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## Why Fixes [#15283](https://github.com/openai/codex/issues/15283), where sandboxed tool calls fail on older distro `bubblewrap` builds because `/usr/bin/bwrap` does not understand `--argv0`. The upstream [bubblewrap v0.9.0 release notes](https://github.com/containers/bubblewrap/releases/tag/v0.9.0) explicitly call out `Add --argv0`. Flipping `use_legacy_landlock` globally works around that compatibility bug, but it also weakens the default Linux sandbox and breaks proxy-routed and split-policy cases called out in review. The follow-up Linux CI failure was in the new launcher test rather than the launcher logic: the fake `bwrap` helper stayed open for writing, so Linux would not exec it. This update also closes the user-visibility gap from review by surfacing the same startup warning when `/usr/bin/bwrap` is present but too old for `--argv0`, not only when it is missing. ## What Changed - keep `use_legacy_landlock` default-disabled - teach `codex-rs/linux-sandbox/src/launcher.rs` to fall back to the vendored bubblewrap build when `/usr/bin/bwrap` does not advertise `--argv0` support - add launcher tests for supported, unsupported, and missing system `bwrap` - write the fake `bwrap` test helper to a closed temp path so the supported-path launcher test works on Linux too - extend the startup warning path so Codex warns when `/usr/bin/bwrap` is missing or too old to support `--argv0` - mirror the warning/fallback wording across `codex-rs/linux-sandbox/README.md` and `codex-rs/core/README.md`, including that the fallback is the vendored bubblewrap compiled into the binary - cite the upstream `bubblewrap` release that introduced `--argv0` ## Verification - `bazel test --config=remote --platforms=//:rbe //codex-rs/linux-sandbox:linux-sandbox-unit-tests --test_filter=launcher::tests::prefers_system_bwrap_when_help_lists_argv0 --test_output=errors` - `cargo test -p codex-core system_bwrap_warning` - `cargo check -p codex-exec -p codex-tui -p codex-tui-app-server -p codex-app-server` - `just argument-comment-lint`
67 lines
4.0 KiB
Markdown
67 lines
4.0 KiB
Markdown
# codex-linux-sandbox
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This crate is responsible for producing:
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- a `codex-linux-sandbox` standalone executable for Linux that is bundled with the Node.js version of the Codex CLI
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- a lib crate that exposes the business logic of the executable as `run_main()` so that
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- the `codex-exec` CLI can check if its arg0 is `codex-linux-sandbox` and, if so, execute as if it were `codex-linux-sandbox`
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- this should also be true of the `codex` multitool CLI
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On Linux, the bubblewrap pipeline prefers the system `/usr/bin/bwrap` whenever
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it is available and supports the required argv-rewrite flags. If `/usr/bin/bwrap`
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is missing or too old to support the required flags, the helper falls back to
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the vendored bubblewrap path compiled into this binary.
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Codex also surfaces a startup warning when `/usr/bin/bwrap` is missing or too
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old to support the required flags so users know it is falling back to the
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vendored helper.
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**Current Behavior**
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- Legacy `SandboxPolicy` / `sandbox_mode` configs remain supported.
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- Bubblewrap is the default filesystem sandbox pipeline.
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- If `/usr/bin/bwrap` is present and supports the required argv-rewrite flags,
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the helper uses it.
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- If `/usr/bin/bwrap` is missing or too old to support the required flags, the
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helper falls back to the vendored bubblewrap path.
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- If `/usr/bin/bwrap` is missing or too old to support the required flags,
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Codex also surfaces a startup warning instead of printing directly from the
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sandbox helper.
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- Legacy Landlock + mount protections remain available as an explicit legacy
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fallback path.
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- Set `features.use_legacy_landlock = true` (or CLI `-c use_legacy_landlock=true`)
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to force the legacy Landlock fallback.
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- The legacy Landlock fallback is used only when the split filesystem policy is
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sandbox-equivalent to the legacy model after `cwd` resolution.
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- Split-only filesystem policies that do not round-trip through the legacy
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`SandboxPolicy` model stay on bubblewrap so nested read-only or denied
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carveouts are preserved.
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- When the default bubblewrap pipeline is active, the helper applies `PR_SET_NO_NEW_PRIVS` and a
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seccomp network filter in-process.
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- When the default bubblewrap pipeline is active, the filesystem is read-only by default via `--ro-bind / /`.
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- When the default bubblewrap pipeline is active, writable roots are layered with `--bind <root> <root>`.
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- When the default bubblewrap pipeline is active, protected subpaths under writable roots (for
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example `.git`,
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resolved `gitdir:`, and `.codex`) are re-applied as read-only via `--ro-bind`.
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- When the default bubblewrap pipeline is active, overlapping split-policy
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entries are applied in path-specificity order so narrower writable children
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can reopen broader read-only or denied parents while narrower denied subpaths
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still win. For example, `/repo = write`, `/repo/a = none`, `/repo/a/b = write`
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keeps `/repo` writable, denies `/repo/a`, and reopens `/repo/a/b` as
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writable again.
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- When the default bubblewrap pipeline is active, symlink-in-path and non-existent protected paths inside
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writable roots are blocked by mounting `/dev/null` on the symlink or first
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missing component.
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- When the default bubblewrap pipeline is active, the helper explicitly isolates the user namespace via
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`--unshare-user` and the PID namespace via `--unshare-pid`.
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- When the default bubblewrap pipeline is active and network is restricted without proxy routing, the helper also
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isolates the network namespace via `--unshare-net`.
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- In managed proxy mode, the helper uses `--unshare-net` plus an internal
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TCP->UDS->TCP routing bridge so tool traffic reaches only configured proxy
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endpoints.
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- In managed proxy mode, after the bridge is live, seccomp blocks new
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AF_UNIX/socketpair creation for the user command.
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- When the default bubblewrap pipeline is active, it mounts a fresh `/proc` via `--proc /proc` by default, but
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you can skip this in restrictive container environments with `--no-proc`.
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**Notes**
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- The CLI surface still uses legacy names like `codex debug landlock`.
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