this adds some more capabilities to the default sandbox which I feel are
safe. Most are in the
[renderer.sb](https://source.chromium.org/chromium/chromium/src/+/main:sandbox/policy/mac/renderer.sb)
sandbox for chrome renderers, which i feel is fair game for codex
commands.
Specific changes:
1. Allow processes in the sandbox to send signals to any other process
in the same sandbox (e.g. child processes or daemonized processes),
instead of just themselves.
2. Allow user-preference-read
3. Allow process-info* to anything in the same sandbox. This is a bit
wider than Chromium allows, but it seems OK to me to allow anything in
the sandbox to get details about other processes in the same sandbox.
Bazel uses these to e.g. wait for another process to exit.
4. Allow all CPU feature detection, this seems harmless to me. It's
wider than Chromium, but Chromium is concerned about fingerprinting, and
tightly controls what CPU features they actually care about, and we
don't have either that restriction or that advantage.
5. Allow new sysctl-reads:
```
(sysctl-name "vm.loadavg")
(sysctl-name-prefix "kern.proc.pgrp.")
(sysctl-name-prefix "kern.proc.pid.")
(sysctl-name-prefix "net.routetable.")
```
bazel needs these for waiting on child processes and for communicating
with its local build server, i believe. I wonder if we should just allow
all (sysctl-read), as reading any arbitrary info about the system seems
fine to me.
6. Allow iokit-open on RootDomainUserClient. This has to do with power
management I believe, and Chromium allows renderers to do this, so okay.
Bazel needs it to boot successfully, possibly for sleep/wake callbacks?
7. Mach lookup to `com.apple.system.opendirectoryd.libinfo`, which has
to do with user data, and which Chrome allows.
8. Mach lookup to `com.apple.PowerManagement.control`. Chromium allows
its GPU process to do this, but not its renderers. Bazel needs this to
boot, probably relatedly to sleep/wake stuff.
The following test script fails in the codex sandbox:
```
import multiprocessing
from multiprocessing import Lock, Process
def f(lock):
with lock:
print("Lock acquired in child process")
if __name__ == '__main__':
lock = Lock()
p = Process(target=f, args=(lock,))
p.start()
p.join()
```
with
```
Traceback (most recent call last):
File "/Users/david.hao/code/codex/codex-rs/cli/test.py", line 9, in <module>
lock = Lock()
^^^^^^
File "/Users/david.hao/.local/share/uv/python/cpython-3.12.9-macos-aarch64-none/lib/python3.12/multiprocessing/context.py", line 68, in Lock
return Lock(ctx=self.get_context())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/david.hao/.local/share/uv/python/cpython-3.12.9-macos-aarch64-none/lib/python3.12/multiprocessing/synchronize.py", line 169, in __init__
SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
File "/Users/david.hao/.local/share/uv/python/cpython-3.12.9-macos-aarch64-none/lib/python3.12/multiprocessing/synchronize.py", line 57, in __init__
sl = self._semlock = _multiprocessing.SemLock(
^^^^^^^^^^^^^^^^^^^^^^^^^
PermissionError: [Errno 1] Operation not permitted
```
After reading, adding this line to the sandbox configs fixes things -
MacOS multiprocessing appears to use sem_lock(), which opens an IPC
which is considered a disk write even though no file is created. I
interrogated ChatGPT about whether it's okay to loosen, and my
impression after reading is that it is, although would appreciate a
close look
Breadcrumb: You can run `cargo run -- debug seatbelt --full-auto <cmd>`
to test the sandbox
Previous to this PR, `SandboxPolicy` was a bit difficult to work with:
237f8a11e1/codex-rs/core/src/protocol.rs (L98-L108)
Specifically:
* It was an `enum` and therefore options were mutually exclusive as
opposed to additive.
* It defined things in terms of what the agent _could not_ do as opposed
to what they _could_ do. This made things hard to support because we
would prefer to build up a sandbox config by starting with something
extremely restrictive and only granting permissions for things the user
as explicitly allowed.
This PR changes things substantially by redefining the policy in terms
of two concepts:
* A `SandboxPermission` enum that defines permissions that can be
granted to the agent/sandbox.
* A `SandboxPolicy` that internally stores a `Vec<SandboxPermission>`,
but externally exposes a simpler API that can be used to configure
Seatbelt/Landlock.
Previous to this PR, we supported a `--sandbox` flag that effectively
mapped to an enum value in `SandboxPolicy`. Though now that
`SandboxPolicy` is a wrapper around `Vec<SandboxPermission>`, the single
`--sandbox` flag no longer makes sense. While I could have turned it
into a flag that the user can specify multiple times, I think the
current values to use with such a flag are long and potentially messy,
so for the moment, I have dropped support for `--sandbox` altogether and
we can bring it back once we have figured out the naming thing.
Since `--sandbox` is gone, users now have to specify `--full-auto` to
get a sandbox that allows writes in `cwd`. Admittedly, there is no clean
way to specify the equivalent of `--full-auto` in your `config.toml`
right now, so we will have to revisit that, as well.
Because `Config` presents a `SandboxPolicy` field and `SandboxPolicy`
changed considerably, I had to overhaul how config loading works, as
well. There are now two distinct concepts, `ConfigToml` and `Config`:
* `ConfigToml` is the deserialization of `~/.codex/config.toml`. As one
might expect, every field is `Optional` and it is `#[derive(Deserialize,
Default)]`. Consistent use of `Optional` makes it clear what the user
has specified explicitly.
* `Config` is the "normalized config" and is produced by merging
`ConfigToml` with `ConfigOverrides`. Where `ConfigToml` contains a raw
`Option<Vec<SandboxPermission>>`, `Config` presents only the final
`SandboxPolicy`.
The changes to `core/src/exec.rs` and `core/src/linux.rs` merit extra
special attention to ensure we are faithfully mapping the
`SandboxPolicy` to the Seatbelt and Landlock configs, respectively.
Also, take note that `core/src/seatbelt_readonly_policy.sbpl` has been
renamed to `codex-rs/core/src/seatbelt_base_policy.sbpl` and that
`(allow file-read*)` has been removed from the `.sbpl` file as now this
is added to the policy in `core/src/exec.rs` when
`sandbox_policy.has_full_disk_read_access()` is `true`.
