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codex/codex-rs/core
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iceweasel-oai 82b15b65e2 [codex] Respect Windows sandbox backend in exec policy (#26307)
## Why

Windows managed filesystem permissions can now be backed by a real
Windows sandbox. `exec-policy` was still treating the managed read-only
policy shape as if there were never a sandbox backend, so benign
unmatched commands such as PowerShell directory listings could be
rejected with `blocked by policy` even when `windows.sandbox` was
enabled.

The inverse case still needs to stay conservative: when the Windows
sandbox backend is disabled, managed filesystem restrictions are only
configuration intent, not an enforced filesystem boundary. That applies
to writable-root restricted profiles too, not just read-only profiles.

## What Changed

- Thread the effective `WindowsSandboxLevel` into exec-policy approval
decisions for shell, unified exec, and intercepted shell exec paths.
- Treat managed restricted filesystem profiles as lacking sandbox
protection only on Windows when `WindowsSandboxLevel::Disabled`.
- Exclude full-disk-write profiles from that no-backend path because
they do not rely on filesystem sandbox enforcement.
- Remove the cwd-sensitive read-only heuristic and the now-stale cwd
plumbing from exec-policy approval contexts.
- Add Windows coverage for both enabled-sandbox and disabled-backend
behavior, including a writable-root managed profile.

## Validation

- Added/updated `exec_policy` coverage for managed filesystem
restrictions, full-disk-write exclusion, enabled Windows sandbox
behavior, and disabled-backend read-only/writable-root behavior.
- `just test -p codex-core exec_policy` — 100 passed, 10 leaky
- Empirical local `codex exec` probe with `--sandbox read-only -c
'windows.sandbox="unelevated"'`: PowerShell directory listing completed
successfully.
- Disabled-backend control with Windows sandbox cleared: the same
command was rejected with `blocked by policy`.
82b15b65e2 · 2026-06-05 11:20:52 -07:00
History
..

codex-core

This crate implements the business logic for Codex. It is designed to be used by the various Codex UIs written in Rust.

Dependencies

Note that codex-core makes some assumptions about certain helper utilities being available in the environment. Currently, this support matrix is:

macOS

Expects /usr/bin/sandbox-exec to be present.

When using the workspace-write sandbox policy, the Seatbelt profile allows writes under the configured writable roots while keeping .git (directory or pointer file), the resolved gitdir: target, and .codex read-only.

Network access and filesystem read/write roots are controlled by SandboxPolicy. Seatbelt consumes the resolved policy and enforces it.

Seatbelt also keeps the legacy default preferences read access (user-preference-read) needed for cfprefs-backed macOS behavior.

Linux

Expects the binary containing codex-core to run the equivalent of codex sandbox when arg0 is codex-linux-sandbox. See the codex-arg0 crate for details.

Legacy SandboxPolicy / sandbox_mode configs are still supported on Linux. They can continue to use the legacy Landlock path when the split filesystem policy is sandbox-equivalent to the legacy model after cwd resolution. Split filesystem policies that need direct FileSystemSandboxPolicy enforcement, such as read-only or denied carveouts under a broader writable root, automatically route through bubblewrap. The legacy Landlock path is used only when the split filesystem policy round-trips through the legacy SandboxPolicy model without changing semantics. That includes overlapping cases like /repo = write, /repo/a = none, /repo/a/b = write, where the more specific writable child must reopen under a denied parent.

The Linux sandbox helper prefers the first bwrap found on PATH outside the current working directory whenever it is available. If bwrap is present but too old to support --argv0, the helper keeps using system bubblewrap and switches to a no---argv0 compatibility path for the inner re-exec. If bwrap is missing, it falls back to the bundled codex-resources/bwrap binary shipped with Codex and Codex surfaces a startup warning through its normal notification path instead of printing directly from the sandbox helper. Codex also surfaces a startup warning when bubblewrap cannot create user namespaces. WSL2 uses the normal Linux bubblewrap path. WSL1 is not supported for bubblewrap sandboxing because it cannot create the required user namespaces, so Codex rejects sandboxed shell commands that would enter the bubblewrap path before invoking bwrap.

Windows

Legacy SandboxPolicy / sandbox_mode configs are still supported on Windows. Legacy read-only and workspace-write policies imply full filesystem read access; exact readable roots are represented by split filesystem policies instead.

The elevated Windows sandbox also supports:

  • legacy ReadOnly and WorkspaceWrite behavior
  • split filesystem policies that need exact readable roots, exact writable roots, or extra read-only carveouts under writable roots
  • backend-managed system read roots required for basic execution, such as C:\Windows, C:\Program Files, C:\Program Files (x86), and C:\ProgramData, when a split filesystem policy requests platform defaults

The unelevated restricted-token backend still supports the legacy full-read Windows model for legacy ReadOnly and WorkspaceWrite behavior. It also supports a narrow split-filesystem subset: full-read split policies whose writable roots still match the legacy WorkspaceWrite root set, but add extra read-only carveouts under those writable roots.

New [permissions] / split filesystem policies remain supported on Windows only when they can be enforced directly by the selected Windows backend or round-trip through the legacy SandboxPolicy model without changing semantics. Policies that would require direct explicit unreadable carveouts (none) or reopened writable descendants under read-only carveouts still fail closed instead of running with weaker enforcement.

All Platforms

Expects the binary containing codex-core to simulate the virtual apply_patch CLI when arg1 is --codex-run-as-apply-patch. See the codex-arg0 crate for details.