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[Low] setupImageVolumes builds host mount paths from vol.Name without a containment check

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@abhisheksharma2411 is already working on this.

Since Oct 20, 2026.

  • #3024 by @abhisheksharma2411 — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
73/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
go
Domain
security

Research direction

Read internal/imagecache/bundle_linux.go at setupImageVolumes and internal/imagecache/spec.go for ImageVolumeMountPath and the createExtraDirs validation pattern. Check how volume names reach this function, then add a containment check before building mount paths. Done when non-local names are rejected and valid volume names still work; the payload names no test file.

Written by the indexing model from the issue text.

Description

area/security kind/bug

Summary

In internal/imagecache/bundle_linux.go, setupImageVolumes constructs mount points using ImageVolumeMountPath(bundlePath, vol.Name) without verifying that vol.Name is a clean, local relative path. If a crafted rootfs-overlay.json containing path traversal sequences (such as ../) is processed, setupImageVolumes can create directories, unmount existing mounts, and mount image layers at arbitrary locations on the host within the privileged ateworker context.

Details

In internal/imagecache/bundle_linux.go#L114-L122:

		mountpoint := ImageVolumeMountPath(bundlePath, vol.Name)
		if err := os.MkdirAll(mountpoint, 0o700); err != nil {
			return fmt.Errorf("while creating image volume mount point %q: %w", mountpoint, err)
		}
		_ = unix.Unmount(mountpoint, unix.MNT_DETACH)

		if err := mountImageVolume(mountpoint, vol.Layers); err != nil {
			return fmt.Errorf("while mounting image volume %q: %w", vol.Name, err)
		}

And internal/imagecache/spec.go#L30-L32:

func ImageVolumeMountPath(bundlePath, volumeName string) string {
	return filepath.Join(bundlePath, "volumes", volumeName)
}

In contrast to createExtraDirs (internal/imagecache/spec.go#L182-L184), which uses os.OpenRoot and enforces filepath.IsLocal, setupImageVolumes performs no checks on vol.Name.

Impact

Exploitability is constrained by upstream controls:

  1. Both ateapi (cmd/ateapi/internal/apivalidation/zz_generated.validation.go#L9511) and atelet (cmd/atelet/internal/apivalidation/zz_generated.validation.go#L4448) enforce validate.ShortName (content.IsDNS1123Label), rejecting slashes and .. traversal sequences in volume names at API ingress.
  2. rootfs-overlay.json is generated by atelet on the host; untrusted sandboxed containers cannot modify it directly.
    An attacker would require a pre-existing host-level compromise or a bypass of the API server validation to write a malicious rootfs-overlay.json.

Suggested fix

Validate vol.Name in setupImageVolumes before joining paths, rejecting non-local paths or path separators:

if !filepath.IsLocal(vol.Name) || filepath.Base(vol.Name) != vol.Name {
    return fmt.Errorf("invalid volume name %q: must be a local filename", vol.Name)
}

Related

  • Related: #1436 (SystemInfoVolumeSource path traversal validation)
  • Related: PR #923 (Added image volumes to ActorTemplate)
  • Related: PR #2826 (Micro-VM image volumes refactor)
Dominant language
Go
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Merged PRs (30d)
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