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fix: overhaul SandboxPolicy and config loading in Rust (#732)

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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`.
This commit is contained in:
Michael Bolin
2025-04-29 15:01:16 -07:00
committed by GitHub
parent 237f8a11e1
commit 0a00b5ed29
21 changed files with 408 additions and 259 deletions
Download Patch File Download Diff File Expand all files Collapse all files

96
codex-rs/core/src/exec.rs
View File

@@ -1,7 +1,6 @@
use std::io;
#[cfg(target_family = "unix")]
use std::os::unix::process::ExitStatusExt;
use std::path::PathBuf;
use std::process::ExitStatus;
use std::process::Stdio;
use std::sync::Arc;
@@ -33,7 +32,7 @@ const DEFAULT_TIMEOUT_MS: u64 = 10_000;
const SIGKILL_CODE: i32 = 9;
const TIMEOUT_CODE: i32 = 64;
const MACOS_SEATBELT_READONLY_POLICY: &str = include_str!("seatbelt_readonly_policy.sbpl");
const MACOS_SEATBELT_BASE_POLICY: &str = include_str!("seatbelt_base_policy.sbpl");
/// When working with `sandbox-exec`, only consider `sandbox-exec` in `/usr/bin`
/// to defend against an attacker trying to inject a malicious version on the
@@ -67,19 +66,17 @@ pub enum SandboxType {
#[cfg(target_os = "linux")]
async fn exec_linux(
params: ExecParams,
writable_roots: &[PathBuf],
ctrl_c: Arc<Notify>,
sandbox_policy: SandboxPolicy,
sandbox_policy: &SandboxPolicy,
) -> Result<RawExecToolCallOutput> {
crate::linux::exec_linux(params, writable_roots, ctrl_c, sandbox_policy).await
crate::linux::exec_linux(params, ctrl_c, sandbox_policy).await
}
#[cfg(not(target_os = "linux"))]
async fn exec_linux(
_params: ExecParams,
_writable_roots: &[PathBuf],
_ctrl_c: Arc<Notify>,
_sandbox_policy: SandboxPolicy,
_sandbox_policy: &SandboxPolicy,
) -> Result<RawExecToolCallOutput> {
Err(CodexErr::Io(io::Error::new(
io::ErrorKind::InvalidInput,
@@ -90,9 +87,8 @@ async fn exec_linux(
pub async fn process_exec_tool_call(
params: ExecParams,
sandbox_type: SandboxType,
writable_roots: &[PathBuf],
ctrl_c: Arc<Notify>,
sandbox_policy: SandboxPolicy,
sandbox_policy: &SandboxPolicy,
) -> Result<ExecToolCallOutput> {
let start = Instant::now();
@@ -104,7 +100,7 @@ pub async fn process_exec_tool_call(
workdir,
timeout_ms,
} = params;
let seatbelt_command = create_seatbelt_command(command, sandbox_policy, writable_roots);
let seatbelt_command = create_seatbelt_command(command, sandbox_policy);
exec(
ExecParams {
command: seatbelt_command,
@@ -115,9 +111,7 @@ pub async fn process_exec_tool_call(
)
.await
}
SandboxType::LinuxSeccomp => {
exec_linux(params, writable_roots, ctrl_c, sandbox_policy).await
}
SandboxType::LinuxSeccomp => exec_linux(params, ctrl_c, sandbox_policy).await,
};
let duration = start.elapsed();
match raw_output_result {
@@ -162,41 +156,61 @@ pub async fn process_exec_tool_call(
pub fn create_seatbelt_command(
command: Vec<String>,
sandbox_policy: SandboxPolicy,
writable_roots: &[PathBuf],
sandbox_policy: &SandboxPolicy,
) -> Vec<String> {
let (policies, cli_args): (Vec<String>, Vec<String>) = writable_roots
.iter()
.enumerate()
.map(|(index, root)| {
let param_name = format!("WRITABLE_ROOT_{index}");
let policy: String = format!("(subpath (param \"{param_name}\"))");
let cli_arg = format!("-D{param_name}={}", root.to_string_lossy());
(policy, cli_arg)
})
.unzip();
// TODO(ragona): The seatbelt policy should reflect the SandboxPolicy that
// is passed, but everything is currently hardcoded to use
// MACOS_SEATBELT_READONLY_POLICY.
// TODO(mbolin): apply_patch calls must also honor the SandboxPolicy.
if !matches!(sandbox_policy, SandboxPolicy::NetworkRestricted) {
tracing::error!("specified sandbox policy {sandbox_policy:?} will not be honroed");
}
let full_policy = if policies.is_empty() {
MACOS_SEATBELT_READONLY_POLICY.to_string()
} else {
let scoped_write_policy = format!("(allow file-write*\n{}\n)", policies.join(" "));
format!("{MACOS_SEATBELT_READONLY_POLICY}\n{scoped_write_policy}")
let (file_write_policy, extra_cli_args) = {
if sandbox_policy.has_full_disk_write_access() {
// Allegedly, this is more permissive than `(allow file-write*)`.
(
r#"(allow file-write* (regex #"^/"))"#.to_string(),
Vec::<String>::new(),
)
} else {
let writable_roots = sandbox_policy.get_writable_roots();
let (writable_folder_policies, cli_args): (Vec<String>, Vec<String>) = writable_roots
.iter()
.enumerate()
.map(|(index, root)| {
let param_name = format!("WRITABLE_ROOT_{index}");
let policy: String = format!("(subpath (param \"{param_name}\"))");
let cli_arg = format!("-D{param_name}={}", root.to_string_lossy());
(policy, cli_arg)
})
.unzip();
if writable_folder_policies.is_empty() {
("".to_string(), Vec::<String>::new())
} else {
let file_write_policy = format!(
"(allow file-write*\n{}\n)",
writable_folder_policies.join(" ")
);
(file_write_policy, cli_args)
}
}
};
let file_read_policy = if sandbox_policy.has_full_disk_read_access() {
"; allow read-only file operations\n(allow file-read*)"
} else {
""
};
// TODO(mbolin): apply_patch calls must also honor the SandboxPolicy.
let network_policy = if sandbox_policy.has_full_network_access() {
"(allow network-outbound)\n(allow network-inbound)\n(allow system-socket)"
} else {
""
};
let full_policy = format!(
"{MACOS_SEATBELT_BASE_POLICY}\n{file_read_policy}\n{file_write_policy}\n{network_policy}"
);
let mut seatbelt_command: Vec<String> = vec![
MACOS_PATH_TO_SEATBELT_EXECUTABLE.to_string(),
"-p".to_string(),
full_policy.to_string(),
full_policy,
];
seatbelt_command.extend(cli_args);
seatbelt_command.extend(extra_cli_args);
seatbelt_command.push("--".to_string());
seatbelt_command.extend(command);
seatbelt_command