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core-agent-ide/codex-rs/linux-sandbox/README.md
viyatb-oai b3202cbd58
feat(linux-sandbox): implement proxy-only egress via TCP-UDS-TCP bridge (#11293) 
## Summary
- Implement Linux proxy-only routing in `codex-rs/linux-sandbox` with a
two-stage bridge: host namespace `loopback TCP proxy endpoint -> UDS`,
then bwrap netns `loopback TCP listener -> host UDS`.
- Add hidden `--proxy-route-spec` plumbing for outer-to-inner stage
handoff.
- Fail closed in proxy mode when no valid loopback proxy endpoints can
be routed.
- Introduce explicit network seccomp modes: `Restricted` (legacy
restricted networking) and `ProxyRouted` (allow INET/INET6 for routed
proxy access, deny `AF_UNIX` and `socketpair`).
- Enforce that proxy bridge/routing is bwrap-only by validating
`--apply-seccomp-then-exec` requires `--use-bwrap-sandbox`.
- Keep landlock-only flows unchanged (no proxy bridge behavior outside
bwrap).

---------

Co-authored-by: Codex <199175422+chatgpt-codex-connector[bot]@users.noreply.github.com>
2026-02-21 18:16:34 +00:00

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codex-linux-sandbox

This crate is responsible for producing:

  • a codex-linux-sandbox standalone executable for Linux that is bundled with the Node.js version of the Codex CLI
  • a lib crate that exposes the business logic of the executable as run_main() so that
    • the codex-exec CLI can check if its arg0 is codex-linux-sandbox and, if so, execute as if it were codex-linux-sandbox
    • this should also be true of the codex multitool CLI

On Linux, the bubblewrap pipeline uses the vendored bubblewrap path compiled into this binary.

Current Behavior

  • Legacy Landlock + mount protections remain available as the legacy pipeline.
  • The bubblewrap pipeline is standardized on the vendored path.
  • During rollout, the bubblewrap pipeline is gated by the temporary feature flag use_linux_sandbox_bwrap (CLI -c alias for features.use_linux_sandbox_bwrap; legacy remains default when off).
  • When enabled, the bubblewrap pipeline applies PR_SET_NO_NEW_PRIVS and a seccomp network filter in-process.
  • When enabled, the filesystem is read-only by default via --ro-bind / /.
  • When enabled, writable roots are layered with --bind <root> <root>.
  • When enabled, protected subpaths under writable roots (for example .git, resolved gitdir:, and .codex) are re-applied as read-only via --ro-bind.
  • When enabled, symlink-in-path and non-existent protected paths inside writable roots are blocked by mounting /dev/null on the symlink or first missing component.
  • When enabled, the helper isolates the PID namespace via --unshare-pid.
  • When enabled and network is restricted without proxy routing, the helper also isolates the network namespace via --unshare-net.
  • In managed proxy mode, the helper uses --unshare-net plus an internal TCP->UDS->TCP routing bridge so tool traffic reaches only configured proxy endpoints.
  • In managed proxy mode, after the bridge is live, seccomp blocks new AF_UNIX/socketpair creation for the user command.
  • When enabled, it mounts a fresh /proc via --proc /proc by default, but you can skip this in restrictive container environments with --no-proc.

Notes

  • The CLI surface still uses legacy names like codex debug landlock.