.
+ mountPoint, err := volume.MountPoint()
+ if err != nil {
+ return "", "", err
+ }
+ if mountPoint == "" {
+ return "", "", errors.Errorf("volume %s is not mounted, cannot copy into it", volume.Name())
+ }
+
+ // We found a matching volume for searchPath. We now
+ // need to first find the relative path of our input
+ // path to the searchPath, and then join it with the
+ // volume's mount point.
+ pathRelativeToVolume := strings.TrimPrefix(pathRelativeToContainerMountPoint, searchPath)
+ absolutePathOnTheVolumeMount, err := securejoin.SecureJoin(mountPoint, pathRelativeToVolume)
+ if err != nil {
+ return "", "", err
+ }
+ return mountPoint, absolutePathOnTheVolumeMount, nil
+ }
+
+ if mount := findBindMount(container, searchPath); mount != nil {
+ logrus.Debugf("Container path %q resolved to bind mount %q:%q on path %q", containerPath, mount.Source, mount.Destination, searchPath)
+ // We found a matching bind mount for searchPath. We
+ // now need to first find the relative path of our
+ // input path to the searchPath, and then join it with
+ // the source of the bind mount.
+ pathRelativeToBindMount := strings.TrimPrefix(pathRelativeToContainerMountPoint, searchPath)
+ absolutePathOnTheBindMount, err := securejoin.SecureJoin(mount.Source, pathRelativeToBindMount)
+ if err != nil {
+ return "", "", err
+ }
+ return mount.Source, absolutePathOnTheBindMount, nil
+
+ }
+
+ if searchPath == "/" {
+ // Cannot go beyond "/", so we're done.
+ break
+ }
+
+ // Walk *down* the path (e.g., "/foo/bar/x" -> "/foo/bar").
+ searchPath = filepath.Dir(searchPath)
+ }
+
+ // No volume, no bind mount but just a normal path on the container.
+ return mountPoint, resolvedPathOnTheContainerMountPoint, nil
+}
+
+// findVolume checks if the specified container path matches a volume inside
+// the container. It returns a matching volume or nil.
+func findVolume(c *Container, containerPath string) (*Volume, error) {
+ runtime := c.Runtime()
+ cleanedContainerPath := filepath.Clean(containerPath)
+ for _, vol := range c.Config().NamedVolumes {
+ if cleanedContainerPath == filepath.Clean(vol.Dest) {
+ return runtime.GetVolume(vol.Name)
+ }
+ }
+ return nil, nil
+}
+
+// findBindMount checks if the specified container path matches a bind mount
+// inside the container. It returns a matching mount or nil.
+func findBindMount(c *Container, containerPath string) *specs.Mount {
+ cleanedPath := filepath.Clean(containerPath)
+ for _, m := range c.Config().Spec.Mounts {
+ if m.Type != "bind" {
+ continue
+ }
+ if cleanedPath == filepath.Clean(m.Destination) {
+ mount := m
+ return &mount
+ }
+ }
+ return nil
+}