21 Commits

  • [codex] Allow socketpair in proxy-routed Linux sandbox (#26625)
    ## Summary
    
    - allow `socketpair(AF_UNIX, ...)` in the proxy-routed Linux seccomp
    mode
    - continue denying `socket(AF_UNIX, ...)` so user commands cannot create
    pathname or abstract Unix sockets
    - extend the managed-proxy integration test to verify both behaviors
    
    ## Root cause
    
    `NetworkSeccompMode::ProxyRouted` treated anonymous Unix socket pairs
    like externally addressable Unix sockets and returned `EPERM`. This
    breaks tools that use socket pairs for local child-process IPC even
    though a socket pair cannot connect outside the sandbox or bypass the
    routed proxy.
    
    `dangerously_allow_all_unix_sockets` controls Unix-socket requests
    forwarded by the managed network proxy; it does not currently configure
    the Linux seccomp filter. Socket pairs should not require that dangerous
    setting because they are unnamed, process-local IPC.
    
    Related but independent: #26553 fixes host proxy bridge socket path
    length handling.
    
    ---------
    
    Co-authored-by: Codex <noreply@openai.com>
  • linux-sandbox: switch helper plumbing to PermissionProfile (#20106)
    ## Why
    
    `PermissionProfile` is the canonical runtime permission model in the
    Rust workspace, but the Linux sandbox helper still accepted a legacy
    `SandboxPolicy` plus separate filesystem and network policy flags. That
    translation layer made the helper interface harder to reason about and
    left `linux-sandbox`-specific callers and tests coupled to the legacy
    policy representation.
    
    This change moves the helper onto `PermissionProfile` directly so the
    Linux sandbox plumbing matches the rest of the permission stack.
    
    ## What changed
    
    - changed `codex-linux-sandbox` to accept `--permission-profile` and
    derive the runtime filesystem and network policies internally
    - updated the in-process seccomp and legacy Landlock path in
    `codex-rs/linux-sandbox` to operate on `PermissionProfile`
    - updated Linux sandbox argv construction in `codex-rs/sandboxing`,
    `codex-rs/core`, and the CLI debug sandbox path to pass the canonical
    profile instead of serializing compatibility policy projections
    - simplified the Linux sandbox tests to build the exact permission
    profile under test, including the managed-proxy path and
    direct-runtime-enforcement carveout coverage
    - removed helper-local `SandboxPolicy` usage from `bwrap` tests where
    `FileSystemSandboxPolicy` is already the value being exercised
    
    ## Testing
    
    - `cargo test -p codex-sandboxing`
    - `cargo test -p codex-linux-sandbox` (on this macOS host, the crate
    compiled cleanly and its Linux-only tests were cfg-gated)
    - `cargo test -p codex-core --no-run`
    - `cargo test -p codex-cli --no-run`
  • fix(network-proxy): harden linux proxy bridge helpers (#20001)
    ## Why
    The Linux managed-proxy bridge helpers are long-lived child processes in
    the sandbox networking path. Before this change they stayed dumpable and
    the network seccomp profile did not block cross-process memory syscalls,
    so another same-user process could potentially inspect or modify bridge
    memory instead of interacting only through the intended proxy interface.
    
    ## What changed
    - reuse the shared `codex-process-hardening` helper to mark bridge
    helper children non-dumpable before they begin serving
    - deny `process_vm_readv` and `process_vm_writev` in the existing
    network seccomp filter
    
    ## Security impact
    Bridge helpers are less exposed to same-user cross-process inspection or
    memory writes, which reduces the chance that sandboxed code can
    interfere with proxy support processes outside the intended IPC path.
    
    ## Verification
    - `cargo test -p codex-process-hardening`
    - `cargo test -p codex-linux-sandbox`
    - attempted `cargo check -p codex-linux-sandbox --target
    x86_64-unknown-linux-gnu`; blocked on missing `x86_64-linux-gnu-gcc` on
    this macOS host
    
    ---------
    
    Co-authored-by: Codex <noreply@openai.com>
  • remove temporary ownership re-exports (#16626)
    Stacked on #16508.
    
