## Problem
Ubuntu/AppArmor hosts started failing in the default Linux sandbox path
after the switch to vendored/default bubblewrap in `0.115.0`.
The clearest report is in
[#14919](https://github.com/openai/codex/issues/14919), especially [this
investigation
comment](https://github.com/openai/codex/issues/14919#issuecomment-4076504751):
on affected Ubuntu systems, `/usr/bin/bwrap` works, but a copied or
vendored `bwrap` binary fails with errors like `bwrap: setting up uid
map: Permission denied` or `bwrap: loopback: Failed RTM_NEWADDR:
Operation not permitted`.
The root cause is Ubuntu's `/etc/apparmor.d/bwrap-userns-restrict`
profile, which grants `userns` access specifically to `/usr/bin/bwrap`.
Once Codex started using a vendored/internal bubblewrap path, that path
was no longer covered by the distro AppArmor exception, so sandbox
namespace setup could fail even when user namespaces were otherwise
enabled and `uidmap` was installed.
## What this PR changes
- prefer system `/usr/bin/bwrap` whenever it is available
- keep vendored bubblewrap as the fallback when `/usr/bin/bwrap` is
missing
- when `/usr/bin/bwrap` is missing, surface a Codex startup warning
through the app-server/TUI warning path instead of printing directly
from the sandbox helper with `eprintln!`
- use the same launcher decision for both the main sandbox execution
path and the `/proc` preflight path
- document the updated Linux bubblewrap behavior in the Linux sandbox
and core READMEs
## Why this fix
This still fixes the Ubuntu/AppArmor regression from
[#14919](https://github.com/openai/codex/issues/14919), but it keeps the
runtime rule simple and platform-agnostic: if the standard system
bubblewrap is installed, use it; otherwise fall back to the vendored
helper.
The warning now follows that same simple rule. If Codex cannot find
`/usr/bin/bwrap`, it tells the user that it is falling back to the
vendored helper, and it does so through the existing startup warning
plumbing that reaches the TUI and app-server instead of low-level
sandbox stderr.
## Testing
- `cargo test -p codex-linux-sandbox`
- `cargo test -p codex-app-server --lib`
- `cargo test -p codex-tui-app-server
tests::embedded_app_server_start_failure_is_returned`
- `cargo clippy -p codex-linux-sandbox --all-targets`
- `cargo clippy -p codex-app-server --all-targets`
- `cargo clippy -p codex-tui-app-server --all-targets`
## Why
After `#13449`, the Linux helper could receive split filesystem and
network policies, but the bubblewrap mount builder still reconstructed
filesystem access from the legacy `SandboxPolicy`.
That loses explicit unreadable carveouts under writable roots, and it
also mishandles `Root` read access paired with explicit deny carveouts.
In those cases bubblewrap could still expose paths that the split
filesystem policy intentionally blocked.
## What changed
- switched bubblewrap mount generation to consume
`FileSystemSandboxPolicy` directly at the implementation boundary;
legacy `SandboxPolicy` configs still flow through the existing
`FileSystemSandboxPolicy::from(&sandbox_policy)` bridge before reaching
bwrap
- kept the Linux helper and preflight path on the split filesystem
policy all the way into bwrap
- re-applied explicit unreadable carveouts after readable and writable
mounts so blocked subpaths still win under bubblewrap
- masked denied directories with `--tmpfs` plus `--remount-ro` and
denied files with `--ro-bind-data`, preserving the backing fd until exec
- added comments in the unreadable-root masking block to explain why the
mount order and directory/file split are intentional
- updated Linux helper call sites and tests for the split-policy bwrap
path
## Verification
- added protocol coverage for root carveouts staying scoped
- added core coverage that root-write plus deny carveouts still requires
a platform sandbox
- added bwrap unit coverage for reapplying blocked carveouts after
writable binds
- added Linux integration coverage for explicit split-policy carveouts
under bubblewrap
- validated the final branch state with `cargo test -p
codex-linux-sandbox`, `cargo clippy -p codex-linux-sandbox --all-targets
-- -D warnings`, and the PR CI reruns
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/13453).
* __->__ #13453
* #13452
* #13451
* #13449
* #13448
* #13445
* #13440
* #13439
---------
Co-authored-by: viyatb-oai <viyatb@openai.com>
## Summary
This PR removes the temporary `CODEX_BWRAP_ENABLE_FFI` flag and makes
Linux builds always compile vendored bubblewrap support for
`codex-linux-sandbox`.
## Changes
- Removed `CODEX_BWRAP_ENABLE_FFI` gating from
`codex-rs/linux-sandbox/build.rs`.
- Linux builds now fail fast if vendored bubblewrap compilation fails
(instead of warning and continuing).
- Updated fallback/help text in
`codex-rs/linux-sandbox/src/vendored_bwrap.rs` to remove references to
`CODEX_BWRAP_ENABLE_FFI`.
- Removed `CODEX_BWRAP_ENABLE_FFI` env wiring from:
- `.github/workflows/rust-ci.yml`
- `.github/workflows/bazel.yml`
- `.github/workflows/rust-release.yml`
---------
Co-authored-by: David Zbarsky <zbarsky@openai.com>
## Summary
This PR introduces a gated Bubblewrap (bwrap) Linux sandbox path. The
curent Linux sandbox path relies on in-process restrictions (including
Landlock). Bubblewrap gives us a more uniform filesystem isolation
model, especially explicit writable roots with the option to make some
directories read-only and granular network controls.
This is behind a feature flag so we can validate behavior safely before
making it the default.
- Added temporary rollout flag:
- `features.use_linux_sandbox_bwrap`
- Preserved existing default path when the flag is off.
- In Bubblewrap mode:
- Added internal retry without /proc when /proc mount is not permitted
by the host/container.
## Summary
Vendor Bubblewrap into the repo and add minimal build plumbing in
`codex-linux-sandbox` to compile/link it.
## Why
We want to move Linux sandboxing toward Bubblewrap, but in a safe
two-step rollout:
1) vendoring/build setup (this PR),
2) runtime integration (follow-up PR).
## Included
- Add `codex-rs/vendor/bubblewrap` sources.
- Add build-time FFI path in `codex-rs/linux-sandbox`.
- Update `build.rs` rerun tracking for vendored files.
- Small vendored compile warning fix (`sockaddr_nl` full init).
follow up in https://github.com/openai/codex/pull/9938
