This PR reorganizes things slightly so that:
- Instead of a single multitool executable, `codex-exec-server`, we now
have two executables:
- `codex-exec-mcp-server` to launch the MCP server
- `codex-execve-wrapper` is the `execve(2)` wrapper to use with the
`BASH_EXEC_WRAPPER` environment variable
- `BASH_EXEC_WRAPPER` must be a single executable: it cannot be a
command string composed of an executable with args (i.e., it no longer
adds the `escalate` subcommand, as before)
- `codex-exec-mcp-server` takes `--bash` and `--execve` as options.
Though if `--execve` is not specified, the MCP server will check the
directory containing `std::env::current_exe()` and attempt to use the
file named `codex-execve-wrapper` within it. In development, this works
out since these executables are side-by-side in the `target/debug`
folder.
With respect to testing, this also fixes an important bug in
`dummy_exec_policy()`, as I was using `ends_with()` as if it applied to
a `String`, but in this case, it is used with a `&Path`, so the
semantics are slightly different.
Putting this all together, I was able to test this by running the
following:
```
~/code/codex/codex-rs$ npx @modelcontextprotocol/inspector \
./target/debug/codex-exec-mcp-server --bash ~/code/bash/bash
```
If I try to run `git status` in `/Users/mbolin/code/codex` via the
`shell` tool from the MCP server:
<img width="1589" height="1335" alt="image"
src="https://github.com/user-attachments/assets/9db6aea8-7fbc-4675-8b1f-ec446685d6c4"
/>
then I get prompted with the following elicitation, as expected:
<img width="1589" height="1335" alt="image"
src="https://github.com/user-attachments/assets/21b68fe0-494d-4562-9bad-0ddc55fc846d"
/>
Though a current limitation is that the `shell` tool defaults to a
timeout of 10s, which means I only have 10s to respond to the
elicitation. Ideally, the time spent waiting for a response from a human
should not count against the timeout for the command execution. I will
address this in a subsequent PR.
---
Note `~/code/bash/bash` was created by doing:
```
cd ~/code
git clone https://github.com/bminor/bash
cd bash
git checkout a8a1c2fac029404d3f42cd39f5a20f24b6e4fe4b
<apply the patch below>
./configure
make
```
The patch:
```
diff --git a/execute_cmd.c b/execute_cmd.c
index 070f5119..d20ad2b9 100644
--- a/execute_cmd.c
+++ b/execute_cmd.c
@@ -6129,6 +6129,19 @@ shell_execve (char *command, char **args, char **env)
char sample[HASH_BANG_BUFSIZ];
size_t larray;
+ char* exec_wrapper = getenv("BASH_EXEC_WRAPPER");
+ if (exec_wrapper && *exec_wrapper && !whitespace (*exec_wrapper))
+ {
+ char *orig_command = command;
+
+ larray = strvec_len (args);
+
+ memmove (args + 2, args, (++larray) * sizeof (char *));
+ args[0] = exec_wrapper;
+ args[1] = orig_command;
+ command = exec_wrapper;
+ }
+
```
This PR introduces an extra layer of abstraction to prepare us for the
migration to execpolicy2:
- introduces a new trait, `EscalationPolicy`, whose `determine_action()`
method is responsible for producing the `EscalateAction`
- the existing `ExecPolicy` typedef is changed to return an intermediate
`ExecPolicyOutcome` instead of `EscalateAction`
- the default implementation of `EscalationPolicy`,
`McpEscalationPolicy`, composes `ExecPolicy`
- the `ExecPolicyOutcome` includes `codex_execpolicy2::Decision`, which
has a `Prompt` variant
- when `McpEscalationPolicy` gets `Decision::Prompt` back from
`ExecPolicy`, it prompts the user via an MCP elicitation and maps the
result into an `ElicitationAction`
- now that the end user can reply to an elicitation with `Decline` or
`Cancel`, we introduce a new variant, `EscalateAction::Deny`, which the
client handles by returning exit code `1` without running anything
Note the way the elicitation is created is still not quite right, but I
will fix that once we have things running end-to-end for real in a
follow-up PR.
Michael Bolin ·
Jeremy Rose ·