    This removes the temporary `codex-core` / `codex-login` re-export shims
    from the ownership split and rewrites callsites to import directly from
    `codex-model-provider-info`, `codex-models-manager`, `codex-api`,
    `codex-protocol`, `codex-feedback`, and `codex-response-debug-context`.
    
    No behavior change intended; this is the mechanical import cleanup layer
    split out from the ownership move.
    
    ---------
    
    Co-authored-by: Codex <noreply@openai.com>
  • ci: run Windows argument-comment-lint via native Bazel (#16120)
    ## Why
    
    Follow-up to #16106.
    
    `argument-comment-lint` already runs as a native Bazel aspect on Linux
    and macOS, but Windows is still the long pole in `rust-ci`. To move
    Windows onto the same native Bazel lane, the toolchain split has to let
    exec-side helper binaries build in an MSVC environment while still
    linting repo crates as `windows-gnullvm`.
    
    Pushing the Windows lane onto the native Bazel path exposed a second
    round of Windows-only issues in the mixed exec-toolchain plumbing after
    the initial wrapper/target fixes landed.
    
    ## What Changed
    
    - keep the Windows lint lanes on the native Bazel/aspect path in
    `rust-ci.yml` and `rust-ci-full.yml`
    - add a dedicated `local_windows_msvc` platform for exec-side helper
    binaries while keeping `local_windows` as the `windows-gnullvm` target
    platform
    - patch `rules_rust` so `repository_set(...)` preserves explicit
    exec-platform constraints for the generated toolchains, keep the
    Windows-specific bootstrap/direct-link fixes needed for the nightly lint
    driver, and expose exec-side `rustc-dev` `.rlib`s to the MSVC sysroot
    - register the custom Windows nightly toolchain set with MSVC exec
    constraints while still exposing both `x86_64-pc-windows-msvc` and
    `x86_64-pc-windows-gnullvm` targets
    - enable `dev_components` on the custom Windows nightly repository set
    so the MSVC exec helper toolchain actually downloads the
    compiler-internal crates that `clippy_utils` needs
    - teach `run-argument-comment-lint-bazel.sh` to enumerate concrete
    Windows Rust rules, normalize the resulting labels, and skip explicitly
    requested incompatible targets instead of failing before the lint run
    starts
    - patch `rules_rust` build-script env propagation so exec-side
    `windows-msvc` helper crates drop forwarded MinGW include and linker
    search paths as whole flag/path pairs instead of emitting malformed
    `CFLAGS`, `CXXFLAGS`, and `LDFLAGS`
    - export the Windows VS/MSVC SDK environment in `setup-bazel-ci` and
    pass the relevant variables through `run-bazel-ci.sh` via `--action_env`
    / `--host_action_env` so Bazel build scripts can see the MSVC and UCRT
    headers on native Windows runs
    - add inline comments to the Windows `setup-bazel-ci` MSVC environment
    export step so it is easier to audit how `vswhere`, `VsDevCmd.bat`, and
    the filtered `GITHUB_ENV` export fit together
    - patch `aws-lc-sys` to skip its standalone `memcmp` probe under Bazel
    `windows-msvc` build-script environments, which avoids a Windows-native
    toolchain mismatch that blocked the lint lane before it reached the
    aspect execution
    - patch `aws-lc-sys` to prefer its bundled `prebuilt-nasm` objects for
    Bazel `windows-msvc` build-script runs, which avoids missing
    `generated-src/win-x86_64/*.asm` runfiles in the exec-side helper
    toolchain
    - annotate the Linux test-only callsites in `codex-rs/linux-sandbox` and
    `codex-rs/core` that the wider native lint coverage surfaced
    
    ## Patches
    
    This PR introduces a large patch stack because the Windows Bazel lint
    lane currently depends on behavior that upstream dependencies do not
    provide out of the box in the mixed `windows-gnullvm` target /
    `windows-msvc` exec-toolchain setup.
    
