## Why
Managed filesystem `deny_read` requirements are administrator-enforced
restrictions on specific paths. Once those requirements are active,
Codex should not drop them just because an execution path would
otherwise leave the sandbox.
Before this change, an explicit escalation, a prefix-rule allow, a
sandbox-denial retry, or an app-server legacy sandbox override could
rebuild the runtime policy without those managed read-deny entries and
expose a path the administrator had marked unreadable.
This is narrower than general sandbox-mode constraints. If an enterprise
only sets `allowed_sandbox_modes`, a trusted `prefix_rule(..., decision
= "allow")` can still run its matching command unsandboxed; this PR only
preserves managed filesystem `deny_read` restrictions across those
paths.
## What Changed
- Mark filesystem policies built from managed `deny_read` requirements
so callers can tell when those deny entries must survive escalation.
- Preserve managed deny-read entries when runtime permission profiles
are rebuilt through protocol, app-server, or legacy sandbox-policy
compatibility paths.
- Keep managed deny-read attempts inside the selected sandbox on the
first attempt and after sandbox-denial retries.
- Preserve the same behavior in the zsh-fork escalation path, including
prefix-rule-driven escalation.
- Add a regression test showing the opposite case too: without managed
deny-read, a prefix-rule allow still chooses unsandboxed execution.
## Verification
Targeted automated verification:
```shell
cargo test -p codex-core shell_request_escalation_execution_is_explicit -- --nocapture
cargo test -p codex-core prefix_rule_uses_unsandboxed_execution_without_managed_deny_read -- --nocapture
cargo test -p codex-core prefix_rule_preserves_managed_deny_read_escalation -- --nocapture
cargo test -p codex-protocol permission_profile_round_trip_preserves_filesystem_policy_metadata -- --nocapture
cargo test -p codex-protocol preserving_deny_entries_keeps_unrestricted_policy_enforceable -- --nocapture
cargo test -p codex-app-server-protocol permission_profile_file_system_permissions_preserves_policy_metadata -- --nocapture
cargo check -p codex-app-server -p codex-tui
```
Smoke-test invocations:
```shell
# macOS exact deny + allowed control
codex exec --skip-git-repo-check -C "$ROOT" \
-c 'default_permissions="deny_read_smoke"' \
-c 'permissions.deny_read_smoke.filesystem={":minimal"="read",":project_roots"={"."="write","secrets"="none","future-secret"="none","**/*.env"="none"}}' \
'Run shell commands only. Print the contents of allowed.txt. Then test whether reading secrets/exact-secret.txt succeeds without printing that file if it does. End with exactly two lines: allowed=<contents> and exact_secret=<BLOCKED or READABLE>.'
# Linux exact deny + allowed control
codex exec --skip-git-repo-check -C "$ROOT" \
-c 'default_permissions="deny_read_smoke"' \
-c 'permissions.deny_read_smoke.filesystem={":minimal"="read",glob_scan_max_depth=3,":project_roots"={"."="write","secrets"="none","future-secret"="none","**/*.env"="none"}}' \
'Run shell commands only. Print the contents of allowed.txt. Then test whether reading secrets/exact-secret.txt succeeds without printing that file if it does. End with exactly two lines: allowed=<contents> and exact_secret=<BLOCKED or READABLE>.'
```
Observed manual smoke matrix:
| Case | macOS Seatbelt | Linux bubblewrap |
| --- | --- | --- |
| `cat allowed.txt` | Pass | Pass |
| `cat secrets/exact-secret.txt` | Blocked | Blocked |
| `cat envs/root.env` | Blocked | Blocked |
| `cat envs/nested/one.env` | Blocked | Blocked |
| `cat envs/nested/two.env` | Blocked | Blocked |
| `cat alias-to-secrets/exact-secret.txt` | Blocked | Blocked |
| Missing denied path | A file created after sandbox setup remained
unreadable | Creation was blocked by the reserved missing-path
placeholder, and the placeholder was cleaned up after exit |
| Real `codex exec` shell turn | Pass | Pass |
Notes:
- The Linux smoke run used the fallback glob walker because the devbox
did not have `rg` installed.
- The smoke matrix verifies the end-to-end filesystem behavior on macOS
and Linux; the escalation-specific behavior is covered by the focused
tests above.
---------
Co-authored-by: Codex <noreply@openai.com>
Co-authored-by: Charlie Marsh <charliemarsh@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.