bazelbuild/bazel

Stronger MacOS Sandbox with FSKit

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#29165 opened on Mar 31, 2026

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P3help wantedteam-Remote-Exectype: feature request

Description

Description of the feature request:

@thesayyn has been studying the new https://developer.apple.com/documentation/FSKit API introduced in recent versions of MacOS. We believe this could allow a sandbox implementation that's both fast and isolated, in the sense that it avoids common sandbox escaping by following symlinks.

Background:

Alternatives:

  • Replace eager symlink creation with an on-demand userland filesystem
  • If cross-device hardlinks were permitted, it might help. The kernel security system might need changes.
  • MacFUSE has a FSkit implementation now, but you have to reduce secure boot.
  • bb-clientd uses an NFS approach but it's brittle (@jsharpe)

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