    - Most of the `rules_rust` patches look like upstream candidates rather
    than OpenAI-only policy. Preserving explicit exec-platform constraints,
    forwarding the right MSVC/UCRT environment into exec-side build scripts,
    exposing exec-side `rustc-dev` artifacts, and keeping the Windows
    bootstrap/linker behavior coherent all look like fixes to the Bazel/Rust
    integration layer itself.
    - The two `aws-lc-sys` patches are more tactical. They special-case
    Bazel `windows-msvc` build-script environments to avoid a `memcmp` probe
    mismatch and missing NASM runfiles. Those may be harder to upstream
    as-is because they rely on Bazel-specific detection instead of a general
    Cargo/build-script contract.
    - Short term, carrying these patches in-tree is reasonable because they
    unblock a real CI lane and are still narrow enough to audit. Long term,
    the goal should not be to keep growing a permanent local fork of either
    dependency.
    - My current expectation is that the `rules_rust` patches are less
    controversial and should be broken out into focused upstream proposals,
    while the `aws-lc-sys` patches are more likely to be temporary escape
    hatches unless that crate wants a more general hook for hermetic build
    systems.
    
    Suggested follow-up plan:
    
    1. Split the `rules_rust` deltas into upstream-sized PRs or issues with
    minimized repros.
    2. Revisit the `aws-lc-sys` patches during the next dependency bump and
    see whether they can be replaced by an upstream fix, a crate upgrade, or
    a cleaner opt-in mechanism.
    3. Treat each dependency update as a chance to delete patches one by one
    so the local patch set only contains still-needed deltas.
    
    ## Verification
    
    - `./.github/scripts/run-argument-comment-lint-bazel.sh
    --config=argument-comment-lint --keep_going`
    - `RUNNER_OS=Windows
    ./.github/scripts/run-argument-comment-lint-bazel.sh --nobuild
    --config=argument-comment-lint --platforms=//:local_windows
    --keep_going`
    - `cargo test -p codex-linux-sandbox`
    - `cargo test -p codex-core shell_snapshot_tests`
    - `just argument-comment-lint`
    
    ## References
    
    - #16106
  • fix: close Bazel argument-comment-lint CI gaps (#16253)
    ## Why
    
    The Bazel-backed `argument-comment-lint` CI path had two gaps:
    
    - Bazel wildcard target expansion skipped inline unit-test crates from
    `src/` modules because the generated `*-unit-tests-bin` `rust_test`
    targets are tagged `manual`.
    - `argument-comment-mismatch` was still only a warning in the Bazel and
    packaged-wrapper entrypoints, so a typoed `/*param_name*/` comment could
    still pass CI even when the lint detected it.
    
    That left CI blind to real linux-sandbox examples, including the missing
    `/*local_port*/` comment in
    `codex-rs/linux-sandbox/src/proxy_routing.rs` and typoed argument
    comments in `codex-rs/linux-sandbox/src/landlock.rs`.
    
    ## What Changed
    
    - Added `tools/argument-comment-lint/list-bazel-targets.sh` so Bazel
    lint runs cover `//codex-rs/...` plus the manual `rust_test`
    `*-unit-tests-bin` targets.
    - Updated `just argument-comment-lint`, `rust-ci.yml`, and
    `rust-ci-full.yml` to use that helper.
    - Promoted both `argument-comment-mismatch` and
    `uncommented-anonymous-literal-argument` to errors in every strict
    entrypoint:
      - `tools/argument-comment-lint/lint_aspect.bzl`
      - `tools/argument-comment-lint/src/bin/argument-comment-lint.rs`
      - `tools/argument-comment-lint/wrapper_common.py`
    - Added wrapper/bin coverage for the stricter lint flags and documented
    the behavior in `tools/argument-comment-lint/README.md`.
    - Fixed the now-covered callsites in
    `codex-rs/linux-sandbox/src/proxy_routing.rs`,
    `codex-rs/linux-sandbox/src/landlock.rs`, and
    `codex-rs/core/src/shell_snapshot_tests.rs`.
    
    This keeps the Bazel target expansion narrow while making the Bazel and
    prebuilt-linter paths enforce the same strict lint set.
    
    ## Verification
    
    - `python3 -m unittest discover -s tools/argument-comment-lint -p
    'test_*.py'`
    - `cargo +nightly-2025-09-18 test --manifest-path
    tools/argument-comment-lint/Cargo.toml`
    - `just argument-comment-lint`
  • linux-sandbox: plumb split sandbox policies through helper (#13449)
    ## Why
    
    The Linux sandbox helper still only accepted the legacy `SandboxPolicy`
    payload.
    
