Wire managed MITM CA trust into child env (#22668)

## Stack
1. Parent PR: #18240 uses named MITM permissions config.
2. This PR wires managed MITM CA trust into spawned child processes.

## Why
When Codex terminates HTTPS for limited mode or MITM hooks, child HTTPS
clients need to trust Codex's managed MITM CA. Exporting proxy URLs
alone is not enough, but blindly replacing user CA settings would be
wrong: it can break custom enterprise/test roots, leak unreadable CA
files into generated bundles, or make the child env disagree with its
sandbox policy.

## Summary
1. Build immutable managed CA bundles under `$CODEX_HOME/proxy` that
include native roots, the managed MITM CA, and only inherited or
command-scoped CA bundles the child is allowed to read.
2. Export curated CA env vars alongside managed proxy env vars while
preserving user CA override semantics, including nested Codex
`SSL_CERT_FILE` precedence.
3. Thread generated CA bundle paths into child sandbox readable roots,
including debug sandbox execution, so the exported env vars work inside
sandboxed commands.
4. Remove only Codex-generated MITM CA bundle env when a child
intentionally drops managed proxying for escalation or no-proxy retry.
5. Document the managed CA bundle behavior and cover env injection,
per-child bundle generation, sandbox readable roots, and no-proxy
cleanup in tests.

## Validation
1. Ran `just test -p codex-network-proxy`.
2. Ran `just test -p codex-protocol`.
3. Ran `just fix -p codex-network-proxy -p codex-protocol`.
4. Tried focused `codex-core` validation, but the crate currently fails
to compile in `core/tests/suite/guardian_review.rs` because an existing
`Op::UserInput` initializer is missing `additional_context`.

---------

Co-authored-by: Eva Wong <evawong@openai.com>

codex-rs/core/src/tools/runtimes/mod.rs

@@ -12,10 +12,12 @@ use crate::shell::ShellType;
 use crate::tools::sandboxing::ToolError;
 #[cfg(target_os = "macos")]
 use codex_network_proxy::CODEX_PROXY_GIT_SSH_COMMAND_MARKER;
+use codex_network_proxy::CUSTOM_CA_ENV_KEYS;
 use codex_network_proxy::PROXY_ACTIVE_ENV_KEY;
 use codex_network_proxy::PROXY_ENV_KEYS;
 #[cfg(target_os = "macos")]
 use codex_network_proxy::PROXY_GIT_SSH_COMMAND_ENV_KEY;
+use codex_network_proxy::is_managed_mitm_ca_trust_bundle_path;
 use codex_protocol::config_types::WindowsSandboxLevel;
 use codex_protocol::models::AdditionalPermissionProfile;
 use codex_sandboxing::SandboxCommand;
@@ -57,21 +59,33 @@ pub(crate) fn exec_env_for_sandbox_permissions(
     if sandbox_permissions.requires_escalated_permissions()
         && env.contains_key(PROXY_ACTIVE_ENV_KEY)
     {
-        for key in PROXY_ENV_KEYS {
-            env.remove(*key);
-        }
-        // Only macOS injects a Codex-owned SSH wrapper for the managed SOCKS proxy.
-        #[cfg(target_os = "macos")]
-        if env
-            .get(PROXY_GIT_SSH_COMMAND_ENV_KEY)
-            .is_some_and(|command| command.starts_with(CODEX_PROXY_GIT_SSH_COMMAND_MARKER))
-        {
-            env.remove(PROXY_GIT_SSH_COMMAND_ENV_KEY);
-        }
+        strip_managed_proxy_env(&mut env);
     }
     env
 }
 
+pub(crate) fn strip_managed_proxy_env(env: &mut HashMap<String, String>) {
+    for key in PROXY_ENV_KEYS {
+        env.remove(*key);
+    }
+    for key in CUSTOM_CA_ENV_KEYS {
+        if env
+            .get(key)
+            .is_some_and(|value| is_managed_mitm_ca_trust_bundle_path(value))
+        {
+            env.remove(key);
+        }
+    }
+    // Only macOS injects a Codex-owned SSH wrapper for the managed SOCKS proxy.
+    #[cfg(target_os = "macos")]
+    if env
+        .get(PROXY_GIT_SSH_COMMAND_ENV_KEY)
+        .is_some_and(|command| command.starts_with(CODEX_PROXY_GIT_SSH_COMMAND_MARKER))
+    {
+        env.remove(PROXY_GIT_SSH_COMMAND_ENV_KEY);
+    }
+}
+
 #[cfg(unix)]
 fn prepend_path_entry(env: &mut HashMap<String, String>, path_entry: &str) -> String {
     let updated_path = match env.get("PATH") {
@@ -235,6 +249,7 @@ fn build_proxy_env_exports() -> (String, String) {
     let mut keys = PROXY_ENV_KEYS
         .iter()
         .copied()
+        .chain(CUSTOM_CA_ENV_KEYS)
         .filter(|key| is_valid_shell_variable_name(key))
         .collect::<Vec<_>>();
     keys.sort_unstable();

codex-rs/core/src/tools/runtimes/mod_tests.rs

@@ -8,6 +8,7 @@ use crate::tools::sandboxing::SandboxAttempt;
 use crate::tools::sandboxing::managed_network_for_sandbox_permissions;
 #[cfg(target_os = "macos")]
 use codex_network_proxy::CODEX_PROXY_GIT_SSH_COMMAND_MARKER;
+use codex_network_proxy::CUSTOM_CA_ENV_KEYS;
 use codex_network_proxy::ConfigReloader;
 use codex_network_proxy::ConfigState;
 use codex_network_proxy::NetworkProxy;
@@ -134,6 +135,9 @@ async fn explicit_escalation_prepares_exec_without_managed_network() -> anyhow::
     for key in PROXY_ENV_KEYS {
         assert_eq!(exec_request.env.get(*key), None, "{key} should be unset");
     }
+    for key in CUSTOM_CA_ENV_KEYS {
+        assert_eq!(exec_request.env.get(key), None, "{key} should be unset");
+    }
     #[cfg(target_os = "macos")]
     assert_eq!(exec_request.env.get(PROXY_GIT_SSH_COMMAND_ENV_KEY), None);
     assert_eq!(
@@ -144,6 +148,24 @@ async fn explicit_escalation_prepares_exec_without_managed_network() -> anyhow::
     Ok(())
 }
 
+#[test]
+fn explicit_escalation_preserves_user_ca_env() {
+    let env = HashMap::from([
+        (PROXY_ACTIVE_ENV_KEY.to_string(), "1".to_string()),
+        (
+            "SSL_CERT_FILE".to_string(),
+            "/tmp/custom-ca.pem".to_string(),
+        ),
+    ]);
+
+    let env = exec_env_for_sandbox_permissions(&env, SandboxPermissions::RequireEscalated);
+
+    assert_eq!(
+        env.get("SSL_CERT_FILE"),
+        Some(&"/tmp/custom-ca.pem".to_string())
+    );
+}
+
 #[cfg(unix)]
 #[test]
 fn apply_zsh_fork_path_prepend_uses_shell_parent() {