46f30d0282
## Why The split filesystem policy stack already supports exact and glob `access = none` read restrictions on macOS and Linux. Windows still needed subprocess handling for those deny-read policies without claiming enforcement from a backend that cannot provide it. ## Key finding The unelevated restricted-token backend cannot safely enforce deny-read overlays. Its `WRITE_RESTRICTED` token model is authoritative for write checks, not read denials, so this PR intentionally fails that backend closed when deny-read overrides are present instead of claiming unsupported enforcement. ## What changed This PR adds the Windows deny-read enforcement layer and makes the backend split explicit: - Resolves Windows deny-read filesystem policy entries into concrete ACL targets. - Preserves exact missing paths so they can be materialized and denied before an enforceable sandboxed process starts. - Snapshot-expands existing glob matches into ACL targets for Windows subprocess enforcement. - Honors `glob_scan_max_depth` when expanding Windows deny-read globs. - Plans both the configured lexical path and the canonical target for existing paths so reparse-point aliases are covered. - Threads deny-read overrides through the elevated/logon-user Windows sandbox backend and unified exec. - Applies elevated deny-read ACLs synchronously before command launch rather than delegating them to the background read-grant helper. - Reconciles persistent deny-read ACEs per sandbox principal so policy changes do not leave stale deny-read ACLs behind. - Fails closed on the unelevated restricted-token backend when deny-read overrides are present, because its `WRITE_RESTRICTED` token model is not authoritative for read denials. ## Landed prerequisites These prerequisite PRs are already on `main`: 1. #15979 `feat(permissions): add glob deny-read policy support` 2. #18096 `feat(sandbox): add glob deny-read platform enforcement` 3. #17740 `feat(config): support managed deny-read requirements` This PR targets `main` directly and contains only the Windows deny-read enforcement layer. ## Implementation notes - Exact deny-read paths remain enforceable on the elevated path even when they do not exist yet: Windows materializes the missing path before applying the deny ACE, so the sandboxed command cannot create and read it during the same run. - Existing exact deny paths are preserved lexically until the ACL planner, which then adds the canonical target as a second ACL target when needed. That keeps both the configured alias and the resolved object covered. - Windows ACLs do not consume Codex glob syntax directly, so glob deny-read entries are expanded to the concrete matches that exist before process launch. - Glob traversal deduplicates directory visits within each pattern walk to avoid cycles, without collapsing distinct lexical roots that happen to resolve to the same target. - Persistent deny-read ACL state is keyed by sandbox principal SID, so cleanup only removes ACEs owned by the same backend principal. - Deny-read ACEs are fail-closed on the elevated path: setup aborts if mandatory deny-read ACL application fails. - Unelevated restricted-token sessions reject deny-read overrides early instead of running with a silently unenforceable read policy. ## Verification - `cargo test -p codex-core windows_restricted_token_rejects_unreadable_split_carveouts` - `just fmt` - `just fix -p codex-core` - `just fix -p codex-windows-sandbox` - GitHub Actions rerun is in progress on the pushed head. --------- Co-authored-by: Codex <noreply@openai.com>
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 linux (legacy alias: codex debug landlock) 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
ReadOnlyandWorkspaceWritebehavior - 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), andC:\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.