    That meant the runtime could compute split filesystem and network
    policies, but the helper would immediately collapse them back to the
    compatibility projection before applying seccomp or staging the
    bubblewrap inner command.
    
    ## What changed
    
    - added hidden `--file-system-sandbox-policy` and
    `--network-sandbox-policy` flags alongside the legacy `--sandbox-policy`
    flag so the helper can migrate incrementally
    - updated the core-side Landlock wrapper to pass the split policies
    explicitly when launching `codex-linux-sandbox`
    - added helper-side resolution logic that accepts either the legacy
    policy alone or a complete split-policy pair and normalizes that into
    one effective configuration
    - switched Linux helper network decisions to use `NetworkSandboxPolicy`
    directly
    - added `FromStr` support for the split policy types so the helper can
    parse them from CLI JSON
    
    ## Verification
    
    - added helper coverage in `linux-sandbox/src/linux_run_main_tests.rs`
    for split-policy flags and policy resolution
    - added CLI argument coverage in `core/src/landlock.rs`
    - verified the current PR state with `just clippy`
    
    
    
    
    ---
    [//]: # (BEGIN SAPLING FOOTER)
    Stack created with [Sapling](https://sapling-scm.com). Best reviewed
    with [ReviewStack](https://reviewstack.dev/openai/codex/pull/13449).
    * #13453
    * #13452
    * #13451
    * __->__ #13449
    * #13448
    * #13445
    * #13440
    * #13439
    
    ---------
    
    Co-authored-by: viyatb-oai <viyatb@openai.com>
  • 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>
  • chore: remove codex-core public protocol/shell re-exports (#12432)
    ## Why
    
    `codex-rs/core/src/lib.rs` re-exported a broad set of types and modules
    from `codex-protocol` and `codex-shell-command`. That made it easy for
    workspace crates to import those APIs through `codex-core`, which in
    turn hides dependency edges and makes it harder to reduce compile-time
    coupling over time.
    
    This change removes those public re-exports so call sites must import
    from the source crates directly. Even when a crate still depends on
    `codex-core` today, this makes dependency boundaries explicit and
    unblocks future work to drop `codex-core` dependencies where possible.
    
    ## What Changed
    
    - Removed public re-exports from `codex-rs/core/src/lib.rs` for:
    - `codex_protocol::protocol` and related protocol/model types (including
    `InitialHistory`)
      - `codex_protocol::config_types` (`protocol_config_types`)
    - `codex_shell_command::{bash, is_dangerous_command, is_safe_command,
    parse_command, powershell}`
    - Migrated workspace Rust call sites to import directly from:
      - `codex_protocol::protocol`
      - `codex_protocol::config_types`
      - `codex_protocol::models`
      - `codex_shell_command`
    - Added explicit `Cargo.toml` dependencies (`codex-protocol` /
    `codex-shell-command`) in crates that now import those crates directly.
    - Kept `codex-core` internal modules compiling by using `pub(crate)`
    aliases in `core/src/lib.rs` (internal-only, not part of the public
    API).
    - Updated the two utility crates that can already drop a `codex-core`
    dependency edge entirely:
      - `codex-utils-approval-presets`
      - `codex-utils-cli`
    
    ## Verification
    
    - `cargo test -p codex-utils-approval-presets`
    - `cargo test -p codex-utils-cli`
    - `cargo check --workspace --all-targets`
    - `just clippy`
  • feat: make sandbox read access configurable with ReadOnlyAccess (#11387)
    `SandboxPolicy::ReadOnly` previously implied broad read access and could
    not express a narrower read surface.
    This change introduces an explicit read-access model so we can support
    user-configurable read restrictions in follow-up work, while preserving
    current behavior today.
    
    It also ensures unsupported backends fail closed for restricted-read
    policies instead of silently granting broader access than intended.
    
