abbd74e2be
`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.
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| BUILD.bazel | ||
| Cargo.toml | ||
| README.md | ||
codex-exec-server
This crate contains the code for two executables:
codex-exec-mcp-serveris an MCP server that provides a tool namedshellthat runs a shell command inside a sandboxed instance of Bash. Every resultingexecve(2)call made within Bash is intercepted and run via the executable defined by theBASH_EXEC_WRAPPERenvironment variable within the Bash process. In practice,BASH_EXEC_WRAPPERis set tocodex-execve-wrapper.codex-execve-wrapperis the executable that takes the arguments to theexecve(2)call and "escalates" it to the MCP server via a shared file descriptor (specified by theCODEX_ESCALATE_SOCKETenvironment variable) for consideration. Based on the Codex.rules, the MCP server replies with one of:Run:codex-execve-wrappershould invokeexecve(2)on itself to run the original command within BashEscalate: forward the file descriptors of the current process to the MCP server so the command can be run faithfully outside the sandbox. Because the MCP server will have the original FDs forstdoutandstderr, it can write those directly. When the process completes, the MCP server forwards the exit code tocodex-execve-wrapperso that it exits in a consistent manner.Deny: the MCP server has declared the proposed command to be "forbidden," socodex-execve-wrapperwill print an error tostderrand exit with1.
Patched Bash
We carry a small patch to execute_cmd.c (see patches/bash-exec-wrapper.patch) that adds support for BASH_EXEC_WRAPPER. The original commit message is “add support for BASH_EXEC_WRAPPER” and the patch applies cleanly to a8a1c2fac029404d3f42cd39f5a20f24b6e4fe4b from https://github.com/bminor/bash. To rebuild manually:
git clone https://github.com/bminor/bash
git checkout a8a1c2fac029404d3f42cd39f5a20f24b6e4fe4b
git apply /path/to/patches/bash-exec-wrapper.patch
./configure --without-bash-malloc
make -j"$(nproc)"
Release workflow
.github/workflows/shell-tool-mcp.yml builds the Rust binaries, compiles the patched Bash variants, assembles the vendor/ tree, and creates codex-shell-tool-mcp-npm-<version>.tgz for inclusion in the Rust GitHub Release. When the version is a stable or alpha tag, the workflow also publishes the tarball to npm using OIDC. The workflow is invoked from rust-release.yml so the package ships alongside other Codex artifacts.