    ## What
    
    - Added `ReadOnlyAccess` in protocol with:
      - `Restricted { include_platform_defaults, readable_roots }`
      - `FullAccess`
    - Updated `SandboxPolicy` to carry read-access configuration:
      - `ReadOnly { access: ReadOnlyAccess }`
      - `WorkspaceWrite { ..., read_only_access: ReadOnlyAccess }`
    - Preserved existing behavior by defaulting current construction paths
    to `ReadOnlyAccess::FullAccess`.
    - Threaded the new fields through sandbox policy consumers and call
    sites across `core`, `tui`, `linux-sandbox`, `windows-sandbox`, and
    related tests.
    - Updated Seatbelt policy generation to honor restricted read roots by
    emitting scoped read rules when full read access is not granted.
    - Added fail-closed behavior on Linux and Windows backends when
    restricted read access is requested but not yet implemented there
    (`UnsupportedOperation`).
    - Regenerated app-server protocol schema and TypeScript artifacts,
    including `ReadOnlyAccess`.
    
    ## Compatibility / rollout
    
    - Runtime behavior remains unchanged by default (`FullAccess`).
    - API/schema changes are in place so future config wiring can enable
    restricted read access without another policy-shape migration.
  • feat(sandbox): enforce proxy-aware network routing in sandbox (#11113)
    ## Summary
    - expand proxy env injection to cover common tool env vars
    (`HTTP_PROXY`/`HTTPS_PROXY`/`ALL_PROXY`/`NO_PROXY` families +
    tool-specific variants)
    - harden macOS Seatbelt network policy generation to route through
    inferred loopback proxy endpoints and fail closed when proxy env is
    malformed
    - thread proxy-aware Linux sandbox flags and add minimal bwrap netns
    isolation hook for restricted non-proxy runs
    - add/refresh tests for proxy env wiring, Seatbelt policy generation,
    and Linux sandbox argument wiring
  • fix(linux-sandbox): block io_uring syscalls in no-network seccomp policy (#10814)
    ## Summary
    
    - Add seccomp deny rules for `io_uring` syscalls in the Linux sandbox
    network policy.
    - Specifically deny:
      - `SYS_io_uring_setup`
      - `SYS_io_uring_enter`
      - `SYS_io_uring_register`
  • feat(linux-sandbox): add bwrap support (#9938)
    ## 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.
  • revert: remove pre-Landlock bind mounts apply (#9300)
    **Description**
    
    This removes the pre‑Landlock read‑only bind‑mount step from the Linux
    sandbox so filesystem restrictions rely solely on Landlock again.
    `mounts.rs` is kept in place but left unused. The linux‑sandbox README
    is updated to match the new behavior and manual test expectations.
  • fix: fallback to Landlock-only when user namespaces unavailable and set PR_SET_NO_NEW_PRIVS early (#9250)
    fixes https://github.com/openai/codex/issues/9236
    
    ### Motivation
    - Prevent sandbox setup from failing when unprivileged user namespaces
    are denied so Landlock-only protections can still be applied.
    - Ensure `PR_SET_NO_NEW_PRIVS` is set before installing seccomp and
    Landlock restrictions to avoid kernel `EPERM`/`LandlockRestrict`
    ordering issues.
    
    ### Description
    - Add `is_permission_denied` helper that detects `EPERM` /
    `PermissionDenied` from `CodexErr` to drive fallback logic.
    - In `apply_read_only_mounts` skip read-only bind-mount setup and return
    `Ok(())` when `unshare_user_and_mount_namespaces()` fails with
    permission-denied so Landlock rules can still be installed.
    - Add `set_no_new_privs()` and call it from
    `apply_sandbox_policy_to_current_thread` before installing seccomp
    filters and Landlock rules when disk or network access is restricted.
  • feat: add support for read-only bind mounts in the linux sandbox (#9112)
    ### Motivation
    
    - Landlock alone cannot prevent writes to sensitive in-repo files like
    `.git/` when the repo root is writable, so explicit mount restrictions
    are required for those paths.
    - The sandbox must set up any mounts before calling Landlock so Landlock
    can still be applied afterwards and the two mechanisms compose
    correctly.
    
    ### Description
    
    - Add a new `linux-sandbox` helper `apply_read_only_mounts` in
    `linux-sandbox/src/mounts.rs` that: unshares namespaces, maps uids/gids
    when required, makes mounts private, bind-mounts targets, and remounts
    them read-only.
    - Wire the mount step into the sandbox flow by calling
    `apply_read_only_mounts(...)` before network/seccomp and before applying
    Landlock rules in `linux-sandbox/src/landlock.rs`.
  • fix: introduce AbsolutePathBuf as part of sandbox config (#7856)
    Changes the `writable_roots` field of the `WorkspaceWrite` variant of
    the `SandboxPolicy` enum from `Vec<PathBuf>` to `Vec<AbsolutePathBuf>`.
    This is helpful because now callers can be sure the value is an absolute
    path rather than a relative one. (Though when using an absolute path in
    a Seatbelt config policy, we still have to _canonicalize_ it first.)
    
    Because `writable_roots` can be read from a config file, it is important
    that we are able to resolve relative paths properly using the parent
    folder of the config file as the base path.
  • fix: allow sendmsg(2) and recvmsg(2) syscalls in our Linux sandbox (#7779)
    This changes our default Landlock policy to allow `sendmsg(2)` and
    `recvmsg(2)` syscalls. We believe these were originally denied out of an
    abundance of caution, but given that `send(2)` nor `recv(2)` are allowed
    today [which provide comparable capability to the `*msg` equivalents],
    we do not believe allowing them grants any privileges beyond what we
    already allow.
    
    Rather than using the syscall as the security boundary, preventing
    access to the potentially hazardous file descriptor in the first place
    seems like the right layer of defense.
    
    In particular, this makes it possible for `shell-tool-mcp` to run on
    Linux when using a read-only sandbox for the Bash process, as
    demonstrated by `accept_elicitation_for_prompt_rule()` now succeeding in
    CI.
  • Fix AF_UNIX, sockpair, recvfrom in linux sandbox (#2309)
    When using codex-tui on a linux system I was unable to run `cargo
    clippy` inside of codex due to:
    ```
    [pid 3548377] socketpair(AF_UNIX, SOCK_SEQPACKET|SOCK_CLOEXEC, 0,  <unfinished ...>
    [pid 3548370] close(8 <unfinished ...>
    [pid 3548377] <... socketpair resumed>0x7ffb97f4ed60) = -1 EPERM (Operation not permitted)
    ```
    And
    ```
    3611300 <... recvfrom resumed>0x708b8b5cffe0, 8, 0, NULL, NULL) = -1 EPERM (Operation not permitted)
    ```
    
    This PR:
    * Fixes a bug that disallowed AF_UNIX to allow it on `socket()`
    * Adds recvfrom() to the syscall allow list, this should be fine since
    we disable opening new sockets. But we should validate there is not a
    open socket inheritance issue.
    * Allow socketpair to be called for AF_UNIX
    * Adds tests for AF_UNIX components
    * All of which allows running `cargo clippy` within the sandbox on
    linux, and possibly other tooling using a fork server model + AF_UNIX
    comms.
  • feat: make .git read-only within a writable root when using Seatbelt (#1765)
    To make `--full-auto` safer, this PR updates the Seatbelt policy so that
    a `SandboxPolicy` with a `writable_root` that contains a `.git/`
    _directory_ will make `.git/` _read-only_ (though as a follow-up, we
    should also consider the case where `.git` is a _file_ with a `gitdir:
    /path/to/actual/repo/.git` entry that should also be protected).
    
    The two major changes in this PR:
    
    - Updating `SandboxPolicy::get_writable_roots_with_cwd()` to return a
    `Vec<WritableRoot>` instead of a `Vec<PathBuf>` where a `WritableRoot`
    can specify a list of read-only subpaths.
    - Updating `create_seatbelt_command_args()` to honor the read-only
    subpaths in `WritableRoot`.
    
    The logic to update the policy is a fairly straightforward update to
    `create_seatbelt_command_args()`, but perhaps the more interesting part
    of this PR is the introduction of an integration test in
    `tests/sandbox.rs`. Leveraging the new API in #1785, we test
    `SandboxPolicy` under various conditions, including ones where `$TMPDIR`
    is not readable, which is critical for verifying the new behavior.
    
    To ensure that Codex can run its own tests, e.g.:
    
    ```
    just codex debug seatbelt --full-auto -- cargo test if_git_repo_is_writable_root_then_dot_git_folder_is_read_only
    ```
    
    I had to introduce the use of `CODEX_SANDBOX=sandbox`, which is
    comparable to how `CODEX_SANDBOX_NETWORK_DISABLED=1` was already being
    used.
    
    Adding a comparable change for Landlock will be done in a subsequent PR.
  • fix: overhaul how we spawn commands under seccomp/landlock on Linux (#1086)
    Historically, we spawned the Seatbelt and Landlock sandboxes in
    substantially different ways:
    
    For **Seatbelt**, we would run `/usr/bin/sandbox-exec` with our policy
    specified as an arg followed by the original command:
    
    
    https://github.com/openai/codex/blob/d1de7bb383552e8fadd94be79d65d188e00fd562/codex-rs/core/src/exec.rs#L147-L219
    
    For **Landlock/Seccomp**, we would do
    `tokio::runtime::Builder::new_current_thread()`, _invoke
    Landlock/Seccomp APIs to modify the permissions of that new thread_, and
    then spawn the command:
    
    
    https://github.com/openai/codex/blob/d1de7bb383552e8fadd94be79d65d188e00fd562/codex-rs/core/src/exec_linux.rs#L28-L49
    
    While it is neat that Landlock/Seccomp supports applying a policy to
    only one thread without having to apply it to the entire process, it
    requires us to maintain two different codepaths and is a bit harder to
    reason about. The tipping point was
    https://github.com/openai/codex/pull/1061, in which we had to start
    building up the `env` in an unexpected way for the existing
    Landlock/Seccomp approach to continue to work.
    
    This PR overhauls things so that we do similar things for Mac and Linux.
    It turned out that we were already building our own "helper binary"
    comparable to Mac's `sandbox-exec` as part of the `cli` crate:
    
    
    https://github.com/openai/codex/blob/d1de7bb383552e8fadd94be79d65d188e00fd562/codex-rs/cli/Cargo.toml#L10-L12
    
    We originally created this to build a small binary to include with the
    Node.js version of the Codex CLI to provide support for Linux
    sandboxing.
    
    Though the sticky bit is that, at this point, we still want to deploy
    the Rust version of Codex as a single, standalone binary rather than a
    CLI and a supporting sandboxing binary. To satisfy this goal, we use
    "the arg0 trick," in which we:
    
    * use `std::env::current_exe()` to get the path to the CLI that is
    currently running
    * use the CLI as the `program` for the `Command`
    * set `"codex-linux-sandbox"` as arg0 for the `Command`
    
    A CLI that supports sandboxing should check arg0 at the start of the
    program. If it is `"codex-linux-sandbox"`, it must invoke
    `codex_linux_sandbox::run_main()`, which runs the CLI as if it were
    `codex-linux-sandbox`. When acting as `codex-linux-sandbox`, we make the
    appropriate Landlock/Seccomp API calls and then use `execvp(3)` to spawn
    the original command, so do _replace_ the process rather than spawn a
    subprocess. Incidentally, we do this before starting the Tokio runtime,
    so the process should only have one thread when `execvp(3)` is called.
    
    Because the `core` crate that needs to spawn the Linux sandboxing is not
    a CLI in its own right, this means that every CLI that includes `core`
    and relies on this behavior has to (1) implement it and (2) provide the
    path to the sandboxing executable. While the path is almost always
    `std::env::current_exe()`, we needed to make this configurable for
    integration tests, so `Config` now has a `codex_linux_sandbox_exe:
    Option<PathBuf>` property to facilitate threading this through,
    introduced in https://github.com/openai/codex/pull/1089.
    
    This common pattern is now captured in
    `codex_linux_sandbox::run_with_sandbox()` and all of the `main.rs`
    functions that should use it have been updated as part of this PR.
    
    The `codex-linux-sandbox` crate added to the Cargo workspace as part of
    this PR now has the bulk of the Landlock/Seccomp logic, which makes
    `core` a bit simpler. Indeed, `core/src/exec_linux.rs` and
    `core/src/landlock.rs` were removed/ported as part of this PR. I also
    moved the unit tests for this code into an integration test,
    `linux-sandbox/tests/landlock.rs`, in which I use
    `env!("CARGO_BIN_EXE_codex-linux-sandbox")` as the value for
    `codex_linux_sandbox_exe` since `std::env::current_exe()` is not
    appropriate in that case.